Metamorfismo de alta temperatura e média pressão de paragnaisses, anfibolitos e hornblenda-biotita gnaisse do Complexo Quatro Cachoeiras, Província Rondônia-Juruena, Rio Guariba - Amazonas

Abstract

This work presents petrography, mineral chemistry, geothermobarometry and P-T psedudosection modeling data from high grade metamorphic rocks from the Quatro Cachoeiras Complex, in the Roosevelt domain, Juruena terrane, Statherain-Caliminian of the Amazonian Craton, outcropping in the course of the Guariba river, Nova Aripuanã, Amazonas – Brasil. The studied area is located in the Roosevel-Guariba belt, a NW-SE trending granite-gneiss belt, that extends from Amazonas to Mato Grosso states. Analysis were performed in three litotypes: (i) sillimanite-cordierite migmatitic paragneiss, (ii) amphibolites and (iii) hornblende-biotite gneiss. The calculated metamorphic peak conditions reached the upper amphibolite facies (>700ºC and 3.3 to 6 Kbar), later retrometamorphosed at lower amphibolite facies (~550ºC and 1 to 3 Kbar). The metamorphism is considered as synchronous to the Serra da Providência magmatism, both related to a thermal-tectonic anomaly that was active at around 1.5 Ga, suggesting strong crustal reworking in a late stage of the Juruena orogeny in this region.