Evolução petrogenética e metamorfismo das rochas ortoderivadas da litofácies tarsira no perfil entre São Gabriel da Cachoeira e Cucuí- Amazonas

Abstract

The Rio Negro Province is located in the northwest of the Amazonian Craton, and is divided into three tectonic domains, Uaupés, Içana and Imeri (where it inserted the study area), represented by orogens with different Geodynamic developments. The surveys were conducted in the Cauaburi Complex, basement Imeri Domain, consisting in a granitic gneiss terrain, subdivided on the basis of compositional and deformational characteristics in Tarsira Lithofacies and Santa Isabel do Rio Negro. Located in the northeast portion of the Rio Negro Province to Tarsira Lithofacies is composed of biotite gneiss, hornblende biotite gneiss and augen gneisses of monzogranitic and granodiorite polideformados composition, with at least three phases of deformation that originated the foliation S1 whose trend is NW-SE, the foliation S2, the main trend is NE-SW and NW-SE secondarily, and S3 that reworks the foliation S2. Analyses of mineral phases, microstructures / microtextures, and mineral chemistry data indicate a progressive metamorphism, which grades a green schist facies to granulite in intermediate pressure conditions. Geochemically have calc-alkaline affinity high- K goal peraluminous. Its composition and trace element patterns suggest represent a typical magmatic arcs. The isotopic data Sm-Nd reveal extraction of parental magma of the Paleoproterozoic gneisses, indicated by the TDM values around 2.05 Ga and the positive values 40Ar-39Ar method hornblende indicate an thermotectonic event around 580 ° C, as well as thermometers made in biotite crystals (between 560 ° C and 656 ° C). This age is compatible with Orogenia Içana (1.54 to 1.48 Ga) and whose field and microscopic observations indicate that this event is responsible for the deformation and metamorphism that generated in the main foliation S2 ortoderivadas rocks that comprise lithofacies Tarsira. Furthermore, this region was also affected by deformational processes younger with main NE-SW trend, attributed to K'Mudku event, which should have reworked the older structures and generated shear zones (S3).