Genetic Modelling of Greisen-Style Tin Systems

Pollard, P. J.; Taylor, R. G.; Cuff, C.

doi:10.1007/978-3-642-72765-8_3

Cited by 8 publications

(3 citation statements)

References 13 publications

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“…Greisenization is a common hydrothermal alteration associated with Sn-W and rare metal deposits that are usually spatially and genetically associated with fractionated crustal granitic intrusions [1][2][3][4]. This postcrystallization alteration, marked by the breakdown of feldspars and biotite, occurs generally on the cupolas of intrusions during the cooling stage of the granitic intrusions and the first stages of hydrothermal activity.…”

Section: Introductionmentioning

confidence: 99%

“…Field observations have shown that greisen can form (i) at a local scale adjacent to veins or fractures present in granite, as at Cligga Head [15], and (ii) on a broad scale as massive greisens that are mainly present in the apical portions of mineralized granite, as at Cinovec, East Kemptville, and Panasqueira [4,[16][17][18][19][20]. These massive greisens may extend to a depth of 200-300 meters and can constitute low-grade, high-tonnage deposits marked by a disseminated mineralization [3,4,21]. Accordingly, the formation of these massive greisens requires the mass transfer of a large amount of fluid through the initially impermeable granitic rock.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic Permeability Related to Greisenization Reactions in Sn-W Ore Deposits: Quantitative Petrophysical and Experimental Evidence

et al. 2019

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Massive greisens are commonly associated with Sn-W mineralization and constitute low-grade high-tonnage deposits. The formation of this type of deposit results from an intense pervasive metasomatic alteration involving a major fluid and mass transfer through a nominally impermeable parental granite. A decrease in the volume of the solid phases associated with the mineral replacement reactions may be a potential process for creating pathways to enhance fluid flow. Here, we explore the effects of the replacement reactions related to greisenization on the granite’s mineralogy and petrophysical properties (density, porosity, and permeability), as well as their potential implications for fluid flow in the case of the world-class Panasqueira W-Sn-(Cu) deposit, Portugal. Mineralogical and microtextural analyses of greisenized facies show that the total replacement of feldspars by muscovite is associated with a volume decrease of the solid phases that induces a significant porosity generation in greisen (~8.5%). Greisenization experiments coupled with permeability measurements show that the replacement of feldspars by muscovite permits new pathways at the crystal scale that significantly enhance the transient permeability. Moreover, permeability measurements performed on representative samples with different degrees of greisenization show that permeability increases progressively with the level of alteration from 10-20 m2 in least granite to 10-17 m2 in greisen. The correlation between the permeability and porosity evolutions demonstrates that the porous texture developed during replacement reactions creates new pathways that enhance significantly the permeability in greisen systems. The occurrences of mineral-bearing metals such as cassiterite in the newly formed porosity of greisen provide evidence that greisenization can be a decisive process for enhancing fluid flow and promoting transport of metals in Sn-W deposits. Finally, we present a model involving a positive feedback between greisenization and permeability, in which mineralizing fluids are able to generate their own pathways in initially impermeable granite via replacement reactions, which in turn promote further hydrothermal alteration and mass transport.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamic Permeability Related to Greisenization Reactions in Sn-W Ore Deposits: Quantitative Petrophysical and Experimental Evidence

et al. 2019

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“…Greisenization at the Santa Bárbara deposit is mostly confined to the host granite -i.e. an endogreisen, which offers one of the best opportunities to study fluid evolution and interaction closest to its origin (Pollard et al, 1988).…”

Section: The Rondonia Tin Provincementioning

confidence: 99%

Caracterização geoquímica, geocronológica, e dos fluidos das ocorrecias de metais raros (ETR, SN, BI, U E TH) nos maciços da mina de Santa Bárbara, província estanífera de Rondonia, Brasil

Guimarães¹

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Agradeço primeiramente a meus pais, que foram os primeiros e mais importantes responsáveis pela minha educação, seriedade e compromisso, e sem o incentivo dos quais eu jamais poderia ter seguido por esses caminhos. À Erika, pela nossa partilha dos casos de laboratório, de revisão de artigos e de experimentos fracassados; e pelo constante incentivo. À Talita, por ser forte o bastante para conseguir suportar as dificuldades e a distância, e ainda sobrar carinho e compreensão. Esses anos teriam sido bem mais difíceis sem vocês.Aos meus orientadores, Dr. Francisco Javier Rios, Dr. Clemente Récio Hernández e Dr. Alexandre Raphael Cabral, pelo inestimável auxílio, discussões acadêmicas e dedicação.Ao gerente geral de geologia da CSN, Henrile Meirelles, pelo interesse em viabilizar etapas de campo, publicações e parcerias. Aos colegas da ERSA/CSN: Moisés, Carlos, Roberto, Curicão, Pará, Pequeno, Alexandre, Wander, Ronaldo e todos que participaram do trabalho de campo em Rondônia, da coleta de amostras, da pescaria, e da busca de afloramentos escondidos na floresta amazônica.Aos pós-doutorandos do LCMM do CDTN, Lucas, Lucília e Mônica, pelo enorme apoio e participação em diversas etapas do trabalho. À Anna, por não me odiar (eu acho) apesar de toda a pressão colocada sobre seu excelente trabalho.

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Intrusion-Related Hydrothermal Mineral Systems

Pirajno

2009

Hydrothermal Processes and Mineral Systems

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Genetic Modelling of Greisen-Style Tin Systems

Cited by 8 publications

References 13 publications

Dynamic Permeability Related to Greisenization Reactions in Sn-W Ore Deposits: Quantitative Petrophysical and Experimental Evidence

Dynamic Permeability Related to Greisenization Reactions in Sn-W Ore Deposits: Quantitative Petrophysical and Experimental Evidence

Caracterização geoquímica, geocronológica, e dos fluidos das ocorrecias de metais raros (ETR, SN, BI, U E TH) nos maciços da mina de Santa Bárbara, província estanífera de Rondonia, Brasil

Intrusion-Related Hydrothermal Mineral Systems

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