Gondwanic magmatism and mineralization in El Arriero alteration zone, La Huerta range, province of San Juan, Argentina

CASTRO DE MACHUCA, BRÍGIDA; CONTE-GRAND, ALICIA; MEISSL, ESTELA; PONTORIERO, SANDRA; SUMAY, CELINA

Salvador, Bahía

Simposio; IV South American Symposium on Isotope Geology; 2003

Companhia Baiana de Pesquisa Mineral (CBPM)

Potassium-argon ages on volcanic and subvolcanic rocks from La Huerta range, Westen Sierras Pampeanas, vary from 259±13 Ma to 246±8 Ma. These ages indicate almost continuous magmatism in the area. The age range is coincident with the gondwanic magmatic cycle that affects the whole Pampean Ranges System. Previous K-Ar dating on a small rhyolite intrusion (El Temblor Rhyolite) and a volcanic acidic breccia (Cerro Blanco district) points out an age of 256±8 Ma and 246±8 Ma respectively. More recently, similar ages were obtained from a porphyritic andesite (PMV: 259±13 Ma) and from a basalt (BMV: 255±13 Ma) in the Marayes Viejo area. All cases were dated by means of the K-Ar whole-rock method. The absolute age here presented (259±8 Ma) agrees with those previously reported, and permits assigning the porphyritic dacite of El Arriero, located in central-eastern Sierra de La Huerta, to the Gondwanic magmatic-metallogenic cycle.