Intermediate sulfidation epithermal Pb - Zn (± Ag ± Cu ± In) and low sulfidation Au (± Pb ± Ag ± Zn) mineralization styles in the Gonzalito polymetallic mining district, North Patagonian Massif

PUGLIESE, FRANCO E.; STIPP BASEI, MIGUEL A.; PUGLIESE, LUIS E.; MARTÍNEZ DOPICO, CARMEN I.; DAHLQUIST, JUAN A.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2021

0895-9811

The Gonzalito polymetallic mining district is located within the northeast tip of the 600 km-long NE-trending20 polymetallic belt of the North Patagonian Massif, in Patagonia, Argentina. It comprises Paleozoic igneous21metamorphic rocks of the Mina Gonzalito complex, which are intruded by Middle Triassic trachytic-andesitic dykes22 of the Monasa Fm. through a complex system of high-angle fractures. Rhyolitic dykes crosscut the pre-Jurassic23 rocks. Numerous semi-parallel vein-like mineral deposits, whose classification and age have been subject of24 debate, sharply crosscut the igneous-metamorphic, trachytic-andesitic and rhyolitic units. Mineralization shows a25 strong structural control through a complex system of semi-parallel NW-N-NE oriented fracture-hosted mineral26 deposits. Extensional jogs and open dilational fractures allow multiband vein infills, vein-like hydrothermal and fault27tectonic breccias, stockwork veins and veinlets with primary growth open-space and boiling-derived textures,28 indicating a brittle geological setting that is properly of the epithermal environment. Based on the structural setting,29 sulfide-gangue-alteration mineral assemblages and textures, sulfide mineral chemistry and whole-rock30 geochemical analyses, two different styles of hydrothermal deposits can be distinguished: massive-sulfide intermediate sulfidation epithermal Pb ? Zn ± Ag ± Cu ± In and disseminated-sulfide low sulfidation 31 Au ± Pb ± Ag ±32 Zn. The first has a main-stage pyrite ? In-rich sphalerite ? chalcopyrite ? galena ore assemblage in scarce quartz -33 carbonates gangue. The second shows disseminated pyrite ± sphalerite ± chalcopyrite ± galena with economic34 grades of Au in abundant quartz ? adularia ± fluorite gangue. SHRIMP U-Pb zircon data of rhyolites reveal Early35 Jurassic ages of 193 ± 2 and 191 ± 2 Ma and, along with their bulk-rock geochemical features, they can be36 included within the Chon Aike magmatic province, locally known as Marifil volcanic complex. Crosscutting37 relationships between the Lower Jurassic rhyolites and the epithermal veins in the Gonzalito district, and the38 presence of Oligocene basalts partially covering the epithermal deposits toward the western area, constrain the39 mineralization event between the Lower Jurassic and the Oligocene. However, the crosscutting relationships of this40 district along with the already proven genetic, temporal and spatial links between epithermal ore and fluorite-rich41 deposits and the Jurassic magmatism-rifting of Patagonia suggest that the studied epithermal deposits might be42 yielded closer or during the Lower Jurassic.