Geology of Porphyry Cu-Au and Epithermal Cu-Au-Ag Mineralization at Filo del Sol, Argentina-Chile: Extreme Telescoping During Andean Uplift

Abstract Filo del Sol is a composite porphyry-epithermal deposit, straddling the frontier between Argentina and Chile at latitude 28°29′ S, that has attracted great deal of recent attention because several drill intersections in excess 1 km long with unusually high Cu, Au, Ag grades. The deposit part 8.5-km-long, N- to NE-trending alignment porphyry high-sulfidation epithermal centers, which, turn, located newly defined Vicuña metallogenic belt unites well-known late Oligocene middle Miocene Maricunga El Indio belts. hosted by Permian felsic volcanic rocks intruded Triassic monzogranite and, nearer surface, shallowly dipping Late Cretaceous volcano-sedimentary rocks. These lithologic units were generations mafic dikes high-level sills Miocene, parallel swarm diorite dikes. An intermineral magmatic-hydrothermal breccia body closely associated subsequently cut shallow levels smaller, finer-grained phreatic possibly, phreatomagmatic origin. Early Cu-Au mineralization, mainly as chalcopyrite, K-feldspar- biotite-bearing potassic alteration accompanying A-type quartz-veinlet stockworks. zone was massively overprinted extensively reconstituted vuggy residual quartz silicification core flanked quartz-alunite more extensive lithocap. types host Cu-Au-Ag mineralization pyrite early enargite later bornite, chalcocite, covellite, numerous Ag-bearing sulfosalts, highest grades typically confined quartz. Largely barren, steam-heated preserved above on results radiometric dating (six U-Pb 22 Re-Os ages) show intrusion began ~15 Ma lasted for nearly m.y., although most molybdenite samples reported ages from 14.7 14.4 ± 0.06 Ma. This short interval coincided pulse regional compressive tectonism accommodated high-angle, thick-skinned, reverse faulting basement-cored blocks, concomitant uplift exhumation. gave rise ~1 erosion during formation thereby accounting extreme telescoping over mineralization. Spatial association these centers dated Eocene suggests deep-seated structural control alignment. Ongoing supergene processes under low-pH conditions produced near-surface resource dominated chalcanthite, minor underlying chalcocite enrichment, well partially oxidizing high-grade