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    Mineral prospecting via biogeochemical signals and surface indicators using hyperspectral remote sensing : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2022) Chakraborty, Rupsa
    Preliminary steps of mineral exploration have traditionally included drilling and other destructive, expensive, and time-consuming techniques. To meet the ever-increasing demand for mineral resources pertaining to the increase in population and technological demand, it is very important to develop environmentally friendly, faster, and cheaper prospecting methods. In this study, we have targeted three known regions of mesothermal gold mineralisation in the South Island, New Zealand to develop hyperspectral remote sensing-based prospect models combined with biogeochemical data. The three study sites have geological similarities around the gold mineralisation including the major pathfinder elements. On the contrary the environmental settings, and other surficial and near-surface processes including the soil and groundwater interactions with the host rock, are vastly different. This led to a wide variation in the physico-chemical properties of the soil cover and the subsequent uptake by the overlying vegetation. The Pinus radiata plantation at the Hyde-Macraes Shear Zone was the first study site to test the feasibility of using biogeochemical responses overlying the gold mineralisation through hyperspectral remote sensing for gold prospecting. Pinus radiata is known to be an accumulator of metals and metalloids with roots reaching as deep as the shear zone beneath it. The data showed a good spatial elemental trend along the shear zone for both the bark and the needle samples although the regression models performed much better with R2CV >0.7 for the bark samples. After confirming the feasibility of utilising the vegetation cover as a medium, the second site in the Rise and Shine Shear Zone was examined to assess the limits of the airborne hyperspectral data over variably exposed soil. The potentially high As anomalies indicating the gold mineralisation were classified coupled with a thorough understanding of the soil cover and its relation to the lithology. The orthogonal total variation component analysis transformed data produced the best-performing models using random forest classification with an accuracy ~50% for the high concentration As zonation. Finally, the third study site in Reefton exhibited a multi-species natural forest overlying the gold mineralisation. Apart from varying elemental responses among the different species the Reefton study area also manifested regions contaminated by previous mining activity which likely impacted the elemental uptake in the overlying vegetation. The regression models performed poorly but the spatial predictions rendered some valid correlations based on ground knowledge from previous studies.
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    The determination of gold in vegetation and its application to specific problems in biogeochemistry : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry in the Dept. of Chemistry and Biochemistry at Massey University
    (Massey University, 1985) Naidu, Shamila Devi
    Studies were carried out to devise a method for determining nanogram quantities of gold in vegetation. The samples (0.5g) were digested with fuming nitric acid over a water bath. After addition of hydrochloric acid, the gold was extracted into a small volume (1 ml) of methylisobutyl ketone (MIBK). The organic layer was back-extracted with distilled water to remove iron interference and gold in the MIBK was determined by an electro­ thermal atomization technique with graphite furnace atomic absorption spectrometry. The optimum instrumental conditions for drying, ashing and atomization of gold were as follows: drying, 4.5V, 20 secs; ashing 6V, 20 secs; atomization 8V, 4 secs. A furnace cooling time of 50 sec. was allowed to attain high precision of signal heights. Tests on the efficiency of the method developed, showed high precision, good accuracy with the limit of detection of 1 ng/g. Recovery studies on the known amounts of gold added to vegetation, showed an average recovery of 99.4%. On the basis of these results, the method developed and outlined can be used on a routine basis for analysis of vegetation, soils and rocks. Biogeochemical and geochemical studies were carried out at 4 areas having different geological, topographical and climatic conditions. These were: Waihi, New Zealand, Seruwila in Sri Lanka, the Serbomaced­onian massif in Northern Greece, and Yathkyed Lake in Arctic Canada. At each of these study areas, different plant species were collected and analyzed together with the soil for biogeochemical studies. Investigations were carried out to determine whether the concent­ration of gold in plants could be used to predict the concentration of this element in the soil and also whether any other elements present could be used as a pathfinder for gold. The results of biogeochemistry showed good correlation existing between gold in plant and gold in soil provided the gold concentration in the substrate was sufficiently high. Arsenic was found to be a possible pathfinder element for gold, particularly when the latter is present with chalcophile elements. The range of plant species analyzed in this study suggest that gold uptake is not restricted to any particular plant species or to plants with deep rooting system provided the substrate is auriferous.
