| Texto completo | |
| Autor(es): |
Pereira, Giovanna de Souza
;
Janasi, Valdecir de Assis
;
Andrade, Sandra
;
Alves, Adriana
;
Hernandez, Viviana Marcela Monsalve
Número total de Autores: 5
|
| Tipo de documento: | Artigo Científico |
| Fonte: | Journal of South American Earth Sciences; v. 131, p. 15-pg., 2023-10-10. |
| Resumo | |
A combination of U-Pb dating by SHRIMP and Lu-Hf isotope and trace-element analyses by LA-ICPMS in zircon crystals from representative samples of the Itu Granitic Batholith, allowed to determine timing, sources and intensive parameters of crystallization (T, fO(2)) of the plutons that generated this large (>300 km(2)) occurrence of A-type granites that locally marks the end of the Neoproterozoic orogeny in SE Brazil. The main episode of batholith construction is dated at 578 +/- 4 Ma, with possible minor manifestations as young as-560 Ma. Negative zircon epsilon Hf(t) as low as-19 to-17 in the Indaiatuba pluton requires a significant crustal input, but a component from enriched mantle (which has epsilon Hf(t) as low as-10, reflecting contamination from previous subduction) is evident in all plutons by the presence of small mafic bodies and frequent mafic microgranular enclaves showing evidence of mixing with the host granites. Distinct sources are implied by large contrasts in redox state, estimated qualitatively from negative Eu anomalies and quantitatively from Ce anomalies in zircon, with samples from the Itupeva and Salto plutons showing fO(2)similar to FMQ+2 and a sample from the Cabreuva pluton closer to FMQ. Significant intra-sample variations of epsilon Hf(t) and trace-elements (e.g., Th, U) in zircon are also indicative that multiple sources have contributed to individual magma batches and were probably preserved by fast crystallization related to magma mixing processes. (AU) | |
| Processo FAPESP: | 15/01817-6 - Geração e evolução de magmas graníticos e implicações tectônicas: uma contribuição da geoquímica isotópica Sr-Nd-Pb e da datação in situ e geoquímica de zircão em granitos do se do Brasil |
| Beneficiário: | Valdecir de Assis Janasi |
| Modalidade de apoio: | Auxílio à Pesquisa - Regular |
| Processo FAPESP: | 19/17550-0 - Identificação de áreas-fonte e condições de cristalização de magmas graníticos com base em geoquímica de minerais e rochas |
| Beneficiário: | Valdecir de Assis Janasi |
| Modalidade de apoio: | Auxílio à Pesquisa - Regular |