Comportamento Cristaloquímico De Monazita Primária E Hidrotermal Durante a Evolução De Granitos E Greisens: Exemplos Das Subprovíncias Tocantins E Paranã, Goiás.

Teixeira, Luciana Miyahara; Botelho, Nilson Francisquini

doi:10.25249/0375-7536.2002323335342

Cited by 6 publications

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“…The phosphorus contents are approximately constant, average of 26wt%. Figure 9 exhibits the results of this study in comparison with average LREE and HREE contents from the studies of Demartin et al (1991b); Teixeira (2002); Suzuki et al (1994) and Van Emden et al (1997). …”

Section: Texture and Composition Of Monazite-(ce)mentioning

confidence: 81%

Occurrence and behavior of monazite-(Ce) and xenotime-(Y) in detrital and saprolitic environments related to the Serra Dourada granite, Goiás/Tocantins State, Brazil: Potential for REE deposits

Santana

Wall

Botelho

2015

Journal of Geochemical Exploration

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The mode of occurrence, mobility and fractionation of REE have been investigated in the geochemical context of the Serra Dourada Granite, an A-type granitic body located in northern Goiás State, Brazil. Several analyses were performed to best characterize each mode of occurrence of REE, from fresh rock to its products of alteration such as the saprolite, placers and clayish horizon. In the fresh rock it was found that the REE budget is related to monazite-(Ce), xenotime-(Y), bastnäsite and allanite. Resistant monazite-(Ce) and xenotime-(Y) withstand fluvial transportation and are concentrated in placers whithin the massif, whereas bastnäsite and allanite do not. The alluvial sediments contain up to 0.87wt% monazite-(Ce) and 0.46wt% xenotime-(Y). Considering only the heavy minerals, monazite-(Ce), zircon and ilmenite represent 60-80% of the total variability, being monazite-(Ce) and xenotime-(Y) the most important REE carriers. The same minerals are also present, although in lower amounts, in the saprolite. Both qualitative and quantitative electron probe microanalysis were carried out in detrital monazite-(Ce) and xenotime-(Y) to assess their main features and composition. Monazite-(Ce) REE contents are 60wt% in average, whilst REE contents in detrital xenotime-(Y) are 55 wt% in average. Low totals are ascribed to the alteration of the minerals caused by the presence of both organic and inorganic ligands present in the system. The results support the idea that REE are mobile under supergene conditions and during granite weathering, tending to be higher and more fractionated towards the products of alteration (saprolite, alluvial sediments and clayish horizon). REE2O3 contents in the fresh granite, saprolite, alluvial sediments and clayish horizon are 0.07, 0.21, 1.2 and 0.11wt% respectively, the clayish horizon being HREE-selective. Placer deposits and the clayish horizon tend to occur in low-slope areas within the Massif, where deposition and accumulation is more favorable. The saprolite occurs preferably in high-slope areas formed in situ at the expense of the granite. The placer deposits could be exploited, but their occurrence is more restricted and local. The saprolite has the advantage of covering extensive areas widely distributed over the granite. Currently a private company, the Serra Verde Mining, posses the mining claims in the area to exploit the REE associated with the saprolite, under the model of ion-adsorption type deposits.

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Section: Texture and Composition Of Monazite-(ce)mentioning

confidence: 81%

Occurrence and behavior of monazite-(Ce) and xenotime-(Y) in detrital and saprolitic environments related to the Serra Dourada granite, Goiás/Tocantins State, Brazil: Potential for REE deposits

Santana

Wall

Botelho

2015

Journal of Geochemical Exploration

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“…On the other hand, the interaction between apatite crystals and the H 2 SO 4 solution formed smaller monazite crystals (< 2 μm) and was considered to be less effective, needing more reaction time, higher temperature and higher H 2 SO 4 concentration. The fact that apatite crystals from the FAAC granites show areas poor in REE + Si associated with monazite crystals as opposed to the non-depleted apatite areas without (Rapp & Watson 1986, Foerster 1998, Zhu & O'Nions 1999, Teixeira & Botelho 2002; carbonatite (Chakhmouradian & Mitchell 1998, Toledo et al 2004, Kim et al 2005; hydrothermal (Zhu & O'Nions 1999, Teixeira & Botelho 2002; and metamorphic (Zhu & O'Nions 1999, Finger & Krenn 2007 monazite. linear correlation (r 2 = 0,9738, Fig.…”

Section: Discussionmentioning

confidence: 92%

Formation of monazite-(Ce, La) by fluid-apatite interaction: the Floresta Azul Alkaline Complex, Bahia, Brazil

et al. 2018

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Monazite is a common accessory mineral in the Floresta Azul Alkaline Complex, occurring in three different rock types, which form this batholith: nepheline syenite, granite and fenite. Two compositional types of monazite can be found: monazite-(Ce) and monazite-(La), the latter being found only in syenites. Monazite occurs in close association with apatite as anhedral crystals ranging in size from 0.1-100 μm, and textures indicate different genetic processes. In nepheline syenite, monazite is closely related to ancylite and apatite, as a late crystallizing phase. Monazite occurs in granites as pore fillings in apatite and was formed by the remobilization of rare earth elements (REE) from apatite by late CO 2 -rich fluids. In fenite, monazite appears as acicular crystals, parallel to apatite's crystallographic c-axis formed by exsolution from apatite by metamorphism. The data show that the monazite genesis was closely related to the activity of fluids associated either with the final stages of crystallization of nepheline syenite and granite or with fenitization of country rock.

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“…Em g1c, há o desaparecimento da apatita e allanita enquanto a monazita, que já era encontrada em granitos g1b mais evoluídos, se torna o principal portador de ETRL (Teixeira & Botelho 2002).…”

Section: Resultados E Discussõesunclassified

“…Esses minerais não são mais encontrados na fá-cies g2d, onde a monazita passa a ser o principal portador dos ETRL (Botelho 1992, Teixeira & Botelho 2002. A diminuição no conteúdo dos ETRL com a evolução magmática se reflete na pequena quantidade de monazita encontrada na fácies g2d.…”

Section: Tabela 1 -Composição Química (Elementos Traço E Elementos Teunclassified

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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Comportamento Cristaloquímico De Monazita Primária E Hidrotermal Durante a Evolução De Granitos E Greisens: Exemplos Das Subprovíncias Tocantins E Paranã, Goiás.

Cited by 6 publications

References 0 publications

Occurrence and behavior of monazite-(Ce) and xenotime-(Y) in detrital and saprolitic environments related to the Serra Dourada granite, Goiás/Tocantins State, Brazil: Potential for REE deposits

Occurrence and behavior of monazite-(Ce) and xenotime-(Y) in detrital and saprolitic environments related to the Serra Dourada granite, Goiás/Tocantins State, Brazil: Potential for REE deposits

Formation of monazite-(Ce, La) by fluid-apatite interaction: the Floresta Azul Alkaline Complex, Bahia, Brazil

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

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