163-G 4.2

Magmatic and hydrothermal processes in the Andean Cu-Au and Sn-Ag ore belts of NW Argentina

The Cenozoic central Andes host orogen-parallel belts of magmatic-related ore deposits with contrasting metal associations (Fe, Cu-Au, vs. polymetallic, Sn-Ag). This project will investigate the role of magmas vs. hydrothermal fluids in metal transport and metallogenesis. There a close linkages to projects G3.5 and G4.1. Besides the potential role of magma processes (differentiation, fluid saturation), other important factors to be studied are the roles of local basement composition and deformation for the metal enrichment, transport, and deposition (faults and shear zones – link to project 10). Both belts are located in an E-W region of 70-km width, and the mineralization and magmatism belong to the main metallogenic epoch in the S central Andes (12-15 Ma), so the geodynamic scenario can be considered invariable. We hypothesize that the different metal associations are controlled by different magma compositions, which depend on source characteristics in addition to the conditions of magma genesis and differentiation, especially oxygen fugacity and volatile contents. To test the roles of magma composition and hydrothermal fluids, the PhD candidate will combine standard geochemistry and petrology of ore and wall rocks with fluid-inclusion studies, melt inclusions and ore minerals with SIMS ion probe analysis, Raman spectroscopy, LA-ICPMS, IR microthermometry, and stable gas isotopes.