85-9 Sourcing Cu and REE for Global Energy Needs: Deposit Variability and Mineralization Drivers in Chilean Iron Oxide-Copper-Gold Systems

Session: The Power of Hard Rocks: Driving the Energy Transition and Serving Society

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As demand for energy continues to grow and societies look for more sustainable solutions, the International Energy Agency predicts the need for raw natural materials including Cu and rare earth elements (REE) will increase by 17% and 35% respectively by 2030. Iron oxide-copper–gold (IOCG) deposits are rich sources of Cu and by-product REE, however exploration for new orebodies is complicated by debate regarding their definition, classification, and generation. Although the characteristics and style of these deposits are highly variable, a substantial body of petrological and geochemical work is bringing their genetic mechanisms into focus. Here we highlight recent work focused on IOCGs in the Punta del Cobre and Mantoverde districts of northern Chile. Mineralization is spatially and temporally associated with regional hydrothermal alteration, the Atacama fault system (AFS), and Early Cretaceous magmatism. Lithologically controlled Punta del Cobre deposits are primarily hosted within a mixed volcanic-sedimentary sequence on sinistral transpressional structures related to the AFS. Sodic-calcic alteration occurred between ~122–114 Ma with additional hydrothermal systems operating until ~95 Ma. Magnetite- and hematite-dominant styles of mineralization were produced by this system at different stratigraphic levels, with 115.7 ± 1.2 Ma garnet U-Pb ages and ∼113–114 Ma sulfide Re-Os ages at La Farola indicating economic mineralization occurred within a 3-million-year timeframe. Although oxygen isotope ratios in garnet and calcite indicate mineralizing hydrothermal fluids were magmatically derived, specific genetic relationships with causative plutons and the magmatic processes involved in the formation of IOCG ores are enigmatic. Zircon U-Pb and trace element analyses on intrusive rocks in the Mantoverde district illustrate magmatism evolved from an early reduced, water-poor composition to a porphyry-like oxidized, water-rich composition. The transition from water-poor to water-rich at ~119 Ma temporally coincides with copper mineralization at the Mantoverde deposit, suggesting the change in conditions facilitated the transport of Cu and S. Shifts in magma composition further correlate to the regional tectonic shift from primarily sinistral strike-slip motion to more orthogonal convergence, which may have resulted in a change from rapid transcrustal melt migration with low water accumulations to multi-stage stagnant magma chambers with increased water concentrations. These results highlight the need for integrated petrological, geochemical, and structural studies to unravel the geologic processes responsible for economic Cu and REE mineralization in IOCG deposits worldwide.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10776

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