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Previous issue date: 2016-04-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A fase final da orogen?se Brasiliana / Pan-Africana, na Prov?ncia Borborema, NE do Brasil, ? caracterizada por um intenso magmatismo gran?tico, dentro desse contexto granitog?nico insere-se o stock gran?tico Flores. O presente trabalho tem como objetivo a caracteriza??o geol?gica, petrogr?fica, geoqu?mica e petrol?gica do stock Flores. Para a efetiva??o do trabalho foram realizadas etapas de campo, prepara??o e descri??o de sec??es delgadas bem como tratamento de amostras para an?lises qu?micas. O stock localiza-se pr?ximo a cidade de Afonso Bezerra, na por??o centro-norte do Rio Grande do Norte, geologicamente inserido no contexto do Dom?nio Rio Piranhas-Serid?, ocorre alongado na dire??o NW expondo uma ?rea aflorante de 8 km2 . Sua morfologia ? ressaltada por extensos pared?es constitu?dos por conjunto de matac?es, os quais comp?em as bordas do stock, destacando-o facilmente do relevo regional. ? intrusivo em rochas gn?issicas paleoproterozoicas, relacionadas ao Complexo Caic?, e augen gnaisses da su?te Po?o da Cruz (borda Noroeste). As rochas do stock Flores s?o monzogranitos equigranulares hololeucocr?ticos, sendo poss?vel distinguir duas f?cies no plut?o em fun??o de seus aspectos texturais: Flores Tipo I, composta por rochas equigranulares m?dia de colora??o rosada, caracterizada pelos matac?es; Flores Tipo II, com rochas equigranulares fina de colora??o acinzentada a rosada, exibindo relevo arrasado na por??o S/SE do stock. Localmente (na f?cies Tipo II) ocorrem enclaves de rochas dior?ticas exibindo fei??es de coexist?ncia de magmas (mixing e migling), al?m de enclaves do tipo schlieren elipsoidais, sendo estes interpretados como estruturas magm?ticas formadas por convec??o magm?tica atrav?s de plumas termais. Os monzogranitos exibem parag?nese essencial composta por quartzo, microclina e plagiocl?sio, que usualmente somam mais de 90% modal. Biotita ? o m?fico principal, ocorrendo ainda, titanita, allanita, apatita, zirc?o e opacos, e, como minerais tardios, fluorita, clorita, ep?doto granular, mica branca e carbonato, estes relacionados a flu?dos em est?gio subsolidus. As an?lises geoqu?micas evidenciam a natureza evolu?da das rochas do stock bem como sua afinidade alcalina. Altos teores em SiO2 (71,43 - 74,87%), Na2O+K2O (8,26- 9,08%), Al2O3 (12,99-13,93%), al?m do empobrecimento em MgO (<0,5%), CaO (?1,4%), Fe2O3 (<2,3%) e TiO2 (<0,4%) refletem o car?ter peraluminoso e leucocr?tico das rochas, ii corroborado pelos baixos teores de m?ficos (< 6%). Diferentes diagramas discriminantes de s?ries/associa??es magm?ticas atestam a afinidade alcalina das rochas do stock Flores, bem como sua analogia com granitos tipo-A. O espectro do diagrama de ERTs exibe um moderado grau de enriquecimento de ETRL em rela??o aos ETRP com raz?es LaN /YbN entre 4,59% - 30,85% e forte anomalia negativa de Eu, caracter?stico de rochas crustais e de granitos tipo-A. Finalmente diagramas geoqu?micos discriminantes de ambiente tect?nico sugerem que o stock Flores ? um plut?o de assinatura p?s-colisional. Tais dados s?o coerentes com a idade U-Pb 553?4 Ma encontrada para o Flores, o colocando dentro do contexto tardi a p?s-orog?nico da orog?nese Brasiliana / Pan-Africana, na Prov?ncia Borborema. / The final phase of Brasiliano/Pan-African orogeny in the Borborema Province, NE Brazil, is marked by widespread granitic magmatism, in which setting the Flores stock is included. The present study aims to characterize the geological, petrographic, geochemical and petrogenetic aspects of this pluton. In order to develop the investigation, field work, thin section preparation and description and sample treatment for chemical analysis were carried out. The stock is located near the city of Afonso Bezerra, central-north of Rio Grande do Norte state, geologically enclosed in the Rio Piranhas-Serid? Domain. The pluton is elongated in the NW direction and has an outcrop area about 8 km2. Its morphology is highlighted by long cliffs made up by sets of boulders, which compose the borders of the stock, clearly contrasting it from the regional topography. It intrudes the paleoproterozoic gneissic rocks related to the Caic? Complex and augen gneisses of the Po?o da Cruz suite (NW border). Rocks of the Flores stock are equigranular, hololeucocratic monzogranites, being possible to distinguish two facies, according to their textural aspects: Flores Type I, made up by monzogranite of medium texture and pink in color, characterized by the boulders; Flores Type II, with fine equigranular rocks, greyish to pinkish in color, exhibiting denudated relief in the S/SE portion of the stock. Locally in Type II facies, there are dioritic enclaves displaying features of magma coexistence (mixing and mingling), in addition to ellipsoidal schlieren enclaves, the latter being interpreted as magmatic structures formed by magmatic convection triggered by thermal plumes. The monzogranites exhibit essential paragenesis composed of quartz, K-feldspar and plagioclase, which usually add over 90% modal. Biotite is the main mafic mineral. Titanite, allanite, apatite, zircon and opaque minerals also occur. Fluorite, chlorite, granular epidote, white mica and carbonate appear as late minerals, which are related to fluids in subsolidus stage. Geochemical analyzes attest the evolved nature of the stock rocks as well as their alkaline affinity. High levels of SiO2 (71.43 to 74.87%), Na2O + K2O (8.26 to 9.08%) and Al2O3 (12.99 to 13.93%) and depletion of MgO (<0 5%), CaO (?1,4%), Fe2O3 (<2.3%) and TiO2 (<0.4%) witness the peraluminous and leucocratic character of the rocks, which is supported by low levels of mafic minerals (<6%). Distinct discriminant diagrams of magmatic series/associations confirm the alkaline affinity of rocks of the Flores stock and their analogy with A-type granites. The REE?s diagram spectrum exhibits moderate LREE enrichment relative to HREE, with LaN / YbN ratios between 4.59% and 30.85% and strong negative Eu anomaly, characteristic of crustal rocks and A-type granites. Geochemical discriminant diagrams of tectonic setting point out a post-collisional signature for the Flores stock. These data are consistent with U-Pb age of 553?4 Ma given by the Flores, inserting it within the tardi to post-orogenic context of the Brasiliana / Pan-African orogeny in the Borborema Province.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/21578 |
| Date | 29 April 2016 |
| Creators | Souza, Viviane Oliveira de |
| Contributors | 08036845415, http://lattes.cnpq.br/9747727150782125, Nascimento, Marcos Antonio Leite do, 90459261487, http://lattes.cnpq.br/5356037408083015, Vilalva, Frederico Castro Jobim, 22140632850, http://lattes.cnpq.br/6227637633613443, Medeiros, Vladimir Cruz de, 28943180497, http://lattes.cnpq.br/9369889068441214, Galindo, Antonio Carlos |
| Publisher | 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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