Brechas em uma caverna hipogênica: petrografia, geoquímica e implicações para cavernas, um caso da Bacia de Irecê, Bahia, Brasil.
This works aims to give a pioneer conception of brecciated rocks from the world class caves of Irecê Basin, Salitre Formation, Bahia. Of Proterozoical age those caves are receiving increasing attention due to its easy access and similarities with hydrocarbon reservoirs analogues, in special, pre-sal...
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| Formato: | bachelorThesis |
| Idioma: | English |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/34396 |
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| Resumo: | This works aims to give a pioneer conception of brecciated rocks from the world class caves of Irecê Basin, Salitre Formation, Bahia. Of Proterozoical age those caves are receiving increasing attention due to its easy access and similarities with hydrocarbon reservoirs analogues, in special, pre-salt. Through pre-field activities selected areas were chosen, in field, described and sampled, and in lab photographed, described, analyzed and correlated. A total of twenty two thin sections were done and a variety of sedimentary process were observed, being silicification the most common, followed closely by limonitization. Using a classification adapted from Osborne (2001) we found two mains classes of breccias, sedimentary (collapse breccia) and hydraulic, and despite only one occurrence of hydraulic breccias two findings were curious: Barium concentrated in clay minerals and sedimentary plagioclase. Indicating hydrothermalism, those elements (Ba and Al) can help locate those fractures corridors , which concentrates in a typical reservoir most of the porosity and permeability, being a sweet spot in an increasing competitive market. Overall, we also could tell the cave evolution by the type of breccia found, in juvenile caves, hydrothermal ones tend to be the most common, and with ageing caves are infilled by an intricated system of mixing between surface sediments and bedrock, in which sedimentary process become dominant, with opal, chalcedony and limonite growing as the hypogenic fluid enters in the system changing the system dynamics. |
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