Massey Documents by Type
Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294
Browse
6 results
Search Results
Item 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, RupsaPreliminary 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.Item Gold ore characterisation, mercury use & value chains analysis of the artisanal & small-scale gold mining sector of Wau, Morobe Province, Papua New Guinea : thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Earth Science, Massey University, Palmerston North, New Zealand. EMBARGO PENDING.(Massey University, 2018) Lucas Ponyalou, Olive KimaleWau, in the Morobe Province of Papua New Guinea (PNG), is a rural township with a growing artisanal and small-scale gold mining (ASGM) sector working with mercury (Hg). It was once the centre of gold mining activities for European prospectors and companies between the 1930s and the late 1980s. Mercury amalgamation is used globally for gold extraction in the ASGM industry but was banned by the Minamata Convention in 2013 due to its toxicity to human beings. Miners and their families in Wau are exposed to Hg contamination during the amalgamation and retorting of the Au-Hg amalgam. The Mineral Resources Authority (MRA) regulates the PNG mining industry using the Mining Act 1992 and the Mining Safety Act 1997. Gravity concentration and mercury amalgamation are gold recovery techniques used in the ASGM sector of Wau. Cyanidation, a common technique for processing free-milling Au and AuAg grains less than 0.2 mm in size, is largely used in the corporate mining sector but has not been used within the ASGM sector of PNG. The purpose of this research is to halt the use of mercury in Wau through an improved understanding of its gold ore characteristics. Hence, a study into the economic value chains system, gold grade distribution and ore characterisation was conducted on nine selected ASGM sites located throughout the Namie and Kaindi prospects in Wau. Although modestly profitable, all sites excluded the fundamental practices of grade control and ore characterisation, which are vital to the mining value chain. Comminution, also an important step for liberating gold, was only practised at one mine site. The average gold grades of the nine sites ranged from 0.06 to 5.45 mg/kg Au with the primary mineralization of Kaindi containing higher gold grades than the secondary deposits of Namie. The main gold minerals observed in the scanning electron microscope (SEM) include native Au and electrum AuAg with a predominant grain size of less than 0.07 mm. Mercury amalgamation is only useful on gold crystals with a grain size of 0.07-1.5 mm. Hylander et al. (2007) discovered that mercury will not efficiently amalgamate gold particles less than 0.07 mm. In addition, mercury amalgamation is only useful on free-milling, liberated native gold but will not recover gold that is attached to or encapsulated within other minerals. This suggests that the Wau miners are losing fine-grained gold less than 0.07 mm or any gold that is insufficiently liberated as waste or tailings. This was confirmed in the tailings sample from Site 1 which had numerous fine-grained Au measuring less than 0.07 mm. Thus, cyanidation would be the appropriate technique to process the gold mineral type (Au and AuAg) and gold grain size observed in most sites in Wau. Cyanidation after comminution are steps that must be included in the Wau ASGM value chain in order to optimize the recovery of the dominantly fine-grained Au.Item Phytoextraction of palladium and gold from Broken Hill gossan : a thesis presented in partial fulfilment of the requirements for the degree of Master of Environmental Management at Massey University, Manawatū, New Zealand(Massey University, 2015) Aquan, Hendra MichaelThe research in this thesis was conducted as part of the Phytocat Project; a collaborative effort between University of York (UK), Yale University (USA), University of British Columbia (Canada) and Massey. The aim of the Phytocat project was to yield a target concentration of 1,000 μg g-1 palladium in plants, so that the plants could be used as catalysts in chemical reactions. This thesis focussed on the phytoextraction of palladium from Broken Hill gossan, a platinum group element-rich rock collected from Australia. The gossan and surrounding soil has an elevated concentration of iron, copper, nickel and precious metals. Samples of species native to the Broken Hill gossan and the associated rhizosphere soil were collected from the field and analysed to screen natural levels of metal