Shrimp U-Pb Geochronology Final Report

Abstract

This report presents SHRIMP zircon U-Pb analyses from the Sierras septentrionales de Córdoba, Sierras de San Luis y Comechingones and the Sierras de Chepes y las Minas areas. Location details, petrographic descriptions and whole rock geochemical analyses are reported separately by Stuart-Smith and others (1996), Sims and others (1996) and Lyons and others (1996), respectively. Geological interpretations of rocks pertaining to this study are to be found in the 1:250 000 sheet reports. The Geoscientific Mapping of the Sierras Pampeanas is a cooperative project between the Australian Geological Survey Organisation (AGSO) and the Dirección Nacional del Servicio Geológico (DNSG) of the Subsecretaría de Minería, funded by the Government of the Argentine Republic. As a pilot second generation mapping program, the project aims to update the geoscientific knowledge base, provide a modern framework for resource assesment, and promote exploration and development in the region. The project covers three separate areas totalling 27 000 square kilometres in the southern part of the Sierras Pampeanas, Argentina where basement Precambrian to Palaeozoic metamorphics and granites crop out on the eastern margin of the Andean Mobile Belt. The area, best known for its production of industrial and construction materials also contains metallic deposits. Mineral resources include gold and polymetallic (Au, Ag, Pb, and Zn) vein deposits with past production of tungsten, bismuth, tin, manganese, and chromium. The three areas were selected to provide key information on their geology and mineral potential through the application of integrated geophysical/ geological mapping and metallogenic analysis and to provide a continuous section of the major tectonostratigraphic packages comprising the southern Sierras Pampeanas. As part of the Work Program, geochronological analyses, using SHRIMP U-Pb, ArAr and Rb-Sr techniques of selected samples were undertaken. The aim of the geochronological program is to provide key data to establish the timing of igneous rock crystallisation, major metamorphic/ deformation episodes, and mineralising events. The data would also allow independent correlation of metamorphic rock packages with numerical age control, assisting geological mapping of the project area, and providing an important database and framework for tectonic interpretation of the Sierras Pampeanas. This report focuses on the SHRIMP U-Pb results.