Magnetic Characterization of the Devonian La Totora Granite, Sierras de San Luis, Argentina

RAPALINI, AUGUSTO E.; LOPEZ DE LUCHI, MÓNICA; FANTÍN, MANUEL

Concepción, Chile

Simposio; . Simposio 5: Evolución del margén pacífico de Gondwana en X Congreso Geol. Chileno; 2003

IGCP-UNESCO

Magnetic Characterization of the Devonian La Totora Granite, Sierras de San Luis, Argentina   Augusto E. Rapalini1,2,  Mónica Lopez de Luchi 2,3 y Manuel Fantín1      1 Instituto de Geofísica Daniel Valencio (INGEODAV), Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CONICET, Pabellón 2, Ciudad Universitaria, C1428EHA, Buenos Aires, Argentina, rapalini@gl.fcen.uba.ar, 2  CONICET 3 Instituto de Geocronología y Geología Isotópica, INGEIS, Pabellón INGEIS, Ciudad Universitaria, C1428EHA, Buenos Aires, Argentina, deluchi@ingeis.uba.ar   Abstract   The La Totora batholith is representative of a widespread Devonian magmatism in the Sierras De San Luis, Argentina. It is a composed batholith with an external coarse grained biotite porphyric monzogranite facies, the La Porteña Granite, and an internal medium to coarse grained light grey biotite monzogranite, the Gobelli Granite. A magnetic fabrics study on 44 sites indicate that all the batholith is ferromagnetic (k ranges between 0.9 and 11.1 x10-3 SI), with the lowest values generally corresponding to the Gobelli pluton. Highest values are located to the north of the La Porteña unit. Ansotropy degree is mainly low (magmatic fabric), with low values at the Gobelli granite and higher at the Las Porteñas, especially near its external border. For sites with P´<1.04 no preferred orienation of the shape parameter can be found. However, a systematic distribution of values with P´>1.04 in the oblate field (T>0) suggests the existence of a late magmatic deformation. Distribution of lineations and folitation planes suggest foliation planes dominantly verticals and concentric. Lineations are mainly subhorizontal except for an area at the south where location of the feeders of the intrusives is supposed.