Química mineral e geotermobarometria do Batólito Serra da Água Limpa, Nappe Socorro-Guaxupé, Faixa Brasília Meridional, Sudeste do Brasil

The Serra da Agua Limpa Batholith, that crops out along the boundary of Minas Gerais and Sao Paulo states, in Brazil, has been interpreted as part of a magmatic arc of the Paranapanema paleocontinent active margin, southern Brasilia belt. Locally igneous features are preserved, but tectonic foliation is common. Mineral chemistry microprobe data are presented for plagioclase, amphibole, biotite and K-feldspar. Crystallization temperatures were calculated by the whole rock zircon saturation method, yielding values between 863 and 1015oC. The pressure was calculated resulting in values in the range from 5 to 6 kbar. Thermometric data yielded two distinct temperature intervals: the cores of minerals rendered temperatures between 830 - 860oC, and the rims from 740 - 770oC. Three hypotheses may be considered: (A) the higher values obtained in the cores are related to magmatic crystallization, whereas the lower ones obtained in the rims represent metamorphism related to continental collision; (B) both cores and rims are metamorphic revealing a metamorphic peak temperature of 830 - 860oC with retrometamorphism in the range 740 - 770oC; (C) cores and rims of amphibole and plagioclase crystals retained their igneous composition and reflect igneous crystallization and subsequent cooling of the magma. The first interpretation seems to be the most likely because it is consistent with other data published for the region.