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Previous issue date: 2015-08-25 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O plut?o Bom Jardim de Goi?s (PBJG) ? um corpo de geometria semi-circular, situado na por??o central da Prov?ncia Tocantins, intrusivo em ortognaisses e metassupracrustais do Arco Magm?tico Aren?polis. Estas metasupracrustais apresentam um bandamento / xistosidade de ?ngulo baixo a moderado, definido por micas, andalusita, silimanita e cordierita, caracterizando um metamorfismo na f?cies anfibolito. Tal estrutura ? truncada pela coloca??o das rochas do PBJG. O car?ter abrupto dos contatos e a aus?ncia de estruturas d?cteis demonstram que a intrus?o se deu em crosta relativamente fria. Em termos petrogr?ficos, o plut?o comp?e-se de monzodioritos, tonalitos e granodioritos, seguindo a trajet?ria evolutiva c?lcio-alcalina de pot?ssio baixo a intermedi?rio. As rochas do PBJG possuem hornblenda e biotita como fases m?ficas principais, al?m da ocorr?ncia subordinada de clinopirox?nio, titanita, ep?doto e opacos. Diques tardios de leucogranito cont?m apenas biotita como mineral acess?rio relevante. Uma data??o U-Pb em zirc?o do monzodiorito forneceu uma idade de 550?12 Ma (MSWD = 1,06). Dados litogeoqu?micos e de qu?mica mineral sugerem que as rochas em foco s?o c?lcio-alcalinas, tendo evolu?do por cristaliza??o fracionada de minerais c?lcicos e ferro-magnesianos, sob condi??es de alta fugacidade de oxig?nio. Utilizando o geoterm?metro do par anfib?lio-plagiocl?sio e o geobar?metro de Al em anfib?lio, foram determinadas temperaturas e press?es em torno de 692-791 ?C e 2,4 e 5,0 kbar para a intrus?o do PBJG, o que ? corroborado por associa??es metam?rficas pr?-existentes nas encaixantes. As caracter?sticas geol?gicas, geoqu?micas e a geocronologia do PBJG demonstram sua natureza p?s-tect?nica ou p?s-colisional, com coloca??o em crosta j? soerguida e relativamente fria, ao final da orog?nese brasiliana nesta por??o da Prov?ncia Tocantins. / The Bom Jardim de Goi?s Pluton (PBJG) is a semi-circular body, located in the central portion of the Tocantins Province, intrusive into orthogneisses and metassupracrustals of the Aren?polis Magmatic Arc. These metasupracrustals present a low to moderate dipping banding or schistosity, have a low to moderate angle of banding / foliation, defined by mica, andalusite and sillimanite and cordierite, which characterize an amphibolite facies metamorphism. This structure is crosscut by the emplacement of the PBJG rocks. The abrupt nature of the contacts and the absence of ductile structures indicate that the intrusion took place in a relatively cold crust. Under petrographic grounds, the pluton consists mainly of monzodiorites, tonalite and granodiorite, following the low to medium-K calk-alkaline alkaline trend. Rocks of the PBJG have hornblende and biotite as the main mafic phases, besides subordinate clinopyroxene, titanite, epidote and opaque. Late dikes of leucogranite contain only mineral biotite as relevant accessory mineral. One U-Pb zircon dating of a monzodiorite yielded an age of 550 ? 12 Ma (MSWD = 1.06). Whole-rock and mineral chemistry suggest that the studied rocks are calc-alkaline, having evolved by fractional crystallization of Ca- and Fe-Mg minerals under high oxygen fugacity. Using the amphibole-plagioclase geothermometer and the Al-in amphibole geobarometer, we calculate temperatures and pressures of, respectively, 692-791 ?C e 2.4-5.0 kbar for the intrusion of the PBJG, which is corroborated by previous metamorphic assemblages in the country rocks. The geological, geochemical and geochronological features of PBJG demonstrate their post-tectonic or post-collisional nature, with emplacement into an already uplifted and relatively cool crust at the end of brasiliano orogeny in this portion of the Tocantins Province.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/21059 |
| Date | 25 August 2015 |
| Creators | Coimbra, Keyla Thayrinne Oliveira |
| Contributors | 15603180404, Vilalva, Frederico Castro Jobim, 22140632850, Concei??o, Herbet, 13383051587, Viana, R?bia Ribeiro, 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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