Interpretación Geofísica (Magnética) Sierras de San Luis y Comechingones

Abstract

This report and accompanying 1:250.000 scale magnetic interpretation map of the Sierra de San Luis y Comechingones region are a product of the Geoscientific Mapping of the Sierras Pampeanas cooperative project between the Australian Geological Survey Organisation (AGSO) and the Dirección Nacional del Servicio Geológico (DNSG) of the Subsecretaría de Minería, República de Argentina. This report details the interpretation of magnetic data obtained during a high resolution, airborne geophysical survey over an area of 12.000 km2, including the Sierras de San Luis and Sierra de Comenchingones in the Provinces of San Luis and Córdoba. For the airborne geophysical survey, magnetic and radiometric (U, K, Th) data were obtained by World Geoscience along flight lines spaced 500m apart, from a nominal height of 100m. To assist the aeromagnetic interpretation, magnetic susceptibilities were measured during field work of exposed rock types. The magnetic data from the airborne survey were processed by Hungerford Geophysical Consultants (HGC) and radiometric data were processed by AGSO. The data were interpreted by HGC and geoscientists from AGSO at 1:1.000.000 scale and a number of geophysical domains have been identified. In conjunction, some individual aeromagnetic anomalies were modelled in order to obtain a dip and an estimation of the depth to source. In general, the Sierras de San Luis y Comechingones may be separated in two distinct regions that are separated by a major NNE-SSW trending thrust fault. East of this fault there is a generally low magnetic background and a number of prominent and well defined circular granite intrusions. West of this fault the magnetic response en generally higher and marked by strong linear trends and moderated to highly magnetic, strike-parallel anomalies. Furthermore, granite intrusions in the west generally form elongated belts and there is more diversity in the basement rock-types. In addition, a number of intense, isolated anomalies, which occur within both regions, are related to Tertiary volcanic plugs.