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| Natura: | Artículo científico |
| Lingua: | en |
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Academia Brasileira de Ciências
2007
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| Accesso online: | https://www.redalyc.org/articulo.oa?id=32779311 |
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Sommario:
- Quantification of porosity evolution from unaltered to propylitic-altered granites: the 14C-PMMA method applied on the hydrothermal system of Lavras do Sul, Brazil André S. Mexias Márcia E. B. Gomes Milton L.L. Formoso Everton Marques Bongiolo Daniela E. Bongiolo Paul Sardini Marja Siitari-Kauppi Multidisciplinaria (Ciencias Naturales y Exactas) 14C PMMA method Lavras do Sul granite porosity propylitic alteration Thiswork is an application of the 14C-Polymethylmethacrylate method to compare the porosity evolution between unalteredand propylitic-altered granites, using samples from Lavras do Sul region, Brazil. This method, when coupled withoptical and electronic petrography has the advantage over other methods to provide the quantification and identificationof total and local porosity of rocks. From petrographic observations, different kinds of porous zones were identifiedand quantified (microfractures, grain boundaries, alteration of minerals, etc). Results show that unaltered graniteshave 0.5 to 0.6% porosity and propylitic-altered ones have 1.7 to 1.8% porosity, even between samples with differenttextures. Porosity of altered rocks increases mainly due to higher porosity of neoformed chlorite, calcite, sericite andmicrofractures. Field observations show that later phyllic alteration halos are wider in equigranular than in porphyriticgranites, which could not be explained by different original porosity between those rocks. The observed differencesof phyllic halos diffusion were controlled by structural and fluid/rock ratio variations between the equigranular andporphyritic granitic facies during the later hydrothermal stage. 2007 artículo científico 0001-3765 https://www.redalyc.org/articulo.oa?id=32779311 en http://www.redalyc.org/revista.oa?id=327 Anais da Academia Brasileira de Ciências application/pdf Academia Brasileira de Ciências Anais da Academia Brasileira de Ciências (Brasil) Num.3 Vol.79