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ANi?LYTICA.L GECYCHEMISTRY 
ASSOC!i .. TED ELEMENTS IN THE 
STUDIES ON THE 
OF URANIUM AND 
HAWKS CRAG BRECCI1? OF NEW ZEli.Ll'.ND 
A thesis 
presented in partial fulfil?ent of the 
requirements for the degree of 
Doctor of Philosophy in Chemistry 
at 
Massey Univer?ity 
NOEL EDVU;.RD COHEN 
1 969 
M All11r(lllil11i i flilii l li li f y 
1061960755 
ACKNOWLEDGEMENTS 
The author wishes to thsnk his supervisors, Dr R. R. Brooks 
and Dr R. D. Reeves, for their enthusiasm and assistance 
throughout the work undertaken. He is also indebted to 
Dr G. Coote of the Institute of Nuclear Sciences for his 
assistnnce in the Gammn Spcctrometry part of the studies; to 
staff of the Geological Survey for vnlunble advice, to 
Mr Simon Nath?n, Mr John Foster and Mr Jock Braithwaite for 
assistance in the field work. 
He also wishes to thank Mrs Barbara Sanderson for typing 
the thesis, Miss Doreen Scott for photographic assistance and 
Mr Peter Herbert for printing the figures. 
The author is most grateful to the Mineral Resources 
Sub-Committee of the New Zenland Grants Committee for the 
provision of funds to support this project. 
Tl,BLE OF CONTENTS 
ACKNOWLEDGEJviENTS 
TABLE OF CONTENTS 
LIST OF T.r,BLES 
LIST OF FIGUHES 
ii.BSTRl?CT 
GENER?L INTRODUCTION 
P .. RT I DEVELOPMENT OF i,N1\LYTIC1-1L PROCEDURES 
INTRODUCTION 
flN,.LYTICi,L PHOCEDUHES FOl\ THOHIUM , YTTRIUH ,i.ND THE R!.RE 
Ei.RTH ELEMENTS 
( a) Optimum SpectroGraphic Condi tions 
( i )  Apparatus 
( i i )  Sampl e Preparation 
( i i i ) Reduction o f  Background 
I .  Investigation o f  Carri ers 
I I .  Inves tigation of Gas Condi tions 
i i  
vi 
vii 
ix 
1 
4 
1 0  
10 
10 
1 0  
1 0  
10 
1 1  
(iv) Investigation of  S ensi t ivi ty  Limi ts  13 
( v) The Volatilisation Behaviour o f  Yttrium , Thorium , 
Lanthanum , Cerium , Europium, Holmium , Palladium, 
and Zirconium 
( vi )  Final Spectrographic Operating Condi tions 
( b )  S tudies On The Interference O f  Thorium , Y ttrium 
15 
17 
Ana Rare Earth ?nalysis  Lines 1 9  
t. Development o f  an Ion-Exchange Separation 1 9  
( i )  S eparation by Use  of  the Acet ic/Nitric  
Acid  ?nion-Exchange Syst em 19 
(ii) S eparation by Use  of the Nitric Aci d  
hnion-Exchange Sys tem 21 
II. Mutual Interference o f  Yttrium, Thorium and 
Rare Earth ?nalysis Lines 21 
( c) The Use of the Combined ?nion-Exchange?
Spectrographic Procedure 
( i )  Dissolut ion of  rlOCk Samples  
(ii ) Analysis of  G-1, W-1 and CAAS Syeni t e  
( i i i ) Evaluation o f  Data 
f,N4l.LYTICflL METHODS FOR URf>NIUH 
(a) Spectrographic Procedure for Macro Amounts of 
Uranium 
(b) Solution Fluorimetry 
( c) Fusion-Bead Fluorimetry 
25 
25 
27 
27 
33 
33 
33 
35 
DISCUSSION 
p;,JT II GEOCH;?tnc;,.L INVESTIG"TIONS IN THE 
Hi,V/I'::S CR,.G BRECCI.h. 
INTRODUCTION 
THE GEOLOGIChL ;?ND PHYSICi.L FE.c?.TURES OF THE UR.?,.NIFEROUS 
:.REf, 
( a) Phys i cal Features 
( b )  General Geology 
37 
39 
( c )  The Pe trology and Mineralogy o f  the Uranium Deposi ts 44 
( i )  The North Side  Depos i ts 
(ii) The South Bank Deposit? 
METHODS 
(a) Sampling Pro c edures 
( b )  An?lyt i c al Techniques 
( c )  S tatis t ic al ?nalysis of Data 
ELEl'!ENTi,L ;?SSOCii,TIONS WITH UR!,NIUM IN MINERALS , SOILS 
riND SEDIMENTS 
(a) Copper  and Uranium 
( b) Beryllium and Uranium 
(c) Lead and Uranium 
( d )  Zinc  and Uranium 
( e ) Rare Earth Elements 
ELEMENTII.L Ri,TIOS AS p:,THFINDERS FOR UH;?NIUM 
DISCUSSION 
PA.HT III 
MINERf,LS BY 
EQUILIBRIUM STUDIES 
HIGH-RESOLUTION GAMMA 
ON URi.NIUM 
SPECTROMETRY 
46 
47 
51 
51 
53 
53 
56 
56 
58 
58 
58 
59 
64 
67 
INTRODUCTION 73 
INSTRUMENTATION 79 
IDENTIFICATION OF SPECTRA 81 
( a) Calibration o f  Pulse Height  Analyser  81 
( b )  Analys is  o f  Spec tra 81 
(i) 1 80-360 KeV Region 83 
( i i)  30-180 KeV Region 84 
EQUILIDRIUH STUDIES ON MINERJ,LS 87 
( a ) Derivation o f  th& Equilibrium Relationship 87 
( b )  The Iso topic Compos i t ion  o f  Uranium Minerals from 
the Lower Buller Gorge 91 
DISCUSSION 
GEN:Z:Ri?L DISCUSSION 
HEFE .. n;;NCES 
95 
98 
1 02 
LIST OF T;?BLES 
p,?.RT I 
I - 1  Effect of  Carriers on Line- to-Background Raiio 
of La4333 i n  a Curbon Dioxide htmosphere 1 2  
I-2 Times for Com?l?te Volatilisution  o f  Yt trium? 
Thorium and Rare Earths in Vari ous Matri ces 1 4  
I-3  Line-to-Background R?tios  and Limi ts ?f  De tec tion  
for Yttrium , Thorium and  Rare Earths 16 
I-4  Spe c trographic  Oper?t ing Condi t ions 1 8  
I-5 Analyti cal Lines  and Interferences 24 
I-6 Recoveri es from Ion-Exchange Se??rations 28 
I-7  Comparison o f  Spec trographi c , Neutron hCtivation 29  
and Hecommended Values for  Thorium , Y t trium ,  
Uranium and the Rare Ear ths i n  G- 1 ,  W- 1 and C:\;?,S 
Syenite  
I-8 Rare Earth Abundance  Ratios  for G- 1 , W-1 and CAAS 
II- 1 
I I-2  
II- 3 
II-4  
I I-5  
I I I- 1 
I I I -2  
Syeni te  30 
PU1T I I  
S tratigraphi c S equence  in  Lower Buller  Gorge 
Analysi s  of S tream S ediments as a Function  of 
Mesh Size 
45 
52 
Statistical Data for Various Elements in Minerals, 57 
Soils  and S tream S ediments 
Rare E?rth Conc entrations i n  Minerals , Matrix and 60 
Stream Sediments 
Elemental rtatios as Pathfinders for Uranium in 66 
S tream Sediments 
Isotopes and Respective  Gamma Ray Energi es  used 82 
for Calibration of a Pulse Height Analyser 
The Equilibrium S tate of Various Uranium Minerals 92 
from the Lower Bull er Gorge 
LIST OF FIGURES 
I - 1  Spec trograms of  Rare Enrth Mixtures ( CN band pp 1 2- 1 3  
region) Arced in Various Atmospheres 
I-2 Line- to-background R?t io as a Function  o f  pp 1 4- 1 5  
:trc ing Current 
I -3  Volatilisation Curves  for  Rare Earths , pp1 8- 1 9  
Yt trium , Palladium and Zirconium 
I -4  An.:1lysi s  ?lement Intensi ty/Palladium Intens i ty pp 1 8- 1 9  
as a Function  o f  the Coeffi c i en t  o f  Vari?tion 
I-5 Elution curves for Analysis  Elements in  Ni trate pp21-22 
Sys tem 
I-6 
I-7a 
I-7b  
I-8 
I - 9  
I - 1 0  
I-11 
I - 1 2  
I-13 
I- 1 4  
Reciproc al Dispersion Ci/mm) and Resolution Ci) pp22-23 
as a Function of  Wavel ength (R) for the Hilger 
E742 Quart z-Opti cs  Spec trograph 
?orking Curves for Cerium ( 4040 ) in the pp25-26 
Presence  of  various c oncentrations o f  Neodymium 
Working Curves for Y 3327 and La 3995 pp25-26 
Neutron  Ac tivation Data from HASKIN and GEHL pp29-30 
as a Funct ion of  Spec trographic  Data from the 
Author for G-1  and W- 1 
Data from the Author as a Function o f  pp29-30 
Spe c trographi c Data from TENN.' .. NT and FELLOWS 
for CAAS Syeni t e  
Rare  Earth Dis tribution for an Average Bas i c  pp31-32 
Rock and CA?S Syeni t e  
Spe ctrographi c Working Curve  for Uranium pp33-34 
Uranium Fluor escence  Intens i ty as a Function  pp34-35 
of Per C ent  Phosphori c Aci d  
Solution Fluorimetry Working Curve for Uranium pp34-35 
Fus ion-Bead Fluorime try Working Curve  for pp36-37 
Uranium 
Pf .. RT I I  
I I - 1  Map Showing Dis tribution  o f  Hawks Crag Brec c ia  pp43- 44 
on Nes t  Coas t of South Island 
I I-2  
II-3a 
Photo Showing Dense Beech Forest i n  H . C . B .  Area pp43-44 
Aerial Photograph of Lower Buller Gorge 
including H . C . B .  area 
pp43-44 
II-3b 
II-4 
II-5 
II-6  
II-7 
II-8  
II-9  
II- 1 0  
II-1 1 
III-1 
III-2 
III-3 
III-4 
III-5 
I I I-6  
III-7 
III-8  
Aerial Photograph o f  H . C . B. Area from Fig .  II-3a pp43-44 
De tailed  Geologi cal Map o f  th8 H . C . D . Area pp45-46 
Pho tosraph and ,:,u toradiograph of itrkos e pp48-49, 
containing Uranini te  
Elemental Relationships in  Minerals , Soils  pp57-5? 
and S tream S ediments 
Cumulative  Frequency Plots  for Various Elements pp58-59 
in  Soils and Stream S ediments 
Rare Earth Distribution i n  Uranium Minerals pp59-60 
and in Stream Sediments Draining H . C . B .  Areas 
Triangular Plot  for C oncentration Ratios  of 
Copper , Lead and Uranium in Minerals, Soils and 
Stream Se diments 
Map of Buller Gorge hrea of New Zealand showing 
Radioactive Horizons and Sampling P oints for 
Soils and S tream Sediments 
Triangular Plot  for C oncentrati on Ratios  o f  
Lanthanum , Yttrium and Thorium from S tream 
S e diments in  Drainage Areas; Ohika-Nui Riv er , 
O tututu River and Hawks Crag Brec c ia 
Pi'.RT III 
Decay S chemes for u238, u235 and Th232 
Comparison o f  Uranini t e  Spec trum Recorded 
wi th Nai( Tl ) and Ge ( L i )  Detec tors 
Gamma Spectroscopy ; Schemat i c  Diagram 
Computer-Assisted Analysis  o f  Gamma Spec tra; 
S chemat i c  Diagram 
Calibration Curve , KeV as a Func t i on o f  Channel 
Numb0r 
Gamma Spe c tra of Uranini t e , Ra226 and Th232 
Gamma Spe c tra of Uranyl N i trate , Extrac ted 
Uranium Fraction and Extrac ted  Thorium Frac tion 
. C(1 85 ) Theoret?cal Curve o f  c(295) as a Func tion  o f  
the "Percentage Equilibrium Radium" 
pp64-65 
pp64-65 
pp71 -72 
pp74-75 
pp76-77 
pp79-80 
pp79- 80 
pp81 -82 
pp83-84 
pp85- 86 
pp90-91 
hBSTRACT 
Part I 
S tudi es  were  carr i ed out on the opt imum condit ions for the 
suc cess ful use  o f  a lnrge quartz  spe c trograph for the determin?tion 
o f  thorium , yttrium and the rare  ear ths in s il i cat e  ro cks . The 
best  l ine-to-background ratios  were  achieved by arcing samples  in  a 
m?trix  of 4% sodium chloride in carbon p owder . An atmosphere  of  
20% argon and 80% oxygen w?s us ed to reduce  background and eliminat? 
cyanogen band int erference .  An anion- exchange pro cedure was used 
to s eparate the rare  earths from other  elements . The result ing 
enr i chment allowed use to  be made of less sensi tive rare earth 
lines  in the ultraviolet end o f  the spe c trum where the spectrograph i c  
dispersion i s  greater . Line  interferences  w e r e  studi ed and 
nec essary corre c t i ons for thes e interferences  were calculate d .  
The t echnique was tested  b y  analysing the s tandard rocks , G- 1 ,  W-1 
and CAhS syeni te . Depending on i ts c onc entratio? uranium was 
analys ed  by e i ther  fluorametric  or  spec trographi c te chniques . 
Good agreem0nt with  the recommended values  for the s tandard rocks 
was obtaine d .  
Part I I  
An investigation  o f  the known areas o f  uranium 
minerali zation  in the Lower Bul ler Gorge o f  New Zealand was 
carri ed  out to i nves tigate the suitab il i ty o f  s tream- sediment 
analysis  for geochemi cal prospec ting for uranium . General analysis  
o f  the  minerals reveal ed  certain el emental associat ions . The 
distribution of these elements in the weathering sequence, minerals, 
soils , s tream-sediments , was s tudied  in  an attempt to dis cover  
sui table p3.thfinders  for ure.nium. ,.11 rcsul ts were tre3.ted 
s t?tis t i cally . Rare ear th analys i s  of s tream sadimants provided  
new inform?tion  concerning the possibl e ori?in of  the Hawks Crag 
Brc:c c ia . 
P<1.rt I II  
Us e  was made of  a high-resolution  gamma spcc trometer  to  
s tudy the gamma radiation of  uranium minerals in the low energy 
r egion of the spec trum , 30-360 KeV . Identi fi cation  of  the gamma 
radiation , in this region , was achi eved by use  of chemi c al 
s ep3.raticns and s tandard sourc es . This provided  the bas i s  for  the 
development ,  and successful us e ,  o f  a new method for the deter?
mination  of "perc entage equ ilibrium radium" . The s igni fi cance  o f  
the values for the "p erc entage equil ibrium radium" of  the minerals 
s tudied  is di s cus s ed .  
GENER?L INTRODUCTION 
1 . 
In 1 956 , two pros)ec tors , Cassin  and Jacobsen , di s covered  
ur?nium in  the Lower Buller Gorge region in the South  Island of  
New  Zealand . In  the  s earch for  radioec tive  minerals this  find 
was of  great geologi cal signi fi cance  because i t  trans ferred 
geologi cal thinkin? from the grani tes and associ?ted rocks t o  a 
hi therto  unsuspe cted arko s i c  b edded formation known as the Hawks 
Crag Bre c c ia .  This discovery by  Cassin  and Jacobs en s timulated  
the  search for  ur3nium i n  this area unt il  the  early 1 960 ' s ,  when 
the fall in  pri c e  of uranium , c ombined w i th unpromising ini t ial 
findings, made further prosp e c t ing unattractive . R e c ently , as a 
r esult  of  Government encouragement , the interest  in  uranium 
prosp e c ting has b e en revived  and many of  the known areas of  
mineral izati on are  be ing re- evaluate d .  The need  for a source  of  
ur?nium has b e en h eightened because o f  the  possible  ins tallation  
o f  a nuclear r eactor  in the  lat e 1 970's . 
Previous  i nvestigations have been carried  out almos t  
ent irely b y  field geologists  and were  mainly of  ? petrologi c?l 
nature . In  v i ew o f  the increasing success  o f  geochemi cal methods 
of ex?lorat i0n in other  parts  of the world ,  there was c learly a 
n eed for such an inves tigation i n  thi s  area.  The benefi ts o f  such 
a s tudy would  not only be  confined to aspects  of  economi c geology 
but also provide inform?tion on the history and origin of the 
uranium de?osits  and on the Hawks Crag Brec cia  i tsel f .  Considering 
the advantages  of geochemi cal obs ervations , i t  is  somewhat 
surprising that w i th the exception  of work by WODZICKI ( 1 959a , 
1 959b ) , l i t tl e  or none of  this  work has been carried  out  in  this  
area . One possible  reason for lack o f  work i s  that the analyti cal 
2. 
me thods of analysing for urnnium and associated  elemants , such  as 
thorium and the rare eGrths , are o f ten tedi8us or unreli able ,  
anu require  specialised equipment not generally av?i lable  in  many? 
geochemi cal laboratori?s . 
Provi ded th?t these analyti cnl problems could be  solved 
?nd a sui table technique could be  developed,  a geochcmi cal survey 
of the area would be  fac il i tat e d .  This thesis  desc ribes  somewhat 
intensive  investigations into  the development of such t echniques 
and their  subsequent a?pli c&t ion  to  geochemicnl studi es  in  the 
H?wks Crag Bre c c ia .  
WHITEHE?D and BROOKS ( 1 969a ) in reconnaissance  work i n  the 
area have highlighted  the defi c i encies  of many s c intillometri c and 
o ther  radiometric  m e thods for the  an&lysis  of  uranium in  minerals , 
soils and s tr eam s ediments . The use of radiometric  methods for  
ac curate quanti tative  analysis  relies  on the assumpti on that the  
uranium sample i s  in  radioactive equilibrium .  However , ? compre?
hens ive  s tudy of  radioactive  equilibrium in  thi s  are? has never  
b een satisfac torily at temp t e d , largely because o f  the lack o f  
sui table  methods . This  problem was there fore investigated as a 
part o f  the present s tudy and has been solved by the appli cation 
o f  ? new t e chnique in gamma spec tromctry .  This is reported  i n  
Part I I I  of  this thesis.  
To summari?e , the aims  of  this  thesis  were  threefold : 
( 1 )  To  develop a ?ethod for the analys is  of  low  concentrati ons 
of yt trium , thorium and r?re  earths wi th the us e of  a large quartz?
opt i c s  spec trograph . 
(2) To inv es t igate the  possible  asso ciation  o f  the above  elements , 
3nd any other elements , wi th uranium i n  the minerals from the 
South S ide o f  the Buller River  and to s tudy the dis tribution  o f  
these  elements in  the weathering s equenc e :  minerals , s o ils , s tream-
s ediments .? From these results , to examine c r i t i cally the 
relntive  mer i ts of dir e c t  analysi s  of uranium and of associated  
el ements  in  s tream- sediments , a s  a geochemical prospec t ing method 
for uranium minerali zation . 
(3) To develop a me thod , using only gamma radiation from u235 
and Ra226 , to  determine  the ;'perc entage  equilibrium radium" of  
uranium minerals . 
DEVELOPMENT OF hN:,LYTIC .. L PHOCEDURES 
4 . 
INTRODUCTION 
The progress of geochemistry depends ultimately on how 
effectively the collected quantitative abundance data are utilised. 
The value of this information is very dependent on the precisi on 
of  the determinations and although it  is  impossible to assess 
the quality of each published analysis, an examination of some 
of the figures provided by the various methods most widely applied, 
does give an indication of the reliability of much of the existing 
data. Furthermore, this  also gives an i dea of the progress in 
the analytical procedures which  are applied. 
The classical or conventional methods of rock analysis 
were fairly well established during the second half of  last century 
( HILLEBRAND, 1900) and have remained essentially unchanged 
(WASHIN?TON, 1950; GROVES, 1 951; HILLEBRAND and LUNDELL, 1953). 
Those who developed the classical procedures, as well as those 
who used them, frequently attempted to indi cate their accuracy, 
but no real insight into the quality of this immense collection 
of  published information was gained until FAIRBAIRN ET AL ( 1 95 1 ) 
organised a world-wide, inter-laboratory investigation on granite 
(G-1 ) and diabase (W- 1 ) .  Numerous analyses of these rocks were 
carried out by a large number of workers using a wide 9ariety 
of techniques. The w ide variation  in the analytic?l data for 
i dentical samples clearly demonstrated the shortcomings of  many 
existing analytical techniques. AHRENS (1 957 ) using published 
data for G- 1 and W-1 ,  showed that for classi cal procedures, the 
logarithm of the standard deviation of  replicate analyses was 
inversely related to the logarithm of the concentration of the 
c onstituent analysed. The signifi cance of this  relati onship 
be comes extremely important  when analysing at  the trace  element 
( ppm ) level . For this reason , the analysis  of many geochemi cally-
important elements such as thorium , uranium , the rare earths 
and yt trium presents  c onsi derable  difficulty . 
Several radiometric  me thods have  b e en used  for  the 
det ermination  of uranium and thorium ( EICHHOLZ ET AL , 1 953; 
CHERRY and ADAMS , 1963; CHERRY , 1 963; HEIR and ROGERS , 1 963; 
VASS ILAKI ET AL , 1 96 6 )  but these  procedures suffer from the dis-
advantage that radioactive  equilibrium must b e  assum ed and this 
is not  always so . Of  the above workers , only EICHHOLZ ET AL 
( 1 953 ) allowed for this p ossibil i ty .  Fluorimetry (GRIMALDI ET 
AL , 1 952; PRICE ET AL , 1 953; ANDERSON and HERCULES , 1 964) i s  
undoub tably one of the mos t  s ensi tive  methods for uranium 
- 10  ) ( limit o f  det e ction 10 g but  has the disadvantage that 
extensive  dilution is needed for samples  containing even 
moderate amounts of this element . O ther  methods such as 
emission  spe c trography are by contras t extremely insensi tive  
for  uranium . I t  i s  c lear , therefore  that a c ombination o f  
m e thods i s  required i f  the conc entrati on range of  this  element  
spans several orders  o f  magnitude . 
Y t trium ,  thorium and the rare earths have b e en analysed  
by  X-ray spe c trography ( GAVRILOVA and TURANSKAYA , 1 958; 
BALASHOV ET AL , 1 964; ALEKSIEV and BOVADJIJ!;VA , 1 966 ) , spark 
s our c e  mass spec trography ( BROWN and WOLSTENHOLME , 1 964; TAYLOR , 
1 965; NI.CHOLJS ET AL, 1967 ) , ac tivation  analys is  ( TOWELL ET AL , 
1 965; BRUNFELT and STEINNES , 1 966; COBB , 1 967; GORDON ET AL , 
1 96 8 )  and emi ss ion spectrography (FARIS , 1 958; RADWAN ET AL , 
1 963; MYKYTIUK 1T AL , 1 966; NELMS and VOGEL , 1 967 ) .  The 
6 .  
relative  merit  of  these techniques will b e  bri e fly discuss ed for 
the sake o f  c omple teness although only emission spe c trography 
was available  for us e at this ins t i tution .  X-ray spe c trography 
has a relatively poor  detection limit  making i t  generally 
unsui table . Spark source  mass spectrography has been  shown to  
be  an  accurate and extremely sens i tive  t echnique and has the 
advantage that all elements may be det ermined s imultaneously . 
Neutron activation i s  also extremely s ensitive  but requires  
c onsiderable  chemical treatment o f  the  sampl e to  eliminate inter?
ference  when using the Nai?) detec tor . Direct  analysis  of 
the sample  can now be achi eved using the recently developed G e (L i ) 
d e te ctor  although "cooling" t imes o f  the order o f  months are 
necessary for s ome  elements in order to  eliminate interference  
problems . 
Emission  spe c trography has been for many years one o f  the 
most  sat i sfacto ry me thods for  the analysi s  of  rare earths in  
s i l i cates  (AHRENS and TAYLOR 196 1 ) .  Unfortunately this  t echnique 
nevertheless  suffers from certain inherent disadvantages . Thes e  
are : production o f  high background due to  the c ompl ex spe c tra 
of the rare earths; interference from o ther rare earths , t i tanium 
and i ron ; the necess i ty of  high amperages ( FASSEL , 1949; ROSE 
ET AL, 1 954) and l ong arcing times b ecause of the relative  
involatility o f  the  rare ear th oxides . This last fac tor  also 
results in high background due to cyanogen emission in the range 
3500-4200 ? where  mos t of the best  analysis  l ines  of  the rare 
earths are found . 
Line interference  may also  b e  reduced  by use  o f  a high-
7. 
dispersion  grating instrument and cyanogen emission  may b e  
controlled  by  arcing in  various nitrogen- free  atmospheres such 
as carbon dioxide (STEADMAN, 1 948) , argon , helium or oxygen 
( VALLE? ET AL , 1 950 )  and a mixture of argon and oxygen ( RADNAN , 
1 963 ; TENNANT and SEV.IELL , 1 967 ) . Use o f  a noble  gas atmosphere  
results i n  an  enhancement o f  ion  line  i ntensi ti es relative  to  
thos e  o f  atom lines and a reduction  i n  background . This is  a 
distinct advantage as the most s ensitive rare earth analysi s  
lines are i o n  lines . The main disadvantage is  that arc ing times  
of  the order  of  minutes are required . Another  approach to the 
problem o f  line interference  is the carri er distillation method 
( SCRIBNER and MULLIN , 1 946; MYKYTIUK ET AL , 1 966 ) which  allows 
arcing  times to b e  reduc ed by increasing volatilisation rates . 
To obtain high-pre c ision quantitative  results , use  o f  z irconium 
( McCARTY ET AL , 1 938 ) , palladium ( YOUNG , PH . D .  THESIS ) and 
c ertain  rare ear ths  ( FASSEL and WILHELM , 1 948; Kl'iiSELY ET AL , ? 
1 958 ; AHRENS and TAYLOR , 1 96 1 ) as internal s tandards has been  
recommended .  
The relatively-high sens i tivi ty o f  rare  earth analyses  
referred to  in  the l iterature ( MITCHELL , 1 948 ; AHRENS and 
TAYLOR , 1 96 1 ) was obtained via  a high-dispersi on i nstrument and 
cannot b e  dupli cated wi th a quar tz- opti cs  spectrograph . There  
is  clearly a ne ed for a method whi ch will  permit the  us e o f  
such Rn ins trument in rare earth analysi s , particularly as such 
spe c trographs greatly outnumber grating instruments in  general 
use. 
