Albite-rich, silica-depleted metasomatic rocks at Emuford, Northeast Queensland; mineralogical, geochemical, and fluid inclusion constraints on hydrothermal evolution and tin mineralization

Charoy, B.; Pollard, P. J.

doi:10.2113/gsecongeo.84.7.1850

Cited by 52 publications

(58 citation statements)

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“…Little experimental work has been done concerning the transport of Be in hydrothermal solutions. Alkaline hydrothermal solutions are known to favour transport of beryllium, particularly during cogenetic albitization and beryl precipitation (Charoy and Pollard 1989). Several carbonatoberylates (general formula [Be4(CO3)6.…”

Section: Thermochemical Sulfate Reduction and Emerald Precipitationmentioning

confidence: 99%

The genesis of Colombian emeralds: a restatement

Cheilletz

Giuliani

1996

Mineral. Deposita

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A renewal of metallogenetical studies of Colombian emerald deposits produced new geological and geochemical data that favour a hydrothermal-sedimentary genetic model for these deposits. A comprehensive model is presented which integrates both chemical and structural aspects and invalidates some aspects of the model recently presented by Ottaway et al. The deposits result from a two-stage process in which shortening tectonics affect the two borders of the Eastern Cordillera of Colombia and provoke decollement planes, thrusting, and thrust-fault related folds in the Early Cretaceous black shale series. Three major descriptive and interpretative aspects of the deposits are presented: (1) time relationships between the two different sets of barren and mineralized extensional veins; (2) the association of graphite and emerald mineralization, and (3) the thermochemical sulfate reduction reaction acting at the site of the emerald deposits to reduce sulfate of evaporitic origin from the hydrothermal brines into hydrogen sulfide by interaction with organic-rich strata.Emerald is one of the most famous exports from Colombia. Even though miners from the mines of Chivor, Muzo or Coscuez recognize from experience the signs of mineralization, no comprehensive genetic model able to explain these mineralizations had been elaborated (Sutill 1994). Following our original paper in Mineralium Deposita in 1990(Giuliani et al. 1990), Ottaway et al. (1994 proposed a model for the formation of the Colombian emeralds, based on the characteristics of the Muzo deposit. This model, rather than elucidating the process of formation of Colombian emeralds, adds some confusion to it. Based on our field and laboratory practise of Colombian emerald deposits, we develop several arguments here against some major points of Ottaway et al. (1994), and we propose a comprehensive model that integrates both chemical and structural aspects.

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Section: Thermochemical Sulfate Reduction and Emerald Precipitationmentioning

confidence: 99%

The genesis of Colombian emeralds: a restatement

Cheilletz

Giuliani

1996

Mineral. Deposita

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“…fluorite, calcite, epidote) could not be identified in these samples. Strontium is likely to be enriched in newly formed hydrothermal albite as proposed by Schwartz and Surjono (1990) or Charoy and Pollard (1989). Strong mass transfer of REE is shown by the isocon plot (Fig.…”

Section: Episyenitesmentioning

confidence: 78%

“…In the course of granite cooling such fluids expelled from crystallizing granite could have been channelled along well defined structures (faults) in already solidified parts of the pluton, and in this way mixed with external fluids to produce episyenites. The mixing of magmatic and meteoric fluids during albitization including episyenitization in granites of the Emuford district, Australia, was proposed by Charoy and Pollard (1989). They emphasize a close genetic link between albitization and subsequent quartz-leaching and suggest that the exchange of Na for K in fluorine-rich hydrothermal fluids caused a substantial increase in quartz solubility and led to quartz dissolution in the albitized rock.…”

Section: Post-magmatic Hydrothermal Alterationmentioning

confidence: 99%

“…Special attention has been given to episyenites in the Hercynian granites of Central and Western Europe which act as hosts for U mineralisation (Leroy 1978;Dill 1985;Cathelineau 1986;Cathelineau 1987;Turpin et al 1990;Hecht et al 1991;Scaillet et al 1996) or Sn-W mineralisation (Cheilletz and Giuliani 1982). Episyenites were also described from other parts of the world in granites of different ages (Charoy and Pollard 1989;Dempsey et al 1990;Schoch and Scheepers 1990;Petersson and Eliasson 1997). Episyenites are usually porous rocks that weather easily.…”

Section: Introductionmentioning

confidence: 99%

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Mineralogical and geochemical characteristics of hydrothermal alteration and episyenitization in the Königshain granites, northern Bohemian Massif, Germany

Hecht

Thuro

Plinninger

et al. 1999

International Journal of Earth Sciences

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The late-Hercynian granites of Königshain underwent multistage hydrothermal processes. Extensive high-temperature late-magmatic alteration is, for example, indicated by low Zr/Hf and an REE pattern displaying the tetrad effect. Intensive post-magmatic alteration of the granite occurred along brittle structures. At least two main stages of post-magmatic hydrothermal alteration are involved. The first high-temperature stage, which is characterized by albitization and/or quartz leaching (episyenitization), resulted from fluid-rock interaction with late-magmatic fluids that very probably mixed with external low-salinity fluids. Quartz dissolution was triggered by vapour condensation and/or the cooling of these fluids (below 450 7C) along brittle structures. The high porosity resulting from quartz leaching during stage 1 assisted subsequent circulation of low-temperature fluids at stage 2; the latter is characterized by the chloritization and illitization of episyenites. Almost all major and trace elements were enriched or depleted during one of the main alteration stages. However, Zr, Hf, Th, and Ti were immobile during post-magmatic alteration. The significant depletion of LREE and the enrichment of HREE in albitized samples is controlled by the dissolution of monazite and the new formation of HREE-rich polycrase-(Y) or aeschynite-(Y) during post-magmatic stage 1. Negative Ce anomalies of episyenites are associated with illitization and suggest oxidizing conditions during stage 2.

