Archean-Ediacaran evolution of the Campos Gerais Domain-A reworked margin of the São Francisco paleocontinent(SE Brazil):Constraints from metamafic-ultramafic rocks  

作　　者：Marco Aurélio Piacentini Pinheiro George L.Guice Joana Reis Magalhães 

机构地区：[1]Geological Survey of Brazil–CPRM,Av Brazil 1731,Belo Horizonte 30140-002,Brazil [2]Department of Mineral Sciences,National Museum of Natural History,Smithsonian Institution,10th Street and Constitution Avenue NW,Washington D.C.20560,USA

出　　处：《Geoscience Frontiers》2022年第5期286-308,共23页地学前缘（英文版）

基　　金：the Brazilian research institutions:National Council for Scientific and Technological Development(CNPq;process n°206612/2014-1);the Fundação de AmparoàPesquisa de Minas Gerais(FAPEMIG;process n°CRA 1.058/04)for the financial assistance;the Geological Survey of Brazil(SGB/CPRM)for the support。

摘　　要：The Campos Gerais Domain(CGD)in southeastern Brazil is an approximately 180 km×35 km area of Archean–Proterozoic rocks located southwest of the São Francisco Craton(SFC).The Archean–Paleopro terozoic evolution of the CGD—alongside its potential correlation with the SFC or other cratonic blocks in the region-is currently poorly-constrained.We present the results of systematic petrography,bulkrock geochemistry,mineral chemistry and geochronology for a suite of scarcely studied mafic–ultramafic rocks from the CGD.We also provide a compilation of previously reported bulk-rock geochemical and spinel group mineral chemical data for mafic–ultramafic rocks throughout the CGD,and geochronological information for various lithotypes in the region.The CGD records a protracted Mesoarchean to Statherian(3.1–1.7 Ga)crustal evolution,which we interpret to share a common history with the southern SFC and their related reworked segments,suggesting that it is a westward extension of this cratonic terrain.The metavolcano-sedimentary rocks of the Fortaleza de Minas and Alpinópolis segments represent a Mesoarchean greenstone belt that is stratigraphically and chemically comparable to Archean greenstone belts worldwide,and that is broadly coeval with a local suite of tonalite-trondhjemite-grano diorite(TTG)gneisses and migmatites.U-Pb SHRIMP zircon data from a subalkaline metagabbro yielded a concordia age of ca.2.96 Ga,revealing a previously unrecognized phase of Archean magmatism in the CGD that can be chrono-correlated with metakomatiite and TTG generation elsewhere in the São Francisco paleocontinent.Our data contradict a hypothesis whereby the metavolcano-sedimentary rocks of the Jacuí-Bom Jesus da Penha and Petúnia segments represent an ophiolite,as previously suggested,instead presenting features that point to formation in association with a continental arc.Coupled with a U-Pb(SHRIMP)crystallization age of ca.2.13 Ga recorded by zircon grains from a metaultramafic rock,these data highlight that a magmatic event

关 键 词：KOMATIITES São Francisco Craton Southern Brasília Orogen Archean geodynamics Rhyacian orogeny 

分 类 号：P548[天文地球—构造地质学] P587[天文地球—地质学]