Research
I am conducting research that combines economic geology, metamorphic and igneous petrology, and structural geology to study metallogenic processes. I am investigating a range of mid- to deep-crustal processes that influence metal distribution and mobility including:
- sulfide melt immiscibility in magmatic mixing zones at the base of arcs (MASH zones) and its role in ore genesis;
- the P-T-t-D window(s) for metamorphic generation of sulfur-rich hydrothermal fluids; [link to new research page,
- the behaviour of metals during silicate anatexis; and
- sulfide partial melting during metamorphism.
An important aim is to link the results of these studies with tectonic models for the genesis of felsic-intermediate magma-related Cu-Au deposits (relates to 1 and 3) and orogenic gold deposits (relates to 2).
Research Projects
Metallogeny of the lower crust
Dr A. Tomkins
Funding for 2006: $128,264 (Monash Fellowship scheme)
With increasing depth in the Earth’s crust, temperature and pressure rise and rocks become progressively more metamorphosed. Most mineral resources from near the Earth’s surface, however in many cases, metals are thought to have come from deep in the crust. During metamorphism in the lower crust some rocks melt and these melts can transport metals upward to ultimately form ore deposits. At slightly cooler temperatures, metamorphism leads to liberation of fluids with the capacity to dissolve metls and transport them into the upper curst. By conducting experiments and comparing the results with natural rocks, this project will investigate the effects of metamorphism on metal distribution in the lower crust.
Potential Honours Projects for 2008
- Sulfide Melting at the Cannington Ag-Zn-Pb Deposit? (Hons/Masters)
- Meteorites of the Mundi Mundi Plain. (Hons)
- Metamorphism of the Menninie Dam Zn-Pb deposit. (Hons)
- Timing of Au deposition at the Griffin’s Find deposit. (Hons/Masters)
- Pressure constraints on metamorphic sulfide melting. (Hons/Masters)
- Hydrothermal mobility of Ti. (Hons/Masters)
- Genesis of the Valhalla uranium deposit, Mt Isa Inlier. (Hons/Masters)
Potential PhD Projects
Role of an Archean basement in genesis of upper crustal gold deposits.
Dr Andy Tomkins and Assoc Prof Roberto Weinberg.
Understanding source region processes is one of the most challenging frontiers of research facing ore geologists. This project will involve fieldwork in China, at a location where Mesozoic felsic magmas (with associated gold systems) intrude Archean gneisses, to address this issue. The will aim to be use mineralogical and geochemical tracers to investigate links between these Archean-aged possible source regions and the Mesozoic granites and ore deposits, and to compare the proportions of metal contribution from the mantle and crust.
Genetic Links Between Reduced U-Ti-P-Zr-REE and Oxidised IOCG Ore-Forming Systems?
Dr Andy Tomkins and Assoc Prof Roberto Weinberg
The Mt Isa Inlier in northwest Queensland, Australia, is endowed with two distinct intrusion-related ore-forming systems. One of these is the well-known iron-oxide copper-gold (IOCG) style of deposits, which are associated with A-type granite intrusions. The other has been the subject of little research to date and consists of numerous small occurrences of refractory uranium mineralisation (U is mainly contained in titanium oxides) with associated enrichments of immobile elements such as Zr, Ti, REE. The association with Ti oxides means that this mineralisation style is comparatively reduced, relative to the IOCG deposits. This second style of mineralisation is also spatially related to a different generation of radiogenically hot A-type granitic intrusions and a genetic link is suspected. This project will initially focus on the genesis of the reduced uranium deposits, ultimately aiming to investigate whether the metallogenic potential of A-type magmas might be controlled by REDOX processes, thereby possibly establishing a genetic link between these two very different mineralisation styles.
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