accumulation in plants of the area. Five native plant species were identified: Solanum centrale (bush tomato), Brassica sp, Ptilotus obovatus (silver tail), Sclerolaena lanicuspis (copper burr) and Tetragonia moorei (annual spinach). The copper concentration in all plant tissues had a strong relationship with copper in soil. An individual Solanum centrale plant recorded a copper concentration of 277 μg g-1 from soil with concentration of 796 μg g-1 suggesting that this species is a copper tolerant plant from Broken Hill. No anomalous levels of nickel were recorded in plant tissues. The average palladium concentration measured in the rhizosphere soil was 28.8 ng g-1. However, the five native plant species could not concentrate palladium in their biomass. Solubility of palladium was suggested to be poor in natural environment. To study the potential of induced hyperaccumulation to increase the palladium uptake in plants, 60 kg of gossan from the field was collected, crushed and used as a plant growth medium for controlled plant trials at Massey University. Two types of gossan rock were collected, classified by the dominant form of iron oxide mineral in the rock structure: goethite dominated (soil A) and hematite dominated (soil B). The goethite material (A) has a higher total and soluble metals concentration than the hematite mateiral. Initial trials focused on Brassica juncea. However, despite germinating, this plant grew poorly on both types of gossan. Insifficient biomass was available to induce uptake of metals, and therefore only the natural levels of metal uptake in the poorly developed plants was quantified. Total harvested aerial biomass was 5.1 g from 39 pots each containing 800 g of gossan. The mean metal concentrations in plants grown in the two soils was not significantly different (p< 0.05). The concentration of palladium in the plant biomass ranged from 2,130 to 2,909 ng g-1. This study proposed that 1,000 ng palladium g-1 is a suitable hyperaccumulation threshold level and therefore B. juncea on the gossan was able to hyperaccumulate palladium. The average copper concentration in the biomass was 759 μg g-1 and it is likely that high copper solubility in the growth substrate affected plant growth performance. A second trial used Cannabis sativa (Hemp) due to recorded metal tolerance of this species. Pots were re-seeded with C. sativa. Hemp germinated and grew well relative to B. juncea. Potassium cyanide solution (50 mL of 8 g L-1) was applied to each pot at the point of maximum biomass to induce the solubility of precious metals and therefore to induce hyperaccumulation. Significant metal concentration values after KCN treatment were as follows: Copper (6,726 μg g-1) > nickel (184 μg g-1) > palladium (62 μg g-1) > gold (9 μg g-1). Following established criteria values, copper, palladium, and gold hyperaccumulation was observed. The mean metal concentrations of copper, nickel, and palladium from Hemp grown in soil B were greater compared to Hemp grown in soil A and control plants (p < 0.05). However, gold concentration between Hemp A and Hemp B was not different significantly (p > 0.05). These results were anomalous compared to the recorded total and soluble metal concentration of the two rocks. This study concluded that total metal in soil is not an indication for metal concentration in plant tissues. Accumulated metal in plants is a function of the concentration of soluble metal in soil that can be readily absorbed by plants. Different characteristics of the substrate (in this case iron oxide) may influence metal uptake in plants. Iron oxide minerals were identified as plant competitors for soluble metals in soil solution. In this case, goethite adsorbs more soluble metal ions than hematite and therefore plants grown on the goethite substrate accumulated less metal relative to the hematite soil despite the goethite rocks having a greater total and soluble metal concentration. Metal tolerance was also highlighted as an important factor in the induced accumulation of palladium. Palladium is often associated with copper in soils and tolerance to copper is a key factor. In this work, Brassica juncea was proven less tolerant to copper than C. sativa. The target of 1000 μg g-1 palladium in plants has not yet been reached but the Broken Hill gossan is highlighted as a useful substrate for ongoing work. There is good potential to test the native copper tolerant species Solanum centrale, for induced metal uptake in the future.Item A systematic search for the global minimum structures of Cs, Sn and Au