| Texto completo | |
| Autor(es): |
Motta, Rafael Gonsalves
;
Moraes, Renato
Número total de Autores: 2
|
| Tipo de documento: | Artigo Científico |
| Fonte: | Journal of South American Earth Sciences; v. 152, p. 12-pg., 2024-12-21. |
| Resumo | |
In the southeastern Brazil, a thick section of lower crust crops out in the Socorro-Guaxup & eacute; Nappe, part of a Neoproterozoic orogenic collage in the southernmost part of the Bras & iacute;lia Orogen. Migmatites, predominantly diatexites, and granulites underwent ultra-high temperature conditions, reaching around 1000 degrees C and 10 kbar during their metamorphic peak. However, these rocks exhibit distinct structural characteristics within the studied area. Late-stage foliation in migmatites displays a more dispersed distribution with a predominant NW-SE orientation, whereas in granulites, the foliation predominantly trends in a WSW-ESE direction. Lineation in the migmatites is defined by feldspars and hydrated minerals, such as biotite and hornblende with a WNW-ESE direction, whereas in the granulites it is defined by anhydrous minerals like pyroxenes and feldspars, exhibiting a WSW-ENE orientation. The quartz c-axis fabric opening-angle for the residuum of granulite shows the highest values (135-154 degrees), followed by the leucosome of granulites (113-130 degrees) and then leucosome of migmatites (86-97 degrees). This implies that the quartz c-axis fabric in granulites records two distinct temperature regimes: the residual portion aligns closely with the metamorphic peak temperatures, ranging between 869 and 923 degrees C, while another stage corresponds to temperatures near the crystallization point of the leucosome, ranging between 796 and 853 degrees C. The migmatites exhibit quartz c-axis fabric temperature between 633 and 685 degrees C. Therefore, the solid-state deformation in granulites occurred at higher temperatures compared to migmatites, which remained in suprasolidus conditions over a broader temperature range (>300 degrees C). Thus, both units reached the metamorphic peak at same crustal level, but their exhumation histories are contrasting: while granulites were crystallized, migmatites remained partially molten, preserving distinct deformation geometries. (AU) | |
| Processo FAPESP: | 15/22355-0 - Formação, transformação e evolução da crosta continental inferior: investigando o orógeno brasília meridional |
| Beneficiário: | RAFAEL GONÇALVES DA MOTTA |
| Modalidade de apoio: | Bolsas no Brasil - Doutorado |
| Processo FAPESP: | 16/22627-3 - Metamorfismo e fusão parcial em Orógenos antigos II |
| Beneficiário: | Renato de Moraes |
| Modalidade de apoio: | Auxílio à Pesquisa - Regular |
| Processo FAPESP: | 13/04007-0 - Metamorfismo e fusão parcial em orógenos antigos |
| Beneficiário: | Renato de Moraes |
| Modalidade de apoio: | Auxílio à Pesquisa - Regular |
| Processo FAPESP: | 16/10276-1 - Formação, Transformação e Evolução da Crosta Continental Inferior: Investigando o Orógeno Brasília Meridional |
| Beneficiário: | RAFAEL GONÇALVES DA MOTTA |
| Modalidade de apoio: | Bolsas no Exterior - Estágio de Pesquisa - Doutorado |