Banca de DEFESA: IB SILVA CÂMARA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : IB SILVA CÂMARA
DATA : 20/08/2021
HORA: 14:00
LOCAL: https://conferenciaweb.rnp.br
TÍTULO:

Graphite in the Tanque Novo-Ioirá Complex, NE of the São Francisco Craton, Bahia, Brazil: Characterization and Metallogenetic Potential

PALAVRAS-CHAVES:

Graphite mineralization, graphitic carbon, Paleoproterozoic,São Francisco Craton

PÁGINAS: 72
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
SUBÁREA: Geologia
ESPECIALIDADE: Metalogenia
RESUMO:

Brazil is the third biggest producer of graphite worldwide and the graphite province Bahia-Minas, located in the state of Bahia, is the second-largest producer in the country. The study area is situated to the north of this province in the Tanque Novo-Ipirá Complex, within the Salvador-Curaçá Orogen, which is a member of the São Francisco Craton. The area is comprised of host rocks with occurrences of graphite such as schists, marbles, and granulites as well as country rocks characterized by quartzites, calc-silicate rocks, marbles, and iron formations. The petrographic analysis supported by MEV/EDS indicates two generations of graphite: the first one, connected to the graphitization process generated by metamorphism (syngenetic), exhibit flakes with three distinct associations related to the greenschist, amphibolite, and granulite facies in which the host rocks were subjected; and the second generation, is related to the percolation of fluids (epigenetic) due to retrograde metamorphism in the greenschist facies that promoted the deposition of graphite in venules or as a result of carbonation. The graphite bodies show a high content of graphite Fixed Carbon (FC), analyzed by LECO infrared, ranging from 8.60 to 14.82wt% and they occur in two distinct lithologies: aluminous and carbonate. The geochemical characteristics of the host and country rocks indicate sedimentary protoliths with signatures influenced by diagenetic alterations and detrital input in a marine paleoenvironment. However, they were not sufficient to change the anomalies of Ce/Ce* = 0.64 to 1.49 that alongside the ratios of U/Th = 0.04 to 1.30, suggest a paleoenvironment dominantly oxide. Despite not possessing the Total Organic Carbon (TOC) content, the analysis of BC with P/Ti, Ba/Ti, Ni, and Cu still carries correlations that denote the deposition of organic matter in a context of high paleoproductivity of the paleobasin. This depositional setting combining with the phosphorus anomalies in the country rocks, deposited during the Paleoproterozoic in an oxide paleoenvironment, suggest that the deposition of organic matter that originates the graphite might be related to the increase in paleoproductivity generated following the Great Oxygenation Event (GOE), which culminated in the first major phosphogenesis event in the geological record.

MEMBROS DA BANCA:
Presidente - 003.403.165-00 - AROLDO MISI - UFBA
Interna - 2334411 - DEBORA CORREIA RIOS
Externo à Instituição - PEDRO MACIEL DE PAULA GARCIA - UFMT