Estudo petrogr?fico e petrol?gico da Forma??o Tombador, Mesoproteroz?ico da Chapada Diamantina, Bahia

• Main Author: Souza, Arn?bio Silva de
• Other Authors: 83933212715
• Language: Portuguese
• Published: PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE PETR?LEO 2017
• Subjects: CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA::TECNOLOGIA QUIMICA::PETROLEO E PETROQUIMICA; Diag?nese; Argilominerais; Anquimetamorfismo; ?ndice de cristalinidade da ilita
• Online Access: https://repositorio.ufrn.br/jspui/handle/123456789/23876

Submitted by Automa??o e Estat?stica ([e-mail]) on 2017-09-05T19:25:26Z No. of bitstreams: 1 ArnobioSilvaDeSouza_DISSERT.pdf: 5771102 bytes, checksum: 83f601b7701ab9229184a97dbff2ea8e (MD5) === Approved for entry into archive by Arlan Eloi Leite Silva ([e-mail]) on 2017-09-13T21:57:43Z (GMT) No. of bitstreams: 1 ArnobioSilvaDeSouza_DISSERT.pdf: 5771102 bytes, checksum: 83f601b7701ab9229184a97dbff2ea8e (MD5) === Made available in DSpace on 2017-09-13T21:57:43Z (GMT). No. of bitstreams: 1 ArnobioSilvaDeSouza_DISSERT.pdf: 5771102 bytes, checksum: 83f601b7701ab9229184a97dbff2ea8e (MD5) Previous issue date: 2017-07-03 === Os dep?sitos silicicl?sticos da Forma??o Tombador, unidade basal do Grupo Chapada Diamantina, de idade mesoproteroz?ica, ocorrem numa faixa aproximadamente Norte-Sul ao longo da Serra do Sincor?, por??o central do Cr?ton S?o Francisco (CSF), Nordeste do Brasil. Esses dep?sitos s?o constitu?dos por uma espessa sequ?ncia de rochas silicicl?sticas. Realizou-se um estudo petrogr?fico e petrol?gico de se??es delgadas de rochas aflorantes da Fm. Tombador, juntamente com o aux?lio de t?cnicas especiais como a Fluoresc?ncia de Raios X (FRX), Difratometria de Raios X (DRX), Espectroscopia de Raios X por Dispers?o de Energia (EDS) e Microscopia Eletr?nica de Varredura (MEV). Com base nas an?lises, verificou-se que essas rochas s?o constitu?das predominantemente por metarenitos. Os seguintes eventos diagen?ticos foram identificados: infiltra??o mec?nica de argilas, compacta??o mec?nica, compacta??o qu?mica, sobrecrescimento de quartzo, sobrecrescimento de turmalina, fraturamento de gr?os, precipita??o de ?xido/hidr?xidos de ferro, dissolu??o de gr?os, cauliniza??o e ilitiza??o. Foram identificados atrav?s da FRX em amostra total, os seguintes elementos qu?micos em ordem decrescente, sil?cio (Si), alum?nio (Al), pot?ssio (K), ferro (Fe), magn?sio (Mg), tit?nio (Ti), zirc?nio (Zr), estr?ncio (Sr) e ?trio (Y). A alta concentra??o do sil?cio (Si), acima de 90% ? decorrente da abund?ncia do quartzo (Q95F3FR2, segundo Folk, 1974), sendo importante indicador da alta maturidade mineral?gica das rochas estudadas. Atrav?s da t?cnica de DRX, foram identificados os seguintes grupos de argilominerais: ilita, caulinita, esmectita e interestratificados de ilita/esmectita. Embora as caracter?sticas das amostras reflitam as condi??es pret?ritas de ambientes diagen?ticos, as medidas do ?ndice de cristalinidade da ilita ou ??ndice de Kubler? (KI), e a presen?a do mineral pirofilita s?o suficientes para demonstrar que as rochas da ?rea de estudo foram afetadas pelo anquimetamorfismo, indicativo da transi??o entre a f?cies prehnita-pumpelita superior e a f?cies xisto verde inferior, e que as condi??es de soterramento atingiram a profundidade da ordem de 10-12 km e temperaturas da ordem de ?300 0C. A ocorr?ncia de determinados argilominerais (ilita, caulinita e esmectita), o alto teor de quartzo, os baixos teores de feldspato e fragmentos de rochas est?o diretamente relacionado aos sistemas deposicionais, mostrando que a composi??o do arcabou?o ? diretamente respons?vel pela evolu??o diagen?tica dessas rochas. === The siliciclastic deposits of the Tombador Formation, basal unit of the Chapada Diamantina Group, of mesoproterozoic age, occur in a north-south range along the Serra do Sincor?, central portion of the S?o Francisco Craton (CSF), Northeast Brazil. These deposits consist of a thick sequence of siliciclastic rocks. A petrographic and petrological study of thin sections of outcropping rocks of Fm. Tombador was carried out, along with the help of special techniques such as X-Ray Fluorescence (FRX), X-ray Diffraction (XRD), X-ray Spectroscopy by Energy Dispersion (EDS) and Scanning Electron Microscopy (SEM). Based on the analyzes, it was verified that these rocks are constituted predominantly by meta-sandstones. The following diagenetic events were identified: mechanical infiltration of clays, mechanical compaction, chemical compaction, quartz overgrowth, tourmaline overgrowth, grain fracturing, iron oxide/hydroxide precipitation, grain dissolution, kaolinization, ilitization and mineral pyrophyllite that reflects the transition stages between diagenesis and anchemimorphism. The following chemical elements in descending order, Si, Al, K, Fe, Mg, Ti, Zr, Sr and Y were identified by X - ray fluorescence in total sample, with values above 85%, together with the high amount of Quartz (Q95F3FR2, according to Folk, 1974), indicate the high mineralogical maturity of these rocks. Through the XRD technique, the following groups of clay minerals were identified: illite, kaolinite, smectite, interstratified of illite/smectite and the mineral pyrophyllite. Although the characteristics of the samples reflect the previous conditions of diagenetic environments, measurements of the illite crystallinity index or "Kubler Index" (KI), and the presence of the mineral pyrophyllite are sufficient to demonstrate that the rocks of the study area were affected by anchemimorphism, indicative of the transition between the prehnita-pumpellyite facies and the below greenschist facies, and that burial conditions reached a depth of the order of 10-12 km and temperatures in the order of ? 300 ? C. The occurrence of certain clay minerals is directly related to the depositional system, showing that the composition of the framework are directly responsible for the diagenetic evolution of these rocks.