Banca de DEFESA: MATEUS DE ARAÚJO SILVA
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.DISCENTE : MATEUS DE ARAÚJO SILVA
DATA : 25/07/2018
HORA: 14:00
LOCAL: Auditório do LGGP I
TÍTULO:
NEOPROTEROZOIC GRANITIC MAGMATISM IN THE RIO PIRANHAS-SERIDÓ DOMAIN: GEOLOGY AND PETROLOGY OF SERRA DA ACAUÃ STOCK
PALAVRAS-CHAVES:
Ediacaran Plutonism; Rio Piranhas-Seridó Domain; Serra da Acauã Stock; Petrology
PÁGINAS: 70
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:
The ediacaran plutonic activity consists of one of the most important geological features in the Borborema Province, NE of Brazil. In this context, the Serra da Acauã Stock (SAS) is inserted in the eastern portion of the Rio Piranhas-Seridó Domain (PSD), between the Currais Novos and Acari cities, state of Rio Grande do Norte. The integrated SAS study (geology, petrography, geochronology and geochemistry) may provide important information for a better understanding/discussion about ediacaran granitic magmatism in PSD. Cartographically, this stock has a surface area of 7km2 divided into two facies: one fine to medium equigranular (subordinate) and a onother unequigranular medium to slightly porphyritic (predominant), with K-feldspar phenocrysts of 1.0 to 3.0cm. U-Pb (SHRIMP) determinations in zircon indicated an ediacaran age of c. 578 Ma for its crystallization, close to those already found for other ediacaran plutons in DPS. Petrographically the SAS rocks are hololeucocratic to leucocratic biotite-monzogranites (M = 1.3% -9.9%), with biotite being the main mafic (0.5% to 8.1%). Opaque minerals, titanite, allanite, apatite and zircon are earliest minerals. Geochemically the SAS rocks are similar, with a weakly peraluminous character (1.00≤A/CNK≤1.04), with normative corundum (0.11 – 0.59%) and transition signature between alkaline and calc-alkaline. The variation of the amount oxides and trace elements suggests the fractionation of plagioclase, biotite, titanite, apatite and magnetite during the crystallization of SAS magma. The Rare Earth Element (REE) diagram shows enrichment of the LREE relative to the HREE, with LaN/YbN ratios between 16.10 and 54.75, and negative Eu anomalies (Eu/Eu* = 0.66 – 0, 90) compatibles with plagioclase fractionation. Tectonic discriminant diagrams insert the SAS in the context of late to post-tectonic granites in relation to the Brasiliana orogenesis. The titanite-magnetite-quartz paragenesis in equilibrium, in addition to the processes of marttitization associated with magnetite crystals indicate relatively high fugacity (fO2) during the evolution/crystallization of magma. Data related to the zircon saturation temperature added to the geochemical discriminant diagrams allow to associate these rocks with a regime similar to that of highly fractionated I-type granites of southern China. The total dataset allows correlating the SAS to the context of late to post-tectonics high-K calc-alkaline granites of PSD.
MEMBROS DA BANCA:
Presidente - 080.368.454-15 - ANTONIO CARLOS GALINDO - UFRN
Externo à Instituição - GORKI MARIANO - UFPE
Interno - 1513243 - MARCOS ANTONIO LEITE DO NASCIMENTO