Geochemistry of oxide minerals of Nb, Ta, Sn, and Sb in the Varuträsk granitic pegmatite, Sweden: The case of an “anomalous” columbite-tantalite trend

Černý, Petr; Chapman, Ron; Ferreira, Karen; Smeds, Sten‐Anders

doi:10.2138/am-2004-0405

Cited by 54 publications

(26 citation statements)

References 30 publications

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“…The presence of anomalous, 'reverse' trends with latestage Nb-Fe-Sn-Ti enrichment, also observed in other pegmatite provinces Smeds et al 1999;Černý et al 2004), is usually considered the result of late, subsolidus, hydrothermal alteration, partially replacing primary crystals, or the result of pegmatite/wall rock interaction. In the BPP, some cases present textures strongly suggestive of a primary nature of these anomalous trends (e.g.…”

Section: Discussionmentioning

confidence: 96%

Nb–Ta–(Ti–Sn) oxide mineral chemistry as tracer of rare-element granitic pegmatite fractionation in the Borborema Province, Northeastern Brazil

et al. 2007

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The Borborema Pegmatitic Province (BPP), northeastern Brazil, is historically important for tantalum mining and also famous for top-quality specimens of exotic Nb-Ta oxides and, more recently, for the production of gem quality, turquoise blue, 'Paraíba Elbaite.' With more than 750 registered mineralized rare-element granitic pegmatites, the BPP extends over an area of about 75 by 150 km in the eastern part of the Neoproterozoic Seridó Belt. The Late Cambrian pegmatites are mostly hosted by a sequence of Neoproterozoic cordierite-sillimanite biotite schists of the Seridó Formation and quartzites and metaconglomerates of the Equador Formation. The trace-element ratios in feldspar and micas allow to classify most pegmatites as belonging to the beryl-columbite phosphate subtype. Electron microprobe analyses (EMPA) of columbite, tapiolite, niobiantantalian rutile, ixiolite and wodginite group minerals from 28 pegmatites in the BPP are used to evaluate the effectiveness of Nb-Ta oxide chemistry as a possible exploration tool, to trace the degree of pegmatite fractionation and to classify the pegmatites. The columbite group mineral composition allows to establish a compositional trend from manganoan ferrocolumbite to manganocolumbite and on to manganotantalite. This trend is typical of complex spodumene-and/or lepidolite-subtype pegmatites. It clearly contrasts with another trend, from ferrocolumbite through ferrotantalite to ferrowodginite and ferrotapiolite compositions, typical of pegmatites of the beryl-columbite phosphate subtype. Large scatter and anomalous trends in zoned crystals partially overlap and conceal the two main evolution patterns. This indicates that a large representative data set of heavy mineral concentrate samples, collected systematically along cross-sections, would be necessary to predict the metallogenetic potential of individual pegmatites. Other mineral species, e.g. garnets and/or tourmaline, with a more regular distribution than Nb-Ta oxides, would be more appropriate and less expensive for routine exploration purposes. The currently available Nb-Ta oxide chemistry data suggest the potential for highly fractionated Ta-Li-Cs pegmatites in the BPP, so far undiscovered, and encourages further, more detailed research.

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Section: Discussionmentioning

confidence: 96%

Nb–Ta–(Ti–Sn) oxide mineral chemistry as tracer of rare-element granitic pegmatite fractionation in the Borborema Province, Northeastern Brazil

et al. 2007

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“…Mots-clés: minéraux du groupe de la columbite, oxydes de Nb-Ta, pegmatite, fractionnement, lithium, Barroso-Alvão, Portugal. Minerals belonging to this group have been studied in detail by previous authors and have been shown to be useful indicators of fractionation and chemical evolution both within and among pegmatites in a district , 1986, 2004, Černý 1989, Ercit et al 1995, Mulja et al 1996, Tindle & Breaks 2000, Novák & Černý 1998, Novák et al 2003, van Lichtervelde et al 2006). In addition, experimental work on the fractionation of Nb and Ta has added to our understanding of the chemical variations observed in granitic pegmatite systems (e.g., Keppler 1993, Linnen & Keppler 1997, Linnen 1998, Linnen & Cuney 2005.…”

Section: (Traduit Par La Rédaction)mentioning

confidence: 99%

GEOCHEMICAL FRACTIONATION OF Nb-Ta OXIDES IN Li-BEARING PEGMATITES FROM THE BARROSO-ALVAO PEGMATITE FIELD, NORTHERN PORTUGAL

Martins

Lima

Simmons

et al. 2011

The Canadian Mineralogist

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The Barroso-Alvão granitic pegmatite field, located in northern Portugal, is known for its numerous occurrences of Li-bearing pegmatites, especially spodumene-and petalite-bearing bodies. Recent work on this pegmatite field characterized other types of pegmatites, and complex mineralization and mineral associations. Minerals of the columbite-tantalite group are found in all the LCT (Li-Cs-Ta) pegmatites from Barroso-Alvão: spodumene pegmatites, petalite pegmatites, and lepidolite pegmatites. In the petalite and lepidolite pegmatites, the columbite-tantalite group of minerals are found spatially associated with cassiterite. Cassiterite is not present in the spodumene pegmatites. The columbite-group minerals have Ta/(Ta + Nb) and Mn/(Mn + Fe) values ranging from 0.20 to 0.60, except in the lepidolite pegmatites, where Mn/(Mn + Fe) is close to 1. The fractionation trend starts in the Mn-poor columbite-(Fe) field (spodumene pegmatites) toward Mn-and Ta-enrichment (lepidolite pegmatites). Our results suggest that Mn enrichment is not controlled by silicate or phosphate phases, but instead by the increasing activity of fluorine. The Ta enrichment, on the other hand, may well be controlled by fractional crystallization. We also observe a decrease in the Ti of the columbite-group minerals from the spodumene to the lepidolite pegmatites, which we consider an evolutionary trend.

