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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Magmatismo gran?tico na por??o central do dom?nio Rio Piranhas-Serid?, Prov?ncia Borborema: geologia e petrologia do Stock Flores (RN)

Souza, Viviane Oliveira de 29 April 2016 (has links)
Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-01-03T19:37:12Z No. of bitstreams: 1 VivianeOliveiraDeSouza_DISSERT.pdf: 10963808 bytes, checksum: 12e9b4d4da9f06196592b134e29e774d (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-01-05T21:26:38Z (GMT) No. of bitstreams: 1 VivianeOliveiraDeSouza_DISSERT.pdf: 10963808 bytes, checksum: 12e9b4d4da9f06196592b134e29e774d (MD5) / Made available in DSpace on 2017-01-05T21:26:38Z (GMT). No. of bitstreams: 1 VivianeOliveiraDeSouza_DISSERT.pdf: 10963808 bytes, checksum: 12e9b4d4da9f06196592b134e29e774d (MD5) 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.
2

Petrologia e geoqu?mica do magmatismo ediacarano Serra do Caramuru, Rio Grande do Norte, NE do Brasil

Mac?do Filho, Antomat Avelino de 19 February 2016 (has links)
Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-08-16T20:54:14Z No. of bitstreams: 1 AntomatAvelinoDeMacedoFilho_DISSERT.pdf: 31646406 bytes, checksum: f6ba113eebabf49dff56fd9add20f343 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-08-19T00:32:03Z (GMT) No. of bitstreams: 1 AntomatAvelinoDeMacedoFilho_DISSERT.pdf: 31646406 bytes, checksum: f6ba113eebabf49dff56fd9add20f343 (MD5) / Made available in DSpace on 2016-08-19T00:32:03Z (GMT). No. of bitstreams: 1 AntomatAvelinoDeMacedoFilho_DISSERT.pdf: 31646406 bytes, checksum: f6ba113eebabf49dff56fd9add20f343 (MD5) 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.

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