Banca de QUALIFICAÇÃO: GIAN DEYVERSON DE ARAUJO FONSECA
Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.DISCENTE : GIAN DEYVERSON DE ARAUJO FONSECA
DATA : 14/07/2018
HORA: 10:00
LOCAL: Sala 1 - PPGG
TÍTULO:
Petrographic and Litogeochemical Characterization of Serra do Capuxu Stock, SW of Rio Piranhas-Seridó Domain, Borborema Province
PALAVRAS-CHAVES:
CAPUXU’S STOCK; LITOGEOCEMISTRY; POST-COLISIONAL MAGMATISM; FRACIONATED I-TYPE GRANITES
PÁGINAS: 20
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:
The Borborema Province, northeastern Brazil, is characterized by an intense Plutonism of Ediacaran to Cambrian age (Orogênese Brasiliana). In this context, occur the Serra do Capuxu Stock’s (SC), geologically located in the southwestern portion of Rio Piranhas-Seridó Domain, north of the Malta’s Shear Zone(dextral transcurrent). Geografically, the SC is located at east of Pombal city, state of Paraíba. SC is intrusive in gneissic rocks of the Caicó Complex, of which include xenoliths and presents a late character evidenced by the absence of ductile tectonic features. Petrographically the stock consists of leucocratic rocks with monzogranitic composition, of equigranular texture occurring phenocrysts of K-feldspar (microcline). The K-feldspar+plagioclase+quartz constitute around of 85% modal, the biotite is the main mafic mineral and the accessory minerals are titanite, opaque, allanite and zircon. Chlorite, mica and carbonate occur as products of late-magmatic transformations of biotite and feldspars. They are highly evolved rocks (SiO2=71,80-73,14), with high alkali contents (Na2O+K2O=8,25-8,77), low calcium contents (CaO=1,23-1,69) and high FeO(t)/(FeO(t)+MgO) ratios, ranging from 0,85 to 0,90. Rare Earth Element (REE) spectrum’s show enrichment of light REE’s in relation to heavy REE’s, and a pronounced negative Europium’s anomaly (CeN/SmN=4,8-5,7; GdN/YbN=1,6-2,2; e Eu/Eu*=0,34-0,44), suggesting an important role of feldspar during the evolution of SC magma. The SC’s Aluminum Saturation Index exhibits a weakly peraluminous character (A/CNK = 1,00-1,03) with low normative corundum (0,13-0,54%). In discriminant diagrams of magmatic series, mostly of SC rocks show chemical affinity with rocks of the subalcaline series (Calc-alkaline of high-K), although in some diagrams an alkaline affinity is suggestive. Classificative diagrams of tectonic environment involving trace elements associate SC with post-collisional environment, corroborating with field aspects by the absence of ductile deformational tectonic features. It is proposed an eminently crustal source for the SC magma, possibly gneisses melts of the basement rocks (low melting degree due to their high and little varied SiO2 contents), already of a high K Calc-alkaline nature. In the literature, rocks with a similar lithochemical signature to that observed in the SC have been identified as "Fractionated I-Type Granites". A U-Pb zircon age of 542 Ma, reported in the literature, corroborates the hypothesis of a late (post-tectonic) emplacement to SC.
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