The majority of  the above  techniques require preliminary 
chemi cal treatment of the sample either to reduce interference 
or to concentrate the elements being determine d .  S eparation 
methods commonly used  are: prec ipitation of r?re earths as 
hydroxides (ROSE ET AL, 1954) or oxctlates (STEkDMAN, 1948), 
solvent extraction (l?cCARTY ET AL, 1938; SCRIBNER and MULLIN , 
1946; VALLEE ET fL, 1950; RADWAN ET AL, 1963; MYKYTIUK ET AL, 
1966) and i on exchange ( CJ._Rm'ELL, 1957; Di\.NON, 1958; NIETZEL 
8 .  
E T  AL , 1958; FARIS and WARTON , 1962; FRITZ and GARRALDA , 1962; 
TAKETATSU, 1963; AHRENS ET AL , 1963; KORKISCH and ARRHENIUS, 1964; 
S'I'RELOW, 1966) ? 
It was clear that a s eparation- enrichment procedure would 
be  required for the present work because  of  line interferences  
and s ensitivity problems . S eparati on i s  parti cularly necessary 
where  samples  contain  more than five percent uranium , b e cause  
the presence  of  a very large number o f  uranium lines  in  the 
range 2500-5000 E results in  a high background i n  the emission  
spectra . This background prevents analysi s  of  elements other 
than uranium in thi s  range . 
Prel iminary investigations showed that precipitation and 
solvent extraction techniques  were unsuitable  because  o f  
incomplete recover i es . Cation exchange chromatography was un?
satisfactory because l?rgc eluting volumes were involved , with a 
subsequent reduction in  the conc entration of  the analysi s  
elements . Anion  exch?nge 2ppcared to be  the most promising and 
was i nvestigated further . 
The f0llowing s e ction reports on the analyti cal pro c edures 
which were developed for the analysis  of uranium , thorium , 
yttrium and the rare earths i n  minerals , s o ils and stream sediments , 
and involves:-
(i) The development of optimum spectrographic 
operating conditions for the ?nnlysis of yttrium, thorium and 
the rare earths, using ? medium-dispersion instrument.  
(ii) Suitable methods for analysing uranium over a 
concentration range of  several orders of magnitude. 
(iii) The development o f  a suitable  ion-exchange 
9. 
separation scheme for yttrium, thorium, uranium and rare earths 
in silicates. 
ANALYTICAL PROCEDURES FOR THORIUM, YTTRIUM 
AND THE RARE EARTH ELEMENTS 
(a) Optimum Spectrographic Conditions 
(i) Apparatus 
The experiments were carried out with a Hilger E742 
Large Automatic Spectrograph w{th quartz optics (reciprocal 
dispersion 1 2  E/mm at 4000 ?.) A Hilger microdensitometer 
with Galvoscale calibrated in B-values (BOSWELL and BROOKS, 
1965) was used for densitometry. 
An image of the arc was focussed on the slit via a 
quartz spherical lens and the spectra were recorded on Ilford 
G-30 spectrographic plates developed for 4? minutes in Kodak 
D 19b developer at 20?. 
(ii) Sample Preparation 
In all cases, solutions of thorium, yttrium and rare 
earths, whether as ion-exch?nge eluants or as pure solutions, 
were treated in the following standard manner. 
A quantity of finely-divided carbon powder (50 mg) was 
added to not more than 50 ml of a solution of thoriu?.yttrium 
10. 
and rare earths contained in a 100 ml beaker. The carbon powder 
( 1 20 mesh) contained an added internal standard. After 
addition of the required amount of carrier, the contents of the 
beaker were evaporated to dryness at 80? and the dry carbon 
powder was removed, ground in a motar and loaded into graphite 
electrodes (cavity 6mm deep and 1.5mm bore) which were dried 
at 130? for 2 hr. 
(iii) Reduction of Background 
I. Investigation of Carriers 
Preliminary experiments in a carbon dioxide atmosphere 
11. 
were carried out on samples with and without various concentr?tions 
of each of the following halides: c?esium chloride, silver 
chloride, sodium chloride and sodium fluoride. Lanthanum was 
added to each mixture to give a final concentration of 100 ppm 
and the samples were arced at 12A d.c. using anode excitation. 
Table I-1 shows the relative intensities of La 4333 to background 
for the various carriers. From this it is seen that for an 
atmosphere of carbon dioxide, 4% sodium chloride was the most 
efficient carrier for a maximum line-to?background ratio. 
Vclatilisation for a maximum line-to-background ratio was complete 
in thirty seconds, but the cyanogen emission and background, 
although less than that without carrier, were still too high. An 
attempt was made to reduce these further by changing the arcing 
atmosphere. 
II. Investigation of Gas Conditions 
Samples containing a mixture of thorium, yttrium and rare 
earths in a carbon matrix, with and without addition of 4% sodium 
chloride, were arced at 12;l (d.c. with anode excitation)successively 
in air, carbon dioxide and a mixture of argon and oxygen in varying 
pr0portions from 100% argon to 100% oxygen. This study showed 
(Fig. I-1) that a mixture of 20% argon and 80% oxygen was the most 
efficient for reducing cy?nogen emission and background. The 
samples with s?dium chloride in each case had a lower background 
than those without carrier but the most striking difference was 
the considerable reduction of cyanogen emission and background with 
the 20% argon and 80% oxygen mixture. This level of background 
was quite acceptable but it was necessary to know whether 4% 
sodium chloride as carrier and 12:. arcing current were in fact 
12. 
TABLE I - 1 
Effect  o f  Carri ers on Line-to-Background 
Ratio of  La  4333 in  a Carbon Dioxide Atmosphere 
Carrier  
NaCl NaF AgCl CsCl None 
2% 4% 6% 2% 4% 6% 2% 4% 6% 2% 4% 6% 
In tensity 1. 2 1.7 1. 0 1.3 1.0 0.8 0.5 0.5 0.5 1. 3 1.0 0.8 0.5 ratio  
A air with 4% sodium chloride matrix 
B air with carbon matrix 
C carbon dioxide with 4% sodium chloride matrix 
D carbon dioxide with carbon matrix 
E 80 20, 02 Ar mixture with 4% sodium chloride matrix 
F Bo 20, 02 Ar mixture with carbon matrix 
Fig. I-1 Spectrograms of rare earth mixtures (CN band region) arced at 10A in various atmospheres. 
A 
B 
c 
D 
E 
F 
Fig. I-1 Spectrograms of rare earth mixtures (CN band region) arced in various atmospheres. 
13. 
s till  the optimum conditions both for background reduction  and 
sens i tivi ty for atmospheres other than carbon dioxi de? It was deci4e d ,  
therefore , t o  investigate  the aff e c t  of  di fferent arcing currents , 
carriers and carri er concentr?tions  in the 20% argon and 80% oxygen 
atmosphere . 
( iv )  Investigation  o f  Sens i tivi ty Limi ts 
AHRENS and TAILOR ( 1 96 1 ) divi de  the rare earth e l ements  
into  three volati l i ty groups . Representative elements ( lanthanum , 
c erium , europium , holmium , and ytterbium )  from each o f  these 
three  groups were taken , as well  as yttrium and thorium . Solutions 
o f  thes e  elements w ere prepared from their respec tive  1 1Specpure" 
oxides. Samples containing 100 ppm o f  each of  thes e  metals were 
prepared in  matri ces  containing 2%, 4% and 6% sodium chloride ,  
s odium fluoride , caesium chloride and silver chlori de respectively 
and wi thout carrier . The samples w ere arced at 8A , 1 0A ,  12A and 
1 4A res?ec tively ( d . c .  wi th anode  exci tation ) in the 20% argon, 
80% oxygen atmosphere wi th the pho tographi? plate being racked down 
t o  expose a fresh area of plate every five  seconds. From these  
volatilisation  curves  the time taken for compl e t e  volatilisation 
was obtained . The results are given  in  Table  I-2. 
For the determination of  l ine- to-background ratios , a 
further s e t  o f  samples  i denti cal to those  above were arced  at 8A, 
10A , 12A and 1 4A respectively . Times of  arc ing were as in Table  I-2r 
It was obcerved  that all carriers increased  the line-to-background 
ratio  and improved th? detec tion l imi t of  each element at each of  
the di fferent concentrations of  carri er us ed  as compared with no  
carrier . Within each carri er conc entration  range , this e ffe ct  
usually increas ed  t o  ? maximum at 1 0A and 12A decreasing again at 
? 
..::t TABLE I - 2 ....-
Times  for  C omp l e t e  Volat i l isation o f  Y t trium ,  Thorium and Rare Earths i n  Various Matr i c es 
Carri er 
NaCl NaF ilgCl CsCl No  Carrier 
2% 4% 6% 2% 4% 6% 2% 49'; 6% 2% 4% 6% 
I 
Volatilisation time(sec) at 8 amp 35 30 25 25 25 30 20 25 25 30 30 30 35 : 
\I " " it 11 " " 1 0  11 30 25 25 20 20 25 25 20 20 30 25 30 35 
11 11 n " 11 11 11 1 2  " 30 25  20 ? 20 20 25 25 25 20 25  30 30 35 
ll " " " il " " 1 4  il 25 25 20 1 5  1 5  20 25 20 20 25 30 25 35 
8 10 12 14 Amps 
Fig, I - 2 Line-to?background ratio as a function of arcing current. 
15. 
14A ( Fig . I-2) . I t  was observed, that 4'76 sodium chloride  and 6% 
sodium chlori de at 10A and 1 2a ?espectively provided  the largest  
increas e in  the l ine-to-background rati o and improvement in  the  
detection limit for every element as  c ompared with no carrier . 
Results obtained  under thesG conditions are shown in  Table  I-3. 
The limit  of  d etection is  taken arbitarily  to b e  that conc entration 
o f  the e l ement  whi ch will  give a line intensi ty  equal to that of  
the  background . Since  the average background intens iti es  were  of 
the order  o f  50 B-value  units , the limit  of  detection  was taken as 
that concentration which would give a value o f  50 B-value  units for 
the line  i ntensity after correction for background. Table  I-3 
shows that  almost  i denti cal r esults were  obtained with e i ther  4% 
o r  6% s odium chloride arc ed  at  b o th 10A and 1 2A respectively. 
The final choi c e  of carrier  concentration  and arcing amperage was 
determined  by the relative volatilisation rates of the analysi s  
elements and internal standard .  F6r accurate , quantitative  
results i t  is  essential that the  behaviour o f  the analysis  elements 
and i nternal standard be as similar as possibl e. As zirconium 
and palladium had been  used  by other  authors (McCARTY ET AL, 1938; 
YOUNG , PH.D. THESIS) it was dec ided to  inves t igatG their 
suitabili ty under  these conditions. 
(v) The Volatilisation Behavi our of  Yttrium, Thorium, Lanthanum , 
Cerium, Europium, Holmium, Palladium and Zirconium 
Samples  c ontaining 100 ppm of thorium , yttrium and each o f  
the above  rare earths end 1000 ppm o f  palladium and zirconium 
were  prepared in matrices containing 4% and 6% sodium chloride  
resp ectively . Each sample  containing a part i cular concentration 
o f  carri er was arced  at 10A and 1 2A in  the 20% &rgon , 80% oxygen 
TABLE I - 3 
Line- to-Background Ratios  and L imi ts  o f  
D e te c tion  for  Yt trium , Thorium and Rare Enrths 
Carri er 
4% NaCl 6% NaCl 
A B A B - - - -
Yb3289 at  1 0  amp 22 . 2 0 . 6 36 . 0 0 . 6 
at  1 2  amp 33 . 8 0 . 6 48 . 0 0 . 4 
Ho3456 at  10  amp 9 . 67 1 .  5 9 .  5 3 . 0  
at  1 2  amp 9 . 00 1 .  5 1 2 .  6 3 . 0  
Y37 1 0  a t  1 0  amp 1 3 .  4 0 . 8 1 4 . 1 1 .  5 
at 1 2  amp 1 3 .  5 0 . 8 1 7 .  4 0 . 8 
Th40 1 9  at 1 0  amp 4 . 65 5 . 0  4 . 0 6 
at 1 2  amp 3 . 47 5 . 0  3 .  2 ? 5 
Eu41 29 at 1 0  amp 9 . 00 1 .  5 9 .  6 3 
at  1 2  amp 8 . 00 1 . 5 8 . 8 1 .  5 
C e4 1 33 at 1 0  amp 0 . 8 1 1 2 . 5  0 . 84 1 2 . 5  
at  1 2  amp 0 . 52 9 . 0  o . 8o 1 2 . 5  
La4333 at  1 0  amp 1 . 78 6 1 ? 4 9 
at  1 2  amp 1 .  54 6 1 . 7 6 
h Line- to-background ratio  
1 6 . 
No Carrier  
A B - -
4 . 2  5 
6 . 2 5 
2 . 2 9 
2 . 3  6 
2 . 9  5 
3 .  1 5 
1 .  4 9 
1 .  4 6 
1 .  2 9 
1 .  0 9 
0 . 1 25  
0 . 2  25 
0 . 5  1 3 
0 . 2 1 3  
B Limit  o f  d e t e c t ion ppm ( relative  line  intens i ti es greater than 
50 B-value uni ts ) . 
17 .  
atmosphere  and suc cessive  exposures  were  made at fiv&  s e cond  
intervals . The curves  obtained arc shown in  Fig . I-3 . This figure 
shows that palladium was , in all cases , a better  element  than 
zirconium for use  as an internal s tandard as i t  follows the 
V?Jlati lisation  behaviour of the analysi s elemEnts  more clos ely . The 
optimum arcing amperage is 10A with 4% sodium chloride as carr i er , 
b?cause  unc er these condi tions ?ll the e l ements exc ept  zirconium have 
volatili Ged comple tely wi thin t?enty five  seconds wi thout becoming 
too  d i fferentiated . Thi s  reason renders the o ther cond i ti ons less  
sui table .  
( vi )  Final Spec trographi c  Operating Cortdi tione . 
? 
Table  I - 4  gives  the final condi tio?s chosen  as a resul t of 
the abo ?,r e investigations . 
The reproducibili ty o f  the spec trographic  analysis  using 
these  condi tions was determined  in  the following manner .  A s eries  
of  standards containing thorium , y ttritim and ra?e earthe w i th a 
wide concentration were prepared  and arced  under  the abo?e  condi tidns . 
Ten repli cate  arcings wore made at each  concentration l evel . The 
analy": i s  l ine  intensi ty o f each el ement and that o f  the internal 
standard palladium , was m?asured over the ctincentration range and 
the ratio  of the two was determined .  This  ratio  was plot ted  aga1rist 
the  c oeffi c i ent o f  variation  ( percent s tandard deviation )  and is 
shown . in Fig.  I - 4 .  This  curve allows tho c o effi c i ent of  variati on 
to  be  determined  for ?ny e lement at any conc entration and i s  more  
meaningful than the v?luc  obtained  from  a singl e d e t ermination .  The 
usual pr?cedure in such work is  to calculate the coefficient of  
vari ation  from repli cate analys es  o f  an  element a t  an eas ily 
measurable  concentrati on . This nuturally pres ents valu&s bet ter  
-------- -- - ---
18 .  
TABJ?E I - 4 
Spe c trographic  Op erating Condi tions 
S l i t  l ength 
S l i t  width 
Wavelength range 
Pho tographi c plates  
Current 
Excitat ion 
Exposute 
Ele c trodes  
Photographi c Process ing 
Op ti cal sys t em 
Arc  gap 
Gas 
1 2  mm 
0 . 0 1 5 mm 
2800 - 5000 9 ,.. 
I l ford  G-30 
1 0h d . c .  
!?node 
25  s econds 
Johnson-Matthey 4B graphite  
( 1 . 5 mm  internal diameter x 6 mm  de ep ) 
4? min at 20?C in Kodak 1 9B developer  
Ima?e o f  arc focussed  at s l i t  w i th 
F95B convex quartz  l ens 
4 mm 
20% argon/80% oxygen 
= 
..... 
-
.... 
..... 
-
.... 
= 
... 
N 
50 
Fig , I - 3 
4 % NaC I  - 1 0  A 
6 I. NaCI - 10 l 
Y O L A T I L I S A T I O N 
30 
T 1 1  E 
C U R V E S  
S E C S . 
4 %  NaC I  - 1 2  l 
6 1.  hCI  - 12 l 
10 20 
Volatilizat ion curves for rare earths , yttrium , palladium and 
zirconium . 
30 
4 
Fig . I - 4 
Coeff ic ient Of Va r iat ion % 
Analysis  element intensity/Palladium intensity as a function 
of the coefficient of variat ion . 
than can be  ob tained  at lo?er concentrat ion l evels . 
( b )  S tudies  on the I nterference  o f  Thorium , 
Y t trium and Rare Ear th Analysis  Lines 
I .  Development of  an Ion  Exchange S eparation  
1 9 . 
( i )  S eparation  by Use  of  the Ac e t i c/Nitr i c  A c id  
Ani on - Exchange Sys t em 
Solutions were  pr epared  containing macro elements  in  the  
propor?ions fo und i n  grani te  ( G- 1 ) as  given by FLEISCHER ( 1 965 )  
and 1 000 ppm each o f  uranium , thorium , yttrium and the  rare earths . 
The solvent was a mixture of  90% glac ial ac e t i c  acid  ?1d 1 0% 
nitri c ac i d . 
The anion- exchange procedure used  was a modi fication o f  
work reported  by KORKISCH and ARRHENIUS ( 1 964 ) . The m e thod used 
was as follows : 
Res i n :  Dowex 1 x 8 ( 1 00 mesh ) , chloride  form . 
Column Dimension :  1 5cm  x 1 cm.  
Flow Rate : 0 . 5  - 0 . 7  ml/min . 
The column was prepared  in  the normal manner as described by 
VOGEL ( 1 96 1 ) and c onverted  to the ni trate  form by  passing 5 M 
nitr i c  acid  until the eluant no longer gave a pos i t ive  t e s t  t o  
s ilver  ni trate . The column was then equilibrat ed w i th 45 ml of  a 
mixture o f  90% glac ial ac e t i c  acid and 1 0% 5 M ni tri c  acid  which  
had  previously been  degassed on a water  pump . The previously 
prepared mixture of elements , in  the  same solvent , was passed  
through the  c olumn followed by 50  ml  of  the  same  solvent to r emove 
any weakly-adsorbed  &lements . Yttrium , thorium , uranium ?nd the 
20 . 
rare earths remained adsorbed  on the resin .  Uranium was s eparated 
fro? thorium , yttrium and the rare earths by eluting with 35 ml 
of 6 M hydrochlori c aci d .  Thi s  converted the uranium into a 
chloro- complex  whi ch remained  adsorbed  on the c olumn whereas 
yttrium , thorium and the rare earths were  eluted ns they do not 
form strong chloro- complexes . The uranium was then eluted w ith 
25 ml o f  0 . 1 M hydrochlori c aci d .  The s eparation  took approximately 
five  hours , but several columns could be  run s imultaneously . I n  
thi s  cas e a battery of  s i x  was found to be  suitable . 
S everal experiments were  carri ed out to i nvestigate the 
e ffe ct o f  flow rate and element concentratio n ,  especially uranium , 
on  the s eparation  proc edure . It was found that the s eparati on  
effi c i ency was  unaffected by flow rates varying b etween  0 . 2  ml/min 
and 1 ml/min . The factor governing flow  rate was  actually the 
room temperature as the a c etic  a c id  b ecame rather viscous around  
1 8? C .  In  most  cases  the flow  rate was between 0 . 5  ml/min  and 
0 . 7  ml/min .  For the column dimensions  given , it was found  that 
s olutions samples containing up to 2500 ppm uranium were  suc c ess?
fully s eparated . Element recovery exp eriments were  also perfJrmed  
to determine  the effi ci ency o f  the  s eparation . The r esults obtained  
indi c ated that there was  mutual i nter ference  i n  the rare  earth 
emissi on sp ectra ,  becaus e many elements gave apparent concentrations 
much higher than the amounts added woul d  hav e  i ndi cated . 
Although the above s eparati on suc c ess fully conc entrates 
the analysi s  el ements and removes  interference  from macro 
c onstituents , there  still  exists mutual interference  from the 
rare  enrths themselves . Results o f  anion exchange s eparations 
r ep -- ?rted by CARS?vELL ( 1 957 ) and DANON ( 1 958 ) indicated that i t  
2 1 . 
might be  possible  to s eparate  uranium , thorium , yt trium and rare 
earths into several groups , hence reducing interference . The 
following i nves tigation  was c arried  out . 
( i i )  S eparation by Use  of  the N i tric  A c id  Ani on?
Exchange System 
Uranium , thorium , y t trium and rare earths were adsorbed  on 
to the  c olumn , as described i n  the above s e c tion , and w?re , in  
s eparat e  experiments , eluted  w i th 2 M,  4 M and  6 M ni tric  aci d  
r espe c tively ( flow rate 0 . 5 ml/min . ) . Aliquots o f  5 ml w ere  taken 
ov er a volume  o f  1 20 ml . Results  o f  these  s eparations are shown 
i n  Fig . I - 5 .  From this  i t  i s  s een th?t the s eparati on i s  
unsatisfac tory and further att?mpts  a t  s eparat ion  were  di s continue d . 
I t  i s  poss ibl e to s eparate the rare earths using ammonium ci trate  as 
eluting agent ( SPEDDING ET AL , 1 950 ) but the time  i nvolved 
r endered  this approach unsat is fac tory . 
An examinat ion  o f  line sp ec tra o f  the analysis  elements 
was then made in an attemp t to  determine the extent of mutual line 
i nterference  of thorium , yttrium and the rare earths , so that these  
el ements might  be  analysed  together as  a group . The following 
results  are e s s ent iRlly thos e  reported  by COHEN ET AL ( 1 968 ) . 
I I .  Mutual Interference  o f  Yttrium, Thorium and Rare Earth 
J>nalysis  Lines 
In  this  s tudy it  was necessary to  know how the resolut ion o f  
the  large quart z  spec trograph vari ed  with wavelength . Thi s was 
determined  in two  s teps . Firstly , a curve of r ec ipro cal dispersion 
( ?/mm ) agains t wavelength C R ) was cons truc ted  from the NBS card  
index by  m0asuring the  distance  ( mm )  apart o f  any two  lines at  
en 
+"' ?-
s:::: ::J 
>. 
+"' ? -(/) s:::: 
Cl) 
+"' 
c: 
-
>. 
... 
ro 
...... ?-
.c 
... 
<( 
0 
0 
1 ?0 
Yb , y ,  Nd , Eu Gd ' Ho , Dy I 6 M Sm Er ' \ Ce  .... .....  .. ,. --..  ----y--.. ,, ....
.. 
,, 
., ..
.. 
; "', '..., ,' , .... , ..... , 
L U ? -
...
.. 
..., 
,
' 
'\ 
,'' .. , 
,' 
..... , ....... a 
, .. 
' ... .. .. ... 
I ,,, 'I" ",
,
 
..
 ,
 '
 
,'  
" '
' 
I I '  I " ' ,.  ' 
,; 
' 
..
.. 
' , ? ,' 
"'
, '"' ...... 
,., No Th detected 
.. 
? , 
., 
', 
... 
....... ,
"" , ,' '? ' ' ,-, ,... ,"" 
I 
,
 ' ?  ' 
.... ,.. ,.. <?* ' , ? , ',  --.... ? ... ... ,. .... ... , ? "' ... 
........ 
.. ? - - -, 
' ,, .... ... __ - - - -- - -, ' .. .... .- "  ... ... 
., ""' ......... - - .... .... -
, ' - ---? 
,.,"' I '.,.J I _ .. ... -.. .. 
Dy , y ,  Nd 
L Yb Ce Er , Eu , 
.. - ... ... -... 
\ 
, ... :: .. ,..._.... / .,' ...... ... ... .... .. -..... <.. ".< ...... ........ , , 
... .. 
,? , ', , ' ', ' . 
'
,, 
,' 
,
' 
', / .. , .... ......... ., .. I 1 V \ 
, 
?-:.. 
, ,' ,
, 
'
, ': ?"' ' - .... .. ... La 
TJ 
,' , ,' \ 
"
,
...
.. ..... ... 
.. ... _ _ 
. , 
, 
' " ,, ....... 
,
, 
, 
.. 
" 
.  
.. 
.. 
,, , ? 
.. " 'l. - - - - - ---
,s 
,' ,, "l.- -- - - '\ , 
, , .. _ _ _ .... ' , ,' !#? ... .._. .. 
, 
I , ... I I I.L.oo"" 
Ce , Nd , Sm , Eu , Gd 
Dy , Ho , Er , Yb , Y 
\_, ..... ., La 
,',-.....- ,' ,, ?- - .... , I ' ;' ' I' ' 
, ,  ' " .... I 1 I .... . I' ' I , I '? ....... I ,, .... ... u 
I ' "  ' .. ' .. .... I I I ' I '-. \ "' 
I I I )( ..,?  .,. 
' I I , , ', .? .. "' "' ' .. 1. '  ? , , , " Th .. ., ?  , ... ' ..... - .. 
- - ... - - -.*- -- - --
-- - - -
4- ,  , ... ... ... _ 
..
.. 
?11' ,""" ' ..... ,
 
........ ..... .._.. --- - -- - - - - - - - - -::-._....._, 
4 M  
2 M  
I ?? ._.,.., ..... ... Q b  -? I -? .... , t  'a, I I I - .... .. -.,;,- - - - - -1-- ,. 1 
50 
m ls .  
70  90 
Fig . I - 5 Elution curves for analysis elements in nitrate system . 
22 . 
a parti cular wavelength . S e condly , the minimum dis tance betw een 
any two resolvable  l ines on the pho tographic  pl?te  was determined  
arbi trarily by use o f  the Hilger  mi crodens i tome ter , w i th and 
w i thout a chart re corder . This dis tance  was found to be  about  0 . 04mm . 
Us ing this  v?lue , a curve o f  resolution ( A )  as a func tion  of  
wavelength ( ? )  was construct ?d .  I t  i s  impor tant to add that the 
term resolvable , as used  previo?sly , means that it was just poss ible  
to  d istinguish  two  separate peaks and  depends somewhat arbi trarily  
on  the  acui ty of  the observer . Fig . I -6 shows the respe c tive  curves . 
From these  figures i t  was poss ible  to d etermine a po tenti al inter?
ference  band of wavel engths on e i ther s i de of any part i cular 
an3lysis  l ine at  any parti cular wavel ength . From NBS Tables  
( MEGGERS ET AL , 1 961 ) poss ible  int erfering rare earth  element l ines  
may be  found . The extent to whi ch the elements  interfere  can be  
obtained approximately from the formula 
% Interference  = 1 00 x Ai Ii 
Aa Ia 
where Ai , Aa are the  respective  abundances  o f  the interfering 
and analysis  elements  and Ii and Ia are the respective l ine 
intens i ti es . I t  mus t be  emphas ised  th?t i f  intens i ty values from 
the NBS Tables  are used  to compute  this  interferenc e ,  the resul ts  
may be  d i fferent  from thos e  obtained w i th experimental condit ions 
di fferent  from those  us ed  by the authors of these  tabl es . 
