| Texto completo | |
| Autor(es): |
Azzone, R. G.
;
Pearson, D. G.
;
Sarkar, C.
;
Cetina, L. M. T.
;
Chmyz, L.
;
Luo, Y.
;
Ruberti, E.
;
Guarino, V.
;
Cabral-Neto, I.
Número total de Autores: 9
|
| Tipo de documento: | Artigo Científico |
| Fonte: | CHEMICAL GEOLOGY; v. 670, p. 19-pg., 2024-09-13. |
| Resumo | |
Kimberlites and related rocks are the focus of research and exploration in the Alto Paranaiba Igneous Province (APIP; Brazil) due to their potential correlation with adjacent diamond fields. New U-Pb perovskite ages were obtained using recommended protocols for error propagation and data interpretation. Despite the utility of perovskites for dating, their incorporation of significant common-Pb (common-Pb of new APIP data: 52-84 % for in situ analyses, 75-95 % for TIMS concentrate analyses) limits the age resolution of this dating approach. Consequently, the APIP U-Pb ages neither confirm nor discredit previously proposed geodynamic models that invoke age progression or distinct magmatic episodes. Comparing the new ID-TIMS and LA-ICP-MS ages of the same intrusions, the LA-ICP-MS data have lower uncertainties, largely due to accessing a greater spread in common-Pb, improving regressions, and tend to yield older ages. For perovskite grains collected from weathering profiles, we found evidence of Pb-loss. This process leads to higher uncertainties in individual analyses, increased data scatter, and consequently higher uncertainties in age estimates. For fresh samples with different degrees of crustal contamination from a single intrusion, we found an indication of some variability in( 207)Pb/Pb-206 and U-238/Pb-206 ratios of the perovskite data, with a tendency towards older ages for more contaminated sample. For almost fresh intrusions with geochemically and isotopically similar mantle sources, related to the same event and in a close geographic area, we prefer to use a unique local Pb-207/Pb-206 ratio as anchoring for each TeraWasserburg plot. This approach is particularly preferred when perovskite data of an intrusion are too clustered and the Pb-207/Pb-206 ratio from the unanchored T-W differs from that predicted from theoretical Pb-isotope evolution model. Despite the high-common Pb in APIP perovskite crystals, our new data using these strategies clearly indicate that APIP magmatism is restricted to the Cretaceous, with most cases crystallized in Upper Cretaceous, but some from Early Cretaceous, such as the diamondiferous occurrence of Catalao-1b (120.6 +/- 6.7 Ma). Different triggers of APIP magmatism are related to both episodes, mainly attributed to supercontinent break-up stages. (AU) | |
| Processo FAPESP: | 17/21397-7 - Xenocristais e cristais cognatos em kimberlitos da Província Alcalina Alto Paranaíba (MG-GO, Brasil): contribuições petrológicas a partir de microanálises in situ elementais e isotópicas |
| Beneficiário: | Rogério Guitarrari Azzone |
| Modalidade de apoio: | Bolsas no Exterior - Pesquisa |
| Processo FAPESP: | 23/12323-0 - Revisitando as idades do Maciço Alcalino Poços de Caldas: Datação 40Ar/39Ar de amostras-chave para solucionar um dilema |
| Beneficiário: | Luanna Chmyz |
| Modalidade de apoio: | Bolsas no Brasil - Pós-Doutorado |
| Processo FAPESP: | 19/22084-8 - A Província Magmática Paraná: petrogênese, cronologia e impacto ambiental do magmatismo toleítico, alcalino e silícico Cretáceo na Plataforma Brasileira |
| Beneficiário: | Valdecir de Assis Janasi |
| Modalidade de apoio: | Auxílio à Pesquisa - Temático |
| Processo FAPESP: | 17/03768-8 - A influência composicional de xenocristais e antecristais em magmas básicos a ultrabásicos alcalinos |
| Beneficiário: | Rogério Guitarrari Azzone |
| Modalidade de apoio: | Auxílio à Pesquisa - Regular |
| Processo FAPESP: | 23/11675-0 - Corpos magmáticos de afinidade básica-ultrabásica insaturados em SiO2 da plataforma brasileira: estudo de fontes e processos de evolução em sistema aberto em complex plumbing systems a partir de abordagem microanalítica |
| Beneficiário: | Rogério Guitarrari Azzone |
| Modalidade de apoio: | Auxílio à Pesquisa - Regular |