Paleoproterozoic juvenile magmatism within the northeastern sector of the Sao Francisco paleocontinent:Insights from the shoshonitic high Ba-Sr Montezuma granitoids

作者：Samuel Moreira Bersan,Alice Fernanda de Oliveira Costa,Andre Danderfer,Francisco Roberio de Abreu,Cristiano Lana,Glaucia Queiroga,Craig Storey,Hugo Moreira

摘要：New,integrated petrographic,mineral chemistry,whole rock geochemical,zircon and titanite UPb geochronology,and zircon Hf isotopic data from the Montezuma granitoids,as well as new geochemical results for its host rocks represented by the Corrego Tingui Complex,provides new insights into the late-to post-collisional evolution of the northeastern Sao Francisco paleocontinent.U-Pb zircon dates from the Montezuma granitoids spread along the Concordia between ca.2.2 Ga to 1.8 Ga and comprise distinct groups.Group I have crystallization ages between ca.2.15 Ga and 2.05 Ga and are interpreted as inherited grains.Group II zircon dates vary from 2.04 Ga to1.9 Ga and corresponds to the crystallization of the Montezuma granitoids,which were constrained at ca.2.03 Ga by the titanite U-Pb age.Inverse age zoning is common within the ca.1.8 Ga Group III zircon ages,being related to fluid isotopic re-setting during the Espinhaco rifiting event.ZirconεHf(t)analysis show dominantly positive values for both Group I(-4 to+9)andⅡ(-3 to+8)zircons and TDM2 model ages of 2.7-2.1 Ga and 2.5-1.95 Ga,respectively.Geochemically,the Montezuma granitoids are weakly peraluminous to metaluminous magnesian granitoids,enriched in LILES and LREE,with high to moderate Mg#and depleted in some of the HFSE.Their lithochemical signature,added to the juvenile signature of both inherited and crystallized zircons,allowed its classification as a shoshonitic high Ba-Sr granitoid related to a late-to post-collisional lithosphere delamination followed by asthenospheric upwelling.In this scenario,the partial melting of the lithospheric mantle interacted with the roots of an accreted juvenile intra-oceanic arc,being these hybrid magma interpreted as the source of the Montezuma granitoids.The Corrego Tingui Complex host rocks are akin to a syn-to late-collisional volcanic arc granitoids originated from the partial melting of ancient crustal rocks.The results presented in this study have revealed the occurrence of juvenile rocks,probably related to an island a

发文机构：Universidade Federal de Ouro Preto Universidade Federal de Ouro Preto Sustain Geologia Ltda University of Portsmouth

关键词：ZirconU–Pb-HfTitaniteU–PbHighBa–SrLate-topost-collisionalSaoFranciscopaleocontinent

分类号： P59[天文地球—地球化学]