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Previous issue date: 2009-12-16 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The general objective of this study was to contribute to the understanding of the chemical
evolution of fluids that percolate through carbonate rocks of the Janda?ra Formation. The oxidation and
reduction conditions in which grains, source and cement were formed was investigated using the
cathodoluminescence technique (CL). The study area is located in the west part of the Potiguar Basin
(Fazenda Bel?m field) and Ros?rio Ledge (Felipe Guerra municipality, State of Rio Grande do Norte,
Brazil). The analysis of thin sections of carbonate rocks under CL revealed that grains (allochemical or
not) and diagenetic products (micritization, dolomitization, neomorphism and cementation) exhibit
since absence of luminescence the various luminescence colors (yellow, orange, red, brown, and blue) in
a variety of intensities. As pure calcite shows dark blue luminescence, the occurrence of different
luminescence colors in calcite crystals suggest one or more punctual crystal defects such as free
electron, free space and impurity. The dyeing of thin sections with alizarin and potassium ferrocyanide
revealed the absence of ferrous carbonate in the different lithotypes of Janda?ra Formation. Therefore,
the different colors and intensities of CL observed in these rocks are probably caused by the presence of
ion activators such as Mn2+ and is not an activator/inhibitor combination. In the same way, the absence
of luminescence is very probably caused by the absence of activator ions and not due to the low
concentration of inhibitor ions such as Fe2+. The incorporation of Mn2+ in the different members of the
Janda?ra Formation must have been controlled by the redox state of the depositional environment and
diagenesis. Therefore, it is possible that the luminescent members have been formed (e.g.,ooids) or have
been modified (gastropod neomorphism) under reduction conditions in the depositional environments, in
subsurface during the burial, or, in the case of Rosario Ledge samples , during the post-burial return to
surface conditions. As regards the sudden changes from low to moderate and to strong luminescence,
these features should indicate the precipitation of a fluid with chemical fluctuations, which formed the
frequent zonations in the block cement of the Rosario Ledge samples. This study suggests that the
different intensities and colors of CL should be correlated with the Mn2+ and Fe2+ contents, and stable
isotopes of samples to determine the salinity, temperature, pH e Eh conditions during deposition / O objetivo geral deste trabalho foi contribuir para a compreens?o da evolu??o qu?mica dos
fluidos percolantes atrav?s das rochas carbon?ticas da Forma??o Janda?ra. As condi??es oxidantes e
redutoras nas quais gr?os, matriz e cimento foram formadas foi investigada usando a t?cnica da
catodoluminesc?ncia (CL). A ?rea de estudo localiza-se a oeste da Bacia Potiguar (Campo da Fazenda
Bel?m) e no Lajedo do Ros?rio (Munic?pio de Felipe Guerra, Estado do Rio Grande do Norte, Brasil).
As an?lises das l?minas delgadas das rochas carbon?ticas sob CL revelou que gr?os (aloqu?micos ou
n?o) e produtos diagen?ticos (micritiza??o, dolomitiza??o, neomorfismo e cimenta??o) exibiu desde
aus?ncia de luminesc?ncia ? v?rias cores de luminesc?ncia (amarela, laranja, vermelha, marrom e azul)
numa variedade de intensidades . Como a calcita pura mostrou luminesc?ncia azul escuro, a ocorr?ncia
de diferentes cores de luminesc?ncia em cristais de calcita sugere um ou mais defeitos pontuais nos
cristais tais como el?trons livres, espa?os livres e impurezas. O tingimento das l?minas delgadas com
alizarina e ferrocianeto de pot?ssio revelou aus?ncia de carbonatos ferrosos nos diferentes lit?tipos da
Forma??o Janda?ra. Portanto, as diferentes cores e intensidades de CL observada nestas rochas s?o
provavelmente causadas pela presen?a de ?ons ativadores tais como Mn2+ e n?o uma combina??o
ativador / inibidor. Da mesma forma, a aus?ncia de luminesc?ncia ? muito provavelmente causada pela
aus?ncia de ?ons ativadores e n?o devido a uma baixa concentra??o de ?ons inibidores tais como Fe2+. A
incorpora??o do Mn2+ nos diferentes constituintes da Forma??o Janda?ra deve ter sido controlada atrav?s
do estado redox do meio ambiente deposicional e diagen?tico. Portanto ? poss?vel que os constituintes
luminescentes tenham se formados (Ex: o?ides) ou tenham sido modificados (Ex: neomorfismo de
gastr?podes) sob condi??es redutoras no meio ambiente deposicional, em subsuperf?cie durante o
soterramento, ou, no caso das amostras do Lajedo do Ros?rio, durante o p?s-soterramento, no retorno ?s
condi??es superficiais. No que diz respeito ?s mudan?as bruscas de luminesc?ncia baixa para moderada
e forte, estas caracter?sticas devem indicar a precipita??o de um fluido com flutua??es qu?micas, nas
quais formou freq?entes zona??es no cimento blocoso das amostras do Lajedo do Ros?rio. Este estudo
sugere que as diferentes intensidades e cores de CL deve ser correlacionado com o conte?dos de Mn2+ e
Fe2+ e is?topos est?veis das amostras para determinar a salinidade, temperatura, pH e Eh durante
deposi??o
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/12934 |
| Date | 16 December 2009 |
| Creators | Fernandes Neto, Severino |
| Contributors | CPF:37923579415, http://lattes.cnpq.br/6050302316049061, Vieira, Marcela Marques, CPF:83933212715, http://lattes.cnpq.br/0930845549110627, Sousa, Maria Osvalneide Lucena, CPF:30159520304, http://lattes.cnpq.br/1224024758602281, Xavier Neto, Pedro, CPF:16361121372, Bezerra, Francisco Hilario Rego |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Ci?ncia e Engenharia do Petr?leo, UFRN, BR, Pesquisa e Desenvolvimento em Ci?ncia e Engenharia de Petr?leo |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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