Geology and geochronology of São Francisco Xavier Charnockite (MG, Brazil) and Ribeirão do Paiol Gabbronorite (SP, Brazil) and its possible relations with extensional crustal processes in the Southern Brasília and Central Ribeira orogens
DOI:
https://doi.org/10.11606/issn.2316-9095.v18-401Keywords:
Southern Brasília Belt, Central Ribeira Belt, Geochronology, Magmatic rocks.Abstract
Metamorphic rocks of medium pressure granulite to amphibolites facies of Socorro Nappe and Embu Terrane crop out extensively in the border region between the states of São Paulo and Minas Gerais, close to the towns of São Francisco Xavier, Monteiro Lobato, Campos do Jordão e São Bento do Sapucaí. Ribeirão do Paiol Gabbronorite and São Francisco Xavier Charnockite are igneous bodies hosted by metagranitoids belonging to the Serra da Água Limpa batholith. Ribeirão do Paiol Gabbronorite is isotropic and shows a hypidiomorphic to xenomorphic inequigranular seriate texture. U-Pb in zircon LA-ICPMS analyses yield a crystallization age of 534 ± 6 Ma for this unit. São Francisco Xavier Charnockite exhibits an igneous, isotropic equigranular to hypidiomorphic inequigranular texture. U-Pb in zircon crystallization ages ranging from 579 ± 5 Ma in the cores to 562 ± 8 Ma in the rims were obtained for this body, indicating its generation occurred during the evolution of the Central Ribeira Belt. The whole rock zirconium saturation geothermometer indicates temperature around 880ºC for the crystallization of the charnockitic magma. Negative εNd (t) values were obtained for both bodies (-7.32 for the gabbronorite, and -12.41 for the charnockite), revealing significant crustal contribution in the respective magmas.
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