Postgraduate Profiles

Stefano Caruso

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Thesis: Geological controls on the fractionation of multiple sulfur isotopes in Archean mineral systems.

Sulfides play a key role in the formation of numerous world-class mineral systems, including gold, nickel, copper and the platinum group elements. It is known that S is a ligand that complexes, transports and concentrates gold in hydrothermal fluids. Similarly, base metals such as nickel, cobalt, copper, zinc, arsenic and lead - due to their high chalcophile nature in S-saturated magmatic and hydrothermal systems - may be concentrated in sulfides, particularly pyrite.

Although the genetic association between S and metal enrichment is well established, it is generally difficult to fingerprint and spatially localize the sulfur and metal sources that play a role in ore genesis. In fact, in any given setting S and other trace metals may occur in a wide range of stratigraphic intervals and/or geological units. However, the specific reservoir implicated in the ore-forming process may be very localized. Therefore, the ability to quickly and reliably map different S and trace metal reservoirs in terms of their metal ratios and isotopic signatures would impact on targeting criteria at the deposit, camp and regional scale, in brownfield and greenfield terranes.

Numerous studies have looked at the sulfur isotopic composition of sulfide-bearing units in a wide range of country rocks and gold mineralized environments in a wide range of Precambrian terranes worldwide. However, most of these studies have only characterized the 34S signature of these S reservoirs, which in itself is not a robust discriminating isotopic system, open to resetting during alteration and metamorphic processes. Conversely, this study aims at characterising the multiple S isotopic signature (Δ33S and Δ36S) of S reservoirs and mineralized occurrences in selected Precambrian terranes of Western Australia.

Why my research is important

Multiple S isotopes are robust and provide an indelible fingerprint of S and metal reservoirs in the Archean. Therefore, the goal is to generate a multiple sulfide isotope map of Western Australia and provide explorers with a reliable tool to discriminate S and metal sources and direct their exploration efforts towards prospective environments.

In nickel systems, recent multiple sulfur isotopic data provide the first step in identifying district- and camp-scale control on komatiite-hosted Ni-Cu-(PGE) deposits (Fiorentini et al., 2012). Similarly, the proposed study addresses gold explorers to generate new multiple S isotopic and trace element maps of key Western Australian Precambrian terranes to enhance their predictive capability to target gold and base metal mineralization. The new data will not only provide explorers with a deeper understanding of gold and base ore forming processes in a wide range of environments, but – given the spatial nature of the dataset - will also help identify areas of enhanced prospectivity that may have been overlooked in the past. Existing and new sulfide samples (particularly pyrite) provided by GSWA will be analysed for Δ33S and Δ36S concentrations using state of the art ion probe technology available at The University of Western Australia. This technology generates quick and inexpensive data of unprecedented accuracy and precision.

Funding

Feb 2015

Aug 2018

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