To check  the validi ty of  this formula under the  condi t ions 
used , s eparat e  solutions were prepared  from 11Spe cpure"  chemicals  
for yttrium , thorium and each lanthani de . S eparate samples c on?
taining 1 00 ppm of  each element were prepared  and arced under the 
t: 
E 241--
0? 
2 0L c 
0 -
tn 
... 
Cl) 16 
Q. 
tn ? -
c 
-
s l  CO CJ 0 ... 
. Q. ?-
CJ 
Cl) 
a: 4 1- / 
I 0 I 3000 
Fig . I - 6 
l / 
/ 
I I 
4000 
I 
I 
1 ?2 
I 1 ? 0 
l -o <( 0?8 --
l 
c 
. o 
0?6 ; 
-
o.J 
0 
tn 
Cl) 
a: 
0?2 
I . I I 
5000 3000 
Wave lengt h 
0 l 
( A ) 
I I I I 
4000 5000 
Reciprocal Dispersion ( ?/mm) and Resolution ( ? )  as a function of Wavelength (R ) for the 
Hilger E742 quartz-optics spectrograph . 
23 .  
standard conditions . The intens i ty o f  nn  analys is l ine  for  each 
element was  measured  together with the  intensity  of  any potentially 
interfering lines of  o ther  elements . The data showed  th?t for  a 
predi c te d  int erf6rence  of  up to  1 0% , no interferenc e was det e c ted  
in  the  spe c trum o f  any o f  these  elements  at the  wavelength of  the 
s elec ted  analysis  l ines . This was no t the cas e for predi c ted  inter?
ferenc es  greater than 1 0% .  Tabl e I-5  l i sts  the analysis  lines  
used  for yttrium , thorium and  the rar e  earths with the  resp e ctive  
interfering lines o f  o ther rare ear th elements and intensi ty ratios  
for subs equent correc tion . The analysis lines tested  are no t 
always the recommended R. U .  lines  but  in  some cases are lines  o f  
lower wavel ength whi ch ,  although of  lower s ensitivi ty , may s till  
be  used  b e cause  of  the  ion  exchange enri chment and s eparation  
proc edure . This use  of  lower wavelength lines has the  obvious 
advantage of b e t ter resolution since  dispersion  increases  wi th 
decreasing wavelength . The t ?ble does  not l ist  ?ll the possible  
interfeiing lines as  given in  the  NBS Tables but  only  those  whi ch  
give a predic ted  interference  of  more th3n 1 0% from the formula 
( considering the normal abundnnce rntios  of these  element? ) and 
whi ch were  detected  in the spec trum of the pure element . In  all 
c ns es , the highest  likely conc entration  of the interfering element 
was taken in  order to  allow for maximum interfer ence  possible .  
When s igni ficant interferenc es arc obtained , corr e c t ions 
are  made as iri the following example .  As the neodymium line  at  
4040 . 80 ? interferes  w i th c erium 4040 . 76 ? ( this line , although 
interfered  w i th ,  was found to  be the most  sui table  c erium line ) , 
the intensi ty ratio  of  the neodymium l ines at 4040 ? and 4061 ? '  
i n  the absence  o f  cerium , wns measured nnd found to b e  0 . 732 . The 
. 
..:t 
(\) 
T,?.BLE I - 5 
Analyti cal Lines  ?nd Interferenc es 
?nal?t i?al l i?e ? i n* 
Interf .:?rence  
i >  ( lnt en?:ntl. e s )  range A 
( from Fig . I-6 )  
Lu 2 9 1 1 . 39 ( 600 ) + 0 . 1 8  
Yb 3289 . 37 ( 2600 ) ? 0 . 27 
Tb 3324 . 40 ( 400 ) ? 0 . 27 
y 3327 . 89 ( 600 ) ? 0 . 27 
Pd  342 1 . 24 ( 1 400 ) * *  ? 0 . 30 
Gd 3422 . 57 ( 700 ) ? 0 . 30 
Ho 3456 . 00 ( 1 800 )  ? 0 . 31 
Tm 3462 . 20 ( 800 ) ? 0 . 32 
Dy 3531 . 70 ( 2000 ) ? 0 . 33 
Er 3692 . 64 ( 700 ) ? 0 . 38 
La  3995 . 75 ( 360 )  + 0 . 48 
Th 40 1 9 . 1 3 ( 300 ) ? 0 . 50 
Ce  4040 . 76 ( 1 50 ) :t 0 . 50 
Nd 406 1 . 09 ( 280 ) :t 0 . 50 
Pr 4 1 79 . 42 ( 460 )  ? 0 . 55 
?u 4205 . 05 ( 4000 ) .?. 0 . 57 
Sm 4256 . 38 ( 1 40 )  .?. 0 . 59 
* Int ens i t i e s  from NBS Tabl es 
* *  Internal S t ?ndard 
Interfering l ines  
in  ? ( intens i ti0s ) *  
Th 291 1 ? 32 ( 8 )  
None 
None 
None 
None 
None 
None 
None 
None 
None 
None 
Ce  40 1 9 . 04 ( 1 4 )  
N d  4o4o . 8o ( 1 8o ) 
None 
Ce  41 79 . 29 ( 5 )  
None 
Ce  4256 . 1 6 ( 1 2 )  
Intensity  ratios  o f  inter-
fering lines and reference  
lines 
Th 29 1 1/Th40 1 9  = 0 . 027  
None 
None 
None 
None 
None 
None 
None 
None 
None 
None 
Ce  40 1 9/Ce 4o4o = 0 . 237 
Nd  4040/Nd4061 = 0 . 732 
None I 
C e  41 79/Ce40 1 9  = 0 . 07 6  
None 
C e  4256/Cc4o4o = 0 . 092 
2 5 .  
correc ted  c erium intens i ty at  4040. 76  R is  obtained  by  subtrac t ing 
73% o f  the  neodymium intsnsi ty at 406 1 . 09 ? ( interference  fre e )  
from the observed  value for the c erium l ine . 
The correc tion  o f  analysis  lines  for interferenc e should be  
carri ed out  in  the following s equenc e .  C e  4040 i s  corre c ted  for 
Nd 4040 interference , followed by  correct ion of  Th 401 9 for  
Ce  40 1 9 ,  using the  corrected  Ce  4040 intens i ty value to  c al culate  
the corr e c t  value for Ce  40 1 9 .  Having obtained  interferenc e- free  
Ce  4040 and  Th  401 9  intens i t i es , Pr  4 1 79 c ?n b e  c orre c t e d  for  
? n?e>dymium , c erium and thorium interferences . 
Working curves for interferenc e- free elements can be  prepared 
by  dilution of a c ommon mixed s tandar d ,  but o ther  working curves 
mus t be  prepared from indivi dual unmixed s tandards . Fig .  I-7a  
shows the  working curve for  Ce  4040 in  the  presence  o f  various 
conc entrations of  neodymium , with and wi thout corre ction , and the 
curve obtained from a pure c erium s t ?ndnrd .  Working curves for  
o ther  elements  (Fig .  I-7b ) are  also  given . The l ow s catter o f  the  
points  gives  an  indi cation o f  the pre ci sion of  the m e thod .  
( c )  The Use  of  the Combined Anion  Exchange?
Spe c trographi c  Proc edure 
( i )  Dissolution  o f  Rock Samples  
The ease w i th which rocks are  dissolved  dep ends primari ly 
on  the n?ture of  the  rock ( s ili cate , sulphide  e t c . ) ,  the  elements 
present, and the solvent use d .  The solvent required  for the anion 
exchange s eparation , i n  this cas e , governed this  cho i c e  and henc e 
presented  c ertain di ffi cul ties . The  main one was that 90% glacial 
a ce t i c  a c id  and 1 0% 5 M ni tri c ac id  i s  an extremely  poor  solvent . 
1? 00  
0?10  
1 0  
Fig , I - 7a 
C e r i um 
a Ce Nd = 1 1 
b Ce Nd = 3 1 
C P,ure Ce 
cl Corrected A and B curves for 
Nd interference 
1 00 
}J9 
Working curves for cerium ( 4040 ) in the presence of 
various concentrations of neodymium . 
y 3327  
L a  3 995 
1 0  1 00 
).1 9  
Fig . I - 7b Working curves for Y3327 and La3995 . 
26 . 
Also , the el ements thorium and c e rium are generally very insoluble 
even in mineral acids . As a result ,  the following rather t edi ous 
scheme had to be used .  
Concentrated nitric  acid  and concentrated hydrofluoric  acids 
( 1 5 ml o f  each ) were added to 1 g o f  finely- divided rock sample 
( 1 20 mesh ) in  a 250 ml te flon beaker  nnd evaporated  to  dryness over  
a p eri od  o f  2-3 hr . Then 1 5  ml o f  c oncentrated nitri c acid  was 
added  to the residue , whi ch  was next transferred to a 1 50 ml glass 
beaker and slowly evaporated to dryness. To this residue was 
added  1 5  ml of  9 : 1 mixture o f  glaci al aceti c acid  and 5 M ni tr i c  
ac i d ,  and the  whole  was transferred to  a tube and c entrifuged . The 
supernatant  l i quid  was retained and the residue was again  treated 
w i th 1 5  ml of  c onc entrated nitric  Rcid , evaporated to  dryness , taken 
up in 1 5  ml of ace t i c  acid-ni tric acid  mixture and c entr i fuged .  
The solution  was retained and the  residue (usually less than 0.3 g)  
was dri e d ,  weighed , mixed in  a 1 : 3 rat io  w i th sodium p eroxide  and 
fused in  a platinum c rucibl 2  at 480? for s even minut es (RAFTER , 1 950 ? . 
The melt was neutralised w i th nitric  acid  and the solu tion  
centri fuged . Any solid  remaining was dis carded . Suffi c i en t  
glacial ncetic  acid to  give the c orrect ratio  o f  acetic  acid t o  
ni tri c aci d  was added and all three  supernatants w er e  combine d .  
The total vulumc was usually 70-80 ml . The solution was degassed for 
twenty minutes and then tr?nsferred to  the prepared ion- exchange 
column . Complete  digestion  o f  the  nnalysis elements was confirmed  
by  arcing the  supernatants and residue of  a t est sample  after  each 
s tage had been completed .  
27 . 
( i i )  Analysis  of  G- 1 ,  W - 1  and CAAS Syeni te 
To evaluate the complete an?lyti cal pro c edure , experiments  
were  carried  out  to test  the recovery of  elements  from the  ion?
exchange column . Table  I-6  shows the results  ob tained  for some 
representat ive  el ements  c arri ed  through a complete  s ep?ration  and 
analysi s  procedure . Analysi s  o f  the standard rocks G- 1 ,  W- 1 and 
CA?S Syeni t e  for thorium , yttrium and rare earths was carried  out  
by  the developed  proc edure . Tabl e  I -7  compares the resul ts  ob t?ined 
w i th the mos t  recent  r?commended values .  
( i i i )  Evaluation  o f  Data 
The agreement b e tween  the spec trographic  results  obtained  
in  this  work for  G- 1 and W- 1 and tho?e  given by FLEISCHER ( 1 969 ) 
are go od .  The neutron ac t ivation  data o f  HASKIN and GEHL ( 1 963 ) 
als o  correlates  extremely well  and i s  shown in  Fig. I-8 .  
The values obtained  for CAAS Syeni t e  give fresh data for  
nine  rare  earth elements whos e  vcl.ues , as r eported  by  WEBBER ( 1 96 4 )  
were  e i ther doubtful o r  were below t h e  d e te c tion  limi t o f  the 
t e chniques  us e d .  The rec ent  summary of SIN? ET AL ( 1 969 )  includes  
v?lues  obt?ined  by  TENNANT and  FELLOWS ( 1 967 ) , also  using emission  
spectrography . These  values  generally correlate  well w i th this  
work  and are  shown in Fig .  I-9 .  Thi s  figures  shows that there  i s  
disagreement i n  t h e  values for samarium , holmium and lut e c ium . I n  
order to evaluate the c orrectness of  t h e  values  obtained , the  r?re  
earth abundanc e  ratios  for an  average acidi c ro ck , a n  average bas i c  
rock  and C?AS Sye? t e were calculated . These values are given i n  
Table  I-8 . ? ?i s  t able  shows that whenever the results  o f  this  work 
and those  o f  Tennant and Fellows agree , the abundance  ratio  
( normal i s ed t o  La = 1 . 00 )  o f  the  rare earths in the  sye nite  
28 . 
TABLE I - 6 
Recoveries  from I on-Exchange Separ?tions 
El ement J>moun t added (fl.g )  ,'-?mount recovered  ( ?g )  
La 300 280 
Ce  300 309 
Nd 300 309 
Sm 1 00 1 02 
Eu 1 00 98 
Gd 1 00 99  
Dy 1 00 1 02 
Ho 1 00 1 02 
y 1 00 1 00 
. 
0' 
(\j 
TABLE I - 7 
CoQparison  o f  Sp e c trographi c ,  Neutron Activation  and Recommended Values for Thoriua, Yttrium , 
Uranium and the Rare earths i n  G- 1 , W- 1 and ChhS Syenite  ( ppm ) 
Element G- 1 W-1  Crti.S Sy?ni t c  
Code  A B c D l'l c D .a B E 
La 1 1 00 80 100 1 02 1 0  1 2  1 1 . 7 1 8? Zlf5 220 
Ce 2 200 1 60 1 70 1 34 20 23 24 350 625 365 
Pr 3 1 9  1 6  1 7 20 . 9 5 4 3 . 68 1 37 1 40 -
Ncl 4 60 43 55  54 . 6  16  1 7 1 5 . 1 300 305 302 
Sm  5 < 5 c: 1 0  9 8 . 6 ? 5 4 3 . 79 4:. 5 245 -
Eu 6 0 . 9  1 1 .  3 1 . 04 1 . 5 1 ? 1 1 .  09 1 5 8 -
Gd 7 7 <: 1 0  5 4 . 88 4 4 4 . 2  72 58 -
Tb 8 < 2 < 50 0 . 6  0 . 5 < 2 0 . 8  0 . 75 ? 2 4: 50 -
Dy 9 2 < 20 2 . 5 n . d .  2 4 n . d .  1 00 1 35 -
Ho 1 0  0 . 4  < 1 0 . 5 0 . 5 3 1 1 .  35 2 1  2 -
Er 1 1  1 . 4 <. 1 0  2 1 . 4  2 . 5  3 2 . 57 57 42 -
Tm 1 2  < 3 <: 1 0 . 2  0 . 2 < 3 0 . 3  0 . 35 < 3 5 -
Yb 1 3  0 . 6 0 . 8 1 0 . 62 1 . 5 2 . 2  2 . 1 90 57 70 
Lu 1 4  0 . 1 .c 1 0  0 . 2  0 . 1 7 0 . 3  0 . 35 0 . 33 1 . 5 < 1 0  -
y 1 5 1 2  1 2  1 3  1 2 . 5 1 1  25 23 . 8  450 450 450 
Th 30 2 1  52 n . d . 1 2 . 4  n . d .  710  1 300 1 338 
u 2 . 6 < 50 4 n . d .  1 . 5 0 . 5 n . d .  2380 2700 2500 
fl - This  work . 
B - Dire c t  :':lr c ing w i th high dispersion  instrument ( TZNN/?NT and FELLO';?s , 1 967 ) . 
C - Recommended values for G- 1 and W- 1 (FL.SISCHER , 1 969) . 
D - Neutron activ :>. t ion ( }bSKIN and GEHL , 1 963) . 
E - Median values  for  CArlS syenite  ( SINE ET tL , 1 969 ) . 
n . d .  - Not  determined .  
I 
E 
0. 
0. 
c 
0 
.. 
nJ 
> 
.. 
(J 
<C 
c 
0 
""" 
.. 
::I 
Q) 
z 
Fig . I - B 
@ 
@ D G - 1  
0 W - 1 
1 0 
Spect rographic pp m 
Neutron activation data from HASKIN and GEHL as a function of 
spectrographic data from the author for G-1 and W-1 . 
1 00 
1 000 
E 
Q. 
Q. 
... @ 0 
.r:. 0 .... 
::J 
<C 10  
1&-----?--?-L-L????----?--L-?????------L---??????-
1 
Fig , I - 9 
10 1 0 0  
T. & F. p p  m 
Data from the author as a function of spectrographic data from TENNANT and 
FELLOWS for CAAS Syenite . 
1000 
Rare 
Tf,BL.S I - 8 
Rare Earth ?bundance  R3tios  for  G- 1 , W- 1 ?nd 
Cl,, .S Syeni te . C-?.11 Data Normal ised  to 
La = 1 . 00 by w0ight ) . 
Syenite  
Ear th Element f, N . E . C .  T . &F .  
La 1 .  00 1 .  00 1 .  00 
Ce  1 . 58 1 . 84 2 . 46 
Pr  0 . 20 . 0 . 72 0 . 55 
Nd 0 . 62 1 . 57 1 . 1 7  
Pm - - -
Sm 0 . 1 0  0 . 025 0 . 96 
Eu 0 . 0094 0 . 073 0 . 029 
Gd 0 . 057 0 . 33 0 . 1 67 
Tb 0 . 0030 0 . 087 0 . 1 74 
Dy 0 . 0 1 8 0 . 45 0 . 46 
Ho 0 . 0034 0 . 092 0 . 0067 
Er 0 . 0090 0 . 25 0 . 1 4  
Tm 0 . 00 1 6  0 . 01 3  0 . 01 6  
Yb 0 . 0035 0 . 38 0 . 1 83 
Lu o . ooo8 0 .- 0055 0 . 03 1  
30 . 
B 
1 .  00 
2 . 73 
0 . 35 
1 .  47 
-
0 . 36 
0 . 1 0  
0 . 39 
0 . 06 
0 . 30 
0 . 081  
0 . 1 8  
0 . 023 
0 . 1 3  
0 . 02 1  
h - kverage Acidic  Rock pattern . Average o f  G- 1 ( HASKIN and 
Gehl , 1 963 ) and Kirovograd grani te  ( G,: ,VRILOVl? and TUR1-\NSKJ\YJ. , 
1 958 ) . 
B - hverage bas i c  rock pat tern . Average o f  W- 1 ( HASKIN and GEHL , 
1 963 ) , and Kilauea- iki ( SCHMITT ET AL 1 963a ) . 
31 . 
approximate  to that o f  ?n average basi c  ro ck .  A plot o f  abundanc e  
ratio  ag?inst  atomi c  number for the average granite  rock , average  
bas i c  ro ck and sy?? i t e  further confirmed  this . 
To help evaluat e  the relat ive merit  o f  the  value of  these  
d iscordant el ements , as  shown in  Fig .  I- 9 ,  the abundance  ratios  
of  the  rare earths i n  the average bas i c  rock and the results 
obtained for the sy? i t e  i n  this work , together with those  values 
o b tained by  Tennant and Fellows , ?ere plot ted  agains t atomi c 
numb er nnd are shown in  Fig .  I- 1 0 .  From this i t  is  clearly s een 
that the elements s ?m?rium , holmium and lutecium do no t l i e  as 
close  to the curve of the average ba9 i c  rock as do the o ther  rare 
earth e lements .  I f  i t  is  assumed that the rare earth abundanc e  
ratio  pat tern i s  consistent  for all member el ements, then the value  
for  the  discordant  clement closer to the  curve o f  the  average 
bas i c  rock is  the value whi ch is likely to be  more correc t .  I f ,  
as i s  the case  o f  samarium , both  the values l i e  far from the 
average bas i c  rock curve , and are widely different , then i t  i s  
l ikely that b o th are incorrec t .  However , i f  this happens , the  
e s t imated  value can be  ob tai ned and is  in  this case  approximately  
37  ppm . On  this  basis  i t  i s  doc ided  that the author ' s value for 
holmium ( 2 1  ppm ) is more likely to be corre c t  than that o f  
Tennant and Fellows ( 2  ppm ) whereas their  value for ytterbium 
( 57 ppm ) is better  ( 90 ppm ) . I t  is  also possible  that the  author ' s  
value for lutec ium ( 1 . 5 ppm )  i s  too low ; a value of  3 ppm i s  more  
cons istent  wi th the average bas i c  ro ck curve . 
It  is  concluded that the results  in Tabl e I-6  and Table  I-7  
have demonstrated  the feasibili ty o f  using ? large quartz-op t i c s  
( me dium dispersion ) sp 1 ? c trograph for the det ermination  o?  tihorium , 
1 ?00 
0 
.... 
CO 
a: 
CU O?l O  0 
r: 
CO 
"C 
r: 
:::J 
.Q 
< 
0?0 1  
L a  Ce Pr 
Fig , I - 10 
Nd  
I 
I 
I 
I 
I 
I 
'? I 
Pm  S m  E u Gd 
? ? 
-o-; - -o- - . 
Tb  Dy  
w - 1  
T & F 
Author 
' 
' 
' 
Ho  ? E r  
' 
' 
' 
' 
' 
' 
' 
' 
' 
r 
' 
' 
I 
? 
R 
, ,  
I I 
I I 
r ' 
I I 
f 
Tm Yb 
Rare earth distribution for an average basic rock and CAAS Syenite . 
I 
6 
L u  
32 . 
yttrium and the rare earths provided  that an ini t ial separati on 
is  previ ously carried  out . 
33.  
ANALYTICAL METHODS FOR URANIUM 
( a )  Spec trogr?phi c Pro cedure for Macro ?mounts  o f  Uranium 
The uranium spec trum i s  extrem0ly complex , and because no 
l ines  show high trans i t ion probab i l i t i es the emi t ted  radiution i s  
dissipated  nmong wnny l ines . As a result ,  the s ensi tiv i ty i s  low . 
Also , when present  in  high conc entrations , uranium emi ts an intense 
c ontinuous background radiation whi ch  interferes w i th i tsel f  and 
o ther elements . B e cause  of thes e  properties  uranium is a difficult  
element to analys e spec trogr:tphi cally . 
Uranium was analysed under the  same  spec trographic 
condi t ions es t ablished for the analys is  of  thorium , yt trium and 
rare c?rths . However , the limi t of det e c ti on was only 0 . 8% uranium ,  
rendering the technique  sui table  only for the analysi s  o f  minerals . 
Fi g .  I - 1 1 shows the working curve obtained . 
( b ) Solution  Fluorimetry 
Soluti on fluorime try was i nvestigated  ns i t  i s  well known 
that thi s tochnique  is  considerably less s ensi tive  than th8 
extremely-s ens itive  fus ion-bead technique and , as a result ,  m ight 
be  a sui table m e thod to analyse for urcnium in  the intermediate 
c ? l ncentration  range between  that of  fusion-bead analysi s  and 
spec trographic  analysi s .  S ILL and PETERSON ( 1 947 ) reported the 
fluores c ence of uranium in orthophosphori c ac i d  and used this  
property to determine uranium visually . As  this  appeared to be 
a poss ible method for analysing uranium in an i nt ermediate c on?
centration rQnge , the following inves tigation  was carried out .  
A uranium s tandard ( 1 0  ppm ) was prepared in  s olutions o f  
5% , 1 0% , 20% , 50% , , 75% and 1 00% phosphori c a c id  respe c t ively and 
the fluorescence measured wi th a fluorimeter . The results  are 
1 0  
1 0  
% u 
Fig . I : - 1 1  Spectrographic working curve for uranium . 
shown i n  Fig .  I- 1 2 .  
?_p e c i fi c c:. ti ons 
Ins trument : Aminco-Bowm3n Spec tro fluorimetcr  wi th  
variable  exc i tation  and eciss ion  monochromators and 
xen::>n sour c e . 
Exc i tation w?vel ength : 264 m?  
Emission  wavel ength : 5 1 3 mp  
34 . 
From Fig . I-1 2 i t  i s  s e en that 5% or  1 0% phosphoric  ac i d  i s  the  
optfmu? phosphoric a c id  conc entration .  All fur ther analysi s  were  
carried  out us ing 1 0% phosphoric  ac i d .  Preliminary working 
curves  were  prepared and i t  was found that Beer ' s  Law was obeyed 
up to  about  13  ppm  uranium . To increase the appli cable  c onc entration  
range , the  following dilution s cheme was developed . Solutions 
with 5 ?g - 50 pg of  uranium were  diluted  to 5 ml  w i th 1 0% 
phosphoric  ac i d ,  samples  w i th 25  pg - 250 ?g were  diluted  to 25  ml  
and amounts  o f  250 ?g  - 1 000 )lg required  dilution  to 1 00 ml . The 
results  are shown in  Fig .  I - 1 3 .  This  allowed  each analysis  t o  b e  
carr i e d  o u t  in  such  a way thut i f  dilution was necessary , the total 
uranium pres ent , and no t a frac tion of  i t , was diluted .  This con?
s iderably reduced  the absolut e  error in  the analys i s  due to 
dilution . The analysi s  was carr i e d  out  as follows : 
The i on-exchange eluate  c ontaining only urani um was taken 
to dryness , 5 ml of phosphor i c  acid  was added and the solution  was 
examined  under  an ul tra violet  lamp ( 254 m? ) . I f  the fluores c ence  
intens i ty was too  high this  volume was further  dilut ed to  25  ml  and 
again examin?d . I f  the intens i ty was s t i ll too  high after  
diluting to a volume o f  1 00 ml , then  a frac tion  o f  this  was t aken 
and diluted  further .  However , thi s s i tuation was unc ommon . 
en 
.... ? -
s::: 8 0 ::J 
? 
+J 
en 
c 
Q) 
+J 
s::: -
? 
? 
cu 
+J ? -
.c 
? 
<t 
60  
40 
20  
0 
0 
Fig . I - 12 
.? 
\ 
2 0  4 0  60 80  100  
% H3 P04 
Uranium fluorescence intensity as a function of per cent phosphoric acid . 
en so +"' 
c 
::l 
en 
c 
Cl) 
+"' 
c -
>a 
? 
ea 
+"' ? -
.c 
? 
<t I ? ?J 
?" 
1 00  200 300 400 )J QU/ 25 m l  
Fig . I - 13 Solution fluorimetry working curve for uranium . 
35 . 
Repl i cate  analys is  of  samples containing 5 ppm U were  analys ed  and 
gave  a coeffi c i ent of variation o f  ten per  c ent . 
( c ) Fusio_'1-Bead Fluorimetr;y 
Melts obtained  by fusing uranium sal ts w i th sodium 
fluoride fluoresce  a brilliant yellow- green when exposed to ultra-
viol et  l ight ( NICHOLS and SLATTERY , 1 926 ) . However 1 sodium 
fluoride  has a high mel ting point ( 992?C )  and t ends to  s t i ck to 
plati : _um and gold c ontainers making it di ffi cul t to work wi th . 
