Geologia da Região da Serra da Esperança - Porto Murtinho (MS): ênfase no Granito Cerro Porã do Arco Magmático Amoguijá – Sul do Cráton Amazônico

Abstract

The lithostratigraphic units that constitute the mapped area and create the morphology of the Serra da Esperança, from bottom to top are: Cerro Porã Granite, Serra da Bocaina Formation, Amolar Group and Pantanal Formation. This dissertation is meant to present the geologic, petrological, and geochronological dates of Cerro Porã Granite (first mapped in this work) belonging to Alumiador Intrusive Suite, located in the areas of Rio Apa Terreno, southern portion of the Amazonian Craton, as well as presenting with a succinctly way, the other lithologies outcropping in the area studied. Geological mapping allowed the identification of two facies in Cerro Porã Granite, which are: Pink Sienogranitic Facies and Gray Monzogranitic Facies. The first facies is characterized of xenomorphcs equigranular to essentially inequigranular texture and of constant presence of the graphic and granophirics intergrowths, and it is constituted of alkali feldspar, quartz and plagioclase, with biotite how single primary mafic. The Gray Monzogranitic Facies shows porphyrytic texture with graphic to granophiric fine-grained groundmass and it consist of quartz, plagioclase, alkali feldspar and mafic aggregates (biotite and amphibole). Both the facies were metamorphosed at greenschist facies and the Pink Sienograticit Facies is milonytic when in shear zones. Where identified one event of ductile-brittle deformation originated in compressive system and it were responsible for the schistosity and mineral stretching lineation, just in deformed rocks. The development of Esperança Shear Zone is related to this deformational phase and reflects the cinematic history of the reverse convergent system with top transport to NWW. Chemically these rock types are classified as type A granitoids of range alkaline potassium saturated on silica. Determination geochronological achieved by U-Pb (SHRIMP) method with zircon ages, supplied 1749 ± 45 Ma age for crystallization to this rocks. From the geotectonic point, admits that Cerro Porã Granite correspond to a magmatic associated with a magmatic arc developed in Statherian period and your placing was in stage late to post-tectonic.