Post-orogenic, Carboniferous (?) Sn-W mineralization in the Sierras Pampeanas Orogen, North-western Argentina

FOGLIATA, A., BÁEZ, M. & SARDI, F.

Keystone, Colorado, USA

Congreso; SEG (Society of Economic Geology) 2010 Conference; 2010

Society of Economic Geology

The Sierra Pampeanas orogen in north-western Argentina hosts a range of diverse metallic mineral deposits, including significant Sn-W deposits in the, for example, Sierras de Mazán and Velasco in the north-eastern part of the La Rioja province. These deposits were exploited in the 1940’s by artisanal miners and companies. The two Sierras are characterized by different types of Sn-W deposits, in the Sierra  Velasco they are mostly hydrothermal vein-hosted, whereas in the Sierra de Mazán they are frquently greisen. The Sierra Mazán and northern part of the Sierra Velasco are both characterized by post-orogenic, calc-alkaline porphyry and peraluminous granite (ASI: 1.10-1.70) stocks. The current genetic model links Sn-W mineralization to Ordovician-Carboniferous(?) post-orogenic granite stocks with the hydrothermal alteration and mineralization temperatures of about 330°C. The exact position of hydrothermal vein type Sn-W mineralization versus the Sn-W greisen could be related to the proximity of the cupola of the granite. In this model the greisens are located at or near the cupola whereas the vein type mineralization is located distal to the cupola.