Genesis of the Gentio Metagranitoid: Post-Collisional High-K Plutonism within the Mineiro Belt, S?o Francisco Craton, Brazil  

作　　者：Marize M.da Silva Ciro A.Ávila Felipe M.Tavares Natali S.Barbosa Wilson Teixeira 

机构地区：[1]Programa de Pós-graduação em Geologia,Universidade Federal do Rio de Janeiro,21.949-900,Rio de Janeiro,RJ,Brazil [2]Museu Nacional,Universidade Federal do Rio de Janeiro,20940-040,Rio de Janeiro,RJ,Brazil [3]Serviço Geológico do Brasil,Divisão de Geologia Econômica,22290-255,Rio de Janeiro,Brazil [4]Instituto de Geociências,Universidade Federal da Bahia,40170-110,Salvador,BA,Brazil

出　　处：《Journal of Earth Science》2021年第6期1374-1396,共23页地球科学学刊（英文版）

基　　金：support of the CAPES and the Brazilian National Research Council (CNPq) for the Doctoral (No. 140411/2013-5)。

摘　　要：The Gentio metagranitoid presents equigranular and porphyritic facies, modal composition ranging from tonalite to monzogranite with calculated T_(Zr)<800 ℃ for most samples. Its mineralogy is dominated by quartz and feldspar(77% to 95%), biotite is the only mafic mineral present(2% to 18%) and, titanite, zircon, apatite, allanite are important accessory phases. These rocks range from metaluminous to weakly peraluminous, and have large variation in major and trace elements, and high alkali contents(>6 wt.%). Zircon analyses by LA-ICP-MS and SHRIMP yielded a concordia age of 2 119±10 Ma for the porphyritic facies and an upper intercept age of 2 111±15 Ma for the equigranular facies. The whole-rock Sm-Nd T_(DM) ages vary from 2.4 to 2.8 Ga with ε_(Nd)(2.1) values between -0.7 and-5.3, indicating crustal derivation from distinct and/or heterogeneous protoliths. Field observations indicate that the Gentio metagranitoid was formed through different pulses of magma. Individual batches were subject to little or even no fractionation process after its emplacement. Although the Gentio metagranitoid crosscuts metamafic and metaultramafic rocks akin to an oceanic arc setting, this pluton is likely originated by partial melting of a more evolved quartz-feldspathic crustal igneous rock in a post-collisional environment, after the accretion of the arcs from the Mineiro belt and rocks of the Mantiqueira Complex.

关 键 词：high-K granites Mineiro belt POST-COLLISIONAL Sao Francisco Craton U-Pb geochronology 

分 类 号：P588.3[天文地球—岩石学] P542[天文地球—地质学]