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Provedor de dados:  Anais da ABC (AABC)
País:  Brazil
Título:  Quantification of porosity evolution from unaltered to propylitic-altered granites: the 14C-PMMA method applied on the hydrothermal system of Lavras do Sul, Brazil
Autores:  Bongiolo,Everton M.
Bongiolo,Daniela E.
Sardini,Paul
Mexias,André S.
Siitari-Kauppi,Marja
Gomes,Márcia E.B.
Formoso,Milton L.L.
Data:  2007-09-01
Ano:  2007
Palavras-chave:  Porosity quantification
14C-PMMA method
Granite porosity
Hydrothermal alteration
Propylitic alteration
Lavras do Sul
Resumo:  This work is an application of the 14C-Polymethylmethacrylate method to compare the porosity evolution between unaltered and propylitic-altered granites, using samples from Lavras do Sul region, Brazil. This method, when coupled with optical and electronic petrography has the advantage over other methods to provide the quantification and identification of total and local porosity of rocks. From petrographic observations, different kinds of porous zones were identified and quantified (microfractures, grain boundaries, alteration of minerals, etc). Results show that unaltered granites have 0.5 to 0.6% porosity and propylitic-altered ones have 1.7 to 1.8% porosity, even between samples with different textures. Porosity of altered rocks increases mainly due to higher porosity of neoformed chlorite, calcite, sericite and microfractures. Field observations show that later phyllic alteration halos are wider in equigranular than in porphyritic granites, which could not be explained by different original porosity between those rocks. The observed differences of phyllic halos diffusion were controlled by structural and fluid/rock ratio variations between the equigranular and porphyritic granitic facies during the later hydrothermal stage.
Tipo:  Info:eu-repo/semantics/article
Idioma:  Inglês
Identificador:  http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000300011
Editor:  Academia Brasileira de Ciências
Relação:  10.1590/S0001-37652007000300011
Formato:  text/html
Fonte:  Anais da Academia Brasileira de Ciências v.79 n.3 2007
Direitos:  info:eu-repo/semantics/openAccess
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