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“…São comumente considerados como elementos pouco móveis, tendendo a permanecer no sistema quando do hidrotermalismo ou metamorfismo (Henderson 1996), sendo importantes indicadores petrogenéticos, já que mudanças nos padrões de ETR de uma suíte de rochas estão diretamente relacionadas com os coeficientes de distribuição mineral/líquido dos elementos envolvidos (Hanson 1989). Entretanto, os ETR podem ser mobilizados durante o metamorfismo/hidrotermalismo na forma de complexos com F -, Cl -, (SO 4 ) 2-, (CO 3 ) 2-, entre outros (Kosterin 1959, Alderton et al 1980, Baker 1985, Cathelineau 1987, Charoy & Pollard 1989, Wood 1990, Bau 1991 (Speer 1982ae b, Chang et al 1996e Deer et al 1997. Quando presentes, esses minerais retêm a maior parte dos ETR em rocha, controlando a forma dos padrões de ETR da rocha e o comportamento dos ETR ao longo…”

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Comportamento Geoquímico De Etr Durante Evolução Magmática E Alteração Hidrotermal De Granitos: Exemplos Da Província Estanífera De Goiás

Teixeira

Botelho

2006

RBG

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Resumo Os maciços graníticos do tipo A das Subprovíncias Estaníferas Paranã (SPP) e Tocantins (SPT) possuem concentrações anômalas de Elementos Terras Raras (ETR) que, em muitos locais, ultrapassam 1000 vezes o observado em condritos. Os granitos da SPP são individualizados em duas suítes: g1, de tendência alcalina a subalcalina, constituída pelas fácies g1a, g1b e g1c; e g2, de tendência metaluminosa a peraluminosa, constituída pelas fácies g2b, g2c e g2d. O Maciço Serra Dourada (MSD), pertencente à SPT, é constituído pelas fácies de borda, principal e porfirítica. Nos maciços da SPP, foram identificados: apatita, allanita, bastnaesita, oxifluoreto de ETR, fluocerita, zircão, xenotima, torita e monazita como minerais portadores de ETR. Destes, apenas a torita não foi encontrada no MSD (SPT). Os Elementos Terras Raras Leves (ETRL) apresentam comportamento incompatível no início da evolução dos granitos g1, tornando-se compatíveis na fácies g1b. Os Elementos Terras Raras Pesadas (ETRP) apresentam caráter incompatível durante a evolução dos granitos g1, tornando-se compatíveis apenas ao final da mesma. Na suíte g2 os ETRL mostram um caráter compatível desde o início da evolução magmática, enquanto os ETRP praticamente não variam nesse processo. No MSD, não há variação significativa nos ETRL durante a evolução magmática, enquanto os ETRP apresentam caráter compatível. Em todos os casos o comportamento dos ETR está em acordo com uma evolução magmática por cristalização fracionada. Os ETR mostram um comportamento contrastante durante a alteração hidrotermal das SPP e SPT. Nos maciços da SPP, na qual se tem principalmente greisenização, há o empobrecimento nos ETR nesse processo. No MSD, onde predomina a albitização e a biotitização, os ETR se enriquecem em rocha com a alteração hidrotermal. A allanita e a monazita e, quando presentes, a bastnaesita e o oxifluoreto de ETR, são os responsáveis pelos conteúdos de ETRL em rocha, enquanto minerais como zircão, xenotima e torita praticamente não influenciam na quantidade desses elementos. Os minerais portadores de ETRL também alojam uma porção significativa dos ETRP em rocha, acompanhados por xenotima e, quando presente, torita. O zircão, embora seja o acessório mais comum e, em algumas amostras, extremamente rico em Y e ETRP, praticamente não influencia nos conteúdos dos ETR em rocha.Palavras chave: elementos terras raras, granitos estaníferos, alteração hidrotermal, minerais portadores de ETR. Abstract REE GEOCHEMICAL BEHAVIOUR DURING MAGMATIC EVOLUTION AND HYDROTHERMAL ALTERATION OF GRANITES: EXAMPLES OF THE GOIÁS TIN PROVINCE.The A-type granitic massifs of the Paranã (SPP) and Tocantins (SPT) tin sub-provinces have anomalous rare earth element (REE) contents, sometimes 10 3 greater than the chondrite. Two suites of granitic rocks are present in the SPP, g1 and g2. Rocks of g1 suite (g1a, g1b and g1c facies) display an alkalic affinity whereas g2 granites (g2b, g2c and g2d facies) are metaluminous to peraluminous. Granites of the Serra Dourada Massif, in the SPT, are di...

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Albite-rich, silica-depleted metasomatic rocks at Emuford, Northeast Queensland; mineralogical, geochemical, and fluid inclusion constraints on hydrothermal evolution and tin mineralization

Cited by 52 publications

References 0 publications

The genesis of Colombian emeralds: a restatement

The genesis of Colombian emeralds: a restatement

Mineralogical and geochemical characteristics of hydrothermal alteration and episyenitization in the Königshain granites, northern Bohemian Massif, Germany

Comportamento Geoquímico De Etr Durante Evolução Magmática E Alteração Hidrotermal De Granitos: Exemplos Da Província Estanífera De Goiás

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