Assoc Prof. Andy Tomkins - Honours Projects

Variation in gold content of arsenopyrite at the Fosterville gold deposit, Victoria

Supervisors: Andy Tomkins, Chris Voisey, Joel Brugger
Field of study: Economic Geology
Preferred Program: Honours

Much of the gold at Victoria’s largest currently operating gold mine occurs in arsenopyrite. Interestingly, the mineralization style in this deposit varies considerably with depth: in the upper part gold is mainly hosted in arsenopyrite, then deeper down stibnite appears and there is some visible gold, then below that there is very high-grade visible gold and less stibnite. Gold occurs in arsenopyrite through the full depth range. Mining is now starting to expand into the nearby Robin’s Hill deposit and there is not much known about gold in arsenopyrite there. This project will conduct a detailed program of sample collection, petrographic evaluation and laser ablation ICP-MS analysis of arsenopyrite through the full depth range of the Fosterville deposit and compare with the arsenopyrite at Robin’s Hill in order to better predict the distribution of gold in both deposits.

Determining the age of undated impact structures in Australia

Supervisors: Andy Tomkins
Field of study: Planetary Science
Preferred Program: Honours

There are five meteorite impact craters in Australia that are undated but could plausibly have been generated in the mid-Ordovician period. The mid-Ordovician was a time characterised by unusually high meteorite impact rates, a unique period in at least the last 550 million years and probably much more. This project will visit one or more of these five Australian impact craters to collect samples for geochronology. The samples will be characterised prior to mineral separation work and then geochronology will be conducted on mineral separates. This work will help determine whether Australia bears several scars from the Ordovician impact spike (one is known already).

Alteration Products of Beryl as Indicators for the Evolution of Rare Metal Pegmatites

Pegmatites often host economic concentrations of incompatible ‘critical metals’ like Li, Be, Rb, Nb, Ta, Sn and the REEs. However, the susceptibilities of pegmatites to hydrothermal overprinting make them complex and challenging to decipher in terms of their magmatic and hydrothermal evolution and how these influence ore deposit and exploration models. This project will conduct detailed analysis (i.e., via SEM/EDS, EPMA, LA-ICP-MS and Raman spectroscopy) of beryl phenocrysts sampled from pegmatites of the Mt. Isa inlier. These beryls are unusual in that they are: 1) heavily altered by magmatic and meteoric fluids; 2) replaced by a wide array of secondary Be-bearing and Be-barren minerals; 3) highly variable in composition, despite existing within the same outcrop, and; 4) hosts of circular granitic ‘cores’ of quartz, feldspar, tourmaline and mica. Their detailed textural and geochemical analysis is thus expected to provide new information as to how the pegmatites at Mt. Isa were emplaced and altered, which can in turn be used to help elucidate the complex histories of rare metal-bearing pegmatites globally in such a way that significantly furthers critical metal exploration.

For further information, contact Andy Tomkins