Petrochemistry in the Exploration for Volcanogenic Massive Sulphide Deposits

Mining Rocks! CIM Toronto 2005
Abstract The application of igneous lithogeochemistry (petrochemistry) combined with stratigraphy and geological mapping can be useful in delineating prospective volcanogenic massive sulphide (VMS) “belts” at the 1:50000 to 1:250000 scale. Most VMS belts from the Archean to Phanerozoic are associated with extensional geodynamic regimes (e.g., arc rifts, back-arc basins, intracontinental-rifts) and evidence for high temperature mafic (e.g., boninites, MORB, low-Ti arc tholeiites) and/or felsic magmatism (e.g., FIII or FII rhyolites, HFSE-REE-enriched rhyolites). In areas underlain by predominantly mafic basement (e.g., mafic, bimodal mafic, and mafic-siliclastic VMS deposit environments) deposits often occur on transitions between high temperature arc magmatism (e.g., boninite, low-Ti tholeiite) and magmatism indicative of the intiation of a back-arc basin (e.g., MORB), with or without high temperature felsic volcanic rocks. In areas underlain by continental crust (e.g., bimodal felsic, bimodal siliciclastic VMS environments) VMS deposits often occur on transitions between calc-alkalic felsic arc magmatism, and rocks indicative of back-arc basin magmatism, including: weakly alkaline (HFSE-REE-enriched) felsic rocks, which in turn are often interlayered or overlain by lithospheric derived alkalic basalts and/or MORB. By combining lithogeochemistry with regional mapping and stratigraphy, this technique has the potential to outline areas for more detailed grassroots exploration and prospecting.
Keywords: Lithogeochemistry, rifting, VMS deposits, Exploration geochemistry
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