| Texto completo | |
| Autor(es): |
Lima, Nicholas M.
[1]
;
Azzone, Rogerio G.
[1]
;
Chmyz, Luanna
[1]
;
Guarino, Vincenza
[2]
;
Ruberti, Excelso
[1]
;
Silva, Simone
[1]
;
Svisero, Darcy P.
[1]
Número total de Autores: 7
|
| Afiliação do(s) autor(es): | [1] Univ Sao Paulo, Inst Geociencias, Rua Lago 562, BR-05508080 Sao Paulo - Brazil
[2] Univ Napoli Federico II, Dipartimento Sci Terra Ambiente & Risorse, Complesso Univ Monte St Angelo, Ed L, Via Cintia 26, I-80126 Naples - Italy
Número total de Afiliações: 2
|
| Tipo de documento: | Artigo Científico |
| Fonte: | CANADIAN MINERALOGIST; v. 58, n. 5, p. 563-585, SEP 2020. |
| Citações Web of Science: | 0 |
| Resumo | |
The Indaia-I and Indaia-II intrusions are hypabyssal. small-sized ultrabasic bodies belonging to the Cretaceous magmatism of the Alto Paranaiba Alkaline Province (southeast-central western Brazil). While Indaia-I is classified as an archetypal group-I kimberlite, Indaia-II (its satellite intrusion) presents several petrographic and chemical distinctions: (1) an ultrapotassic composition (similar to kamafugites), (2) lower volumes of olivine macrocrysts, (3) diopside as the main matrix phase (in contrast with the presence of monticellite in Indaia-D, (4) high amounts of phlogopite, and (5) abundant felsic boudinaged and stretched microenclaves and crustal xenoliths. Disequilibrium features, such as embayment and sieve textures in olivine and clinopyroxene grains, are indicative of open-system processes in Indaia-II. Mineral reactions observed in Indaia-II (e.g., diopside formed at the expense of monticellite and olivine; phlogopite nearby crustal enclaves and close to olivine macrocrysts) point to an increase in the silica activity of the kimberlite magma; otherwise partially melted crustal xenoliths present kalsilite, generated by desilification reactions. The high Contamination Index (2.12-2.25) and the large amounts of crustal xenoliths (most of them totally transformed or with evidence of partial melting) indicate a high degree of crustal assimilation in the Indaia-II intrusion. Calculated melts (after removal of olivine xeuocrysts) of Indaia-II have higher amounts of SiO2, Al2O3, K2O, slightly higher Rb/Sr ratios, lower Ce/Pb and Gd/Lu ratios, higher Sr-87/Sr-86, and lower Nd-143/Nd-144 than those calculated for Indaiit-1. Crustal contamination models were developed considering mixing between the calculated melts of Indaia-I and partial melts modeled from the granitoid country rocks. Mixing-model curves using major and trace elements and isotopic compositions are consistent with crustal assimilation processes with amounts of crustal contribution of ca. 30%. We conclude that (1) Indaii-II is representative of a highly contaminated kimberlitic intrusion, (2) this contamination occurred by the assimilation of anatectic melts from the main crustal country rocks of this area, and (3) Indaii-I and Indaii-II could have had the same parent melt, but with different degrees of crustal contamination. Our petrological model also indicates that Indaii-II is a satellite blind pipe linked to the main occurrence Indaia-I. (AU) | |
| Processo FAPESP: | 12/06082-6 - A província magmática Paraná-Etendeka no Brasil: relações temporais e petrológicas entre o magmatismo toleítico e alcalino e suas implicações geodinâmicas |
| Beneficiário: | Excelso Ruberti |
| Modalidade de apoio: | Auxílio à Pesquisa - Temático |
| Processo FAPESP: | 18/15731-4 - Mobilidade de elementos em processos de fenitização: o metassomatismo carbonatítico nas províncias alcalinas do Alto Paranaíba e Arco de Ponta Grossa |
| Beneficiário: | Luanna Chmyz |
| Modalidade de apoio: | Bolsas no Brasil - Pós-Doutorado |
| 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 |