GRIMhLDI E? AL ( 1 952 ) employed a mixture o f  sodium fluoride , s odium 
carbonate and potass ium carbonate  whi ch has the advantages of  a 
lower  melt ing temperature ( about 700?C ) ,  do es not s t i ck to 
platinum or  gold containers and gives about the same fluoresc ence  
as sodium fluoride . These  authors  also  discuss the  effe c t  of  
fusion  temperature and time  of  h0ating on the  fluoresc ence  
intens i ty .  De tails  o f  the procedure used  i n  the  pres ent work are 
as follows . 
A mixture o f  ANALAR sodium fluoride , sodium carbonate and 
potass ium carbonate in  the ratio  ( by weight ) 9 : 45 . 5 : 45 . 5  was pre-
pared . One hundred and eight  grams o f  this mixture was mixed in  a 
Waring bl ender w i th 1 00 ml o f  water until  a smooth paste  was 
obtained . This was then poured i nto the pellet  mould .  The mould 
2 c ons i s ted  of  a 1 5  cm x 1 cm t eflon s lab ( to  pr event contaminati on ) 
w i th one hundred  holes  ( 1  cm i . d . ) . A glass plate , fas tened  by 
screw clips , was used as a base  and could be  unfastened to remove 
the p ellE: ts . ? 0 The mould was heated  for 2-21 hrs at  1 05 C and the 
p ellets  were  extruded , trans ferred  to  a glass beaker and dri ed  for  
a further two  days . Finally , b e fore  use  they were  graded into  
groups a c cording to  their  weight . Pellets  weighing 1 . 0 ! 0 . 5  g 
--------------
were  used  for  this  work . The i on- exchange eluates  were  tuken t o  
dry?ess  and then redi ssolved  in  2 ml o f  2 M ni tr i c a c i d .  One ml 
of each s?mpl e  ?as trans:?rred  to euch of s ix 1 ml capac i ty 
hc?isphcri cal  gol d mi c ro -- dishes . A further  thr ee  mi cro- dishes  were  
fil led  w i th 1 ml  o f  each o f  thr e e standards co ntaining 1 ?g , 3 ?g 
a :1 < :l 6 1' g o ::'  u:rRni?.:  ".i. . The gold  d ishes  were  plac ed  nn o. verti cal  
s o r tion  of  quartz  tub ing mounted  in  a s tainless  s t eel  holder  whi ch 
??s heat ed  in  an oven  at 1 05? unt il  the contents  of  the  dishes were  
evaporated  to  dryness . On  removal , one  fusi on  pellet was  added  to  
each mi cro-dish  and the  holder was plac ed in  a furnace  at 700?C for  
10  cinutos . After remov?l , the  dishes  were  pl?c ed in  a fluorimeter  
hol?er  and allowed  to  c ool . Analys i s  was carr i e d  out  with  a 
spec ially  des igned fluorimetr i c  at tachment  to  a Techtron  AA3 atomi c  
absorp t i on  sp e c tropho tometer  ( BROOKS and WHITEHEAD , 1 968 ) . As a 
pre caution  against errors in  the  fusion  procedure , as a result  o f  
une?8? o r  variable  heat ing , uranium standards were  always included  
in  e2ch  s e t  of  six analyses . Fig .  I - 1 4  shows the slight di fferen c es 
obta ined  in  the  working curves from d i fferent  runs . The us e ful 
concc?trat i on range is  b e tween 0 . 5  ppm and 6 ppm uranium and 
repli cate  analys es  gav e a c oeffi c i ent of variation  of t en per  c ent . 
1 00 
80  
6 0  
4 0  
20  
0?----?----?------?----?----?------?-----
0 2 4 6 
p pm U 
Fig . I ? 14  Fusion-bead fluorimetry working curves for uranium . 
37 . 
DISCUSS ION 
In the intro duc tion  to  this  analyti cal s e c ti on i t  was clearly 
shown that the use whi ch can be made of r esults from the analysis  of 
geologi c al samples  depends criti cally on the accuracy of the 
determinatians . For this reason cons i derable  e ffort and care was 
exer c i s ed to develop the methods availabl e to the author to the ir  
utmos t  pre o i s i on and s ens i tivity .  The results given in  Table I-7  
for  G- 1 , W- 1 and CAAS Syen i tc indicate  that this  was achieved .  To  
the  author ' s  knowle dge , this  i s  the  first  t ime  a medium-dispersi on 
quartz-op ti cs  spec trograph has been suc c essfully used  to  analyse  
rare  earths at thi s  l evel . I t  i s  important to  note  that although 
the analyti cal proc edure for thorium , yt trium and rar e earths was 
developed spe ci fi c?lly for a quartz-opti cs  spec trograph , use  o f  a 
grating-sp e c trograph in  conjunc tion with this m e thod should y i eld  
even better  r esults . W i th a grat ing-spec trograph , b e tter  
pre c i s i on would be  obtained because  of  greater  dispers ion( re ciprocal 
dispersion  of  the order of  2 . 5? - 5 . 0?/mm ) and the s ensi tivity  
should be  higher due  to  the  corresponding redu c tion  in  background .  
During the development o f  the t e chnique  for analysi s  o f  the 
rare earths , fresh data were obtained for the abundance  of these  
elem?nts , and f or  yt trium and thoriu? in  s tandard rocks G- 1 ,  W- 1 
and CAAS Syeni t e .  The good correlation  o f  the data for G- 1 and 
W- 1  obtained in this work w i th that obtained by Haskin  nnd Gehl 
using neutron activation  analysi s , a te chnique which  i s  now 
generally acc epted  as probably the most  accurate method for trace  
analysi s , i mplies  that emission  spe c trography is  s till  an  extremely 
useful m e thod for rare earth analysi s , provided care is  taken to 
optimisc  the c ondi tions . 
38 . 
The chemical me thods used  for uranium analysi s  in  this 
s e c ticn  enabl ed  a w i de concentration  range to be  covered w i th a 
good degree o f  ac curacy .  Ion- exchange s eparation  of  uranium from 
all o ther  elements  enabled  fluorimetric  analysi s  to be  c arrie d  out  
wi thout the  risk o f  quenching due to  the  presence  of  o ther  i ons . 
Thi s i s  p ?rt i cularly important , for quenching problems i n  fluorime try 
c?n be s evere . The chemi cal me thods are better  than the maj or i ty 
o f  radio chemi cal t e chniques because  they determine the absolute  
amount of  uranium present . The pre c ision  of  radio chemi cal  me thods , 
whi ch  usually involve the measurement of  the activity  of  daughter  
products  rather  than uranium i t s elf , i s  heavily  dependent on the 
degre e  of iso topi c  equilibrium in  the samples  analys ed . 
The s eparation  procedure developed i s  prac t i c al , but suffers 
as a rou tine m e thod because o f  the time  involvGd in  dissolution o f  
the rocks i n  a n  unfavourable  solvent  and becaus e of  the amount o f  
attention  required  during s eparation . The time problem c an b e  
improved by  operating more c clumns s imultaneously bu t  prac t i cal 
considerations limi t this to a maximum of  about  twelve columns . 
However , i n  all t e chniques used for trac e analysi s  o f  rare earths 
there usually exis ts some t edious operation  such as chemical 
s eparation , or  in  the cas e  of  d irect  neutron activation analysi s , 
long " cooling" times . 
I t  i s  concluded that the analyti cal proc edure develop ed  for 
the analysi s  of thorium , yt trium and rare earths compares  favourably 
w i th o ther t e chniques on the bas is  of time  i nvolved and preci sion  
obtained .  
GEOCHEMIC.? INVESTIG?TIONS IN THE 
H. ,VJK.S CR11.G BRECCL,  
39 . 
INTRODUCTION 
The s earch for uranium in New Zealand during and following 
World  War Two was extensive  but did not  at first  yield eny 
discoveri es . In  1 954 GRhNGE issued a guide  to  prospec tors  i n  an 
effort  to  create  interest  in  the s earch for uranium . hs a r e sul t 
of  thi s , two prospe c tors , Jacobscn and Cassin , dis covered  radio?
active  mat erial in  the Middle-Cre tace ous Hawks Crag Bre e c ia of  the 
Bull er Gorge late  in  1 955 . Sinc e thi s  date , there has been a 
surge of  int erest  in  uranium prosp 8 c t ing in New Zealand , partly 
due to a greater  world demand for thi s  element and partly  b e c ause  of  
the  urgent n e c es s i ty to find domest i c  suppli es for  a nucl ear 
reac tor whi ch  is propos ed for New Zealand in the late  1 970 ' s .  
The radioac tive  area is  s i tuated  in  the Lower  Buller  Gorge 
region of the South Isl?nd of  New Zealand  and i s  some fifteen  miles  
eas t  o f  the  township of  W es tpor t .  Thi s  region  has been  i nvest igated  
by various workers who h?ve s tudi 8 d  extensiv ely the geologi cal , 
p e trologi cal and mineralogicel features  o f  the area (BECK ET AL , 
1 958 ; ?HITTLE , 1 960 )  and recently this  whole  region has b e en 
surveyed by airborne gamma-s cintillometry . Exc ep t  for a s tudy on  
th e  sui tab i l i ty of  s tream water analysis  (WODZICKI , 1 959a) , l i ttle  
o r  no geo chemic?l work has been carri ed  out . 
Many m e thods have b e en used  i n  various par ts o f  the world  
for uranium prosp e c ting with  varying degrees o f  suc c ess . The 
uranium content  of  res idual soil  has been  used as an ore  guide  
under many di fferent climati c  condit i ons w i th s ome suc cess  ( JONES 
ET AL , 1 956 ; GANLOFF ET AL ,  1 958 ; ILLESLEY ET AL , 1 958 ) . Analysi s  
of  plants  f or  uranium i n  t h e  Colorado Plate?u , has been on e  o f  the  
mos t suc c es s ful o f  the biogeochemi cal me thods ( CANNON and 
40 . 
KLEINHAMPL , 1 956 ; CANNON , 1 960a ) and h as the advantage that this  
method  can give an indi cation of  buried  ore through thi cknesses  
of  as much as  fi fty feet  of  barren overburden . However , a dis?
advantage of  this method is  that a specialized  knowl edge  o f  the  
uptake behaviour o f  various plan t  spe c i es i s  required  and  an 
ori entati on survey mus t  always be carried  out  b e fore rou t ine 
sampling c an b e  undertaken . Measurement of  the ?rnnium content  o f  
s tream w?ter  has also been shown t o  be  a n  effe c t ive  method o f  
reconnaisance  exploration  ( JUDSON and OSMOND , 1 955 ; DENSON ET AL , 
1 956 ; FIX , 1 956 ) provided that the deposits  are reasonably large 
compared w i th the to tal drainage area . The advantages of sampling 
soils , s tream sediments , plants and s tr eam waters for uranium are 
th?t unexpos ed  ore deposits  c an be  more easily loc?ted  and l arge 
areas can be covered  at a relatively low cos t .  However , one maj or  
diffi cul ty is  that uranium (VI ) is  extremely solublq and  often  in  
areas of  high rainfall , the  uranium c oncentration  can be  very low . 
A cri ti cal  revi ew o f  s c intillometri c ,  geochemical and b iogeochemi cal 
methods for prospe c t ing for uranium has b een  given by WHITEHEAD and 
BROOKS ( 1 969a ) . The same au thors have also carried  out  b iogeo?
chemi cal prospec t ing in  the New Zealand radioac t ive areas ( 1 969b ) . 
In  potentially uraniferous areas o f  New Zealand , the  rugged 
topography and dense bush cover would sugges t  that the analysis  o f  
stream sediments  and stream waters should be  a useful method for 
the d e te c tion of  uranium mineral i zati on since  s treams are o ft en the 
only means of access  to  such areas . Unfortunately due to the high 
rainfall ( 200 inches  p er annum ) , analysis  of  s tream wat ers draining 
the . known uranium mineraliz ation  in  the Lower Buller Gorge  showed 
4 1 . 
that this  approach was unsatisfactory as the conc entration  o f  
uranium found depended cri t i cally  on  t h e  rainfall and t h e  relat ive 
s i ze o f  the mineraliz ed  area in relation to  the total drainage 
area ( WODZICKI , 1 959a ) . This  prevented  dire c t  c orrelation o f  results 
from creeks sampled  under di fferent weather condi tions QS the 
uranium values would often vary by  a fac tor of  three  in  s ?mples  
taken b e fore  and after several hours o f  rain . As  a resul t o f  this 
high rainfall and the high mobility  of the  uranium ( vi ) , it  was 
susp e c t e d  that the dir e c t  analysis  of s t ream sediments m ight  also 
be  unsui table  as a prospec ting gui de for uranium . In  such cases , 
and parti cularly where s tream sediments are the only accessible  
material available for  prosp ec ting purposes , the  rol e  o f  pathfinders 
for  uranium is  parti cularly important . Exc ept for the d iscovery o f  
radi oac t ive boulders in s treams (WODZICKI , 1 959b ) s tream s ediment 
' 
analysi s  as a method o f  prospe c t ing has no t been used  before  in  this 
area . 
Although the use  of  gener?l pathfinders i n  geochemical 
prosp e c ting has received  consi deration  i n  the past (WARREN and 
DELAVAULT ,  1 959 ; H?WKES and WEBB , 1 96 2 ) , very l i ttle  attention  
has b e en paid  to  uranium pathfinders beyond the  use  o f  s elenium 
in  the  urani ferou? areas o f  the Colorado Plateau ( CANNON , 1 960b ) . 
Thi s negl e c t  o f  p athfinders for uranium probably arises partly 
from an undue reliance  on  radiome tri c data whi ch  do not  always 
reliably indi cate the presence  o f  uranium (WHITEHEAD and BROOKS , 
1 969a)  and partly from the fac t  that elemental assoc i at ions wi th  
uranium , vary from area to area and are not  c ons i s t ent . 
The main aims o f  the work reported  in  this s e c tion  were : 
42 . 
( 1 )  To i nvestigat e the  sui tabil i ty of  using the uranium content  
of  s tream s ediments  for  dir e c t  prosp e c t ing for  uranium in  the 
Lower Bull cr  Gorge of New Zealand.  
( 2 )  To es tabl ish any el emental ass o c iations which  exis t in  
uraniu?  m inerals o f  this nrea an d to s tudy the cha?ges o f  these  
asso c iati ons in the weathering s equenc e :  minerals-soils-s tream 
s ediments , to as certain the ir  suitab i l i ty as pathfinders fo? 
ura?ium . 
Preliminary investigations  o f  the uranium minerals for all 
? 
elements , using emiss ion spec trography and atomi c absorp tion 
spec tropho tome try , gave eviden c e  that the elements , copper , l ead , 
zinc  and b eryll ium held  some  association  wi th uranium . Thorium , 
y t trium and the rare  earths could not  be  analys ed  direc tly  due to 
the ir  low conc entration  and poor  d e t e c tion  limi t with the  instruments 
used . The analysi s  of these  el ements  was impor tant  be cause of 
thei r  l ikely geochemical asso c iation  w i th uranium ( GOLDSCHMIDT , 
1 958 ) and their  frequent o c currence  i n  e conomic  deposi ts o f  uranium 
such as i n  the Mary Kathle en Mine in  Que ensland , Aus trali a .  These  
elements were , however , suc cessfully analys ed  w i th the  m e thods 
desc ribed  in  Part I of  thi s thesis . 
There ??s clearly a need  for a more  de tail ed geochemical 
survey o f  this  area and the work reported  in  this s e c t ion  was 
carri ed  out  w i th this  in  vi ew .  
THE GEOLOGICAL AND PHYSICAL FEATURES OF THE 
UR?NIFEROUS AREA 
( a )  _?h:y_s i cal Featur?? 
The area under inves tigation i s  s i tuat ed  in  the Lower Buller  
Gorge  region  o f  the  South Is land of  New  Zealand and i s  some  fi fteen 
miles  eas t of  the to?nship of  W e s tport  ( Fig . I I - 1 ) .  The mos t 
s triking feature of  the climate  in  this  area i s  the heavy rainfal l .  
?hi s  var i es from abo?t  80 inches  per annum near the coast  t o  200 
inches  per annum fi fteen miles  inland , with periods of up to one 
month when l i ttle  or  no rain falls . The climate is temperate ,  
average w inter  and summer temperatures not varying by  mor e than 
1 5?F .  
Below 3 , 500 feet , the area i s  covered  wi th dens e b eech for est  
typ i cal o f  this  part of  New Zealand ( F ig .  I I -2 ) . The s treams are 
short and the i r  profi le? are s t eep . The rel i e f  var i es b e tween  
2 , 000 ft and 4 , 000 ft making the country rugged and d i ffi cult  to  
travers e .  Aerial photographs are shown i n  Fig .  I I-3a and Fig .  I I- 3b .  
A c cess  i s  restr i c t ed  mainly t o  the numerous s treams which  drain 
the are a .  The s teepness  of  the topography precludes the 
accumulation  of  produc ts of  weathering except  at  the foo t of  bluffs 
and in river  valleys . Excluding the Oh ika beds , whi ch are well  
j o int ed , the  ro cks are massive  and weathering extends only a shor t 
dis tanc e below the sur fac e . The soils  in  the more st able parts 
of  the t errain have b een cl?ss i f i ed as moderately-weathered , 
ppdzol ised , yellow-brown earths . Skele tal soils  are found on the 
s teeper  slopes . The pH  ranges b etwe en 4 . 5  and 6 . 5  in  all hori zons 
of  the soils . 
Fig . II  - 1 
L E G E N D .  
H a wk s  C r a q  Br? c c i a  ? 
Ra i lway s 
Sca le  
?r?==31==??======31P 
Map Showing Distribution of Hawks Crag 
Breccia on West Coast of South Island 
of New Zealand . 
Fig . II-2  Photo showing dense beech forest in  H . C . B .  area . 
?ig . II-3a Aerial photograph of Lower Buller Gorge including 
H. C . B. area. 
Fig . I I -3b Aerial photograph of  H . C . B .  area from Fig . I I-3a . 
44 .  
( b )  General GPology 
The?  geology of  the Lower  Buller Gorge has been described  
by MORGAN and BARTRUM ( 1 9 1 5 ) , BELLM?N ( 1 950 ) and BECK ET  AL  ( 1 958 )  
and is  shown in  Fig . I I -4 . Table  I I - 1  gives the  s trati graphi c  
s equence  o f  rocks i n  this area .  A bri ef  outline o f  the ; .o?O[J i s  
given b elow for c omple teness . 
The bas ement ro cks include Paparoa grani te-g?eiss  whi ch  
var i es in  c omposi tion  from gra?i t i c ' to granodi ori ti c ,  Greenland 
Series  s ediment , and quartz-phorphypy ins trus ives . G?e i s s i c  
banding i s  c ommon and in  some lo cali t i es the g?eiss  is  porphyri ti c .  
Greenland S er i es cons i s t  of  well- indurated phyll i ti c  
greyw?ckes of  Pal?ozo i c  age and Ot :ka b eds , o f  Upper Juras s i c  age , 
whi ch  rest  uncomformably on  the basement rocks and cons i s t  o f  
non-marine shales , tuffs , sands t nnes  and con?lomerates . 
The Hawks Crag Bre c c ia  ( M i ddl e to  Upper Cre tac eous ) rests  
unconformably on  the  Ohika beds  and has been divided  into  three  
fac i es dep ending on  the  relative  amo?nts  of  parent material 
present . Thes e  are :  ( 1 )  The Tiroroa faci es c onsis ting of  rounded 
to  sub- ?ounded grani te p ebbles  and boulders whi ch  are set i n  a 
coars e , angular , arkos i c  matrix .  
( 2 )  Dee  Point  faci es consis ting of  angular 
to  sub-angular greywacke fragments  s e t  in  a s ilty  matrix .  
( 3 )  Blackwater  faci es consist ing o f  grani t e  
and greywacke  pebbles and boulders s e t  in  a s i l ty matrix . 
( c )  The Petrology and Mineralogy o f  the Uranium Deposi t? 
A more  detailed  des crip t i on o f  the p etrology and mineralogy 
o f  the  deposi ts i s  given than was for the geological  and phys i cal 
TllBLE II  - 1 
S tratigraphic  Sequence in Lower Buller Gorge 
Tertiary 
Porphyry 
Lamprophyre 
Hawks Crag Breccia 
Ohika 
Quartz porphyry 
Grani te 
Greenland 
Li thology 
Non-marine at base 
UNCONFORMITY 
Soda trachyte  
Cnmptonite , vogesite  
monchiqui te  
,, 
Conglomerate , breccia ,  
s ands tone , siltstone 
UNCONFORHITY 
Shales , conglomerates , 
vitric  ttiffs 
UN CONFORMITY 
Quartz porphyry , granite  
porphyry 
Granite  ? eiss , diori te  
gn eiss , pegmatite , horn?
fels , s chis t 
Greywacke , phyllite , 
s chis t  
Age 
Eoc ene-Pliocene 
Upper  Cretaceou?( ? )  
Upper Cretaceous ( ? )  
Middle  Cretaceous 
Jurassic  
Jurassi c ( ? ) 
Lower Paleozoic  and/ 
or Pre-Cambrian ( ? )  ? 
Lower Paleozoic  or  
Pre-Cambrian ( ? )  
lEGEND-
[?2] TERTIA  U COAL H EAS URE{S :?::::?:-::??:--?: ?-?-?- ??;??:? 
HAWKS CRAG aRE CC I A 
Off POINT ? - - - - _I'"'""'?-? I 
T I ROI\OA lcd A _ _  I.;::'i"AV-_,...1 
OH UtA lt:DS - - - - - - - - - - - - - - - - - - - --'..,,?, .. ..! 
GREENLAND GROUP-- - - - - - - - - - - - - - - - - ??????:!Ill 
ciUN ITE _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  F?c???\'1 
INTRUSIVE ROCKS. 
LAHPROPHYIU: 
T"-ACHYT I C  POR?HYI\Y 
QUAftTZ POI'-PHYRY 
MDIOACTIV E HO"-IIONS ??,-
FAULTS  ?? 
N.Z.  JOURNAL OF GEOLOGY AND GEOPHYSICS 
"'--'ao_ ... o___ <_..o ___ ,ao, ChoiN. 
Scale. 
8 
HCT ION ALONC LINE A-1. 
Natural Scale. 
Fig .  I I -4 Detailed  geological map of  the H . C . B .  area 
( From BECK ET AL , 1 958 ) . 
7bSOOO 
N 
7SOOOO 
A 
46 . 
features as the p e trology and mineralogy is  p ertinent to  both  
this Part and Part III  of  the Thes i s . 
The greater proportion  o f  the uranium mineralization i n  
t h e  Buller  Gorge o c curs in  the bedded  deposi ts in  t h e  Tiroroa 
fac i as on  b o th the North and South s i des  of  the Buller River . 
M ineral i zation  on the North side  i s  primarily coffini te  ( hydroxyl-
subst i tu ted  uranous s i l i cat e )  whereas minerali zation on the South 
s i de i s  mainly uranini t e .  
( i )  The Nor th S ide Deposits : The mineralization  on the 
Nor th s i de is  found in hori zons whi ch  o c cur w i thin  the  arkose  and 
vary in  wi dth from a few inches to s everal feet . The horizons, 
al though disposed  parallel to bedding are lensoid  and di s continuous , 
w i th uranium concentrations varying from less  than 0 . 025% to 6 . 4% 
u3o8 ( BECK ET AL , 1 958 ) . The c ountry rock i s  a medium-grained  
arkos e  whi ch cons i s ts o f  angular quartz , potash feldspar , acid  
plagi oclas e , calci t e , s eri c i t e , blotite , chlorite  and  tourmaline . 
The interstial material or matrix , which  binds the ditr ital grains 
together is  predominantly fine-grained c alc i t e  with sub-ordinate  
chlori t e  and s eri ci te . Thes e  minerals form a country rock whi ch  
is  l ight  grey in colour and granular in  app earance . The rad i o-
ac tive  hori zons are d istingui shed by a dark grey colour which 
deepens w i th increas ing radioactivi ty and the whi te  or p ink 
feldspars , which  are characteri s t i c  o f  the  country rock , c hange 
to a red  colour wi thin the radioact ive  bands . No o ther l i thologic a? 
or  s truc tural feature distinguishes  the ore-bearing rock from 
inac tive  country rock . The contact  b e tween  ore  and country rock 
may be qui t e  sharp and dis tinguished  by sudden colour change , or 
47 . 
i t  may b e  gradati onal and characterised  by darkening of  the 
arkose  over a trans i tional zone of  an inch or so  thi ckness . 
The change from c ountry rock  arkose  to ore  through the  
grad?t ional zone  has  been s tudi ed  by  WHITTLE ( 1 960 ) who then 
observed  that the darkening of  the  arkos e  and the formation  of 
v 
ore  is  due to the progressive emplacement  of  black opaque 
co ffinit e  in the intersti ces b e tween  d e tri tal grains , along 
their  borders  and in  cracks which  intersect  them . Coffini t e  
in  t he  interstial areas , i . e .  w i thin  t h e  matri x ,  replaces  the 
c al c i t e  and p enetrates the micas along their cleavages . The 
introduc ed  co ffini te  forms thin discontinuous shee ts , wrapping 
round the grain boundaries and locally thi ckening or  thining . 
Large-scale  o r  complete  replacement of  the matrix is  rar e .  The 
darker  colour of the more active  bands is simply due to  a greater  
mult ipli c i ty o f  thin coffini te  replacement masses . 
( i i ) The South Bank Deposits : Uranium mineralization  on  
the 3outh  S ide of  the Buller Gorge  i s  concentrated  in two 
hori zons named  T-J and S-C respec tively . The T-J horizon i s  
s i tuat ed  across Centre  Creek about  1 100 f t  above th e  road and the  
S-C  hor i zon  s ?ret ches b e tween  Centre  Creek  and Big  Tick  Creek  
about  800 ft  above the road (Fig .  I I - 1 0 ) . 
T-J Hori zon : A cleared quarry fac e  in  the T-J horizon disclosed  
three  radioactive hori zons some  4 ' 6 " apart . About 1 958 an  adi t  
was driven into  non-folded conglomerate and  arkose  whi ch  dips at  
a flat  angl e into the  hills ide . The ore band which the adi t  
follows varies  i n  thi ckness from '1 "  - 3 1 1  and follows an interface  
b e tween pebbly arkose above and granite boulder conflomerate below . 
