Petrología magnética de la trondhjemita Calmayo (Ordovícico, Sierra Chica de Córdoba)

GEUNA, S.E.; D´ERAMO, F.; PINOTTI, L.; MUTTI, D.; DI MARCO, A.; ESCOSTEGUY, L.D.

Río Cuarto

Congreso; Minmet 2010, 10º Congreso de Mineralogía y Metalogenia; 2010

Magnetic properties of the Ordovician Calmayo trondhjemite, in the Sierras Pampeanas Orientales de Córdoba, were studied. It is paramagnetic overall, due to the virtual absence of magnetite, the classical ferromagnetic mineral in crustal rocks. The opaque mineralogy is dominated by exsolved hematite-ilmenite instead, which would indicate relatively oxidizing conditions during the crystallization. The hematite-ilmenite carries an intense, highly stable magnetic remanence, typical of lamellar magnetism, probably acquired during slow cooling of the pluton and simultaneously with the exsolution of hematite and ilmenite from the initial solid solution. In addition to hematite-ilmenite, the NE sector of the pluton carried also magnetite, interpreted as a secondary mineral introduced during later shearing along the Soconcho belt. This secondary magnetite imprints locally a moderately ferromagnetic character to the effected pluton.