Discovery of strongly peraluminous granitoids in the Sierra de Famatina, Famatinian orogeny

Abstract

The strongly peraluminous Cerro Toro unit is formed of cordierite- and garnet-bearing granitic rocks and constitutes one of the most western outcrops of the Sierra de Famatina. Combined petrology, chemistry/mineralogy and whole-rock geochemistry studies indicate that the parental magma of this igneous unit was derived from the partial melting of metasediments under high temperature (762°C) and moderate pressure (4,1 Kb) conditions. The higher Rb/Sr, Rb/Ba and lower CaO/NaO₂ ratios (< 0.34) suggest that the parental magma was derived from a metasedimentary source of psamopelitic plagioclase-rich composition (metagreywacke), suggesting anatexis of metasediments from an immature continental platform. This paper presents the first report of strongly peraluminous granitic rocks in the Sierra de Famatina. These granitic rocks are very similar to those of the Tuaní Granite peraluminous unit of the Sierra de Chepes, formed of typical Famatinian granitoids, suggesting that similar petrogenetic processes occurred in both regions of the magmatic arc during the Famatinian orogeny.