Boiling horizon determination at Dios Protégé Vein, Castaño Nuevo mining district, Cordillera Frontal, Argentina

COCOLA, A.; D'ANNUNZIO, M.C.; STRAZZERE, L.; GUIDO, D.

Conferencia; SEG 2019 ? South American Metallogeny: Sierra to Craton; 2019

Castaño Nuevo mining district is located in the eastern rim of Cordillera Frontal, San Juan Province, Argentina (S 31°00?12?? ? S 31°01?51?? and W 69°34?00?? ? W 69°32?12??), and comprises a group of Quartz-Adularia veins, related to Permo-Triassic magmatism of Choiyoi Group. The main vein, Dios Protege, records a complex multistage filling history. It has been identified six stages, each one with a specific location along with the strike of the structure, and a particular mineralogy, texture, ore grade and fluid inclusion entrapmentfeature (Figure 1). First stage is scarce and mainly composed of criptocrystalline grey quartz. It is often found as fragments within the second stage, which is essentially form by alternating bands, frequently surrounding and growing concentric from host rock fragments. Two different pulses were identified on the second stage, immediately to the walls crystalline quartz and big subrhombic adularia crystals are common, while on thecentre is more usual to find very narrow bands of cryptocrystalline silica, now recrystallized and represented by feathery and flamboyant textures under microscope. The third stage cuts the previous and develops a breccia with massive white recrystallized quartz (minor adularia) as cement. Fourth stage again shows concentric banding (as stage 2) but the main mineral within the bands correspond to amethyst, alternating with crystalline grey quartz. The fifth stage is represented by carbonates, mainly calcite (minor siderite), as massive and lattice bladed infills. Finally, the sixth stage has fragments from all the former stages cemented by recrystallized silica, resulting on mosaic texture with chlorite and other fine clays between crystals.