Resumo

FERNANDEZ, Raúl R et al. Geología y mineralización del área “Estancia San Pedro”, Macizo del Deseado, provincia de Santa Cruz. Rev. Asoc. Geol. Argent. [online]. 2016, vol.73, n.3, pp.388-404. ISSN 0004-4822.

This paper present the results of the study carried out in the Chon Aike Formation (Middle to Upper Jurassic) in the San Pedro ranch area, located in the southwestern portion of the Deseado Massif. The detailed geological survey enabled the definition of the lithological units and the establishment of their spatial relationship, as well as the finding of Au-Ag mineral occurrences so far unknown in the area. The lithological units are subvolcanic porphyries, lava domes, pyroclastic flow deposits and volcanogenic-sedimentary deposits. Petrographic studies and geochemical analysis of the volcanic lithologies, indicate that the subvolcanic rocks are dacitic and the pyroclastic and effusive rocks more evolved and rhyolitic, both with magmatic arc geochemical signature. Field data indicate an evolution of the volcanic processes in the area, which begins with subvolcanic intrusive bodies probably in an igneous-metamorphic basement that is not exposed at present. Lately these rocks were completely or partially covered by explosive volcanic deposits followed by lava effusions and dome complexes. Finally, during the final stage (or late) and as a consequence of the waning of the volcanism, volcanogenic-sedimentary deposits were produced in a fluvial system of high energy, which was gradually decreasing. The epithermal mineralization was originated during the latest stages of the volcanic episode, when the input of meteoric water in the geothermal system was higher.

Palavras-chave : Volcanism; Jurassic; Chon Aike Formation; Mineral occurrences.

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