Estudo geoquímico e isotópico dos folhelhos e evaporitos do grupo Santana (Bacia do Araripe): implicações para os sistemas deposicionais e evolução térmica da materia orgânica.

• Autor(a) principal: Pontes, Naedja Vasconcelos
• Data de Publicação: 2018
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Ceará (UFC)
• Texto Completo: http://www.repositorio.ufc.br/handle/riufc/40925
• topic: Geoquímica orgânica; Isótopos de enxofre; Paleoambiente

The aim of the present study was to investigate the organic geochemistry and stable isotopes of sulfur in shales and evaporites of the Santana Group of the Araripe Basin in order to interpret depositional systems, formation conditions, hydrocarbon generation potential, thermal maturity, quantity and quality of organic matter. A total of 17 samples werecollected from outcrops and quarries, being submitted to analyses of Total Organic Carbon (TOC), Total Sulphur (TS), Rock-Eval pyrolysis, VitriniteReflectance, X-Ray Diffraction (XRD), Fluorescence (XRF) and stable sulfur isotopes (δ34SV-CDT). The results showTOC values range from 0.01 to 23% and TS from 0.01% to 3.41%. Only 7 intervals showed values superior to 1% of TOC, being considered good potential generators. The results of rock eval pyrolysis revealed the existence of type Ikerogen (corresponding to the best type of organic matter for the generation of liquid and gaseous hydrocarbons) and immature sediments reinforced by vitrinite results. The mineralogy is composed mainly by quartz and secondarily clay minerals. As for the unconventional potential, the indications regarding the characteristics of TOC (average of 3.7%) and type of kerogen I were favorable and unfavorable for thermal maturity (immature shales) and mineralogy. The paleoenvironmental/depositional interpretationswere based on the C/S ratio in terms of paleosalinity where the results suggest salinity variation, indicating that most of the shales were formed in brackish water conditions with saline-influenced, with tendency to increase salinity to the top of the profile, where hypersaline conditions were reached between the end of the Ipubi Formation and the beginning of the Romualdo Formation. In turn, the isotopic data showed that there are indications of possible marine invasions in the depositional systems.