Re-Os Geochemistry to Test Recurrent Fluid Flow in the Crust

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India is the next frontier for partnerships in global resource discovery and management. Exploration for mineral resources in central India urgently needs broad application of modern geologic understanding. Specifically, the age of the rocks that host ore minerals, and the timing of introduction of economically important minerals are very poorly constrained. Age relationships are the foundation for interpretation of the geologic record. The team builds on preliminary work that has shown, for example, that the introduction of gold ore was nearly two billion years later than previously assumed. This realization demands new models for ore formation in central India - models that suggest Au formed during breakup of the last major supercontinent, Pangea. The investigators will concentrate on a study area in central India, roughly mid-way between Mumbai and Kolkata, which straddles a major geologic lineament that cuts across the Indian subcontinent. This lineament, the Central Indian Tectonic Zone (CITZ), has been active for more than two billion years, and continues to generate earthquakes today. Because ore deposition is tied to movement of hot fluids in the Earth's crust, dating the ore minerals also dates fluid movement. This age control will help our understanding of the full geologic history of the CITZ with implications for its on-going seismic activity. The project brings together a unique multi-disciplinary team with complementary skills. Two US geoscientists and a PhD student with advanced understanding of tectonics and ore-forming processes will team with two Indian geoscientists and an Indian student with solid knowledge of the regional geology. The unique tool underpinning this project is rhenium-osmium (Re-Os) geochemistry, as developed for application to mineral exploration and tectonic reconstructions by the AIRIE Program at Colorado State University. These two rare elements comprise a radioactive pair, as an isotope of Re decays to a specific isotope of Os with a half-life nearly ten times the age of the earth. Both elements are concentrated in the ore-forming environment, and thus provide a mechanism for dating precious metal-sulfide ore deposits. In addition, the isotopic composition of Os serves as a tracer, revealing the primary source of the metals in the earth?s crust or upper mantle. The Re-Os system offers a new window into the tectonic causes and timing of fluid movement in the earth?s crust. Historically, those working in ore geology have looked to tectonics for understanding of ore-forming processes. In the proposed reverse approach, the team will use the evidence from the ores to understand the tectonic processes. The project thus opens a new approach to the broad field of tectonics, while simultaneously providing the geochronologic framework for the next century of sustainable mineral development ? a critical base for the burgeoning global economy.