The ore  bed  has not a flat con tac t but  is  crenulated  as i t  passes  
48 . 
over and round large granite  boulders whi ch pro j e c t  upwards into  
the  pebbly arkose . The ore  hori zon i s  not  lo cated on a shear pl?ne 
but merely on an interface  between  s l ightly di ffering sedimentary 
fac i es . Thi s  is indicated  by the abs en c e  of rotated  boulders or  
o f  boulders whi ch are s tressed  or  shat tered  in areas where they 
0 
pro j e c t  above  the average plane of  the interfac e .  The arkose  
ad j ac ent  to the  ore  band i s  an  irregularly-grained rock  composed 
of  angular quartz , fekSpars and muscovites , some of  whi ch  i s  
qui t e  coars e-graine d .  Thes e  o c cur in  a matrix  of  finer quar t z , 
feldspar and micas w i th s eri c i t e  and clay .  Cal careous material 
i s  absent , a fac tor  whi ch provides  an immediate  distinction from 
the arkos e  of the Nor th s ide . The contact  w i th the ore band i s  
very sharp and is  due to  the  sudden appearance  o f  uranin i te i n  
the matrix i n  such great quanti ti es a s  to  change the r o ck  colour 
qui t e  black . The uranium content  o f  the ore band in  such 
ins tances  can be as high as 35% U308 over a width of  an inch o r  
more . Fig .  I I-5  shows an autoradiograph and clearly illustrates  
thi s . Uranini t e  replaces  only  the clays and seri c i t i c  material 
whil e  the finer  detri tal quart z  and feldspar of  the matrix are 
pres erved as i nclusions in the uraninite . There  i e  an abundance  
o f  c hal copyri t e  in  the  areas where uraninite  i s  emplaced  and in  
the s il i c eous detri tal material but  t o  a l esser extent . Both 
uraninite  and chalcopyri t e  were  observed to have penetrated mi ca  
cleavages ( WHITTLE , 1 960 ) . 
S-C  Hori zon : This  hori zon is  int erse c t ed in Big  Tick and in  Centre  
Creek and the following describes  samples  taken from these  inter-
s e c t ions ( WHITTLE , 1 960 ) . 
Fig. II-5 
Photograph 
?Autoradiograph 
Photograph and autoradiograph of arkose 
containing uraninite . 
49 . 
The material from Big Tick Creek is  a pebbly arkose  
comparable  w i th that in the vi c ini ty of  the  adi t and it  contains 
grani ti c , s chistose  and phylli t i c  p ebbles  but  no carbonate 
minerals are pres ent . The rock is  very ext ensively  altered  and 
is impregnated  w i th l imonit e  which exis ts w i th arsenopyrite  
remnants  mainly in  the  ?ntrix . Radi oactivi ty is  due to s e condary 
minerals o c curring with  limoni t e  in the matrix and along the 
surfac es  and cracks within boulders . Skeletal r esiduals of 
highly altered  primary mi?ral wi thi n the matrix  probably  supplied  
this  s e c 8ndary material . 
The material from Centre  Creek  is  pebbly arkos e  similar 
to th?t at the adi t .  I t  contains grani t i c , schis?ose  and phylli t i c  
fragments  in  a s trongly mi cac eous arkosic  hos ?  rock . Samples  
were  sele c t ed  from the  eas t ?nd west  s ides  of  the  creek for  
comparison . The rock on the West  s i de is  a dominantly granite  
c onglomerate wi th large , thin pebbles  o f  phyllite  or  s chis t .  
The matrix contains cal c i t e  whi ch i s '  unevenly dis tributed,  b e ing 
abs ent  i n  some areas and ?eavily conc entrated in o thers . Radio?
ac t ivity  is  spread throughout the spe c imen due  to  disp ersed  
s e condary mineral? but  i s  concentrated  principally in the dark?
coloured areas where uranini t e  and its  included suphides  
impregnate  the  matrix . Cal c i t e  and  chlori t e  are pres ent in both  
the w eakly and s trongly radioac tive  areas . 
The material from the S-C  hori zon on the eas t s i de o f  
Centre  Creek is  b y  c ontras t , ? dark grey , almos t  black , 
irregularly-g?aine d ,  mi cac eous arkos a  whi ch  contains abundant 
chlori t e  and s eri c i t e  but no c arbonat e in i t s  matrix . The 
dark colour of this arkos e is due to dis s eminated  organic  mat t er , 
50 . 
abundant chlorite  and general s taining by iron oxide . Some  o f  
the organi c  mat ter  i s  homogeneous and anis trop i c  and appears t o  b e  
extrins i c  hydrocarbon . I t  has a textural relati onship to  the  
hos t  arkose  which  sugges ts it  is  epigene t i c  in  origin . The 
major  radioac tivi ty is conc entrated along the edges of the l ong 
vein- like hydro carbon bodi es al though they themselves are no t 
radioac tive . This  radioac tivi ty is  due to relicts  o f  uraninite  
whi ch o c curs in  the  arkose  matrix  in  j uxtapos i t i on to  the  
carbonaceous masses . Mos t ?f  the uraninite  has vanished  due to 
l eaching , but  areas in  which rel i c ts remain are cl early marked by  
hosts  of  minute  sulphide minerals . The texture of  this  rock 
indi cates  that i t  has been  sub j ected  to  mild  shearing and the  
vein-like  hycro carbons are dispers ed parallel  to the direction  of  
s train .  
The geochemical survey reported  in  thi s part o f  t h e  thesi s  
was confined to  the Tiroroa facies  o n  the Sou th Side o f  the Buller  
River . Thi s  side  was chosen be caus e only a minimum of  prospe c ting 
had b e en done in  this  area .  This lack of  explorat ion was due to  
two  reasons . F irs tly , the deposits  on  the Nor th S ide  w ere  found 
fir s t  and hence  attrac t ed most of the attent ion .  S e condly , the 
later discovery of the South S ide  deposits , whi ch are somewhat more 
extensive  than those of the North Side , coinc ided w i th the fall 
in  the world pri c e  for uranium . The comb ination  of  these  two 
fac tors made the mini ng of this uranium uneconomic and as a r esult  
the  interest  in  uranium prospe c ting fell considerably at  this time . 
As has b e en mentioned  previously , this  trend has been  c omple tely 
revers ed  in rec ent  years wi th the advent of  an era of  int?nsive  
ac t ivi ty in  the  search for  uranium . 
51 . 
!1ETHODS 
( a ) Sampling Procedur8s 
Minerals were ground , dri ed  at 1 1 0?C and were s i eved  to 
1 00-mesh s i ze before  further treatment . Samples  were taken from 
the radioac tive  hori zons T-J and S-C on the South S ide ( uranini t e ,  
torbern i te , l?u tuni te, gummi te ) and from the radioact ive 
hori zons on the North Side  ( C < > ffini te ) .  
Soil  samples w ere  taken from various points on  the 
dr?inage slop es o f  the South Bank horizons and were air drie d ,  
pas s ed through a 40-mesh nylon sieve  anu then igni ted  at  450?C 
to  remove the organic  mat ter . Further grinding to  1 00-mesh 
followed .  
S tream sediments were coll e c t ed from various s treams 
draining ond adjoining the urani ferous areas on the South Bank 
in the following manner . Samples were  taken from s tream deposits  
and were wet-si eveG through a 40-mesh , nylon cloth stretched  
over  the  mouth o f  a plast i c  funnel .  The fraction passing the  
s i eve  was collec ted  in a plast i c  bag and  the fines  were  allowed  
to settle  for approximately two  to three  minutes  before the  water  
was  decant ed o f f .  The posi tion of  the sampling point  and the  
bng marking was noted . The sedim2nts were dri ed  at  1 1 0?C and 
separat ed into three frac tions by the use o f  nylon s ieves . The 
frac tions were : less  than 80 mesh , between 60 and 80 mesh , and 
between 40 and 60 mesh . Preliminary analysis  of  these fractions 
showed that the "less  than 80 mesh" c ontained the highest  
conc entration of  nearly all  el ements investigated (Tabl e II-2 ) .  
Sample  
B 1  
BC4  
T.4BLE I I  - 2 
hnalysi s  o f  S tream Sediments as a Function 
of  Mesh Size  
Mesh  Size  La  Ce  Pr Nd  Gd  Dy  Yb 
Less  than 80 54 1 34 1 5  34  1 3 4 . 8 4 . 1 
B etween 60 and 80 36 67 1 0  1 4  8 . 5  2 . 7  2 . 3  
Between  40 and 60 42 95 1 3  1 6  8 . 5  3 . 8  2 . 4  
Less  than 8o 26 50 1 1  9 7 2 . 3  1 .  0 
Between 60 and 8o 20 44 1 2  1 1  4 . 6  1 .  7 1 .  1 
B etween  40 and 60 2 . 8 40 2 1 2  3 . 2  0 . 4  0 . 5  
52 . 
y Th u 
1 2 . 5  1 1  1 3 . 6  
1 4  1 1  1 0 . 0  
2 1  1 4  9 . 8  
4 . 8  3 . 1 4 . 8  
5 . 6  6 . 0  4 . 8  
1 1 3 . 8  
53 .  
( b )  ?nalyti cal Techniques 
Emi s sion spec trography was used to an?lyse beryllium , 
thorium , uranium , yttrium and rare earths as described  in  Part  I .  
Solution fluorime try and p ellet  fluorimetry were  used  to 
analys e uranium , the parti cular m e thod used depending on the 
uranium conc entration . 
A Techtron Ah3 atomi c absorption  spe ctropho tometer was 
used to analyse copper , zinc  ?nd l ead . The sample  was treated  
w i th a m ixture of  hydrofluori c  and hydrochloric  aci ds and taken  to 
dryness . The residue was redissolved  in  2 M hydro chloric  ac i d ,  
filtered  and stored  i n  plas t i c  bot tles  until  the t ime o f  analys i s .  
( c )  Statis t i cal Analysis  of  Dita 
To be  abl e  to make careful int erpretation of the int er?
element analyti cal results , correlation c alculations were c arried  
out  on a IBM 1 620 ( I I )  computer . 
Correlations between two variables are usually c arr i e d  out  
by the method o f  l inear regress ion , but  MIDDLETON ( 1 963 ) notes  
that this  i s  applied  to determine whether  one  variable  is  
dependent  on the o ther when the  latter  is  not  sub j e c t  to  error . 
However , in  this  work , as in  most  geochomi cal work , neither 
variable  can be said  to be absolut ely known . Therefore , i t is 
b e t ter  to  c alculate  the reduced  maj or  axis , rather than the 
regression  l ines . The advantages of  the reduced  major ? axi s  are 
that : 
1 .  i t  makes  no assumptions  of  independence ; 
2 .  i t  is  invari ent under change o f  s c al e ;  
3 .  i t  i s  s imple  t o  c ompute ; 
4 .  results obtained from i ts us e are intui tively more 
54 . 
reasonable  than corresponding resul ts  obtained from regr ession 
analys is . ( IMBRIE , 1 956 ) . 
For all thes e correlations , the logari thms o f  concentrations 
0 
were  compared , since  the conc entrations often  spanned s everal 
orders of magni tude and appeared  to  be  log-normally dis tributed  
( AHRENS , 1 954 ) . Thus the posi tion  o f  the reduced major  axis on  a 
log-log  bas i s , was calculated  for each pair o f  analyti cal data , and 
the s igni fi cance  of the correlation determined by c al culation  o f  
the correlation coeffic ient  ( r )  and reference  t o  the tables o f  
FISCHER and YATES ( 1 957 ) ? . 
. Cumulative  frequency s tudies  of  some o f  the data were  also 
carried  out . A plot of the cumulative  frequency of the 
concentrations o f  the samples , as a perc entage of the total 
number of  s amples , plotted  on probabili ty paper  agains t the 
concentration value , has been shown to be  useful for geochemi cal 
and biogeochemi cal data interpretation ( TENNANT and WHITE , 1 959 ; 
WILLIAMS , 1 967c ) .  In parti cular , l og-normal dis tributions will  
show  a straight line when plo t ted on log-probability paper , and 
similarly w i th normally- distributed  data on linear-probabil ity 
paper . In o thei cases , curves will  ensue . However , i f  there i s  
more than one  dis tribution s e t  wi thin the data , such a s  could  
o ccur in  mineralized  and unmineralized  soil  samples , a dist inc t 
change o f  slope or  a poin?  of  inflexion in  the graph will  b e  
observed .  This break can b e  consi dered  t o  oc cur a t  the minimum 
concentration of mineralized  samples , al though some overlap o f  
dis tributions will  oc cur (WILLI?MS , 1 967c ) .  I t  mus t b e  remembered  
that the  s ignifi cance o f  interpretation from this analysis is  
55 .  
somewhat limited unless  the  set  contains about 80  to 1 00 samples . 
However , generalised  conclus ions can be  obtained on sets  less  
than 80 . 
ELEMENTAL ASSOCIATIONS WITH UR?NIUM IN  
MINERALS , SOILS AND SEDD1ENTS 
This s ection reports  on the v?rious elemental 
assoc iations w i th ur?nium and discusses  their  
sui tab ility as pathfinders . Thi s  i s  essentially 
the same as was reported  by COHEN ET AL ( 1 969 ) . 
( a )  Copper and Uranium 
56 . 
Analysi s  of  copper and uranium in mineral s , soils  and 
L) 
s tream s ediments , combined w i th a s tatisti cal i nterpretation  o f  
the dat a ,  showed a meaningful correlation between this pair o f  
elements for the whole of  the weathering s equenc e minerals - soils -
s tream s e diments . Correlation  coeffic i ents are shown in  
Table  II-3  and  plot s  o f  the  data  are shown in  Fig .  II-6 . 
Correlation coefficients  decrease  regularly in the 
s equ8nc e  minerals - soils - stream s e diments and indicate that 
ass o ciat i on between this pair of  elements originates i n  the 
minerals and i s  preserved throughout the weathering s equenc e .  
WHITTLE ( 1 960 ) has obs erved  that chalcopyri te  i s  assoc iated  w i th 
tiranium in  the South Bank depos its  o f  the Lower Buller Gorge and 
thi s is  probably the source  of the c opper det e c ted . Further 
m obilisation  and transport  of  both elements i s  fac ili tated  by the 
porous nature of  the arkosic  matrix whi ch allows oxidation  and 
movement to  take place . 
The pres ervation  o f  the ini t i al copper-uranium 
relati onship throughout the whol e  weathering s equence  is a 
fortunate  o c currence  whi ch renders c opper a useful pathfinder i n  
minerals , soils  and s ediments . 
Cumulative frequency plots  for  c opper i n  soils  and 
. 
['-. 
li\ 
TABLE I I  - 3 
S tat i s t i cal Data for  Vari ous  Elements i n  Minerals , Soils  and S tream Sediments 
Firs t C orrelati ng S e c ond Correlating  Minerals  Soils  Sediments 
Variable  Variable  
Log  concn . o f  U L o g  c oncn . 
Log  concn . o f  U Log  concn . 
Log  o oncn . o f  U L o g  concn . 
Log  c oncn . o f  U Log  concn .  
Log  c oncn . o f  Cu Log concn .  
Log  c oncn . o f  Cu Log concn . 
r = c orrelation  c o e f f i ci ent  
Si g .  = l evel  of  s igni fi cance  
of  Be  
of  Cu  
of  Pb 
of Zn 
of Pb 
o f  Zn 
r 
0 . 88 
0 . 79 
0 . 95 
0 . 02 
0 . 78 
0 . 04 
S i  g .  r Sig.  r - -
S * *  0 . 68 s ? ? o . o? 
S * *  0 . 66 s ? ? 0 , 42 
S * *  o . 8o s? ? -0 . 25 
NS 0 . 34 PS 0. 1 2  
S * *  0 . 74 s ? ? -0 , 1 4  
NS 0 . 32 PS 0. 20 
N . B .  Levels  o f  s ignif i can c e  ( BROOKS ET AL , 1 96 6 )  shown above  are as follows : 
S * *  = s i gnifi can t  at  0 . 1 % l evel  o f  probab i l i ty ( very highly significant)  
S*  = s igni fi c an? a t  0 . 1 - 1%  level  of  probab i l i ty ( h ighly signi ficant )  
S = s ignifi cant at  1 -5% l evel  of  probabil i ty ( si gnifi cant ) 
PS = s igni fi can t  a t  5- 1 0% level  o f  probabil i ty ( possibly signifi cant ) 
NS = no t s ign i fi can t  
Sig . 
NS 
PS 
NS 
NS 
NS 
NS 
P.eM. u 
100,000 
10poo 
1/) _, 
< 
a: 
w 
z 
? 
1000 
P.P.M. U 
c:! 100 
0 
1/) 
10 
P.I?M. U 
u - cu 
? 
20 
10 
1/) 
1-
z 
w 
? 
0 
w 
1/) 
. ? 
20 
ttM. Cu 
Fig . II - 6 
U - Pb ? 
? ? 
? 
? 
10 100 
? 
? ? 
? . 
? 
? 
? ? 
? ? 
10 
Pl'M. Pb 
? 
? 
? 
? 
? 
? 
? 
? 
? 
? 
? 
? 
? 
? 
? 
? ? ? ? 
? 
? 
P.P.M. Be 
Elemental Relat ionships in Minerals , Soils and Stream Sediments . 
? 
? 
10 
10 
--------- - --
58 .  
s ediments ( Fi g .  II-7 ) show that anomalous amounts  c orrespond t o  
greater  than 60 ppm i n  soils  and greater than 40 ppm in  sediments . 
Such  values may repres ent indire c tly the presence  o f  uranium 
mineralization .  
( b )  Beryllium and Uranium 
Statisti cal analysis  of beryllium and uranium data showed 
a meaningful correlation b e tween this pair of elements in  the 
minerals , and soils but  not in the s tream s ediments . Correlation 
c o e ffic i ents  are given in  Table  II-3  and plots  of  the data are 
shown in Fig.  I I- 6 .  Cumulative  frequency plots for the soils  
are  shown i n  Fig .  II-7 , from whi ch it  i s  s een that b eryllium 
(j 
values above 4 ppm ( normal background distribution  for grani t i c  
rocks ) i ndi cate  abnormal values  and would sugges t th e  presence  
o f  uranium . 
( c )  Lead and Uranium 
The association  o f  l ead wi th uranium in  the minerals i s  
extremely c lose  ( Table  I I -3  and Fig .  II-6 ) . The correlation is  
so  good  ( r  = 0 . 95 )  that the  author believes that mos t  o f  the  lead 
is  radiogeni c in  nature . 
In the  soils , two dis tinc t distributi ;ns are evident  
(Fi g .  I I-7 ) and a value  o f  70 ppm appears t o  indi cate  the  threshold 
value for  anomalous l ead . The correlation b e tween uranium and 
this  element  in soils  is  still  good ( r  = 0 . 80 )  but not as good  
as in  the minerals whereas in  the  s tream sediments no c o rrelati on 
b e tween these  elements exis ts at all . 
( d )  Zinc  and Uranium 
-
No s igni fi cant correlati on was obs erved  for this pair of  . 
P.P.I. 
A 
B 
Fig . II  - 7 
2 5 1 0  20 30 .40 50 60 70 80 
150 PPm 
C U M U L A T I VE 
P.P.I 
c. 
c 
D 
E 
F R EQ U E N C Y  
? 
? .40 ppm 
2 5 10 20 ? .40 50 tll 70 80 98 99 . 99?8 
Cumulative Frequency Plots for Various Elements in Soils and Stream Sediments . 
A - Uranium in soils 
B - Lead in soils 
C - Beryllium in soils 
D - ? Copper in soils 
E - Copper in sediments 
59 . 
e l ements  in  minerals or s ediments  ( Table  I I -3 )  but there  was a 
poss ibly- signifi cant  relationship in  soils  ( r  = 0 . 34 ) . A z inc-
uranium relationship in  soils  has  also  been obs erved by WHITEHEAD 
and BROOKS ( 1 969b ) . How ever , the author cons i ders zinc  as an 
unsui table  pathfinder for uranium since  the value of r is s o  low . 
( e )  R?re Earth Elements 
The analysis  of minerals  for  y t trium , thorium and the 
rare earth el ements was carried  ou t using the analyt i cal proc edure 
described  in  Part I of  this  thes i s . The r esults  ore shown in 
Table  I I- 4 .  Thi s  table  shows that although the l evels of  these 
elements  are slightly  higher in  the mineralized  fraction  c ompared 
0 
wi th the  unmineralized  frac ti on , they are s t ill  extremely low . 
However , desp i t e  their  low conc entration , the normal 
Oddo-Harkins dis tribution  exis ts , ( Fig  II-?, that i s , the even-
) 
numbered  rare earths have a h i gher  conc entration  than the  uneven 
numbers and thus show that no frac t ionation has o c curred  wi thin 
the group . S tatisti cal analysis  o f  the data was  not at tempted  
as  i n  most  c ases  the conc entration of  the  el ements was almos t  a t  
the  d e te c tion  limi t .  
Visual inspection o f  the  results  show that there are no 
meaningful correlations b e tween  any of the el ements and uranium 
and thus yt trium , thorium and the rare earths are unsui table  as 
pathfinders . 
Ho?ever , the low valuas  obtained  are s igni ficant  in  them-
selves  as they sugges t  that e i ther  the original uranium was not  
asso c iated  w i th rare earths or  that the  uranium has b e en mob i l i s ed 
and because  of  the greater  solub i l i ty o f  uranium ( VI ) c ompare d  
. 
:!: 
a: 
0.: 
M inera ls  
M inera l i zed  Frac t ion  
,JJ., 
lit 'JJ. Unm inera l i zed  Fraction 
Stream Sed i ments 
1 
? Var iat ion a ro u nd mean  
1 
La Ce Pr Nd Pm Sm Eu  Gd Tb Dy Ho E r  Tm Yb Lu  
Fig . I I  - 8 Rare Earth Distribution in Uranium Minerals and in Stream 
Sediments Draining Hawks Crag Breccia Areas . 
? 
0 
\.0 
TABLE II  - 4 
Rare Earth Con?entrations i n  Minerals t Matrix and Stream Sediments (ppm ) 
Sample  La Ce  Pr  Nd Sm Gd Dy Yb y Th u - --
MINERilLS 
Uranini t e  1 1 0  1 8  n . f .  n .  f .  n . f . 7 1 . 5 1 .  4 8 . 5 4 1 62 , 000 
Matrix 1 6 8 n .  f .  n .  f .  n . f . 2 0 . 9 0 . 5 1 . 0 n . f .  1 0 , 000 
Uro.nini te  2 7 19 n . f .  n .  f .  n . f . 8 . 5 0 . 6  3 . 0  1 4 . 0  n. f .  1 20 , 000 
fhtrix 2 7 8 n . f .  n . f .  n . f .  6 . 5 1 ? 1 0 . 8  3 . 4 n .? f .  1 0 , 000 
Uranini t e  3 n . f .  n .  f" ? n . f . n .  f .  n . f . 9 . 5 4 . 4  4 . 4  9 . 5 n .. f .  1 10 , 000 
Mntrix .3 n . f .  n .  t?. n . f . n .  f .  n .  f .  n .  f .  0 . 9 0 . 9 1 . 9 n . f .  248 
Matrix 4 1 9 n . f .  n .  f .  n . f . n . f .  n .  f .  n .  f .  0 . 8 n . f . n. f.  843 
Torb e?itic ) 3 1  42 n.  f .  30 n .  f .  6 . 5 n .  f .  1 .  8 4 . 8 n .. f .  750 
Mntr?x 5 
i\utuniti c ) Matrix 6 4 n . f .  n .  f .  n . f .  n .  f .  5 . 9  1 .  7 1 .  7 6 . 5 n. f .  8 
Gummite  n . f .  n .  f .  n . f .  n . f .  n . f .  n. f.  n . f .  n .  f .  n . f . n . f .  250 , 000 
STREAN SEDINENTS 
01  28  50 1 4  1 7 n .  f .  n . f .  1 . 6 1 .  0 2 . 5  4 . 6  3 . 4  
02 47 95 1 8  40 n . f . n .  f .  4 . 8  1 . 6  1 2  1 8  8 .6 
03 28 54 1 2 1 1  1 0 3- 7 2 . 2 0. 6 3 . 4 5 . 6  2 . 4  
04 1 6  26  5 1 0  n . f . n . f . 0 . 6 0 . 1 1 . 9  3 . 4  2 . 0 
05 30 40 1 3  1 6  8 3 . 6  2 . 7  1 . 0  6 . 0  7 . 0  1 .  2 
1 4  4 . 0  
' 
4 . 5  07 1 5 25 1 0  n .  f .  11. f ? 0 . 7 0 . 5 1 . 5  
08 30 38 1 1 . 0 1 6 . 0 9 . 0  4 .0 2 . 4  0 . 9  6 . 0  6 . 0  3 . 4  
B 1 3  23 46 1 2  1 1  n . f .  5 . 0  2 . 5 2 . 0  8 . 0  5 . 4  8 . 6  
B 1 4  20 30 10 7 n . f .  3 . 6  0 . 8 1 .  2 2 . 6  6 . 4 0. 8 
B 1 5  26  45 9 1 1  n . f .  5 . 6  1 . 3 0 . 7  5 6 . 4 2 . 9  
B 1 6  54 1 34 1 5  34 n . f .  1 3  4 . 8 4 . 1 1 2 . 5  1 1 . 0  13 . 6  
B 1 7  27 57 1 2 1 9 4 1 2 . 0  0 . 9  6 . 5  4 . 8 1 . 4  
B1 8 42 60 1 8  30 n .  f .  8 . 5 2 . 4  1 .  3 1 6  9 1 . 7 
'I""" 
\() 
TABLE I I  - 4 continued 
S ampl e  Ln  Ce  
STREAM SEDIM?NTS cont . 
BR1  29  
BR2 46 
BR3 45 
BC 1  25  
BC2 2 6  
BC3 30 
BC4 26 
BC5 28 
n . f .  not  found . 
90 
70 
6 1  
46 
52 
60 
50 
74  
Pr  
1 0  
1 4  
1 0  
1 0  
1 2  
1 4  
1 1 
1 5  
Nd  Sm  
n . f .  n . f .  
30 1 0  
36 1 2  
1 3  n .  f .  
1 5  n . f .  
22  n .  f .  
9 4 
1 5  6 
Gd Dy Yb y Th 
3 . 4  n . f .  1 .  5 4 . 8 1 7  
1 1 . 5 2 . 5  0 . 8  9 . 0  1 6  
1 0  3 . 6 1 . 5 1 3 . 0 1 1  
1 2  1 .  5 0 . 7  4 6 . 0  
7 1 . 8 0 . 7 4 . 4  5 . 6  
9 2 . 6  1 . 1 6 . 0  6 . 5  
7 2 . 3  1 .  0 4 . 8  3 . 1  
6 2 . 3  o . B  4 . 4  5 . 0  
01  represents  sample  1 from  the  Ohika- i t i  River as  shown in Fig . II-9 . 
B1 3  represents  sample  1 3  from Tiroroa  Creek as shown i n  Fig . I I-9 .  
BR represents  Big River  area ( Fi g .  I I - 1 ) .  
BC repr esents  Bullock Creek area (F ig .  I I- 1 ) . 
