Petrogênese e geocronologia U-Pb do Granito Sana, Faixa Ribeira, e dos Complexos Intrusivos de Santa Angélica e Várzea Alegre, Faixa Araçuaí

Abstract

The post-collisional stage in the Araçuaí and Ribeira mobile belts is marked by intense magmatism from the Cambro-Ordovician age. Such magmatism develops in different ways in each mobile belt. In the Ribeira Belt, post-collisional magmatism, represented by the Suruí, Nova Friburgo and Sana, suites, includes a series of igneous bodies essentially comprised of granitoids, with little or no variation into intermediate and/or basic members. In the Araçuaí Belt, magmatism is represented by the G4 suite, comprised of S-type granites, and by the G5 supersuite, comprised of a series of igneous bodies whose main feature is the mixing of magma. The Sana Granite is one of the examples of post-collisional magmatism from the Ribeira Belt, and was classified as S-type granite, whose partial fusion of paragneiss (São Fidélis Group) was generated by the dehydration of minerals such as biotite and muscovite. Maximum temperature of the magmatism that originated the Sana Granite is at around 800ºC and the heat that led to the partial fusion of rocks was transferred to the crust through the thermal conduction process. Sana’s magmatism lasted from 516 to 474 Ma at least. The Santa Angélica Intrusive Complex, also known as the Santa Angélica Massif, is a bimodal pluton, which was generated during the post-collisional stage of the Araçuaí Belt. That pluton presents intense mixing of magma from the crust and the mantle. Magmatism that originated the Santa Angélica Intrusive Complex lasted for approximately 25 Ma. Lu-Hf isotopic data obtained on the Santa Angélica Intrusive Complex suggest that the crustal source of that magmatism is the Caparaó Complex. The Santa Angélica Intrusive Complex is another sample of the G5 supersuite. U-Pb ages obtained on the Santa Angélica Intrusive Complex indicate a magmatic event that lasted about 38 Ma, and Lu-Hf isotopic data corroborate the presence of both crustal and mantle-derived magmas