. Las rocas máficas de la Sierra de la Invernada, Precordillera Central, San Juan.

PÉREZ LUJÁN, S.B.; BOEDO, F.; ARIZA, J.P.; VUJOVICH, G.I.; ALVARADO, P.

San Juan

Congreso; 11° Congreso de Mineralogía y Metalogenia; 2013

Universidad Nacional de San Juan

The Ordovician Sierra de la Invernada formation is characterized by the presence of maficbodies that can be followed along the range of the same name in Central Precordillera.Petrographic and magnetic susceptibility studies were performed on two sill-like mafic bodies in thearea of Quebrada La Puerta. The western body is a gabbro with a modal banding. Three layerswith variable proportions of augite, diopside, plagioclase, olivine and magnetite were identified.Their modal variations and grain sizes correlate with a significant increase in magneticsusceptibilities. The whole sill is characterized by the presence of granitic veins at the top andsegregations with the same composition at the bottom. In contrast, in the thinner eastern body, nosignificant variations in the modal ratios have been observed. The magnetic susceptibility surveyshows quite homogeneous data which is consistent with their modal composition. We note thatthese gabbroic sills look like other similar bodies lying in the Western Precordillera. However weprovide the first evidence for a modal banding in this area. A more detailed study definitely willimprove the understanding of these bodies? origin.