Uranini t e  1 ,  2 and 3 represent  thr e e  di fferent  mineral sampl?s  and 
Matrix  1 ,  2 and 3 represent  the assoc iated matrix fraction ( Fi g .  II-5 ) . 
u 
8 . 8  
0 . 8 
0 . 4 ! 
6 . 8 
4 . 0  i 
3 . 8 
4 . 8  
4 . 0  
6 2 .  
w i th rare earths , frac tionation  has taken plac e .  This lat t er 
reason is  beli eved to  be  more l ikely as mineralogical s tudies  by  
WHITTLE ( 1 960)  have also  shown evidence  for  the  epigenet i c  nature 
of uranium . 
During the current investigation , TENNANT and SEWELL ( 1 967 ) 
published  the results of  a survey of  the rare earth contents  in  
s tream s ediments o f  the  adj acent  O tu tu tu River and Ohika-Nui 
River  no t including the Hawks Crag Bre c c ia drainage are a .  These  
results  showed that the  Otutu tu area was rich  in  " c erium- earths" 
whereas t he Ohika-Nui River  area was r i ch in  "yttrium- earths " .  
The conc entration range o f  the elements  Lanthanum , C erium , 
Neodymium , Yttrium and Thorium varied  from s everal tens to  
several hundred ppm . This variati'on  was generally unpredi c table 
as element  concentrations from samples  taken wi thin s ev eral 
hundred  yards of  each other could  vary by an order o f  magni tud e .  
Overall , however , the rare ear th pat t ern for each area was qui te  
dis tinc t ive . 
The Hawks Crag Bre c c ia is found on  b o th sides  o f  the 
Ohika-Nui River  and O tututu River ( Fig . I I- 1 ) and al though it is 
generally believed  that it has no t travelled  very far , due t o  the 
pres enc e of  angular parent rock , i ts origin is  s till  far from 
clear . P etrologi cal c omparisons of the grani tes  in  the Brecci a  
wi th those in  neighbouring areas s e ems t o  sugges t that the Brec cia  
could  p ossibly be  derived  from the  O tututu grani t e  ( NhTHAN , pers . 
cornm . ) .  I t  was hoped that analyses  o f  s tream s edirnents from the  
Hawks Cra.g Brec c ia  would r e fl e c t  characteris t i c  rare ear th 
pat t erns whi ch  when c ompared w i th tho s e  obtained by  TENNANT and 
SEWELL might  show whether the Breccia  c ould have b e en derived  from 
e i ther  the Ohik?-Nui granite  o r  the Otututu granite  or  possibly 
both . The results obtained  ?re shown in  Table  II-4  and are 
discussed  later . 
---?----------------------
64 . 
ELEMENTAL Ri,TIOS i\.S P .. THFINDEHS FOR UR'"'NIUM 
From Fig . I I -7 i t  appears that an anomalous uranium 
dis tribution  may b e  detected  by the pres ence  of  > 70 ppm lead , 
"> 4 ppm beryllium and > 60 ppm copper i n  the soils  and >40 ppm 
cop?er  in  the s tream sediments . Although the analysis  of s tream 
s ediments for copper as a pathfinder for uranium appears to be  a 
likely m e thod , the possib i l i ty of  s ingle anomalous copper values  
due  to  o ther fac tors  i s  s ti ll a danger to the  reliabil i ty of  the  
metho d .  For this  reason vari ous ratios  and combination  o f  ratios  
o f  all the associ ated  elements were  investigated  in an  attempt to 
es tablish  a more reliable  crit erion for the detection of anomalous 
areas . The use  of ratios or c ombination of ratios tends to l e ssen 
I 
the importanc e of  any spurious , anomalous resul t .  
Figure I I -9  shows a triangular plot  for  uranium , l ead and 
copper concentrat ions in whi ch each const i tuent is  expressed as a 
perc entage  o f  the ?urn of  the three .  The data are there fore not  
based  on  the absolute  perc entage of  each  element in  tho enti re 
mineral , s o il  or  s tream-s ediment sample .  
1l  decreas e in  the uranium content  i ndi cates the progress ion  
o f  weathering through the  s equence  minerals- soils-s tream 
sed iments . I t  i s  s een  that in  the s ediments , the uranium content  
de creases  t o  very low values and  the  importance  of  the  l ead- copper  
relationship becomes much great er . Visual insp ec tion  of  the data 
for the s tream s ediments in  Fig .  II- 9 ,  shows that there  is  a 
t endency for  c ertain  samples  to  b e  grouped  toge ther  in  the 
copper-r i ch corner  of the graph . Thi s  implies  higher copper/lead 
rati os , part i cularly for s ediments 1 0 ,  1 3 ,  1 5 ,  1 6  and 1 7 ,  the 
sampling positions of whi ch arc shown i n  Fig .  I I- 1 0 ? 
1 3  
100% Cu 
Fig . II - 9 
100% u 
... 
... 16 
... 
M INERALS 
H IGHLY-M INERAL ISED  SO I LS 
UNMIN.  SEDTS . 
8 ? 
3 5 7 12 
.,. - So i ls 
1 , 2, 3,- ? ? -Sediments 
11 
100%Pb 
Triangular Plot for Concentrat ion Ratios of Copper , Lead and Uranium in  
M inerals , Soils and Stream Sediments , 
11 
' 
I 
I 
Fig .  I I  - 10 
N 
r 
A A A RAD IOACTIVE AR EAS 
? SOIL  SAMPLING AREAS 
0 NEW RADIOACTIVE AREA 
SCAL E : 1 inch : 700yds 
ltap of Buller Gorge Area of New Zealand showing Radioactive Horizons and Sampling Points for 
Soils , and Stream Sediments ? 
-------------- ---- --- --------? 
The copper/l ead ratios  are shown also in  Table  II-5 whi ch  
includes the uranium c ontent and  indicates whether the  s tream from 
whi ch  the sample  was taken (Fig . I I- 1 0 )  was known to drain a uranium 
anomaly .  hs far as  was  known at  the time , Tiroroa Creek ( sampl e  
1 0 )  was not known to  drain a radioac tive  area .  
As i t  s eemed  that  higher  copper/lead ratios  in  s tream 
s ediments might  in?i cate  uranium anomali es in  the drainage area o f . 
the s tream , further sampling was carried  out  in  Tiroroa Creek.  
These  samples  gave further evidence  of  uranium mineral i zation  in  
this  area  wi th absolute  uranium values  ranging from  1 8- 62 ppm  and 
w i th associated  hi gh copper/lead ratios . 
No . 
1 
2 
3 
4 
5 
6 
7 
8 
9 
1 0  
1 1  
1 2  
1 3  
1 4  
1 5  
1 6  
1 7 
1 8  
TJ:..BLE II  - 5 
Elemental Ratios as Pathfinders for 
Uranium in  Stream Sediments 
Name o f  Stream Cu/Pb ratio  u concn .  
( ppm )  
Trib . Ohika- i ti R .  0 . 42 3 . 4  
Main Stream - 0 . 58 8 . 6  Ohika- i t i  R .  
Trib . Ohik3.-i t i  R .  0 . 44 2 . 4 
Trib . Ohika- iti  R .  0 . 42 2 . 0  
Trib . Ohika- i ti R .  0 . 44 1 .  2 
Tri b . Ohika- iti  R .  0 . 73 4 . 3  
Trib . Ohikn- i t i  R .  0 . 36 4 . 5  
Trib . Ohika-i ti R .  0 . 44 3 . 4  
Trib . Ohika- iti  R .  0 . 70 1 .  6 
Trib . Ohika- i ti R .  0 . 80* 0 . 8 
Trib . Ohika- iti  R .  0 . 1 8  3 . 4 
Trib . Ohika-iti  R .  0 . 25 1 .  5 
Tiroroa Creek 7 . 69*  8 . 6  
Batty Creek 0 . 67 0 . 8  
Big  Tick Creek 0 . 83*  2 . 9  
Centre Creek 2 . 27 * 1 3 . 6  
Hawks Crag Creek 0 . 83*  1 .  4 
Blackwater R .  0 . 70 1 . 7 
66 . 
Vvhether mineral-
i zation  previously 
known 
No 
No 
No 
No 
No 
No 
No 
No 
No 
Yes 
No 
No 
No * *  
Doubtful 
Yes 
Yes  
Yes  
No  
* Ratio  indi cating presenc e o f  minerali zation in drainage area.  
* *  Evidence  o f  mineral i zation found at later  date . 
67 
DISCUSSION 
Geochemi cal prospec ting i s  conc erned  w i th the detec t i on o f ? 
anomalous amounts of  any element as a guide  to the d etection o f  
i ts ore . Thi s  problem may essentially be  appro?ched in  two ways i 
Samples  collected  from a grid survey may be  analys ed  e i ther 
directly for the element conc erned or for its  assoc iated  elements ? 
The cho i c e  o f  e i thGr o f  these  two appro?ches depends on  the answers 
to  the following ques tions . Firs tly , is  the me tal being  sought 
capable  of b eing transported  far enough from its source  and in 
suffi c i ent quanti ties , to j us t i fy direct  geochemi cal s earch? 
S e condly , will  normal variations in the background of the  area 
render  any geochemi cal method  unreliable . In view o f  these  
questions , pathfinder elements. may b e  defined  as  elements  whi ch , 
b e cause o f  s ome  parti cular property or properties , provide  
anomali e s  or halos  more  r eadily  usuable  than the sought-after  
element with whi ch they  are assoc iated . 
Uranium i s  well known for i t s  solubil i ty and extreme 
mobility and as d iscussed previously , i s  a di ffi cul t element to 
prosp e c t  for dire c tly in areas ' o f  rugged topography and high 
rainfall . Hence  the impor tant role o f  p?thfinders i n  this  
ins tance .  However , i t  i s  interesting to  note  that Table  I I-4  
shows a uranium value whi ch i s  dis t inctly higher i n  a sample from 
a known mineraliz ed  stream ( B 1 6 ,  C entre Creek ) and thre e  other  
high values ( Big  River 1 ,  Tiroroa Creek LB127 and Ohika- i ti 
River L027) . I t  was found that BR 1 was taken thirty yards down?
s tream from an i solated  uranium anomaly ( FOSTER , p ers . comm . ) and 
more detailed  investi gation  in  Tiroroa Creek indicated  a general 
radiation l evel two or three  tim2s  background . The sample  from 
the Ohika- i t i  River was taken in  the main stream and the high value 
68 .  
obtained is  thought to be  due to  an unrepresentative  fraction .  
?11 these  anomalies  detected  by  the  d ir e c t  ?nalysis  of  
uranium have two features in common . These  are : 
,1 ) the  sample  taken was very  close  ( wi thin fi fty yards ) 
of  the uranium anomaly , and 
2 )  the uranium anomaly was a cons iderable  part o f  the 
drainage area  and regis tered  at leas t  three  t imes above background 
on  a s c intillometer . 
Although dir e c t  analysi s  of  uranium in  s tream-sediments 
regist ered some  succ ess , this  survey  has shown that generally ?n 
an area of  rugged topography and high rainfall this approach is 
unsui table .  
S tat i s t i cal evaluation o f  the elements  associated  wi th  
uranium throughout  the weathering s equence  minerals , soils , 
s tream-s e diments , show ed that only copper  was suitable  as a path?
finder in the s tream-sediments whereas l ead , b eryllium and copper 
were suitable  pathfinders i n  minerals and soils . To unders tand 
these  results  i t  i s  necessary to CJns ider the different  
w eathering pro cesses  involved and  to evaluate  their relative  
s i gni ficanc e .  
Three main types  o f  weathering may b e  distinguished : 
physi cal , chemi cal and biologi cal . Phys i c al proc esses  include  
those  that c ause  rock disintegrati on wi thout appreciRble  chemi c al 
or  min?ralogi cal changes .  As the rock disintegrates , the  sur face 
area b e comes larger and this  facili tates  chemi cal w eathering due 
to reac tions w i th water , o xygen and carbon dioxid e .  Biologi cal 
ac tivi ty c an contribute  e i ther  direc tly or  indirec tly to  both 
phys i cal and chemi cal weathering . G0nerally , thes e pro c es s e s  t ake 
place  s i de by  side  and their  relative  importance  vari es 
according to the environment .  
I n  the Buller  Gorge region , although the to pography i s  
rugged and the annual rainfall i s  high ,  both condi ti ons being 
sui table  for physi cal weathering , the area is  dens ely covered  
with  vegetation whose  natural rain  shield  and  large root  ne twork 
successfully prevents erosion . Thi s  dens e vegetation cover  may 
also play an important role  in the b iological weathering process  
as  uptake o f  elements such  as  copper , zinc  and uranium by  the 
flora has been shown to be qui t e  s ignifi cant (WHITEHEAD and BROOKS f 
1 969b ) . 
Although b iologi cal effects  can make an appreciable  
contribution  to the overall weathering pro cess , as  does physi cal 
weathering , the author feels that the c ontribution of  this effect 
i s  low as the levels o f  element concentrations found i n  the s o il  
" 
are too  high to have accumulated  from decayed vegatation .  
Evaluation  o f  the  e ff e c t  of  physi cal and biologi cal 
w eathering processes  for the d istribution o f  the elements 
indicates  that the largest  cont!ibution  comes from chemi cal 
weathering .  Acc ep tance  th?t chemi cal weathering is the maj o r  
fac tor  i s  s trengthened  when i t  i s  remembered  that the Hawks 
Crag Breccia  is a porous sands tone matrix  and as a result  o f  the 
high rainfall , oxi dation and transport  of  the soluble e l ements 
is  easily facili tated . 
0 
A comparison of  the solubi li ties  of  the elements uranium , 
copp er ,  lead  and beryllium shows that uranium ( VI )  is the most  
soluble followed by copper , l ead and then beryllium . Further 
evi dence  substantiating the importanc e of  chemi cal weathering i s  
70 . 
shown by the fac t that b e caus e o f  solub i l i ty differences , l e ad and 
b eryll ium do no t correlat e wi th uranium beyond the soils  whereas 
c opp er do es . Because copper i s  less  s o luble than uranium i t  i s  
m o r e  sui tab l e  f o r  analys i s  in s tr e am- s ediments than t h i s  element  
and i s  henc e a sui table pathfinding element  for uranium . 
?nalys is o f  uranium minerals for yttrium , thorium and the 
rare ear ths did not  provi de any us e ful i nforma tion conc erning 
possible  pathfinders for uranium . I n  all cas es the levels o f  
the s e  el em ents  i n  the minerali zed r ocks were  extremely l ow , w i th 
the levels  i n  the minerali zed frac t i on be ing slightly high e r  than 
tho s e  in the unmineral ised  frac tion . S tream s e diment concentrations 
were  higher again and probably r e fl e c t  the greater prop o r t i on of  
grani t i c  mat erial in the Br e e c i a .  The resul ts  presented  i n  
Tabl e  I I - 4  f o r  t h e  analys i s  o f  s tr eam s ediments from t h e  Hawks 
Crag Bre c c i a  for yttrium , thorium and rare e ar ths show that 
overall the concentrations of  these e l ements are low compared  w i th 
the majority o f  those  values ob tained  by TENNANT and SEWELL from 
the Otututu and Ohika-Nui grani t i c  areas . The generally low 
levels ob tained for yttrium , thorium and the rare earths are 
probably du e to dilution w i ?h the w eathered  matrix mat erial whi ch ,  
as shown by resul ts  in Tabl e  I I - 4  for the matrix , i s  d e f i c i ent  
i n  rare  G ar ths . An  a t t emp t was  made  to compare the  rare  earth 
d i s t ributi ons found in the Hawks Crag Bre c c i a  areas wi th thos e  
found i n  the Ohika-Nui and Otututu River areas b y  computing the 
amounts of lanthanum , yttrium and thorium in each samp l e  as a 
perc entage o f  the sum o f  the thre e , and by p l o t ting these values  
on  tri angular graph paper . The  elements , lanthanum yt trium and 
thnrium w?re chosen  b e c aus e they were  shown by TBNN.!?NT and SE'.'JELL 
7 1 .  
to  be  the most  discriminating for the r espe c tive  areas . 
F ig .  I I - 1 1 shows the r esults obtaine d .  The overlap o f  samples 
from the Ohika-Nui area into  that area on the graph representing 
the O tututu area and v i c e  versa ,  i s  a result o f  the fluc tuat i on 
o f  the element concentration wi thin each area . I t  i s  s een however , 
that the greates t concentration  o f  samples from both the 
Ohika-Nui and O tututu areas do fall into  s eparate ?reas on  the 
graph which may be  taken as 1 1 c haracterising11  that part i cular area  
sampled . I t  i s  c l early seen th?t  the  samples from the Hawks Crag 
Breccia  fall closer to the area  charact erised  as Otututu than 
that c harac terised  as Ohika-Nui  River . This  would indi cate  that 
the Hawks Crag Brec c ia  was derived  from the O tututu grani t e . 
The author consi ders , how 0ver , that for a more definite  
indication of  this relationship , analysis o f  a large number  o f  
samples  from all the Hawks Crag Bre ccia  areas would be required .  
I n  summary , i t  i s  c oncluded  that this work has shown that  
i n  the Hawks Crag Breccia  ar ea , prosp e cting for uranium by us e 
o f  pathfinder elements , l ead ,  b eryll ium and c opper  in  soils  and 
c opper in s tream sediments provi des a relatively speedy and 
s imple  m e thod . Dir e c t  analysi s  for  uranium was shown to  be , i n  
general , unsui table  unless  the sampling s i t e  was close  t o  the  
radioac tive  area .  Although yttrium , thorium and rare earths 
did no t prove sui table  as pathfinders for uranium , the analysi s  
o f  stream sediments for these  elements did  provide new evidence  
to  support  the  suggestion  that  the  Hawks Crag Bre c c ia was 
derived  from grani t e  from the O tututu area .  
The uncertainty concerning this origin is  refl e c ted  i n  the 
various theories  for the origin of the  uranium mineral i zat ioJl. 
100%Th Fig , II - 11 
0 
? 
D 
(,? D 
l OO% La 
0 
CJ) ? ? 
? ? ?0? ? 
0 
? 
D ? ? ? ? 
? 
? ? ?? ? ? ? 
? 
? 
? 
? 
? ? Oh i ka - Nu i  
? Otu tu t u  
? D B ig  R iv e r  
? Bu l ler  
? 
? Bu l l o ck  C r ee k  
? 
0 Oh i ka - i t i  
? 
? 
? 
? ? 
? 
? 
Triangular Plot for Concentration Ratios of Lanthanum , Yttrium and Thorium from Stream Sediments in 
Drainage Areas ; Ohika-Nui. River , Otututu River , and Hawks Crag Breccia , 
lOO% V 
H. C. B. 
72 .  
i ts elf  ( BECK ET  AL , 1 958 ; WODZICKI , 1 959b ) . The final par t  
o f  t h e  thesi s  inter ali a reports  on  low  energy gammR ray s tudies  
carried  out  w i th the  minerals t o  d e termine their  c omposi tion  and 
s tate  o f  equilibrium ; an impor tant  cons i deration for any 
discussion  conc erning the origin  of these  radi oactive  deposi t s . 
EQUILJBRIUM STUDIES ON URi-iNIUM MINZRALS ?  
BY HIGH.-RESOLUTION a;LMHA SPECTROMETRY 
and 
73 .  
INTRODUCTION 
Natural ur?nium , cons i s t ing of 99 . 28? u238 , 0 . 7 1% u235 
. 234 . 0 . 0 1%  U , 1 s  an unstable  element whose  i s 0 topes decay t o  
s impler  nucli des  w i th emiss ion o f  alpha , b e tn  and gamm? radiation .  
The recording o f  this  radioactivity w i th appropriate  elec troni c  
ins truments  has , f or  many years , b een  a c onvenient method f or  the 
dGt e c tion  of uranium and has formed the basis  of  0 method  used  
extensively  in  exploration for  uranium mineral i zation . At firs t ,  
hand-borne Geiger-Muller  counters , whi ch  detect  alpha and beta  
radiation , w ere  us ed , but  these  instruments have now been super-
s eded  by the more s ensi t iv e  s c intillome ter . The s c inti llometer  
detects  gamma radiation , whi ch  i s  considerably more energet i c  than 
?lpha or  beta  radiation , and hence  fac ili tat es  detec tion of radio-
ac t ive  substances  at a much greater  r?nge than do es the  Geiger  
count er .  B e caus e o f  the hi ?her  sens i tivi ty achieved , the 
s c intillomet er can be  operated from moving v ehic l es . The lat e s t  
dev elapm?nt in  radiometric  survey t e chniques i s  the use of  
highly-sensi t ive  s c intillometers  capable of  di fferentiating b e tween 
40 radiations  from uranium , thorium and K ? 
I t  i s  well known that the maj or fraction  o f  gamma radiation 
o f  the uranium series comes  from the decay o f  daughter  products  o f  
Ra226 ? An approximate  det ermination of  the amount of  uranium 
present  can be  made directly from the measurement o f  the gamma 
radiation  i f  i t  i s  assumed that the mineral is in radioac tive  
equi librium . In thi s , i t  is  implied  that the rate  of  produc t ion 
of  Ra226  from u238 must equal the rate o f  decay of  Ra226 , a 
c ondi t ion whi ch i s  no t always satisfied  in  practi c e .  For the 
purpose  of ore  de te c t ion , however , where we are conc erned wi th  the 
74 . 
order o f  magni tude o f  the uranium concentration , the state  o f  
equilibrium is  unimpor tant . ?s i t  has baen found that many 
uranium minerals are not  in equilibrium , di rec t measurement o f  the 
gamma radiation  for uranium c .nt ent leads to incorrect  values . 
This  probl em can be  overcome by measuring both beta  and gamma 
radiati0n  ( ZICHHOLZ ET ?1 , 1 953 ) . However , the importanc e  o f  
knowing the s tat e o f  equi librium o f  a uranium min2rQl is  no t 
confined  to  the qu nti tative  analysis  o f  uranium .  In  order to  
obtain  the age o f  a uranium mineral it  i s  also ne c essary to know 
i ts state  o f  equilibrium , as deviations from the equilibrium st?te  
ch?nge the  Pb206;u238 or Pb207;u235 r?tios . ( Pb206 and  Pb207 are  
the  s table  end products  o f  the  decay o f  u238 and u235 respectively , 
as shown in  Fig .  I I I - 1 ) . 
The t erm generally acc ep ted  t o  describe  the s tate of  
equilibrium o f  a uranium minerc:-.1 i s  npercentnge equilibrium r .?tdium " .  
Thi s  is  defined  ?s the amount o f  radium ac tu?lly present  i n  a 
sample e xpressed  ?s ? perc entage o f  the amount of  r?dium whi ch  
would  b e  present if  a state  n f  radioac tive equilibrium existed  
between the  uranium and the products o f  i ts d e cay .  ts has b e en 
ment i oned  previously , this s t?ge is  reached when the rat e  o f  radium 
decay becomes  equ&l to the rate of  radium formation . There are 
tw :.> m::t in  re-=tsons for the 1 1p erc en to.ge equilibri  urn radi urn" devi[t ting 
frnm one hundred p erc ent . 
( a ) Insuffi c i ent  time  may have elapsed  since  tho d 0 ?osit i nn  c f  
the uranium t o  allow tho form?t ion o f  the equi librium amount o f  
radium . The rate  at  which the Ra226 activity builds up to  that 
o f  the u238 parent is  limi ted  by the hal f-l i fe of one of the 
intermediate  members of the s eri0s , u234 ( ti = 2 . 0 . 1 05 yr ) . Only 
Element 
Uranium I 
Uranium x1 
Uranium x2 
Uranium ri ? 
Ionium 
Rad ium 
Radon  
Rad ium A ? Rad ium B I Astfitine Radium c I Radium c ?  I ?  Radium C"  I 
Radium D 
Radium E I Radium F I Thallium ,.:: I 
Radium G 
( end produc t )  
El ement 
Ac tinouranium 
Uranium Y 
Protac tinium 
Ac tinium ==-----1 
Radioactinium 
I Ac tinium 
Ac tinium X 
Actinon 
Ac t inium A I Ac t inium B 
I .Astatine 4! I 
Ac t inium ? .? Ac tinium 
I Ac tinium I 
A t " '!E D c :t.n:t.um 
( end produc t )  
Fig.  III-1  
K 
C "  
Uranium Series  ?-'--'??--
Symbol 
238u 
234Th 
234 Pa 
234 . u 
230T? 
226 Ra 
222Rn 
2 1 8Po 
2 1 4Pb 
2 1 8At 
2 1 4Bi 
2 1 4Po 
2 1 0Tl 
2 1 0Pb 
2 1 0Bi 
2 1 0p0 
206Tl 
206Pb 
Actinium Series  
Symbol 
235u 
231 Th 
231 Pa 
227Ac 
227Th 
223Fr 
223Ra 
2 1 9An 
2 1 5p0 
2 1 1 Pb 
2 1 5At 
2 1 1 Bi 
2 1 1 Po 
207Tl 
207Pb 
Rad iat ion 
a. 
? 
? 
a. 
a. 
a. 
a. 
a. , ?  
j3 
a. 
j3 , a. 
a. 
? 
? 
? , a. 
a. 
? 
-
Radiation 
a. 
? 
a. 
[3 , a.  
a. 
? 
a. 
a. 
a. , ?  
j3 
a. 
j3 , a. 
a. 
? 
-
Hal f-Life 
4 . 5X1 0
1 0  years 
24 days 
1 . 1  minut es 
2 . 3X1 05 years 
8 . 0X1 0
4 years 
1 .  6X 103 years 
3 . 8 days 
3 . 0 minutes  
27 minutes  
2 sec ond s 
20  minut es  
-4  1 . 5X1 0 second 
1 . 3 minut es 
22  years 
5 . 0  d ays  
1 40 days  
4 . 2 minut es 
Stable 
Half-Life 
7 . 1 X1 08 years 
24 hours 
4 
3 . 2X1 0 y ears 
22 years  
1 9  days 
2 1  minut es  
1 1  days 
3 . 9 sec onds  
1 . 8X1 0-
3s ec ond 
3 . 6 minut es 
-4 1 0  second 
2 . 2  minutes  
5X1 0-3second 
4 . 8 minutes 
Stable  
Thorium Series  
Element Symbol Radiation  
Thorium 
232Th a. 
Mesothorium I 228Ra ? 
Mesothorium II  22 8Ac ? 
Radiothorium 
228Th a. 
Thorium X 
224Ra a. 
Thoron 
220Tn a. 
Thorium A I 2 1 6Po a. Thorium B 2 12Pb ? , a. I _ 2 1 6At Asta?ine a. 
Thorium c ~ 
2 1 2Bi ? , a. 
Thorium C 1 
2 1 2Po a. 
