Chemical-Abrasion U-Pb zircon geochronology reveals 150 Myr of partial melting events in the Archean crust of the São Francisco Craton  

作　　者：Lorena Martins Cristiano Lana Ariela Mazoz Tiago Novo 

机构地区：[1]Applied Isotope Research Group,Departamento de Geologia,Escola de Minas,Universidade Federal de Ouro Preto,Morro do Cruzeiro,Ouro Preto,MG,35400-000,Brazil [2]Universidade Federal de Minas Gerais,Programa de Pós-Graduação em Geologia,IGC-CPMTC,Campus Pampulha,Av.Antônio Carlos 6627,Belo Horizonte,MG,31270-901,Brazil

出　　处：《Geoscience Frontiers》2022年第5期169-189,共21页地学前缘（英文版）

基　　金：financial support from the CNPq(National Council for Scientific and Technological Development)under grant 141707/2016-0 to Lorena Martins;financial support provided by CNPq awarded to Cristiano Lana。

摘　　要：Field observations and CA-LA-ICP-MS U–Pb zircon ages and Hf isotope compositions obtained from migmatitic orthogneisses and granitoids from the Belo Horizonte Complex,southern São Francisco Craton,indicate a major period of partial melting and production of felsic rocks in the Neoarchean.Our observations show that the complex is an important site for studying partial melting processes of Archean crystalline crust.Much of the complex exposes fine-grained stromatic migmatites that are intruded by multiple leucogranitic veins and sheeted dikes.Both migmatites and leucogranite sheets are crosscut by several phases of granitoid batholiths and small granitic bodies;both of which are closely associated with the host banded gneisses.Chemical abrasion followed by detailed cathodoluminescence imaging revealed a wide variety of zircon textures that are consistent with a long-lived period of partial melting and crustal remobilization.Results of U-Pb and Hf isotopes disclose the complex as part of a much wider crustal segment,encompassing the entire southern part of the São Francisco Craton.Compilation of available U-Pb ages suggests that this crustal segment was consolidated sometime between 3000 Ma and 2900 Ma and that it experienced three main episodes of partial melting before stabilization at 2600 Ma.The partial melting episodes took place between 2750 Ma and 2600 Ma as a result of tectonic accretion and peeling off the lithospheric mantle and lower crust.This process is likely responsible for the emplacement of voluminous potassic granitoids across the entire São Francisco Craton.We believe that the partial melting of Meso-Archean crystalline crust and production of potassic granitoids are linked to a fundamental shift in the tectonics of the craton,which was also responsible for the widespread intrusion of large syenitic bodies in the northern part of the craton,and the construction of layered mafic–ultramafic intrusions to the south of the BHC.

关 键 词：ARCHEAN São Francisco Craton Crustal reworking U-Pb geochronology Lu-Hf isotopes 

分 类 号：P542[天文地球—构造地质学] P597.3[天文地球—地质学]