Magmatic evolution of the Peñón Rosado granite: petrogenesis of garnet-bearing granitoids

DAHLQUIST, J.A., GALINDO, C., PANKHURST, R.J., ALASINO, P.H., SAAVEDRA, J., FANNING, C.M.

LITHOS

Elsevier Science Ltd

Lugar: Oxford; Año: 2006 p. 1 - 30

0024-4937

Garnet is an uncommon accessory mineral in igneous rocks but is petrologically significant. The Peñón Rosado granite (469 ± 4Ma) at Cerro Asperecito is an S-type granite emplaced during Famatinian orogeny (Early to Mid Ordovician). Combined petrology, chemistry/mineralogy and whole-rock geochemistry indicates that the magma was produced by partial melting of the surrounding metasedimentary rocks and subsequent differentiation by fractional crystallization process during emplacement. Three facies are recognized: PRG1 represents cumulates, PRG2 represents a differentiated melt, and PRG3 a residual melt. The pluton crystallized at high T (785 ºC) and Intermediate P (4.4 kb), at middle crustal depths (~ 17 Km). major (CaO, Na2O) and trace element (Rb, Sr, Ba) contents in the Peñón Rosado granite strongly suggest anatexis from immature continental platform material, and it s concluded that emplacement of a major metaluminous igneous suite during the Middle Ordovician induced local anatexis of the surrounding metasedimentos. The model established here contributes to better understanding o garnet crystallization in granitic rocks.