Apatite (U–Th)/He thermochronology and Re–Os ages in the Altar region, Central Andes (31°30′S), Main Cordillera of San Juan, Argentina: implications of rapid exhumation in the porphyry Cu (Au) metal endowment and regional tectonics

MAYDAGÁN, LAURA; ZATTIN, MASSIMILIANO; MPODOZIS, CONSTANTINO; SELBY, DAVID; FRANCHINI, MARTA; DIMIERI, LUIS

MINERALIUM DEPOSITA

SPRINGER

Lugar: Berlin; Año: 2020

0026-4598

Altar is a large porphyry Cu (Au) deposit located in the Main Cordillera of Argentina, 20 km to the north of the giant LosPelambres?El Pachón porphyry copper cluster, at the southern portion of the Pampean flat-slab segment of the Andes. Althoughthis region hosts telescoped porphyry-epithermal deposits, the precise temporal relationship between porphyry emplacement,mineralization, cooling, and regional orogenic uplift are still poorly understood. New Re?Os molybdenite ages indicate that Altarorebodies are associated with two magmatic hydrothermal centers: Altar East (11.16 ± 0.06 Ma) and Altar Central (10.38 ±0.05 Ma) formed at temporally distinct periods. New (U?Th)/He ages from the Early Permian and Late Eocene plutons, and theMiddle Miocene subvolcanic stocks associated with Cu?Au mineralization of the Altar region reflect a rapid cooling pulse duringthe Middle Miocene (15.02 to 10.66 Ma) coeval with a major phase of tectonic shortening and regional uplift. The main pulse ofrapid cooling and related tectonic uplift in the Altar region was synchronous with the formation of the hydrothermal systems andresulted in an increased focused metal endowment (Au?Cu grades) due to the telescoping of epithermal mineralization over therapidly uplifted porphyry system. This 11?10 Ma tectonically triggered exhumation event coincides with the collision of the Etrending segment of the Juan Fernández Ridge with the Peru?Chile trench, at this latitude. Collision and ensuing ridge subductionmay have driven a localized pulse of rapid cooling and exhumation of the Main Cordillera that has not been well documented tothe north or south of the Altar?Los Pelambres region