Paleoproterozoic sources for Cordilleran-type Neoproterozoic granitoids from the Aracuai orogen (SE Brazil): Constraints from Hf isotope zircon composition

Autor(es)

Schannor, Mathias ^{[1, 2]} ; Lana, Cristiano ^[2] ; Mazoz, Ariela ^[2] ; Narduzzi, Francesco ^{[2, 3]} ; Cutts, Kathryn ^[2] ; Fonseca, Marco ^[2]

Afiliação do(s) autor(es)

^[1] Univ Cambridge, Dept Earth Sci, Cambridge CB2 3EQ - England

^[2] Univ Fed Ouro Preto, Dept Geol, Appl Isotope Res Grp, BR-35400000 Ouro Preto, MG - Brazil

^[3] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, IAG USP, Rua Matao, 1226 Cidade Univ, BR-05508090 Sao Paulo, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: LITHOS; v. 378, DEC 15 2020.
• Citações Web of Science: 0

Resumo

The Aracuai orogen of SE Brazil exposes numerous amounts of magnesian, metaluminous, calc-alkaline, and mediumto high-K granitoid batholiths that were emplaced during early convergence between the SAo Francisco and Congo cratons during West Gondwana assembly in the late Neoproterozoic. Previously proposed sources for these pre-collisional granitoids include the Paleoproterozoic basement and mantle-derived magma based on isotopic signatures, abundant microgranular enclaves and contemporaneous mafic intrusions. Zircons from migmatitic basement gneiss, a noritic intrusion and five granitoid intrusions were analysed for U-Pb-Hf isotopes to evaluate their magma source. Paleoproterozoic migmatites represent addition of juvenile crust in an accretionary orogenic setting at ca. 2.2-2.0 Ga evidenced by their positive zircon epsilon Hf values. The Hf isotopic composition of zircon from pre-collisional granitoids has a large range of negative epsilon Hf values between -28.8 and -1.7 indicating crustal protoliths. This range of unradiogenic Hf isotopic compositions is explained by inefficient mixing of magmas derived from felsic and mafic Paleoproterozoic sources that hybridised during incremental growth of the plutons. Zircon grains of contemporaneous mafic intrusions display slightly higher, yet enriched, Hf isotopic compositions consistent with crustal contamination of mantle magmas. The new Hf isotope data, integrated with other chemical and isotopic evidence, suggest derivation of the pre-collisional granitoids from lower crustal sources of the Paleoproterozoic basement, with only minor contributions from mantle-derived magmas. Thus, magmatism of the Aracuai orogen related to the assembly of West Gondwana was dominantly a crustal-reworking event. (C) 2020 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 15/16235-2 - Evolução da vida e oxigenação da Terra primitiva: uma perspectiva a partir da América do Sul
• Beneficiário: Pascal Andre Marie Philippot
• Modalidade de apoio: Auxílio à Pesquisa - Programa SPEC
• Processo FAPESP: 18/14617-3 - Limites temporais, condições de oxi-redução e fontes dos sedimentos relacionados ao aumento na oxigenação atmosférica no Proterozóico no Brasil
• Beneficiário: Francesco Narduzzi
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 19/17732-0 - O papel das grandes províncias ígneas subareas na modelagem de mudanças ambientais e climáticas durante o aumento do oxigênio atmosférico no Proterozoico no Brasil
• Beneficiário: Francesco Narduzzi
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado