Petrografia, faciologia e litogeoquímica do Stock Itambé da Suíte Granítica Estrela do Sul – MG, porção meridional da Faixa Brasília

Abstract

The Itambé Granite is one of the seven stocks belonging to the Estrela do Sul Granite Suite that occurs in the state of Minas Gerais, near the homonymous city. This neoproterozoic magmatism is intrusive in rocks of the metasedimentary sequence of the Araxá Group, the Ortogneisse Goiandira and the Monte Carmelo Complex, located in the inner domain of the Southern Belt of Brasília. Aiming to improve the geological data of the research area, systematic mapping was carried out, which implemented the petrographic, faciological and geochemical characterization, in addition to the instruction, individualization of the possible facies and their more precise areal delimitation of the intrusive body. From the geological surveys, it was observed that the Itambé Granite represents a granitic stock of about 6.2 km², defining an intrusion with an “ameboid” format with composition ranging from sieno- to monzogranitic. In general, the rocks are exposed in the form of blocks and boulders of equigranular to inequigranular rocks from fine to coarse grains. Six facies referring to the Itambé Granite were described, denominated tourmaline-biotite monzogranite, biotite monzogranite, biotitemuscovite syenogranite, biotite-muscovite monzogranite, muscovite monzogranite and muscovite-biotite monzogranite, exhibiting a mineralogy composed mainly of quartz, microcline, plagioclase, biotite (I and II), muscovite (I and II), corundum, garnet, tourmaline, monazite, epidote, opaque and secondary minerals. The Itambé Granite rocks showed little variation in SiO2 contents, distributed in the range, considered low for the granitic types, between 67.09 and 69.91%, but high percentages of Al2O3 and K2O, in addition to high concentrations of Rb, Ba, Th, U and K, exhibiting enrichment in Light Rare Earth Elements (ETRL) relative to Heavy Rare Earth Elements (ETRP). The lithotypes analyzed are classified as collisional peraluminous leucogranite, with a signature corresponding to a S-type two-mica granite, generated by partial crustal melting of sequences of aluminous metasedimentary rocks, probably from the Araxá Group, and associated with the final evolution of the Brasília Orogenic Belt