Petrogenesis of cordierite-bearing S-type granitoids in Sierra de Chepes, Famatinian orogen, Argentina

During the Lower Paleozoic Famatinian orogeny in the Sierra de Chepes, NW Argentina, emplacement of a major metaluminous igneous suite in the middle crust caused high-temperature (>700 °C) and low-pressure (2-3 kbar) metamorphism. Heating was sufficient to induce local anatexis of the surrounding metasediments. Combined petrology, chemistry/mineralogy, and whole-rock geochemistry studies indicate that the cordierite-bearing granitoids of the Tuaní Granite unit (479 Ma) were mostly produced by in situ partial melting of the surrounding metasedimentary rocks and represent a primary melt. Major (CaO, Na2O) and trace (Rb, Sr, Ba) element contents in the Tuaní Granite unit strongly suggest anatexis of immature continental platform material. The granitic bodies in the unit are typical S-type granitoids, and the petrogenetic model established here contributes to a better understanding of the transition from high-grade metamorphic to igneous rocks and the link between peraluminous melts and source rocks.