Banca de DEFESA: MARIA CLARA MARTINS CARDOSO DUARTE

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : MARIA CLARA MARTINS CARDOSO DUARTE
DATA : 15/12/2020
HORA: 09:00
LOCAL: https://conferenciaweb.rnp.br/webconf/colegiado-de-pos-graduacao-em-geologia-ufba
TÍTULO:

GRANITOGENESIS ASSOCIATED WITH BRUMADO-BAHIA GRANITE-GREENSTONE, GAVIÃO BLOCK, SÃO FRANCISCO CRATON: PETROGENETIC CONSIDERATIONS

PALAVRAS-CHAVES:

Granitogenesis; Lithogeochemistry; Petrography, Geochronology

PÁGINAS: 88
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
SUBÁREA: Geologia
ESPECIALIDADE: Petrologia
RESUMO:

The granite-greenstone terrains of the Brumado region are inserted in the geotectonic macrounity of the São Francisco Craton, more specifically in the southern portion of the Gavião block, and represent the primitive substrate of the region, with Archaean age. Nine different lithotypes were identified: the Brumado Greenstone-belt, Gavião orthogneiss, monzogranitic orthogneiss, Caraguataí orthogneiss, metassienogranite, metagranodiorite, leucogranite, Serra da Franga granite and porphyritic metassienogranite. The objective of the present work was to carry out petrographic and geochemical studies (especially the ETRs standards) of granitogenesis and basement in the Brumado region, in addition to geochronological analyzes focusing on granitogenesis. It was possible to suggest that the metasienogranite is the result of partial fusion of monzogranitic orthogneiss (because it presents partial fusion relationships, same ETR pattern and same geochemical behavior of major elements and trace) and, leukogranite is a result of partial fusion of Gavião orthogneiss ( TTG Archean), when also analyzing this comparison of the behavior of the major elements and trace, in addition to the ETR standard. Both Serra da Franga granitoids, porphyritic metassienogranites and metagranodiorites are possibly intrusive granitoids in the final stages of formation of these lands. The study of the tectonic ambience of these lithotypes corroborated the results obtained through the analysis of the major elements, trace and ETRs, and revealed an intraplate origin for the syenogranite and the monzogranitic orthogneisses. The Gavião orthogneiss, together with leucogranite, revealed the same origin, that of a magmatic arc. Serra da Franga granitoid, metagranodiorite and porphyritic metassienogranite also have a magmatic arc origin, related to late intrusions common in these types of terrain. U-Pb analyzes were performed on zircon (LA-ICP-MS), on three intrusive granitoids in the BG: porphyritic metassienogranite, metagranodiorite and Serra da Franga granite from the region. The porphyritic metasienogranite showed a protolite crystallization age of 3216 ± 48 Ma indicating paleoarquean magmatism. The metagranodiorite revealed a crystallization age of 2697 ± 12 Ma, registering neoarquean magmatism, thus demonstrating the importance of a magmatic event of this age, since neoarquean granitoids occur in a small proportion in the state of Bahia. The Serra da Franga granitoid revealed an age of 2107 ± 27 Ma, corroborating with Riacian magmatism, in accordance with other intrusive bodies in the southern BG of similar ages. The obtained ages suggest the existence of paleoarquean and neoarquean magmatism in this sector of the Gavião block, in addition to intrusive paloproterozoic granitoids in this region.

MEMBROS DA BANCA:
Presidente - 1295799 - ANGELA BEATRIZ DE MENEZES LEAL
Interno - 2982944 - JAILMA SANTOS DE SOUZA DE OLIVEIRA
Externo ao Programa - 285991 - AMALVINA COSTA BARBOSA
Externo à Instituição - ERON PIRES MACEDO - SGB
Externo à Instituição - MARIA ZÉLIA AGUIAR DE SOUZA - UFMT