Caracterización geoquímica de los diques máficos del río Mallín (Valle de Punilla, Córdoba

FERNANDO COLOMBO ; ASSADOUR TOROSSIAN ; MINA, ALANA; EDGARDO G. BALDO

Córdoba

Congreso; XIII Congreso de Mineralogía, Petrología Ígnea y Metamórfica, y Metalogénesis; 2019

COMPETRO

In the bed of the Mallín river, close to Bialet Massé town (Punilla Department), there are four mafic dikes intruded in a granite that belongs to the Achala Batholith (Córdoba, Argentina, coordinates 31°18?51?? S ? 64°30?41?? W). The outcrops have a combined length of 100 m and are between 0.5 and 1.5 m wide; they strike 13-20°N and dip 85°W. The mafic rocks contain rounded (partially dissolved and melted) xenoliths of granitoid, metapelitic and syenitic rocks, along with fragments of hydrothermal veins (massive quartz + chlorite) and xenocrysts of quartz, potassic albite (anorthoclase), ilmenite and kaersutite. According to the bulk rock composition they are shoshonites [basaltic trachyandesites with K2O>(Na2O-2)]. Immobile trace elements, P and Si contents classify these rocks as alkaline basalts, straddling the boundary with the trachyandesite field. Taking a typical Carboniferous basalt as the initial composition, geochemical modelling suggests that the basaltic composition has been modified by assimilation of country rocks (syenite and, to a lesser degree, metapelites). Chondrite-normalized REE patterns do not show an Eu anomaly, and they resemble those of OIB in overall shape, concentrations and slope.Field, petrographic and chemical features suggest that these dikes can be linked to those cropping out at Cabalango (9.8 km SSW), interpreted as the result of the Upper Carboniferous extension that affected this area of Gondwana. The heat input to the crust associated to this event may be responsible for hydrothermal mineralizations scattered in Sierras de Córdoba, such as that described by Maffini et al. (2017).