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| Bongiolo,Everton M.; Bongiolo,Daniela E.; Sardini,Paul; Mexias,André S.; Siitari-Kauppi,Marja; Gomes,Márcia E.B.; Formoso,Milton L.L.. |
| 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... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Porosity quantification; 14C-PMMA method; Granite porosity; Hydrothermal alteration; Propylitic alteration; Lavras do Sul. |
| Ano: 2007 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000300011 |
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| Pimentel,Márcio M.; Silva,Maria da Glória. |
| The Fazenda Brasileiro gold mineralization is hosted by a gabbroic sill, intrusive into metavolcanicmetasedimentary rocks of the Rio Itapicuru Greenstone Belt, São Francisco Craton. The 2.05 Ga old mineralization is associated with intense shearing and hydrothermal alteration, and the host gabbro is altered to a series of rocks rich in sericite, chlorite, actinolite, carbonate and quartz. Twelve whole-rock samples of the gold mineralization, representing varied degrees of alteration, from rocks with preserved igneous textures to the ore (quartz-carbonate-sulfide-chlorite), were studied by the Sm-Nd method. All analytical points resulted in an isochron (MSWD = 1.9) indicating the age of 2142 +/- 47 Ma (1s) and Epsilon Nd (T) of +1.2.... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Rio Itapicuru greenstone belt; Fazenda Brasileiro; Paleoproterozoic; Gold mineralization; Sm-Nd; Hydrothermal alteration. |
| Ano: 2003 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652003000300009 |
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