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| Oliveira,Marisa T.G. de; Furtado,Sandra M.A.; Formoso,Milton L.L.; Eggleton,Richard A.; Dani,Norberto. |
| Kaolin at Campo Alegre Basin, Santa Catarina State, Brazil was formed from alteration of volcanic acid rocks. Halloysite clays dominate the clay fraction of the matrix of the kaolin body, whereas a poorly crystalline kaolinite is abundant in veins. Some primary blocky structures have high amounts of illite, in one mine, but in general, only low contents of illite-smectite, illite, chlorite-vermiculite, vermiculite and quartz were identified in the clay fraction of the samples. Toward the top of the mines, hematite and lepidocrocite appear in horizontal red and ochre colored levels and the amount of kaolinite increases compared to halloysite. The vertical zoning of alteration levels, the changes in mineralogy, the positive correlation between depth and... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Kaolinite; Halloysite; Halloysite morphology; Kaolin; Weathering; Clay genesis. |
| Ano: 2007 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000400008 |
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| Mexias,André S.; Berger,Gilles; Gomes,Márcia E.B.; Formoso,Milton L.L.; Dani,Norberto; Frantz,José C.; Bongiolo,Everton M.. |
| A geochemical modeling of gold deposition was performed using the EQ3/EQ6 software package using conditions inferred from geological, petrographic, geochemical and fluid inclusion data from the Bloco do Butiá gold mine, Lavras do Sul, RS. Gold in the mine occurs only in the pyrite structure (invisible gold). The pyrite occurs associated with white mica (phengite) in the zone of phyllic alteration. The process of gold deposition showed to be related to temperature and pH decrease. The pH decrease was fundamental to gold deposition by destabilization of sulfur species [Au(HS)2- , HAu(HS)2(0) and Au(HS)0] dissolved in the aqueous solution, being Au(HS)0 the main gold transporting complex. The addition of KCl is hard to accept as cause of gold precipitation... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Geochemical modeling; Gold; Pyrite; Sulfur; Fluid-rock interaction. |
| Ano: 2005 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652005000400010 |
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