Hydrothermal fluid evolution in the Escondida porphyry copper deposit, northern Chile: evidence from SEM-CL imaging of quartz veins and LA-ICP-MS of fluid inclusions

The origin of hypogene alteration and mineralization features in the Escondida porphyry Cu deposit resulted from intense overprinting related to three main hydrothermal stages. beginning each stage is recorded by deposition bright quartz crystals on vein walls that precipitated high-temperature fluids. In deepest zones deposit, earliest started with exsolution intermediate-density fluids, which transported high concentrations Cu, whereas Mo was not detected. However, shallow zones, early began depressurization unmixing generated both a hypersaline vapour-rich fluid phase, producing an important geochemical segregation between phases. transitional also circulation fluids but never experienced unmixing. These highest deposit; however, displays lower relative stage. late associated fluids; were below detection limits most analysed During evolution stages, gradual cooling, promoted precipitation euhedral zoned overgrew high-luminescence generations. Sometimes, sulfide minerals display crystal boundaries quartz, suggesting during these latest events detected are linked cooler low-salinity dark sulfides along microfractures interstitial spaces developed earlier