Petrologia e geocronologia U-Pb (SHRIMP) e SmNd do granito betel : magmatismo de arco continental da orogenia San Ignácio : SW do Cráton Amazônico

Abstract

The Betel Granite in the southwest of the Amazon Craton, in the Paraguá Terrane of the Rondoniana-San Ignacio Province. It is hosted in gneisses of the Complexo Serra do Baú/Chiquitania and is partially covered by the Aguapeí Group. Based on the study of Betel Granite rocks from the granulation, color and form of occurrence, three facies were identified: Inequigranular Medium to Fine Gray Facies, most abundant; Leucogranite with Garnet and Muscovite Facies, Fine to Very Fine Rose Facies, aplite dykes. With the exception of the Leucogranite with Garnet and Muscovita Facies, the others present similar mineralogical compositions, both with respect to essential minerals and accessories, being classified in the QAP diagram from granodiorites to sienogranites. Geochemical studies reveal the rocks of Bethel Granite representing a calcic-alkaline/alkalic-calcic magmatism, essentially peraluminous and magnesian, whit fractional crystallization process played an important role. Through the U-Pb (SHRIMP) zircon geochronological method the age of 1327±6.3 Ma is interpreted as the crystallization age. The Sm-Nd (whole rock) analysis indicates TDM age 1,75 Ga, εNd (1,34 Ga) of -0,10 suggesting a crustal involvement in the genesis of this magma. The results obtained indicate that the Betel Granite is part of the Pensamiento Intrusive Suite of the Rondoniana-San Ignácio, probably generated in a continental magmatic arc settings during the San Ignácio Orogeny.