Th I . ?n C"  208Th ? Thor?um I 208Pb or?um -
( end produc t ) 
Fig .  I I I - 1 238 235 232 Decay S c hemes for U ,  U ,  Th 
Hal f-Life 
1 0  1 .  4X1 0 y ears 
6 . 7 y ears 
6 .  1 hours 
1 . 9 years 
3 . 6 days 
51+ sec onds  
0. 1 6  sec ond 
1 0  hours 
-4 
3X1 0 sec ond 
60  minutes  
3X1 0-7sec ond 
3 . 1  minutes  
Stable 
75 . 
ft  . . d th R 226 t . .. t a er  a li ttla  more th?n one m1ll1on  years oes e a ac 1v1  y 
reach  97% of  i ts  equilibrium value . 
( b )  There may h ?vc  ? ecn s ome preferenti ?l loss  ( e . g . by  l eaching ) 
of  one or  more  of  the i s otopes  in  the dec?y series . I f  radium has 
been los t preferenti:1l ly ,  a "percGnt r>.ge equilibrium rEJ.dium" value  
o f  l ess  th?n one  hundred  percent  is  to be  expe c ted , whereas 
pre ferentinl loss  of  uranium will  l ead to  values of  "per c entage 
equilibrium radium" greater  thc:n one hundred percent . 
The mos t  c omm0n method used  to  determine the "perc en tage 
equilibrium radium" reli es on the measurement o f  the known trpes  
of  radiation aris ing from the disintegration of  uranium and i ts 
daughter  pr?ducts . I t  is  necessary in  this  method to measure b o th 
beta  and gamma radi ation . The beta  radiation  ?rises  from both the 
immediate  uranium daughter  produc t s  and also  from radium . The 
major  fraction  of the gamma radi?tion ar?ses from radium and i ts 
daughters . The gamma radiation ?i gure is  used  to calculate  the  
amount of  beta  radi?tion due  to radium , and  this is  then dedu c ted  
from the to tal b e ta  me?surement to determine the  amount o f  b e ta  
radi?ti on aris ing from the  uranium . From this correc t ed  figure , 
the amount o f  urc.nium is  determined  .:::md the 0percentnge equil ibrium 
radium 1 1  c alculated .  This  i s  essentially the  method used  by BOSIN  
and BOGDr,N ( 1 960 )  and STERN and STIEFF ( 1 959 ) . iLno ther approach is  
that  of  GR&CE and BATES ( 1 959 ) who  det ermined the equil ibrium using 
alpha and fiss ion- fragment radiography . Thi s  technique has the  
advantage that  i t  can be  appl i ed on a micro s cal e  but suffers from 
the disadvantage that it can no t be used  in the presence  of  
natural thorium . 
76 .  
The main weakness in  th? me thod involving the measurement 
of both beta  and gamma radiat i on is  the assumption  that nll the 
gamma radiation  detec ted  is  due to the decay of radium or  i ts 
daugh ters . This  is  not  s o , as Th234 and u235 both produce  gQmma 
radiation , ?nd although the activi ty is only a frac tion  of that 
from radium and i ts Gaughters , i t  is s t ill  s ignificant . As a 
result  o f  this , the correc ted beta  figure for uranium would be  
too  low , ::1.nd therefore  the  asso ciated  ; 'perc entage equilibrium 
radium ' ' , value  would be  rather too high . The advantage  offered  
by  a method  whi ch  independently measures  the  radiation  from only 
226 235 Ra and a uranium iso tope is  c learly seen ( U  i s  the mos t 
sui table  uranium i so tope for a gamma ray s tudy as the decay o f  
U238 t P 234 d . ? . . d u234 . o a ocs not  1nvolve gamma em1ss1on  an 1s  
insuffi c ien tly abundan t ) . LEDERER ( 1 969 )  s tates  that  the principal 
g?rnma rays from bo th u235 and Ra226 fi ?ve an energy o f  1 85 KeV and 
the princ ipal g?mma rays from Pb2 1 4  ( a  daught er of Ra226 always i n  
equilibrium , due to  i t s  short half- l i fe )  have energi es o f  242 , 
295 and 352 KeV respec tively .  From these gamma rays i t  i s  
thc:oreti cally possible  . to calculat e t h e  1 1 percen tage equilibrium 
radium 1 1 ? To n chi eve this exp erimentally ,  however , i t  i s  nec essary 
2 1 4  t o  resolve  the three Pb gamma rays , and to determine the 
extent  to which the Ra22? 1 85 KeV gamma ray interferes  wi th 
the 1 85 KeV gamma ray from u23
5 . 
Prior to the  devel opment o f  the Ge ( Li )  detec tor , the 
Pb2 1 4  gamma rays could  no t be s::J..t i s factorily  resolved , as the  
Nai ( Tl ) d e te ctor  di d no t possess  suffi c i ent  resolution  in  this  
energy region .  Fig .  III-2  clearly illustrat es this  point . 
,:,1 though the  Ge ( L i )  detector  was developed primarily for the 
Cl) 
c 
c 
ea 
? 
(.) 
.... 
Cl) 
a. 
en 
.... 
c 
::s 
0 
(.) 
If c 
I 
I \  210 Pb  
100 
>I 
., ... 
? 
? 
aJ 
'6 
I I f 
? 
1 1  ? 
300 
C ha nne l 
235 2 26 
U + R a  
1 8 5 
500 
N u mbe r 
2 1 4  
Pb  
2 4 2  
700 
Fig . I I I  - 2 Comparison of uraninite spectra recorded with Nai (Tl ) and Ge (Li ) detectors 
214  
Pb 
2 95 
2 1 4  
P b  
3 5 2  
900 
Nal (TI ) 
K eV 
Ge (  Li ) 
77 . 
b enefi t o f  the nuclear spectros c opis t ,  i t  h?s b e en used  in  many 
o ther fi elds  o f  research.  These  include decay- s cheme s tudi es  w i th 
radioactive  iso topes , b eam spec tr?s copy , low- t emperature nuc lear 
ori entation  and a c t ivation analysis . An E xc ellent  review o f  the 
impac t o f  s emic?nductor  d e t e c tors on gamma-ray and elec tron 
sp e c troscopy i s  given by HOLLANDER ( 1 966 ) . The preparation , 
maint enance  ?nd relevant theory of  the s emiconductor  det e c tor  
i s  given by  Mr,NN ?T ;,1 ( 1 966 ) , DZ:;,RN"LY and NORTHROP ( 1 966 ) and 
CQ?:}TE ( 1 967 ) . 
The geochemist  and analytical chemist  h?ve gained  mos t  
benefit  from the Ge (Li ) detec tor i n  the fi eld o f  ac tivation  
analysis  b ecause the  high resolution obtained has , in m?ny c ases , 
made possible  the dire c t  measurement o f  the irradiated  s ample .  
Previously , using th? Nai ( Tl )  detec tor , t ? dious chemi cal 
s eparat ions were required .  To  the author ' s  knowledge , the  only 
?ppli cati on of the Ge ( Li )  detec tor to naturally- oc curring radio?
active  material , is  that of M?THEVON ET AL ( 1 967 ) , who used  the 
gamm? radiat i ?n o f  spe c i fi c  i so top es to  determine uranium , 
thorium and radium c ontent o f  such samples . The method used  by 
these  authors required  that  the sample  w as in  radioactive  
equilibrium and that ?n  ac curately known uranium s tandar d ,  also  in  
equilibrium , was av?ilable  as  r e: ference . l'LTHEVON ?T !cL also 
developed  a method t o  compare the radioactive  equilibrium of  each 
sample  with that of the s t3ndard rock . How ever , due to an error 
in the ass ignment of  the 1 85 K eV gamma radi ?ti on by  the above  
authors , the  pres ent au thor cnnsi ders  that the  reported  work i s  in 
s erious error  and r equires  further elucidation . 
The  aim o f  this part o f  the thesis  was three- fol d :  
78 .  
( 1 )  To i dent i fy the various peaks in  the  low energy regi?n o f  the 
gnmm? spec trum ( 30-360 K e V )  of  naturally a c currin5 urnnium ores . 
( 2 )  From the results  o f  ( 1 ) , to  develop a me thod for determining 
the 1 1p ercentage e quilibrium radium" . 
( 3 )  To invest igat e tha equilibrium s tate  o f  uranium minorals i n  
t h e  Buller  Gorge in  order to  provide  more  i nformation on  the 
his tory of these depos its . 
79 . 
INSTRUMENTATION 
?ll ma?suremants were obtained vi?  a high- resolution g?mma 
spe c trometer  at the Inst i tute  of Nuclear S c i ences , Department o f  
S c i enti fi c  and I ndustrial Research , Wellington . 
High resolution in  the l ow- energy region ( 40-360 KeV)  was 
ob tained by using a 5 cm3 Ge ( L i ) d e t e c tor , dri fted  from five s ides 
nnd w i th the open end fac ing the radiation . In a germanium 
d ete ctor  only 3eV is  required  to  produce  an elec tron-hole  pai r ,  
whereas a Nai ( Tl )  crystal requires  abou t 300 eV per  pho to-ele c tron 
from the c athode and henc e has a much poorer resolution . 
Fig . I I I-2  c learly illus trates the d i fference  in r esolution o f  
these  d e te ctors . 
The Ge ( Li ) detec tor was coupled  t o  a SIMTEC P- 1 1 ,  low-noise  
Field-Effect- transistor  pre-ampli f i er ; the  combination provided  
resolution  o f  2 . 5 KeV . These  two  c omponents were  housed  in the  
radiation  area  thirty to  forty feet  from  the control room . Coaxial 
cables from the pre- ampli fi er l ead to  the c ontrol room , where  the 
pulses w ere  ampli fi ed  by an ORTEC 4 1 0  transis tor main amplifier  
whi ch  was  ?onnec ted  to  an  'RCL 256- channel pulse-height analyser  
( P . H . ? . ) .  For very ac curate calibration work a KICKSORT 
4096- channel pulse-height  analyser  was us ed .  Data s tored  i n  the 
memory of  e ither P . H . h .  were  recorded  as a spe ctrum l isting via  a 
typ ewri ter , for  later manual plotting ,  o r  were  punched dir e c tly 
onto paper  tape  whi ch provided the i nput informat ion for computer?
assisted  analysi s .  Figures  -I II-3  and I II-4  show s chematic  diagrams 
of the gamma spe c trome ter , and the sys t em used  for c ?mputer?
assisted  analysis 0f  gamma spe c tra , respe c t ively.  
/ 
? - r ays 
\ Th i n  AI  
Ga mma Spect  roscopy 
Field Effect Transistor  
Preampl if ier  
C opper  rod  at l i q . N 2  
A I mount  
t he rma l r ad i a t i on  
~ 
Spe c t rum L i s t i n g  
. . 
Ma in  Ampl i f ie r  
\ 
L ong coa x i a l  c ab le  to 
contro l  room  
. . . ? 
Typew r i t e r  
Fig . I I I  - 3 Gamma spectroscopy - schemat ic diagram 
0 Q;) 0 0 
0 I I I I I J 
0 
Pulse  He i g ht Ana lyse r ,  
256  C hanne l s  
Tape  fo r C omputor  A na l y s i s  
Pu n c h e d  Paper  Tape From 
P. H. A .  
,!-.. -, .- :' :? 
.
. 
'1 
I 
C ompu t e r  P rog r ams  On 
Pape r  Ta pe  
C ompute r - ass i sted Ana lys is- of G a m ma Ray S pect ra  
. - . . ' . ' ' . " ? '  
. ... ... , . ' ' . . . ...  I . . . . . . I . . . . . . . . . . . . I I I I I I I I I I I I I 
Paper Tape R eader  P D P-8 D ig i t  a I Compute r 
?? ? . D? ? ?  . . . .  ? . . . . . . 
Te l e t y p e  For  I nput  C o mmands 
A nd Prog ram  L i st i n g  
/?.-7? 
P l ott e d  Spec t r u m  
? 
X - V R e c o rd e r  
Fig . I I I  - 4 Computer-assisted analysis of gamma spectra 
?? ? 
Fast Paper ""'Tape  P u n c h  
1 
? : .?. : .? : : . ? 
ou?tput  Paper  Tape  To Be 
U s e d  When  Req u i re d  
8o . 
Operation  Proc edure 
Five  to fi fteen grams ( dep ending on the activi ty ) o f  
powdered rock ( less than 80 mesh ) wcs placed  i n  a cylindri c al 
glnss phial ( 5cm x 2cm  diam . ) and posi tioned in  front o f  the 
detec tor next to the thin ?luminium window . The s?mplc  was 
counted for a suffi c i ent time to  allow a well-defined spec trum to 
be  obt?ined .  For most uranium minerals thi s  was between  fifteen  
and  thiry  minutes . ? check  on the  number o f  c ounts per  channel i n  
each channel comprising th e  spe c trum was easily obtained a t  any 
time  via  an oscillos cope  in the P . H . A .  When a well-de fined 
spec trum had been  obtained ,  the number  i n  each channel was e i ther 
listed  by the typ ewri t er or  punched on to pap er tape  and then 
analysed  wi th the computer as h?s b e en previously describe d .  A 
typi cal sp e c trum 0b tained i s  shown i n  Fig .  I I I- 2 . 
IDENTIFICATION OF SPECTRA 
( a )  Calibration  o f  Puls e  Height  tnalyser  
As  has been previously menti oned , the  gamma spec trum is  
r e corded  by the  P . H . ? .  cs  counts in  ? given time  for  each  channel . 
I n  order  to  assign sp e c i fi c  ener?i es  to each p eak a calibration 
curve o f  energy as a function  c f  channel number  mus t be  determined . 
The calibrati on curve was c ons truc ted  from the gamma sp e c trum o f  a 
s t ?ndard source , consis ting o f  s everal i s o topes , by plot t ing the 
known energi es  of  the gamm3 rays frpm these iso topes ?gains t their  
corresponding channel numbers . Tabl e III- 1 shows s ome o f  the 
i sotopes  used , w i th their respe c tive  gamma ray energi es , and 
Fig .  I II-5  shows a typ i cal cal ibration curve obtained .  Provi ded  
that the  s e t tings on the  spe c trome ter  are kept c0ns tant , the 
calibration  curve can be  used for all spectra taken over  several 
hours . I f ,  however , ?n ass ignment of  an energy to a peak i s  
doub tful the cal ibration curve i s  redetermined ei ther immediately 
b e fore  or  after  the parti cular sp ec trum being s tudie d .  
( b )  ?nalys is  of  Spec tra  
The  analysis  of  the low- energy gamma ray region ( 30- 400 KeV)  
was  carried  out  in  two  parts . The firs t , and mos t  impor tant to  
thi s work , was  a qu?li tative  and quanti tative  s tudy confined  t o  the 
region 1 80- 360 KeV . This  region includes the main gamma radiation  
from  u235 and Ra226 ( 1 85 KeV ) and the main  gamma radiation from 
2 1 4  Pb ( 2 42 , 295 , and 352 K eV ) . These are the most  important  gamma 
radir:ctions for the calcul?tion  o f  radioactive  equilibrium . The 
s e cond  part was c oncerned only wi th ident ifi cation  of the 
observed  peaks in the region 30- 1 80 KeV.  The energy region above  
360 KeV  was not  c ons i dered  because  it  contains only gamma rays 
f B . 2 1 4  . f th rom 1 and y 1 elds no n ew in formation . Use  of one o ese  
> 
Q) 
280 
240 
200 
? 160 
20 
Fig . III  - 5 
40 60 80 100 1 20  
Channe l 
140 160  
Numbe r  
Calibration curve , keV as a function of channel number 
180 200 220 240 260 
T1-.BLE III  - 1 
Iso top es and Respec tive Gamma Ray Energi es  Used  for 
Calibration of  ? Pulse  Height AnRlys er 
Iso topes  Energi es ( KeV )  
Ba1 33 30 . 9 , 8 1 . 1 ' 276 . 5 ,  303 . 0 ,  356 . 3 ,  
Ra226 1 85 . 7 ,  241 . 9 , 295 . 2 ,  352 . 0  
it m 2lt 1  26 . 35 ,  59 . 54 
Co57 1 2 1 . 97 ,  1 36 . 33 
Co6o 1 1 73 . 2 , 1 332 . 4  
Pb2 1 0  46 . 5  
82 . 
384 . 1 
gamma rays  as a det ermination o f  Ra226 was no t attempted  b e cause  
of  the  very low  d?tec tnr  effic i ency in this energy range . hlthough 
no apprec iabl e  amounts o f  the thorium s eries  were  dete ct ed  in the 
urani?m minE rals from the Huller Gorge ( a  s i tuation whi ch  reduced 
the  complexi ty of the spec trum ) , the quantitative  study carried  
out  included the  possibili ty o f  the  presence  o f  thorium in o rder 'V?, 
to ensure th?t this method of  calculating radio?ctive  equilibrium 
had general appli cation . 
( i )  1 80-360 KeV Region 
Fig .  I II-6  shows ( i )  t?e  gamma spe c tra  obtained from a 
uranium mineral ( uranini tc ) , ( i i )  
and Bi2 1 4 , ( i i i ) "uraninite  minus  
R 226 . ' l ' b  . "' J.' th Pb2 1 4 a J.n equJ. 1 r1um  
Ra226 :' and ( iv )  an aged thorium 
nitrate sample . The spectrum labell ed  "uraninite  minus Ra226 1 1  
was obtained  by counting the uranini te  for two hours and sub-
trac ting the c ounts obtained from the radium s ourc e  over the s am e  
t im c .  T o  normalize  the two count rates , the position o f  the 
radium s ourc e . in front of  the dete c tor  was altered  until  the 
"perc entage l ive  time"  meter  regi s tered  the same  value  .:ts when the 
uranini t e  sample  was count e d .  Thi s  approach was consi dered  to  be  
the  mos t suitable way to  determine  the  extent o f  interference  o f  
the Pb2 1 4 peaks i n  natural samples , aris ing from u235 o r  o ther  
decay p roduc ts . I t  i s  es tim?ted  that  the error incurred by this 
procedure would not be  greater than one p ercent . 
From F ig .  I II-6  i t  i s  clearly s e en that the 1 85 K eV gamma 
226  ray from  Ra canno t be  distinguished  from the  1 85 KeV gamm? ray 
from u235 , and that the 239 KeV gamma ray from Pb2 1 2  ( a  daughter  
o f  Th232 ) interferes  s trongly w i th the 242 KeV  gamma ray  from  Pb2 1 4 
A s  a result  o f  a systematic  s earch  through TABLE OF ISOTOPES 
N 
1 0  
Cl) 
c: 
c: 
Ill 
? 
u 
... 
Cl) Q. 
1/) -
c: 
:I 
0 
(.) 
6 
5 
4 
3 
2 
0 
3 
2 
0 
235 226 
U ? Ra 
185 
120 
Fig . Ill  - 6 
214 Pb 
214 Pb 
295 
352 
352 
U r a n i n i t e  
R a d i u m  226 
" 
Uran i n i t e  - R 
Thor i u m  N i t ra t e  
160 
Chann e l  
200 
Numbe r  
240 
Gamma spectra of uranini te , Ra 226 , Th 
232 ( Energies of peaks in keV ) .  
84 . 
( LED?RER , 1 969 )  these interferences  were  exp e c t e d  but their  
respe c t ive  quanti tative contr ibutions were  unknown . The "uranini te 
? R 226 ? r  t h k t 350 7 K V m1nus a ' spec  rum s ows a p ea a ? e ? 'I'his  i s  
b bl  d t o  Bl.. 2 1 1 , d ht  f u235 B . 2 1 1 . th 1 pro  a y ue a aug er o , as 1 1 s  e on y 
isotope  present which  has a . favourable  decay path to  produce  a 
gamma ray o f  this energy.  Hence  there  i s  interference  of  the 
Pb2 1 4  352 KeV peak by the B i2 1 1  350 . 7  KeV peak . Thi s  B i2 1 1 
interference  prevents the Pb2 1 4  352 KeV peak from b eing use d  as a 
measure o f  Ra226 pres ent in  the  sample  b e cause the B i2 1 1 
2 1 4  contribution to t h e  Pb  p eak w i ll  vary a c cording to  the amount 
of u235 present in the sample .  Further  c onfirmation  that the 
Pb2 1 4  352 KeV peak i s  contaminated  i s  shown by comparing the 
ratio - 352 KeV peak/295 K eV peak from the uraninite  wi th the 
226 same ratio  from the  Ra spectrum . The values o f  thi s  ratio  
are 1 . 31 9  and 1 . 257 respect ively , which  shows that  the  value of  
the 352 KeV  peak from the uranini te is  higher than would be  
expected  if  it  was  free from interferenc e .  The spec trum ob tained  
' 
from the aged thorium ni trate  sample  shows a s trong peak due to  
Pb2 1 2  at  239 KeV .  h S  the resolution  of  the sys t em used  i s  
2 1 2  2 . 5 Kev ; i t  i s  seen that the P b  239 KeV peak will interfere  
with  the  Pb2 1 4  242  K eV p enk and render  i t  unsui table  as a measure 
for Ra226 ? These  results show that 6nly the Pb2 1 4  2 95 KeV p eak 
is  free  from interferenc e ,  and i s  suitable  for use as ? measure 
f R 226 t ?  . t o a ac 1v1. y . 
( i i ) 30- 1 80 KeV Fegion 
The  i denti fi cation of  peaks from uranium sampl es in  this 
energy range of the spec trum was att empted  as l i t t l e  information  
is  available i n  the  li terature ? Preliminary exp eriments , w i th 
dissolved  uranihi t e  as s ?mple , were  carri ed out to investigate 
the sui tabi l i ty of  us ing solvent extrac tion t e chniques to  s epar?te 
the various i sotopes nnd hence fac ili tate  identi fi cation  of  their  
gamm? radiat ions . The sys tem chosen was tributyl phosphate/HCl as 
this  was the best  d<:> cumented ( s:.To , 1 966 ) . However , incompl ete  
s eparations w ere  ob tained  w i th this  syst em . h successful 
s eparation was achi eved by using the anion- exchange t echnique 
reported  in Part II  of  this  thesis for the s eparation  of uranium 
and thorium . Fig . I I I-7  shows the spec tra obtained .  The 
exc ellent  s eparation of uranium from thorium assisted  i dent i fi cation 
of  u235 gamma radiation  and Th234 gamma radiation in this  e nergy 
region .  The spe c trum of  the  uranium frac tion  shows that u235 
emi ts the  following gamma radiation and X-rays in  the 30- 1 80 KeV 
region :  49 , 68 , 85 , 93 , 98 , 1 1 0 ,  1 43 , 1 63 KeV . The spe c trum of 
the  thorium fraction shows tw:. peaks due to the 63 KeV and 93 KeV 
gamma rays from Th234 . The u235 sp ec trum obtained in  this  work 
comp.'lres well  w i th that obtained  by  MilNN ET i\.1 ( 1 966 ) ' .::J.lso using  
a G e ( Li ) detec t ,Jr , from a u235 source  of  93% purity . The 
ur::::.n in i t e  spec trum (Fig .  I II-2  s!J.ows two p eaks at 76 and 89  KeV 
whi ch are absent from the uranyl ni trate  S)..:: c trum . These  peaks 
are Bi K x-rays , following the decay o f  Pb2 1 4 ? Their  absence  
2 1 4  from the  uranyl ni trate spe ctrum i s  due t o  the abs ence  o f  P b  , 
b e cause o f  the young age o f  the  sample . Similarly , a peak at  
2 1 0  46 . 5  KeV , due t o  P b  , appears i n  tha uranini te  spec trum , but  
not in  that  o f  the uranyl ni trate . 
The above resul ts show that this  low- energy region 
( 30- 1 80 KeV)  i s  extremely complex . The features  with the b e s t  
C"' 
' a  
0 
Q) c 
c 
RI 1 0  .s= 
() 
... 8 
Q) a. 
6 
!/) -c 
::I 4 0 
() 
2 
0 
Fig . I l l  - 7 
234 
Th 
63  
235 
u 
96 
2 ,., t! 
X 
235 
u 
1 10  
235 u 
1 85 
Uranyl  N i t rate 
U ran ium F ra c t ion  
135 :.:: u 
48 
50 
234 
Th 
93 
143 
Thor i um Fr act ion  
100 150 
Channe l N umber  
200 
Gamma spectra of uranyl nitrate , extracted uranium fraction and thorium fraction 
( Energies of peaks in keV ) .  
86 . 
possibilities for us e ful applic ?tions are the 63 KeV  gamma radiation  
from Th234 ( as an  indication  o f  u238 ) ,  and the 46 . 5  K eV gamma 
. 2 1 0  radiation ( as a measure of  Pb . ?  ) . However , the higher energy end 
( 1 80- 360 KeV)  of  this low energy region appears to contain the 
most s ignifi cant informati on .  
EQUILIBRIUi"' STUDIES ON MINERALS 
( a )  Derivation o f  the Equilibrium Rel?tionship 
J:.s h:ts been previously menti oned , the term ' 'perc entage 
equilibrium ra.dium ; '  is  the a c c epted  way of expressing "the  s tate  
o f  equilibrium o f  a uranium mineral . This term is  defined  as the 
amount of radium ac tually pres ent in  the sample , expressed as a 
perc ant?ge o f  the amount o f  radium which  would b e  pres ent i f  the 
sample  was of suffi c i ent age to  have attained a st?te o f  
equilibrium b etween the uranium and the products o f  i t s  decay . 
From the previous resul ts  i t  i s  s een that i t  i s  possible  
to de termine the  numb er of  radium atoms present  from  the count 
rate  obtained  from ?he Pb2 1 4  295 K?V peak . The number of c ounts 
in  uni t time  at an energy of  295 KeV , C ( 295 ) , i s  given by  
where  APb ' NPb are  the decay c onstant and number  of  atoms 
respec tively , of Pb2 1 4 , PPb ( 295 ) is the frac tion of disintegr?tions 
f Pb2 1 4  . . E (  ) ? rom g1v1ng a gamma ray of 295 KeV , and 295 1s the 
G e ( Li ) d e t e ctor effi c i ency at  this energy . 
When Ra226 is  in  radioactive  equilibrium with Pb2 1 4 , 
A N - A N Pb Pb - Ra Ra 
where ARa ' NRa are the decay constant and number of  atoms 
respec tively , o f  Ra226 ? This  equilibrium is  ?ttained i n  a Ra226 
sample  after only a few weeks have  elapsed . 
Hence  the number of  radium atoms in  the sample  is  given by 
C ( 295 ) 
However , the  absolute  9alue of  the detec tor effi c i ency , whi ch i s  
88 . 
di fficult  to obtain w i th b e t ter thRn ten  perc ent ?c curacy , mus t  be  
dt:tcrmined  experimentally for each detector used . ; _ s  3. resul t , 
this appro?ch is  c ?nsider e d  unsatisfac tory . To overcome this 
problem nn attempt was made ta ob tain a relationship b e tween  the 
"percentnge equi l ibrium rc!.dium; '  .:md the rati o  of  the 1 85 KeV 
( u235 + Ra226 ) peak to the 295 K?V (Pb2 1 4 ) peak in  which the 
d 2 t e c tor  effic iency term is no t involved . The following shows how 
this  relationship was develop e d .  
