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Previous issue date: 2016-02-19 / Os stocks Serra do Caramuru e Tapuio, localizados no extremo NE do Dom?nio Rio Piranhas-Serid? (RN), s?o representantes do magmatismo ediacarano a cambriano, uma fei??o magm?tica marcante da orog?nese Brasiliana / Panafricana na Prov?ncia Borborema. Estes corpos s?o an?logos litol?gicos, intrusivos no embasamento gn?issico paleoproterozoico, estando separados por uma t?nue faixa de ortognaisses milon?ticos. As rela??es de campo mostram uma estratigrafia magm?tica iniciada pela f?cies dior?tica que coexiste com as f?cies gran?tica porfir?tica e gran?tica equigranular I e, em menor frequ?ncia, com a f?cies gran?tica equigranular II. Estas rochas s?o cortadas por diques e sheets gran?ticos tardios NE-SW a NNE-SSW. A f?cies dior?tica (dioritos, quartzo dioritos, quartzo monzodioritos, tonalitos e granodioritos) ? leucocr?tica a melanocr?tica, rica em biotita e anfib?lio. As f?cies gran?ticas s?o hololeucocr?ticas a leucocr?ticas, com biotita ? anfib?lio. Dados petrogr?ficos e geoqu?micos (rocha total) provenientes em maior propor??o do plut?o Serra do Caramuru, sugerem o fracionamento de zirc?o, apatita, clinopirox?nio (em dioritos), opacos, titanita, biotita, hornblenda, allanita, plagiocl?sio, microcl?nio e granada (em diques). O comportamento dos elementos tra?os Zr, La e Yb indicam que dioritos n?o constituem o magma parental dos granitos. Por outro lado, as f?cies gran?ticas s?o cogen?ticas entre si, apresentando trends de diferencia??o e espectros de elementos terras raras (ETR) an?logos [12.3?(La/Yb)N?190.8; Eu/Eu*=0.37-0.68]. Rela??es de campo e padr?o de ETR [6.96?(La/Yb)N?277.8; Eu/Eu*=0.18-0.58] demonstram que os diques e sheets gran?ticos n?o s?o cogeneticamente relacionados ao magmatismo Serra do Caramuru. A f?cies dior?tica ? metaluminosa (A/CNK = 0.88-0.74), shoshon?tica, ao passo que granitos s?o metaluminosos a peraluminosos (A/CNK = 1.08-0.93), c?lcio-alcalinos de alto pot?ssio. Diques e sheets s?o estritamente peraluminosos (A/CNK = 1.01-1.04). Diagramas bilogar?tmicos relacionando elementos compat?veis e incompat?veis e microtexturas indicam a cristaliza??o fracionada como o mecanismo dominante na evolu??o magm?tica das diversas f?cies. Os stocks Serra do Caramuru e Tapuio mostram trama magm?tica bem preservada, aus?ncia de minerais metam?rficos e s?o estruturalmente isotr?picos, com rela??es de contato discordantes da trama d?ctil do embasamento gn?issico. Estas observa??es conduzem a um est?gio de relativa estabilidade tect?nica, compat?veis com o per?odo de relaxamento orogen?tico da cadeia Brasiliana / Panafricana. Os diagramas qu?micos discriminantes envolvendo ?xidos e elementos tra?os indicam um ambiente tardio ? p?s-colisional. Neste contexto, o mecanismo de coloca??o que melhor explica o alojamento dos stocks seria a abertura de espa?o em fraturas de Ridel tipo T, com vetor de estiramento orientado ENE-WSW. A idade U-Pb de 553 ? 10 Ma permite correlacionar o magmatismo Serra do Caramuru aos grupo de granitoides tardios a p?s-colisionais, c?lcio-alcalinos de alto pot?ssio equigranulares, do extremo NE do Dom?nio Rio Piranhas-Serid?. / The Serra do Caramuru and Tapuio stocks, located in the extreme NE of Rio Piranhas-Serid? Domain (RN), are representative of the Ediacaran-Cambrian magmatism, an important magmatic feature of the Brasilian / Panafrican orogeny of the Borborema Province. These bodies are lithologically similar, intrusive in paleoproterozoic gneiss embasement, being separated by a thin belt of mylonitic orthogneiss. The field relations show a magmatic stratigraphy initiated by dioritic facies that coexists with the porphyritic granitic and equigranular granitic I facies, and less frequently with equigranular granitic II facies. These rocks are crosscut by late granitic dykes and sheets with NE-SW / NNE-SSW orientation. The dioritic facies (diorite, quartz diorite, quartz monzodiorites, tonalite and granodiorite) is leucocratic to melanocratic, rich in biotite and hornblende. The granitic facies are hololeucocratic to leucocratic, and have biotite ? hornblende. Petrographic and geochemical (whole rock) data, especially from Serra do Caramuru pluton, suggest fractionation of zircon, apatite, clinopyroxene (in diorites), opaque minerals, titanite, biotite, hornblende, allanite, plagioclase, microcline and garnet (in dykes). The behavior of trace elements such as Zr, La and Yb indicates that the dioritic magma does not constitute the parental magma for the granitic facies. On the other hand, the granitic facies seems to be cogenetic to each other, displaying differentiation trends and very similar rare earth elements (REE) spectra [12.3?(La/Yb)N?190.8; Eu/Eu*=0.30-0.68]. Field relationships and REE patterns [6.96?(La/Yb)N?277.8; Eu/Eu*=0.18-0.58] demonstrate that the granitic dykes and sheets are not cogenetically related to the Serra do Caramuru magmatism. The dioritic facies is metaluminous (A/CNK = 0.88-0.74) and shoshonitic, whereas the granitic ones are metaluminous to peraluminous (A/CNK = 1.08-0.93) and high potassium calc-alkaline. Dykes and sheets are strictly peraluminous (A/CNK = 1.01-1.04). Binary diagrams relating compatible and incompatible trace elements and microtextures indicate the fractional crystallization as the dominant mechanism of magmatic evolution of the various facies. The Serra do Caramuru and Tapuio stocks have well preserved magmatic fabric, do not show metamorphic minerals and are structurally isotropic, showing crosscutting contact with the ductile fabric of the basement. These observations lead to interpretate a stage of relative tectonic stability, consistent with the orogenic relaxation period of the Brasiliano / Pan-African orogeny. Chemical plots involving oxides and trace elements indicate late to post-collisional emplacement. In this context, the assumed better mechanism to describe the stocks emplacement within an extensional T Riedel joint, with ENE-WSW extensional vector. The U-Pb zircon age of 553 ? 10 Ma allows correlating the Serra do Caramuru magmatism to the group of post-collisional bodies, equigranular high potassium calc-alkaline granites of the NE of Rio Piranhas-Serid? Domain.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/21185 |
| Date | 19 February 2016 |
| Creators | Mac?do Filho, Antomat Avelino de |
| Contributors | 15603180404, http://lattes.cnpq.br/1259445348649589, Vilalva, Frederico Castro Jobim, 22140632850, http://lattes.cnpq.br/6227637633613443, Barros, Carlos Eduardo de Mesquita, 66679800978, http://lattes.cnpq.br/3850881348649179, Souza, Zorano S?rgio de |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM GEODIN?MICA E GEOF?SICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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