Evaluation of thermal effects of intrusive rocks on the kerogen present in the black shales of Irati Formation (Permian), Paraná Basin, Brazil

Shale samples from outcrops of the Irati Formation (Permian), Paraná Basin, Brazil were analyzed based on organic geochemistry, palynofacies, and stable carbon isotopes with the aim of evaluating thermal effects of igneous intrusions on the kerogen. The potential for hydrocarbon generation, the depo...

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Bibliographic Details
Published in:Journal of South American earth sciences 2020-06, Vol.100, p.102559, Article 102559
Main Authors: Martins, Cintia Mayra S., Cerqueira, José Roberto, Ribeiro, Helio Jorge P.S., Garcia, Karina S., da Silva, Neiva N., Queiroz, Antônio Fernando de S.
Format: Article
Language:English
Subjects:
Biomarkers
Depositional paleoenvironment
Igneous intrusion
Irati Formation
Organic matter
Thermal maturity
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Summary:Shale samples from outcrops of the Irati Formation (Permian), Paraná Basin, Brazil were analyzed based on organic geochemistry, palynofacies, and stable carbon isotopes with the aim of evaluating thermal effects of igneous intrusions on the kerogen. The potential for hydrocarbon generation, the depositional paleoenvironment, and the input of the organic matter were also studied. Most samples have high total organic carbon content, excellent hydrocarbon source potential, and type I kerogen, except some samples which showed changes in their compositional characteristic due alteration in the depositional paleoenvironment and due to the high maturation caused by the heat of diabase intrusions. The composition and distribution of saturate and aromatic biomarkers and stable carbon isotopes provided evidence that the composition of organic matter in the shales is marine, except at the upper part of the outcrops where the shales have contribution of terrestrial organic matter. Saturate biomarkers results indicated thermal immaturity for hydrocarbon generation, except the samples that were influenced by the heat of intrusive rocks. •Paleoenvironmental variation and organic matter input in Irati Formation.•Palynofacies, biomarkers, and δ13C indicate predominantly marine organic matter.•SCI shows that the Irati Formation kerogen was burned near the igneous intrusions.•Igneous intrusions were the conditioning factors in the generation of hydrocarbons.
ISSN:0895-9811
1873-0647
DOI:10.1016/j.jsames.2020.102559