Batólito Guaporeí: uma extensão do Complexo Granitoide Pensamiento em Mato Grosso, SW do Cráton Amazônico

Abstract

The Guaporeí Batholith is located in the Vila Bela da Santíssima Trindade region, at Mato Grosso State (Brazil), and crops out over 240 km2 along the NW direction. It is situated in the Paraguá Terrane, included in the Rondonian-San Ignacio Province, in the southwestern portion of the Amazonian Craton. The batholith is made up of monzogranite, with subordinate granodiorite, quartz monzonite and syenogranite, shows coarse porphyritic/porphyroclastic texture, is metamorphosed in the greenschist facies and mylonitized along shear zones. The biotite is the main primary mafic mineral, sometimes associated with amphibole. Geochemical data indicated high-potassium calc-alkaline and metaluminous to peraluminous character, probably generated in continental arc environment, and evolved by fractional crystallization associated to crustal assimilation. Two stages of deformation related to the evolution of San Ignacio compressional orogeny were identified and are characterized by stretching and lineation, and development of S1 and S2 foliations. Dating by single zircon Pb-evaporation method yields a crystallization age of 1,314 ± 3 Ma, whereas Sm-Nd whole rock isotope data indicate a TDM model age of ca. 1.7 Ga and a negative value for εNd (t = 1,3) of -14, suggesting crustal contribution in the magma genesis. The obtained data indicate similarities between these rocks and those of the Pensamiento Granitoid Complex, in the Bolivian counterpart, and put in evidence that the Guaporeí Batholith is an extension of this complex.