ANÁLISIS DE LAS COMPOSICIONES ISOTÓPICAS DE SULFUROS EN EL DEPÓSITO LOMA GALENA, PROYECTO NAVIDAD, CHUBUT, ARGENTINA

VERÓNICA BOUHIER; ANA LAURA RAINOLDI; MARTA FRANCHINI

San Miguel de Tucumán

Congreso; XII Congreso de Mineralogía y Metalogenia- Avances en Mineralogía y Metalogenia y Petrología; 2016

Asocación Mineralógica Argentina-Fundación Miguel Lillo-CONICET

Loma Galena is one of the eight depositsthat constitute the Navidad Project (Ag + Pb Cu + Zn), located southwest of the North Patagonian Massif in Chubut province, Argentina (42º4?S - 68º8?W). The polymetallic mineralization has epithermal characteristics and is hosted in volcanic and sedimentary rocks deposited in a northern depocentre of the continental Jurassic Cañadón Asfalto basin. Sulfides and sulfosalts occur in 3 levels that differ from each other by their styles of mineralization, they are called: lower, middle and upper levels.The d34S isotopic data from pyrite-galena suggest a magmatic sulfur source (+ 4 and 6.7 ?) in the lower level, a sedimentary source in the upper level (-11.6 ?) and mixing of both in the middle level (-5.5 and 6.1 ?). In the upper level, the sedimentary sulfur would have been input by the dissolution of evaporite levels of the Cañadón Asfalto Fm. and in contact with the carbonaceous shaleswould have produced the reduction of sulfur by biogenic activity or thermochemical processes. In the lower level, positive isotopic signatures of d34S suggest a contribution of magmatic sulfur by hydrothermal fluids. At the middle level, the d34S isotopic compositions with intermediate values between lower and upper levels, indicate mixing between fluids hosted in sedimentary rocks with hydrothermal fluids. Isotopic data from late-stage Cu sulfides, correspond to inheritance values ofbase metal sulfides previously formed.