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“…Values of Ta/(Ta + Nb) are typically found to be equal in the products of replacement of primary minerals such as stibiotantalite, simpsonite, manganocolumbite (Černý & Ercit 1985, Ercit 1986, Ercit et al 1986, Novák & Č erný 1998a, 2001, Smeds et al 1999, Cerný et al 2004, and they were also retained in pyrochlore-group minerals during geochemical alterations (Lumpkin & Ewing 1992. Uher et al (1998) and Baldwin (1989) are the only authors to have described minor changes in Ta/(Ta + Nb) between primary and secondary phases.…”

Section: Implications To Fractionation Of Nb From Ta In the Crustmentioning

confidence: 99%

FERROTAPIOLITE AS A PSEUDOMORPH OF STIBIOTANTALITE FROM THE LASTOVICKY LEPIDOLITE PEGMATITE, CZECH REPUBLIC; AN EXAMPLE OF HYDROTHERMAL ALTERATION AT CONSTANT Ta/(Ta + Nb)

Novák

Černý

Cempírek

et al. 2004

The Canadian Mineralogist

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Dark brown porous ferrotapiolite is a dominant product of alteration in pseudomorphs after primary stibiotantalite from the lepidolite pegmatite at Laštovičky, western Moravia, Czech Republic. Two compositionally distinct varieties of ferrotapiolite were recognized, a volumetrically dominant Fe 3+ -rich phase and a very rare Sb-rich phase. Niobium-rich ferrotapiolite, with up to 17.51 wt.% Nb 2 O 5 (0.61 apfu), is highly heterogeneous, with Ta/(Ta + Nb) of 0. 3 Fe 2+ -2 R 5+ -1 dans la seconde variété pourrait exprimer une solution solide vers le pôle SbTaO 4 , c'est-à-dire la stibiotantalite; toutefois, il est probable que le déplacement en composition est dû à la présence de reliques microscopiques de stibiotantalite primaire dans la ferrotapiolite, cachées sous la surface des échantillons polis. La stibiotantalite est remplacée par la ferrotapiolite le long de fractures distribuées de façon irrégulière selon la réaction hypothétique 2Sb(Ta,Nb)O 4 + Fe(OH) 2 + 2H 2 O = Fe(Ta,Nb) 2 O 6 + 2Sb(OH) 3 . Un tel enrichissement important en fer (stibiotantalite transformée en ferrotapiolite), documenté par la présence d'une abondance de ferrotapiolite secondaire à Laštovičky, est exceptionnelle parmi les produits du remplacement des oxydes primaires de (Nb,Ta) dans les pegmatites granitiques. Les teneurs élevées en Fe 2 O 3 de la ferrotapiolite indiquent des niveaux élevés mais variables de f(O 2 ) au cours de l'altération. Les valeurs de Ta/(Ta + Nb) dans la stibiotantalite primaire et la ferrotapiolite secondaire sont presqu'égales, ce qui fait penser que le Nb et le Ta ont une mobilité très faible. L'absence de fractionnement hydrothermal de Nb par rapport au Ta dans les pegmatites granitiques et la faible mobilité de Ta et Nb, établie ici et dans d'autres travaux, soulignent l'importance des processus magmatiques dans le fractionnement du Ta par rapport au Nb dans la croûte. (Traduit par la Rédaction)Mots-clés: ferrotapiolite, stibiotantalite, altération hydrothermale, fractionnement du Ta par rapport au Nb, pegmatite granitique à lépidolite, Laštovičky, République Tchèque.

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Geochemistry of oxide minerals of Nb, Ta, Sn, and Sb in the Varuträsk granitic pegmatite, Sweden: The case of an “anomalous” columbite-tantalite trend

Cited by 54 publications

References 30 publications

Nb–Ta–(Ti–Sn) oxide mineral chemistry as tracer of rare-element granitic pegmatite fractionation in the Borborema Province, Northeastern Brazil

Nb–Ta–(Ti–Sn) oxide mineral chemistry as tracer of rare-element granitic pegmatite fractionation in the Borborema Province, Northeastern Brazil

GEOCHEMICAL FRACTIONATION OF Nb-Ta OXIDES IN Li-BEARING PEGMATITES FROM THE BARROSO-ALVAO PEGMATITE FIELD, NORTHERN PORTUGAL

FERROTAPIOLITE AS A PSEUDOMORPH OF STIBIOTANTALITE FROM THE LASTOVICKY LEPIDOLITE PEGMATITE, CZECH REPUBLIC; AN EXAMPLE OF HYDROTHERMAL ALTERATION AT CONSTANT Ta/(Ta + Nb)

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