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    The feasibility of biogeochemical and geobotanical prospecting at Spargoville, Western Australia : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry at Massey University
    (Massey University, 1972) Nielsen, Jeppe Søndergaard
    Several plant species together with their associated soils from Spargoville, Western Australia, were analysed for chromium, copper, cobalt, manganese, nickel and zinc by atonic absorption spectrophotometry. Particular reference was given to nickel and copper to evaluate the usefulness of plant analysis for biogeochemical prospecting. The nickel content in the soils gave plateaus of high values over ultrabasic rock types whereas the copper levels in the soils gave peaks over areas of mineralization at ultrabasic contacts. Consideration of the plant data showed that each species accumulated different amounts of the above elements, and that they distributed these trace elements in different ways between their leaves and twigs, or between their bark and wood. Relationships between nickel and copper concentrations in the plants and in the soils were evaluated by computing correlation coefficients; promising statistical results were checked graphically. The nickel and copper concentrations in the bark of Eucalyptus lesouefii most accurately depicted the concentrations of these metals in the soils. It was also found that the barks of Eucalyptus lesouefli, Eucalyptus longicornis and Eucalyptus torquata could be used together for prospecting purposes. In the cases where the soil-plant relationship was either very good or very poor, it seemed to make no difference whether parametric or non-parametrie correlation coefficients were used. When the relationship was intermediate between these extremes, however, the non-parametric statistic was superior. A geobotanical study was also carried out tn determine whether the distributions of the plant species was related to the geolory. Dodonaea lobulata. Pittosporum phillyraeoides and Trymaliun ledifolium were found to grow only on ultrabasic rook types, and the outer, black bark of E. lesouefii growing in mineralized ground was observed to grow to a greater height on the trunk than occurred when this species grew in non-raineralized soils. when discriminant analysis was applied to plant mapping data, the different rock types could be effectively discriminated using the relative abundances of as few as one-third of the species present. These results were markedly superior to those obtained when discriminant analysis was applied to some biogeochemical data.
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    Biogeochemical studies in South East Asia by use of herbarium material : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry at Massey University
    (Massey University, 1977) Wither, Ewan David
    A biogeochemical survey of Indonesia was undertaken analyzing herbarium samples by atomic absorption. (Indonesia was chosen because it has been well surveyed botanically, but poorly surveyed geologically.) Background concentrations of copper, nickel and zinc were determined using various species, predominantly members of the families Flacourtiaceae and Violaceae. Rinorea bengalensis (wall) O.K. (Violac.) was discovered as a hyperaccumulator of nickel (Brooks et al., 1977) and this led to an in depth study of R. bengalensis and other species of the genus. From this study two areas of doubtful geology were predicted as containing ultrabasic rocks, R. javanica (B1.) O.K. was shown to be a hyperaccumulator of nickel and R. albersii Engl. was found to yield a very high cobalt/nickel concentration ratio. Three hyperaccumulators of nickel were discovered after analysis of a selection of herbarium samples collected on Obi Island by Dr. E. de Vogel. (They were: Myristica laurifolia Spruce ex DC var. bifurcata (Myrist.); Planchonella oxyedra Dubard (Sapotac.); Trichcspermum kjellbergii Burret (Tiliac.).) Ambon Island was predicted as consisting of ultrabasic substrates. Plants collected from Salajar Island were shown to contain anomalously high concentrations of copper possibly due to anomalous copper concentrations in the soil.
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    Aspects of radiobiogeochemistry : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University
    (Massey University, 1970) Whitehead, Neil Evan
    Section I: A routine assay for uranium was instituted, and a fluorimeter suitable for the assay designed and constructed. A new method of fusion-pellet manufacture is described. The optimum conditions for the assay were determined. The calibration curve is linear up to about three micrograms of uranium; the lowest limit of detection is about twenty nanograms (about 0.10 microgram/g of sample). Routine alpha and beta counting of samples was developed. Section II: The forms of naturally occurring data distributions are discussed, and customary methods of examining these noted, together with their defects. A versatile computer programme was developed to determine the form of natural distributions, and to calculate correlation coefficients and their significances. Section III: An orientation survey of a known mineralised area in the Buller Gorge of New Zealand showed that C.australis, N.fusca, Q.acutifolia, and W.racemosa are suitable for biogeochemical prospecting for uranium. Analysis figures were more nearly log-normally distributed than normally distributed, and multiple distributions were often present. Alpha counts of plant material also proved suitable as indicators of the amount of uranium in the soil, as did the amount of iron in the leaves. Section IV: Aquatic bryophytes from streams draining mineralised areas were analysed and the results found to be indicative of the presence or otherwise of uranium in the various catchment areas. Even better was the use of specially prepared peat, allowed to soak in the stream water. The accumulation factor for uranium, from stream water, was about ten thousand. Section V: The gamma-ray spectra of plants and soils were carefully characterised by solvent extraction, and ion-exchange techniques. Plants were found to absorb radium and uranium and lead, but not thorium. B.procerum, and M.berteroana, however absorbed both thorium and actinium. Calculation showed that most of the alpha particles emitted by the samples studied were from 238U. Section VI: Extraction and characterisation of uranium complexes in C.australis leaves showed the presence of a protein-uranium complex, and an RNA-uranium complex. The latter is at least partially an artefact of the extraction technique, and examination of fresh material showed that more than half the uranium was bound to cell wall proteins. No other types of compound besides protein and nucleic acids possessed measurable binding capacity for uranium.