A Rusty Record of Weathering and Groundwater Movement in the Hyperarid Central Andes

The Atacama Desert, on the western margin of Central Andes, hosts some world's largest porphyry copper deposits (PCDs). Despite a hyperarid climate, many these PCDs have undergone secondary “supergene” enrichment, whereby has been concentrated via groundwater-driven leaching and reprecipitation, yielding supergene profiles containing valuable records weathering landscape evolution. We combine hematite (U-Th-Sm)/He geochronology oxygen isotope analysis to compare histories two Andean test relative importance climate tectonics in controlling both enrichment water table movement. At Cerro Colorado, Precordillera, precipitation prolonged from ∼31 ∼2 Ma, tracking descent following aridity-induced canyon incision late Miocene onward. By contrast, at Spence, within Depression, is mostly younger than ∼10.5 suggesting exhumation ended much later. A heavy isotopic signature for Spence suggests that upwelling formation an important source groundwater, accounting high modern despite persistent hyperaridity, whereas isotopically light Colorado formed presence meteoric water. Compared with published paleo-environmental sedimentological records, our data show can persist beneath appreciable post-exhumation cover, under conditions unconducive enrichment. susceptibility each deposit descent, deep controlled by recharge characteristics morphotectonic setting. Erosional exhumation, rather decay, appears be more development