L e t  C ( 1 85 )  b e  the numb er b f  counts i n  uni t time  a t  an 
energy o f  1 85 KcV , and l e t  the det e ctor  e ffi c i ency at this  energy 
b e  E ( 1 85 ) . 
Then C ( 295 ) 
and 
- - - ( 1 )  
- -- ( 2 ) 
where A.U ' NU are the clec3.y cons tant ,J.nd number o f  3.toms , 
respec tively , o f  u235 , PRa ( 1 85 ) , PU ( 1 85 )  are the  fract i ons o f  the 
disintegrations from Ra226 , u235 giving n gamma ray of the  s tated  
energy . 
L e t  A PPb ( 295 ) E ( 295) = Ra 
A PRn ( 1 85 E( 1 85 )  = Ra 
A uPu ( 1 85 ) E ( 1 85 )  = 
then C ( 295 )  = k1 NRa  
C ( 1 85 )  = k2NRa + k3NU 
NRa = C ( 295 ) /k1 
and NU = ? iC( 1 85 )  
3 
k1 
k2 
k3 
hence  Nu k 1 C ( 1 85 )  - k2 C ( 295 ) NRa 
= k7C(295) 
;; 
= !szck1 k3 k2 
C ( 1 85 )  - 1 )  . C(295 )  
--- ( 3 )  
( 4 )  
( 5 )  
-? -- ---------------------
- !2 ( k1  ) - k3 k2 X - 1 
C ( 1 85 )  where  x = C(295 ) . 
/ 
- - - ( 6 )  
Now P involves  the reL;.tive  effi c iency  o f  the  det e c tor  K2 
at 1 85 and 295 KeV , and mus t b e  det?rmined experimentally by  
226 
me2suring xRa ' the  value of  x for the spec trum of  pure Ra in  
equilibrium w i th i ts daughters . In this  cas e , NU = 0 and henca  
X - !2_ Rn - k 1 
( 7 ) 
Thus ( 6 )  becomes  
( !!Z From 3 ) , k = 3 
? - ? 
NRa 
- k3 
A. RaPRa ( 1 85 )  X
upu( 185 )  
(? - 1 )  xRa 
4 ? 32 . 1 0- 4 . 4  
= 9 ? 7 5 . 1 0- !0. 54= 
4 3 . 29 . 1 0 
( 8 ) 
where PRa
( 1 85 ) and PU ( 1 85 ) are obtained from LEDERER ( 1 96 9 ) . 
- 1 )  - - - ( 9 )  
238 - 226 When radioactive  equilibrium exi s ts b e tween U and Ra , 
where  A. U 1 ' NU 1 ' are the decay c ons tant  and numb er o f  atoms 
respe c tively , o f  u238 ? 
But = 
0 . 7 1 
99 . 28 
4 ? 32 . 1 0- 4 0 ?? 1  
= 1 ? 53 . 1 0-10 . 99 ? 28 = 
and the value o f  x for  a sample  in  equilibrium , x8 , from ( 9 )  i s  
given by  
90. 
Consi der  . a  s3mple  c ont?ining NU atoms ?f  u
235 . I f  the  
sample  were  in  radioactive equilibrium , 
( N  ) = Ra eq  Nu 3 ? 29 . 1 04c xe _ 1 )  xRn 
In general , however , NR w ill  b e  a 
Henc e  the p ercen tage equi l ibrium radium , R ,  i s  
= 
0 . 6 1 . 1 00% --- ( 1 1 )  
For the  spec trometer sys tem used  in  the pres ent work the  
value o f  xRa was found to b e  0 ? 607 (Fig .r III-6 ) .  I t  may be  noted  
that  the  relative  d e t e c tor effi c i ency can now  b e  calculated , that 
is 
E ( 1 85 )  
E(295) = = 2 . 86 
Subst i tut ion of  the  value xR = 0 . 607 i n  equation  ( 1 0 )  gives  a 
Xe = 0 . 98 
Thi s  allows a graph to  b e  drawn giving p ercentage equilibrium 
radium , R ,  as a func tion  o f  x ,  using ( 1 1 ) .  Thi s  i s  shown i n  
Fig .  I I I-8 . From this  graph , R can b e  determined  d irec tly from 
the  experimental count-rates  C ( 1 85 )  and C ( 295 ) . The  appropriate  
value of  xR for  any o ther Ge ( L i )  d e t e c tor  can  be  found by  1 a 
? th t . C ( 1 85 )  R 226 measurlng e ra lO  C(295) for a pure a sour c e .  
11')1 11') CO 0.. ? N 
u u  
2 ? 2  
2 ? 0  
1 ? 8 
1 ? 6 
1 1 ? 1 ? 4 
>< 
1 ? 2 
1 ?0 
0 ? 8 ----;:;-----:;;-????????=:::L::::. 20 30  40 70 80 1 20 1 40 1 50  100 1 1 0  1 30 50 60 90 
Fig . I I I  - 8 
R % 
Theoret ical curve of C ( l B S ) as a function of the percentage equilibrium radium 
C ( 295 ) 
( b )  The Isotopic  Composition o f  Uranium Minerals from the 
Lower Buller Gorge 
91 .  
The gamrna spec tra o f  thr.? e  uranium s tande.rds and various 
primary and s e condary miherals , s elected  from both  the North and 
South Side  deposits  wore  obtained , and their respec tive  
C ( 295 )/C ( 1 85 )  ratios  were  measured . From this ratio  the  
i lperc entage equilibrium rnclium" , R ,  was calculat ed .  T9.bl e  I II-2 
shows the values obtained .  
As has  been previously mentioned , the mineralogy o f  the 
uranium deposits has been thoroughly investigated  and has been 
shown to cons is t  meinly o f  co ffini te  on the North Side  and 
ure.nini t o  on  the South Side , w i th b o th s ides c ontaining the 
s e condary minerals , gummi te , t0 rberni te , autuni tc  and ur.'lnophane . 
However , b e cause  o f  the physi c ?l d i f ferences  obs erved among many 
o f  the 1 1uranini t e "  samples measured , i t  wo..s considered  necessary to 
i nves tigate their mineral form . For example , the  so..mples  labelled  
4 and  5 i n  Table  I I I-2  wer e in  fact  obtained from the  same  rock , 
the top half o f  whi ch was black and the b o t tom hal f bright yellow . 
An.'llysis  o f  each frac t ion gave 1 7 . 5  and 1 6 . 0  perc ent uranium 
resp ectively . The corresponding values o f  R show that the black 
frac tion  is nearer to equilibrium than i s  the yellow frac tion . 
M ineral i denti fi cation was effected  by the use  o f  an X-ray 
powder d i f fractome ter .  The samples  s tudied  had previously b e en 
s eparated  into three  dens i ty frac tions by use  o f  bromo form , 
methylene iodide and cleri c i  solution . The frac tion o f  the original 
sampl e whi ch h?d a dens i ty greater than c l eri c i  solution was used  
for  the  powder  mount . The i denti fi cati ons ob tnined are given i n  
Tabl e III-2 . From this table  i t  is  s e 0n  that none o f  the uranium 
T;,BLB I I I  - 2 
The Equilibrium S tnte  o f  Various Uranium Minerals  
from the  Lower Bull8r  Gorge 
Su.mple  I No . Mineral Form 1 85 295 
1 13 - uo2 3 .  1 4  3 . 00 
2 !3 - uo2 6 . 75 5 . 50 
3 13 - uo2 1 1 . 60 1 1 . 30 
4 13 - uo2 1 3 .  1 0  1 2 . 90 
5 I .:mthini te  uo2 . 5uo3 . 1 oH2o 8 . 30 7 . 55 
6 Co ffini te  8 . 40 7 . 1 0  
7 Coffinit e  1 0 . 30 8 . 48 
8 Torberni t e *  7 . 80 6 . 90 
9 U03 " 2H20 4 . 80 4 . 78 
1 0  1\.u tuni t e *  4 . 83 2 . 80 
1 85/295 
1 . 045  
1 . 225  
1 . 030 
1 .  02 
1 . 1 70 
1 . 1 85 
1 . 2 1 5  
1 . 1 30 
1 . 050 
1 . 725  
Samples  1-5  and 9 taken from T-J hori zon ( Se e  Fig . I I- 1 0 ) . 
Snmples 6 and 7 taken from North S i de . 
Samples 8 and 1 0  taken from S-C  horizon . 
* Identified  visually.  
92 . 
R% 
83 
59 
85 
86 
65 
64 
6 1  
70 
83 
33 
93 . 
minerals taken are in equilibrium . This  is  not unexpe c ted , as 
petrologi cal s tudies  by  WHITTLZ ( 1 960 ) showed  that i n  many cases 
the uranium minerals were al tered  due to weathering proc esses . The 
f::tc t thnt the value o f  R is  l oss  th.:m one hundred  perc ent means 
that e i ther  radium has baen lost  from the sample  or  the sample  i s  
. l ess than one million ye'lrs old , the time  t?ken to  attain 
equil ibrium . WILLI.'\MS ( 1 957 ) quo tes  nn age determination of  tha 
Rio Tinto Company on a sample  of  c offini te  from the North Bank as 
lying wi thin the rnnge of  one hundred  million  to one hundred and 
fi f ty million years . This  indi cates  a Cretac eous age for the 
mineral i zation . Approximate  age determin ::tti ons were ob tained for a 
sele c tion  of  uranini te  samples , from the South S i ce , by using 
the Pb206;u238 method ( KULP ET f,L , 1 954 ; ECKELM1?NN and KULP , 1 957 ) 
and by  making t?e following assumptions : 
( 1 )  The total uranium measured was t?ken to  b e  u238 . 
( 2 )  The to tal l ead measured ,  l ess an es timated  b?ckground value ,  
The background vqlue w2s obtained by  
analysing l ead in  a non-radioac tive  por tion of  the  matrix  materials . 
W i th these  assumptions the ages of  four uranini te  samples  were  
calculated to  be  77 , 97 , 1 30 ?nd 1 80 million years . These  values , 
supported  by the value ob.tained for the North Bank c offini t e , 
indicate  qui te  c learly that the minerali zation is  of  the order o f  
one hundred million years old  and therefore the "percentage 
equilibrium radium"  values of l ess than one hundred p erc ent must  
be  due  to  preferential loss of  rqdium . I t  i s  usually assumed  that 
uranium is  leached  preferentially to radium b ecaus e of i ts greater 
solub i l i ty . However , i f  this  s equence  held  for the samples s tudied , 
the vnlue 0f  the 1 1perc ent <:>.:;e equilibrium r.:d.ium" obtained  would b e  
94 . 
greater than one hundred  p orc cnt . Therefore  i t  is  c oncluded by 
the ?u thor that preferential  leaching of radium has taken place . 
This  c onclusion  is  supported  by the resul ts  ob tained from two 
separate experiments carri ed out by SThRIK ET AL ( 1 95 1 ) to 
inves t ignt? the relat ive  d iffi cul ty of l eaching of uranium and 
radium from uranini te . These  authors showed that when uranini t e  
was l eached  w i th d?st illed  water , or  w i th various c oncentrations 
of  ni tri c ac i d ,  or  w i th sodium carbonate  solutions , the radium was 
l eached  pre ferenti ally w i th respect  to uranium in  all cases . The 
s e cond experiment involved the analysi s  for uranium and radium o f  
the outer- surfac e ,  mi ddle-portion and c entral core  o f  ? b o th intact  
and deformed  uranini te  sampl es . The  intac t samples  showed no 
di fferences  but the deformed samples  showed that radium had been  
preferenti ally removed w i th respe c t  to  uranium . hs WHITTLE has 
shown that the uranini te  s?mples  are slightly w eathered , the 
author ' s  expl?nation of the values of the "p erc entage equilibrium 
radium"  obtained for these  samples appears consistent . Tabl e  III-2  
also shows that uranium samples  in  whi ch the  uranium exists as 
U ( VI ) are of ten  further from equilibrium than those samples  in  
whi ch  the uranium exis ts as U ( IV ) . The low values o f  ' ' perc entage 
equilibrium radium ' '  obtained for such samples , may be due to 
continuous l eaching or  as a result  of insuffi c i ent time  to attain 
equilibrium since  the ini t ial depos i tion  of  the uranium from i ts 
original  primary mineral . Because o f  the c omplexity of  this 
s i tuation , i t  i s  C8nsi dered  by the author , that equilibrium 
s tudies  on s econdary uranium minerals provide  l i t tle  information  
conc erning the history o f  these  minerals . This  is  no t so  w i th 
primary miner?ls where a knowledge o f  this equilibrium i s  most  
informative . 
9 5 .  
DISCUSSION 
The results  pres ented  in Par t I I I  of thi s  the s i s  cl early 
show that the development of the repor ted  t e chnique for the 
d e termination  of the 1 1?wrc ento.ge equilibrium radium " was :tJrim <.:trily 
dependent on the eluc idati on of  the low- energy gamma ray sp e c trum . 
The successful i dent i fi c?tion  o f  most  peaks was obtained as a 
result  o f  effici ent chemi c?l s eparati ons , which  reduced  the 
number  of int erferences  from the various  iso topes  pres ent , 
ac curo. te  pulse-height analys er calibrations , judic i ous use  o f  
s tandard sources  and care ful , syst emati c  evaluation o f  the data o f  
2 1 4  
LEDERER ( 1 969 ) , Thes e  results  showed that the Pb 295 KeV gamma 
ray was the most  sui table  to measure , . d .  t "  
. 
f R 226 as an ln 1 c a  lOll o a ? ? as 
i t  was free  from interferenc e .  Thi s  made i t  possible  to derive  
the relationship b e tween the 1 85 KeV  peak ( u235 and Ra226 ) and 
295 KeV peak in  t erms of the "percentage equilibrium radium" . 
Thi s  method  will  b e  referred t o  in  future as the  "Dire c t  Gamma 
Hethod 1 1  ( D . G . M . ) .  
The advantages of  this  m e thod over  previous methods  are 
thr e e fold . Firs tly , and most  important , only radiation  from 
s p e c i f i c  i s o topes  is  measured whereas i n  previous proc edures , the 
total beta  and total gammn radiation  of all i s o topes  pres ent i s  
measured .  S e condly , the derivation o f  the equilibrium relationship 
shows tho.t the 1 1D . G . H . 1 1 is independent of detec tor  effi c i ency and 
as such is su,erior  to  the previous methods whi ch require  thi s  to  
be  accurat ely known , a determination  whi ch i s  d iffi cult t o  obtain . 
Thi rdly , the "D . G . M . " i s  s impl e to  us e and requires , depending on  
the ac tivi ty o f  the sample , only  fi fteen to  thirty  minu tes 
counting t ime . The main disadvo.ntage is  that it  requires  a Ge ( L i )  
det e c tor , high resolution  pro-ampl i f i er and r easonably sophisti cated 
96 . 
?lec truni c s . 
The use  of  the nn . G . M . 1 7 for determining the  nperc ent ".!ge 
equilibrium radium ' '  of uranium ores from the Buller  Gorge showed 
th?t i n  no  ins t ?nc e were any of  them in  radio?ctive  equ ilibrium . 
The s i gni ficGnce  o f  this  has been d is cussed  and apart from re?
emphas ing that  the  mineral i zation  appears t o  be  o f  Cr?tac eous age 
nnd has undergone slight  weathering , will  not be discussed  further , 
as the origin and his tory o f  the minerali zation i s  outs i de the 
s cope of  this  thes i s . 
I t  is  importan t  to add that the "D . G . M . "  can nlso be  applied  
for  the  quantitative  det srmination  o f  uranium . This simply involves 
obtaining n spec trum of the ur?nium sampl e ,  measurement of the  295 
and 1 85 KeV peaks and the calculation of  the ac tual number  o f  
1 85 KeV gamma rays from u235 as described  earlier  i n  this  s e c tion .  
A plo t o f  the  numb er  o f  counts per  uni t t ime  as  a func t i on o f  
uranium content , obtained e i ther  by chem i cal me thods or  from 
s tandards , nllows a working curve to be constructed  whi ch  is  
appli cable  to  any uranium ore  i rr espec tive  o f  i t s  s tate of  
equilibrium . 
To summ?ris e ,  this  part o f  the thesi s  reports  on the 
i dentifi cation of  gnmm? radiation in the low energy region of the 
spec trum , 30- 360 KeV for naturally- o c curring uranium minerals . To 
the author ' s knowledge , this  is the firs t time  that this  has b een 
suc cessfully achi eved . Reported  also , is  the development nnd 
suc cessful use , of a new metho d for the determination o f  "percentage  
equilibrium rndium11 , an  important  quanti ty in  the s tudy of  
uranium mineral i zation . 
G'ENERAL DISCUSSION 
97 . 
The aims o f  this thesis , as mentioned in  the General 
Introduc tion  were  threefold :  
( 1 )  To develop" a me thod for the analysi s  o f  low conc entrations o f  
yttrium , thorium and rare e ?rths with  the use o f  a l arge quartz-
opti c s  s?ec trograph . 
( 2 )  Tn inves tigate the possible  ass oc iation of  the above  elements , 
and any other elem ents , w i th uranium in  the minerals from the South 
Side  o f  the Buller  River and to s tudy the dis tribution  o f  thes e 
elements in  the weathering s equenc e :  minerals , soils , s tream 
s ediments . From these  results , to examine criti cally the relative  
merits  of  direct  analysis  of  uranium and of  asso c iated  elements in  
s tr eam s ediments , as a geochemi cal  prosp e c ting method  for uranium 
minerali zation . 
( 3 )  To develop a metho d ,  using only gamma radiation from u 235 and 
R 226 a , to  d etermine  the 1 1p ercentage equilibrium radium"  of  uranium 
minerals . 
The resul ts  presented in  Parts I ,  I I  and I I I  of  this  thesi s  
show that the above  aims have lareely been  achi eved . 
The analyt i cal s e ction  in  Part I showed that , by  careful 
s elec tion of conditions , together wi th an e ffi c i ent s eparation  
s cheme , a large quartz-opt i c s  emission spectrograph could b e  
successfully used  t o  analyse low conc entrations of  yttrium , thorium 
and rare earths . The results  obtained for the standard ro cks G- 1 
and W- 1 subs tanti ated  this claim and indicat ed  the ac curacy that 
can be ob tained .  Fresh data for the ?bove elements in  C?hS s yenite  
were  also  provided  and these  agreed  well  wi th the  results o f  
TENiL ?NT and FELLOWS ( 1 967 ) anc? CHii.HP ( 1 96 8 ) , the only other results 
ob tained for thes e  e l ements in  this s tandard rock .  The main dis-
98 . 
advanta3e of  the reported  technique i s  that i t  is  not readily  
appli cabl e as  a rautin8  method for  the rnpid  analysis  o f  yttrium , 
thorium and rare earths in  geologi cal sampl es . This is  due to the 
l imi tation of the dissolution stage in the preparat i on of the 
sample  for the ion-exch?nge column . The solution necessary to 
ensure  separation  on  the resin , a mi xture of  acetic  ac i d  and nitric  
acid , is  an  extremely poor  solvent for  geologi cal samples . However , 
i f  the s eparation stage of  the analytical procedure could be  
improved , this  would then render the  method qui t e  suitable  for 
rapid ,  routine analysi s .  
?lthough the geochemi cal study i n  Part I I  showed  no 
apparent associati on o f  yttrium , thorium and the rare earths wi th 
uranium , the data were , nevertheless , important as they provi ded  new 
evi dence  for the possible  origin of  the Hawks Crag Brec c ia from 
the Paparoa Range . Copper , b eryllium and l ead di d ,  however , show 
good correlations at various stages  down the weathering sequence ;  
o f  these  elements , copper  showed  the  best  c orrelati on in  the 
s tream sediments . This s tudy showed that in this  area  o f  high 
rainfall and rugged  topography , the analysis o f  c opper as a 
"pathfinder" for uranium app eared to  be  a b et ter indi cation o f  the 
known mineral i zation than was the analysi s  of  uranium . Thi s  was 
explained by the lower  solub i l i ty of c opper c ompared w i th uranium . 
However , the use o f  copper alone ns an indi cation of  uranium 
mineral i zat ion was not c ?nsi dered comple tely reliable  becaus e  o f  
unrepresentative  sampling and the presence  o f  di fferent amounts 
of unmineralized  matrix material . This variati on in sampling 
9 9 .  
o ften arose  as a result o f  a l ack o f  f ine  s ediment in  the  main flow 
of  the streams . To overcome these twn problems , ratios  of l ead , 
zinc  and copper  were  taken in an at tempt  t?  minimise  such 
fluctuat i ons . In general the  results obtained from these  r?ti os 
showed similar patterns t o  those  reflected  by the analysi s  o f  
copper alone . I t  i s  cons idered  by the author , however , that 
al though the results appear promising , a more de tailed  s tream-
sediment sampling programme would need  to be carri G d  out b e fore  this  
t echni que could be  considered  completely rel iabl e . ? i th regard to  
d irec t  analysis  o f  uranium in s treGm sediments , this study d i d  
show tha t , except  when samples  w ere taken wi thin thirty to forty 
yards of a reasonably large , active  outcrop of uranium 
mineral i zation , the  analys is  o f  s tream s ediments for uranium gave 
no indi cation  o f  surrounding mineral i z?tion . In  fac t ,  uranium 
anomali es in stream s ediments could only be detected  over distances 
simi lar to  those  for whi ch radiome tric  i nstruments were  useful . 
I t  i s  consi dered  that Part I I  o f  this thesis  has clearly 
shown that , b ecause  of  climat i c  or  topographi cal d ifferences , 
t e chniques whi ch are used  for geochemical ?respec ting o f  uranium 
mineral i zation in  o ther parts o f  the world may not  be  invariably 
applicable  in o ther areas . I t  i s  t o  be  expected  that  the pathfinder 
elements will also vary from one  uranium depos i t  to ano ther and 
i t  is there fore  always nec essary to carry out  ? preliminary 
or i entation survey of each new area . From a knowl edge o f  the 
geology of the qrea , e l ements l ikely to be  associated  w i th the  
mineral be ing sought can be  cho sen . 
Part I I I  o f  thi s thesis  i s  l argely a s tudy o f  the gamma 
L I BRARY 
l. J A CCCV 1 1  .. 1 1 \ /C nC' ITV 
1 00 .  
ray sp ec tra  o f  uranium mineral s , and s hows the  deve lopment  of a 
new  t .; chnique  for  the  de t err.1ina t ion  of "pcr c en t.:"tge equ i l i  bri  urn 
radium ' 1  ( i n  this  thes i s  cF.J.llecJ.  the  1 1Dir e c t  G 'i.mmo. He tho ,J l ' ) ,  whi ch  
w i l l  prov i d e  geolo?i s t s w i th a use ful tool  for  the  s tudy of the  
origin  and h i s t ory of  ur'lnium minerali zation .  Oth er me thods are 
av?i labl e  to  d e t ermine the  nperc entage equ i l ibrium radium" , but  
the  "D . G . tvl . "  ho.s two  m :tin  advcm t o.ges . Firs tly , it  measures  only 
rad i?tion aris ing from the  i s o topes  conc erned , whereas the  
previous me thods  involve  as sump ti ons  concerning  the  o.s s i gnmcnt  of  
radiation to  the  parent  iso top e s . S e c ondly , the  "D . G . N . n  i s  
ind ep endent o f  d e t e c tor  e ff i c i ency and relies only on o. ra t i o  of  
the  numb er  of counts  obtained  from the  1 85KeV and 295KeV gamma rays 
resp e c ti vely and n o t  0n the  absolute  det ermination  of the  number  
o f  be tn  and g;:,mma rc.di .".. t i ? ms emi t t e d .  The 11 c curo.cy  of the  "D . G . M . 1 1  
dep ends only on  the ac curacy  of  the  valu es for  the  de cay 
constants , ?Ra  and ?W ' and on  the  a c curacy of  the  values determined  
for  the  r e sp ec tive gamma ray decay path  PR3 ( 1 85 )  and P0 ( 1 85 ) . 
The ac curacy of the?e  values  i s  cons i dered to  be  ? 2% , whi ch yi el ds 
../cin error of + 5% i n  the  value  for  the  "per c entage equi l ibrium 
radium ' i . The error due  to coun t i ng s tat i s t i c s  can be made almos t 
negl i gibl e by  increasing the  c o unting t ime . A t  the  present  s tage 
of developmen t , the  : 'D . G . M . " cnn be  us ed to  d e t erm ine  the 
i 'p er c ent3.ge equi l ibrium radium 1 1  for  minorals  c ont;:cin ing 0 . 1 %  u3o8 
or grea t er  w i th  ?n accuracy of ? 5% . 
The r esults  from age det erminati ons and the values  obtained  
for the  "perc entage equilibrium ro. c? ium"  sugge s t ed , qui t e s trongly , 
th?t  the  uranium mineral i za tion  has remained  i n  i ts original  s i te 
1 01 . 
of  ?eposition  over 2 period  of  approxim?t ely one hundred  million 
years . These results  do provide information c onc erning the 
h i s tory of the uranium but they do no?  tell  us anything about  i ts 
origin .  ?l though s ome  consi deration of  the origin was made in  
Part II , a fuller  d iscussi on of  thi s  sub j ec t  i s  outside  the 
scope of this  thes i s . 
To summarise , this thesis  has developed  two analytical 
methods , one in the f ield  of  el emental analysi s  nnd the o ther  in  
the  field  of  radiochemistry , whi ch should  find applicat i ons in  
the fields of  analytical chemis try , geochemistry and  geology . The 
cri t i c al evaluation  o f  geochemical prospecting methods , 
dis cussed  in this thesis , should provide  the basis  for the  
development o f  such  techniques for use  in further  uranium 
prosp e c ting in  New Zealand . 
The author considers  that  future studies  in  the urani ferous , 
Buller  Gorge region  should be  c arri ed out w i th the following aims : 
( 1 )  To subs tantiat e  further the val id i ty of  the  use o f  copper  as 
a pathfinder for uranium by a more detailed  and comprehensive  
survey of  the  s treams draining thi s area .  
( 2 ) T o  t e s t  the hypothesis  that uranium was l eached from i ts 
origin  in  the  grani t e  of  the Paparoa Range and redeposi ted  i n  the 
present s i te in  the  Hawks Crag Bre c c ia . Such a study would 
include the analysi s  of the trace-el ement content  of the grani t es 
from ?o th the Paparoa Range and Hawks Crag Breccia  in  con junc tion 
w i th  p e trological investigati ons . 
The resul ts  o f  this  res earch should provide  valuable  
informati on which would  indicate  sui table  areas for  fur ther 
uranium prospecting in  New Zealand . 
1 02 .  
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