Alasino P.H.,CONICET |
Dahlquist J.A.,CONICET |
Galindo C.,Complutense University of Madrid |
Casquet C.,Complutense University of Madrid |
Saavedra J.,Institute Agrobiologia y Recursos Naturales
International Journal of Earth Sciences | Year: 2010
The La Costa pluton in the Sierra de Velasco (NW Argentina) consists of S-type granitoids that can be grouped into three igneous facies: the alkali-rich Santa Cruz facies (SCF, SiO2 ~67 wt%) distinguished by the presence of andalusite and Na- and Li-rich cordierite (Na2O = 1.55-1.77 wt% and Li2O = 0.14-0.66 wt%), the Anillaco facies (SiO2 ~74 wt%) with a significant proportion of Mn-rich garnet, and the Anjullón facies (SiO2 ~75 wt%) with abundant albitic plagioclase. The petrography, mineral chemistry and whole-rock geochemistry of the SCF are compatible with magmatic crystallization of Na- and Li-rich cordierite, andalusite and muscovite from the peraluminous magma under moderate P-T conditions (~1.9 kbar and ca. 735°C). The high Li content of cordierite in the SCF is unusual for granitic rocks of intermediate composition. © 2009 Springer-Verlag.