clusters and corresponding electronic properties : a thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Massey University, Albany, New Zealand(Massey University, 2007) Assadollahzadeh, BehnamClusters of atoms or molecules form the building blocks of nanoscience and are regarded as a new type of material, as they constitute a bridge between microscopic and macroscopic forms of matter. The experimental and quantum theoretical study of structures, chemical and physical properties and reactivities of nanoclusters represents an innovative and very active field of research, which has resulted in a wide range of applications. Independent of the model used to describe the bonding in these clusters, one of the prime objectives is to find the geometrical arrangement of the atoms or molecules, for a given cluster size, which corresponds to the lowest energy on the potential energy hyper-surface, the global minimum. In order to find such an arrangement, a density functional theory based genetic algorithm code, which is rooted in the Darwinian evolution concept of the survival of the fittest, is developed and utilized to systematically search for the global minimum isomers of homo-nuclear clusters consisting of up to twenty atoms of cesium, tin, gold and of nine atoms of copper. The performance of this algorithm is excellent as numerous energetically lower-lying cluster isomers (compared to those reported in the literature) are found. Extensive valence basis sets together with energy-consistent scalar-relativistic pseudopotentials are employed to optimize the geometry of these clusters and to calculate their electronic properties accurately at the density functional level of theory. Moreover, in collaboration with the Technische Universit??t Darmstadt, the mean static polarizability of tin clusters are measured by a beam deflection method. The qualitative agreement between measured and calculated dipole moments and static electric dipole polarizabilities of tin clusters up to twenty atoms is satisfactory, thus confirming the accuracy of the theoretical models used in this work. Furthermore, the performance of density functional theory in the field of metallophilicity is investigated for dimeric and trimeric [X-M-PH3] compounds (X = Cl, Br, I; M = Cu, Ag, Au) and it is found that the metallophilicity decreases down the group 11 elements of the periodic table of elements.Item The Induced Accumulation Of Gold In The Plants Brassica juncea, Berkheya coddii and Chicory(Massey University., 2001-09-01) Lamb, A. E.; Anderson, C. W. N.; Haverkamp, R. G.In this study the growth stubstrate of the plants Brassica juncea, Berkheya coddii and chicory were amended with thiocyanate and cyanide solutions to induce uptake and the gold concentrations in the different organs determined. Both species showed maximum uptake with cyanide amendment although thiocyanate also induced hyperaccumulation. Gold concentrations ranged from negligible in the leaves of B. coddii amended with thiocyanate, to 326 mg Au/kg dried biomass in the leaves of B. juncea amended with cyanide. The chemical additives KI, KBr, NaS2O3 were also used with the B. juncea and chicory. The results showed varying degrees of hyperaccumulation with all chemical treatments. Cyanide again gave the best results with 164 mg Au/kg dried biomass measured in the chicory plant. NaS2O3, KI and NaSCN gave maximum results of 51, 41 and 31 mg Au/kg dried biomass respectively. This technology has potential application in the economic recovery of metals.Item Robust SERS Platforms Based on Annealed Gold Nanostructures Formed on Ultrafine Glass Substrates for Various (Bio)Applications(MDPI (Basel, Switzerland), 2019-06) Zhou L; Poggesi S; Casari Bariani G; Mittapalli R; Adam P-M; Manzano M; Ionescu REIn this study, stable gold nanoparticles (AuNPs) are fabricated for the first time on commercial ultrafine glass coverslips coated with gold thin layers (2 nm, 4 nm, 6 nm, and 8 nm) at 25 °C and annealed at high temperatures (350 °C, 450 °C, and 550 °C) on a hot plate for different periods of time. Such gold nanostructured coverslips were systematically tested via surface enhanced Raman spectroscopy (SERS) to identify their spectral performances in the presence of different concentrations of a model molecule, namely 1,2-bis-(4-pyridyl)-ethene (BPE). By using these SERS platforms, it is possible to detect BPE traces (10-12 M) in aqueous solutions in 120 s. The stability of SERS spectra over five weeks of thiol-DNA probe (2 µL) deposited on gold nano-structured coverslip is also reported.