Magmatic evolution of the Peñón Rosado Granite, Cerro Asperecito, western flank of the Famatina range

Abstract

Garnet is an uncommon accessory mineral in igneous rocks and is a relevant petrologic topic. Combined petrology, chemistry/mineralogy, whole-rock geochemistry, and isotopic geochemistry studies in the cerro Asperecito indicate that the garnet-bearing granitoids of the Peñón Rosado Granite (PRG) were produced by partial melting of metasedimentary rocks and subsequent differentiation during their emplacement at the Early-Middle Ordovician. In this way the PRG1 facies represent an early crystallized, the PRG2 facies represent a differentiated melt, and the PRG3 facies a residual melt. The Peñón Rosado Granite, was emplaced in moderated-T (785ºC) and middle-P (4.4 kb) conditions in middle crustal depths (~15 km). The almost synchronous emplacement in the middle crust of a major metaluminous igneous suite during the Early-Middle Ordovician (468 Ma in the cerro Asperecito) was sufficient to induce local anatexis of the surrounding metasediments. Major (CaO, Na₂O) and trace element (Rb, Sr, Ba) contents in the Peñón Rosado Granite strongly suggest anatexis from immature continental platform material. Thus the Peñón Rosado Granite is a S-type garnet-bearing granitoid and the present model established here contributes to better understanding about the garnet crystallization in granitic rocks.