Sm-Nd systematics of metaultramafic-mafic rocks from the Arroio Grande Ophiolite(Brazil): Insights on the evolution of the South Adamastor paleo-ocean

作者：Rodrigo Chaves Ramos,Edinei Koester,Daniel Triboli Vieira

摘要：In this contribution we present new insights on the evolution of the Dom Feliciano Belt,southernmost Mantiqueira Province,integrating new whole-rock Sm-Nd isotopic data for the Arroio Grande Ophiolite(Punta del Este Terrane,Brazil/Uruguay border)with previously published bulk-rock and isotope geochemistry of the South Adamastor paleo-ocean metamafic rocks located in Uruguay(Paso del Dragon Complex,Punta del Este Terrane)and Namibia(Chameis Subterrane,Marmora Terrane,Gariep Belt).For the regional geology,the new data corroborate previous hypothesis and demonstrate the depleted mantle features of the amphibolites and metagabbros of the studied ophiolite.The Arroio Grande Ophiolite rocks are compared with its Uruguayan and Namibian counterparts,demonstrating their isotopic and geochemical similarities and differences,and the backarc affinity of the South Adamastor paleo-ocean.The MORB-affinity amphibolites from the Arroio Grande Ophiolite-Paso del Dragon Complex are,so far,the most juvenile rocks in the eastern sector of the Dom Feliciano Belt,yielding εNd(640)Ma)between+7.3 and+9,and high 147Sm/144Nd(>0.169)and 143Nd/144Nd(640 Ma)ratios(0.51219-0.51229).The South Adamastor is interpreted in this paper as an internal back-arc ocean,with limited lateral extension,opened at around 750-650 Ma as the result of the closure of the older Charrua-Goianide paleoocean during the Brasiliano/Pan-African orogenic cycle and final configuration of the West Gondwana paleocontinent.

发文机构：Programa de Pòs-Graduação Em Geociências Departamento de Geologia

关键词：WestGondwanaBrasilianoorogeniccycleAdamastorocean

分类号： P58[天文地球—岩石学]