U.S.-Australia Cooperative Research: Fluids in Amphibolite-to Granulite-Facies Lode Gold Deposits

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This award will support collaborative research between Dr. Philip E. Brown of the University of Wisconsin-Madison and Dr. David Groves of the Key Centre for Strategic Mineral Deposits of the University of Western Australia. Most available data on the nature and genesis of Archean lode gold mineralization has been gathered on mesothermal deposits. Fluid compositions and the timing of mineralization are reasonably well agreed upon. There is however considerable continuing debate as to the source of the ore components and the fluid. The objective of this collaborative project is to conduct a fluid inclusion study of lode gold deposits of the Yilgarn Craton in western Australia. The area to be studied contains gold deposits hosted in amphibolite-to granulite- facies metavolcanic and metasedimentary rocks. This research will compare these results which are representative of lower crustal levels and therefore less modified, more proximal, ore fluids to data from the better-studied mesothermal deposits. Extending the range of deposits studied through this project will allow the development of genetic models and general understanding of the mechanisms of gold mineralization, and their relationships to late-Archean tectonics. The project represents excellent U.S. and Australian collaboration. Dr. Brown has many years of experience in fluid-inclusion studies involving ore deposits and/or metamorphic terranes and the background in theoretical fluid modeling that will be necessary to interpret the pressure- temperature-composition history of the fluids trapped in inclusions in high-grade metamorphic rocks. The Australian research group has an excellent international reputation, and the documentation of mineralization in the Yilgarn Craton required for the study. In addition to providing useful data on the fluid characteristics and conditions of mineralization, the research has the potential for broader application in interpretation of gold deposition world-wide in Archean terranes and in exploration models for similar gold deposits.