Banca de QUALIFICAÇÃO: MATEUS DE ARAÚJO SILVA
Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.DISCENTE : MATEUS DE ARAÚJO SILVA
DATA : 19/12/2017
HORA: 16:00
LOCAL: Sala 1 - PPGG
TÍTULO:
NEOPROTEROZOIC GRANITIC MAGMATISM IN THE RIO PIRANHAS-SERIDÓ DOMAIN: GEOCHEMISTRY AND GEOCHRONOLOGY OF SERRA OF ACAUÃ PLUTON
PALAVRAS-CHAVES:
ediacaran plutonism, mineral province of seridó, serra of acauã granitic pluton
PÁGINAS: 20
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:
Ediacaran plutonic activity comes to be considered as one of the most important geological features of the Rio Piranhas-Seridó Domain (PSD), Borborema Province, NE of Brazil, represented by a series of granitoid bodies in the form ofbatholiths, stocks and dikes. In this context, the Serra of Acauã Granitic Pluton (SAGP) is inserted on the border between the municipalities of Currais Novos and Acari (RN). Geologically, SAGP is located in the central portion of the PSD in the area known as the Mineral Province of Seridó (MPS), which stands out for presenting a wide variety of mineral resources, among them: W-Mo skarn deposits, iron in BIFs, Ta-Nb and gemstones associated with pegmatites, as well as gold in quartz veins. Therefore, the integrated study of the SAGP (geology, petrography, geochronology, and geochemistry) can provide important information for a better understanding/discussion about the relationship between "Ediacaran granite magmatism versus mineralizations" in the context of the MPS. The referred pluton is elliptically oriented in the N-S direction and intrudes the mica schists of the Seridó Formation. Cartographically the SAGP is divided into two facies: one equigranular medium to fine-grained (subordinate) and one inequigranularmedium to weakly porphyritic (predominant) with phenocrysts of K-feldspar of 1.0 to 3.0 cm. From the petrographic point of view, the two facies show similar modal composition. They are hololeucocraticto leucocraticbiotite monzogranite (M = 1.3% -9.9%), light gray to slightly pink. Quartz, microcline, and oligoclase plagioclase constitute the dominant and felsic paragenesis, biotite is the main mafic (between 0.5% to 8.1%), and opaque minerals, titanite, allanite, apatite, and zircon are considered as traces (always ≤ 1.5 %), and appear as the earliest mineral phases. Chlorite, white mica, and carbonate are late phases and products of biotite and feldspar alterations, respectively. The lithochemicaldata associated with major, minor and traceselements also pointed a similarity regarding the chemistry of the two facies of the SAGP. Both are peraluminous (A/CNK ≥ 1), and always with normative corundum (0.9 to 1.4%). In discriminant geochemical diagrams of series/magmatic associations show a transitional chemistry between alkaline and calc-alkaline rocks, being called as subalkalines or high-K calc-alkaline. Discriminant diagrams of tectonic environments insert the SAGP in the context of sincolisional granites. Harker-type diagrams show negative correlations for Al2O3, CaO, Fe203(t), MgO, TiO2, P2O5 suggesting plagioclase fractionation, accompanied by the primary mafic phases, especially biotite, titanite, apatite and opaque minerals (ilmenite and magnetite) during the evolution of the SAGP magma. The analysis of the rare earth elements (REE) diagram shows an enrichment of light REE compared to the heavy ones, with LaN/YbN ratios between 16.10 and 54.75, and negative Eu anomaly (Eu/Eu* between 0.40 and 0.65) compatible with plagioclase fractionation. Determination (SHRIMP) of U-Pb in zircon showed an age of 579 ± 3 Ma (Ediacaran) for its crystallization, close to that already found for other Ediacaran plutons in PSD (Acari, São Rafael, among others). Finally, the petrographic, textural and chemical data allowed to associate the SAGP to the granitoids of the high-K calcium-alkaline suite of Nascimento et al., widely distributed in the PSD.
MEMBROS DA BANCA:
Presidente - 080.368.454-15 - ANTONIO CARLOS GALINDO - UFRN
Interno - 2042352 - FREDERICO CASTRO JOBIM VILALVA
Interno - 1513243 - MARCOS ANTONIO LEITE DO NASCIMENTO
Externo à Instituição - VLADIMIR CRUZ DE MEDEIROS - SGB