Revista de la Asociación Geológica Argentina
versión On-line ISSN 1851-8249
DAHLQUIST, J.A. et al. Magmatic evolution of the Peñón Rosado Granite, Cerro Asperecito, western flank of the Famatina range. Rev. Asoc. Geol. Argent. [online]. 2006, vol.61, n.1, pp. 93-111. ISSN 1851-8249.
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.
Palabras clave : Cerro Asperecito; Garnet; S-type granitoid; Partial melting.