Chemical and mineralogical characterization of elbaites from the Alto Quixaba pegmatite, Seridó province, NE Brazil

Ferreira, Ana Cláudia Mousinho; Ferreira, Valderez P.; Soares, Dwight Rodrigues; Vilarroel-Leo, Hugo S

doi:10.1590/s0001-37652005000400011

Cited by 6 publications

(9 citation statements)

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“…The 165 analytical data-points discussed in this paper were obtained using a JEOL instrument, model JXA-8600, with four wavelength-dispersion and one energy-dispersion spectrometers at the Instituto de Geociências da Universidade de São Paulo (IG-USP). Operating conditions were 15 kV and 20 nA, with a beam diameter of 3 mm and 30 seconds acquisition time, using the standards: wollastonite (Si Ka, CaKa), TiO 2 (synthetic rutile) (TiKa), anorthite (AlKa), fayalite (FeKa), spessartine (MnKa), diopside (MgKa), micro-iNtRoDuctioN Published chemical data on tourmaline-group minerals from the Borborema Pegmatite Province (BPP) in northeastern Brazil were mainly intended for mineralogical determination (Henn & Bank 1990, Soares, 1998, Ferreira 1998, Ferreira et al 2005 or gemological purposes, mainly to identify chromophore elements (Fritsch et al 1990, Rossman et al 1991, Barreto 1999. As most of the samples were taken by mineral dealers or panners and not collected by geologists, little attention was given to the variation in chemical composition of tourmaline according to pegmatite types or their location in different zones of the pegmatites.…”

Section: Methodsmentioning

confidence: 99%

“…However, some late dark blue and green growth-zones of multicolored crystals of elbaite from the Boqueirão pegmatite are exceptional, with up to 2.43 wt.% ZnO. Data from greenish blue elbaite from the Quixaba pegmatite, hosted in biotite schists, also in the BPP (Ferreira et al 2005), also presented high levels of Zn, in the range of 2.73 to 3.01 wt.% ZnO (dark blue and green gemquality elbaite).…”

Section: Major and Trace Elementmentioning

confidence: 97%

“…It is also well known (e.g., Henn & Bank 1990, Soares 1998, Ferreira 1998, Ferreira et al 2005, Fritsch et al 1990, Rossman et al 1991, Barreto 1999) that the gem-quality "PT" is distinguished by its high Cu content, up to 2.5 wt.%. Therefore the presence of copper sulfides in pegmatites (e.g., Capoeira 1) is assumed in some cases to explain the formation of the "neon blue" tourmaline variety.…”

Section: Comments On the Occurrence Of The "Electric Blue "Paraíba Tomentioning

confidence: 98%

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Compositional Variation of Tourmaline-Group Minerals in the Borborema Pegmatite Province, Northeastern Brazil

Soares¹,

Beurlen²,

Barreto³

et al. 2008

The Canadian Mineralogist

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Various species of the tourmaline-group are common accessory minerals in the Boqueirão, Capoeira and Quintos Li-Be-Ta-Nb-bearing, LCT-family, rare-element-class granitic pegmatites from the Borborema Pegmatite Province (BPP), northeastern Brazil. Tourmaline from the border and wall zones of the pegmatites is enriched in Mg and Fe, crystallizing as Mg-rich members of the dravite-schorl solid-solution series. Tourmaline from the intermediate zone is richer in Fe and Al+Li, crystallizing as schorl. The Fe-Mg-free and Li-Al-rich elbaite is typical of the transition between the intermediate zone and the quartz core, and of replacement pockets. The bright turquoise blue elbaite known as "Paraíba tourmaline" is produced in the Capoeira 2 and Quintos pegmatites and is distinguished by high Cu contents, up to 1.07 wt.% CuO. In other occurrences of the "Paraíba tourmaline" in the BPP, up to 2.37 wt.% CuO were reported. Differences in the geochemical evolution trend of tourmalines among the pegmatite bodies investigated (vacancy at the X site, Fe, Mg, Zn, Li and F contents), suggest that they reached variable degrees of fractionation. This observation agrees with chemical data on white mica, feldspar, garnet and gahnite, and therefore permits the use of tourmaline composition as an indicator of the degree of evolution of the hosting pegmatite. According to these data,"Paraíba tourmaline"-producing pegmatites share the following characteristics: 1) they are the most evolved pegmatites so far known in § Volume 46October 2008 Part 5 the cANADiAN miNeRALogist the BPP; 2) they are hosted by quartzites or metaconglomerates (iron-poor host rocks); 3) they exhibit comb-textured dravite in the border zone (early saturation in tourmaline) and 4) the elbaitic "Paraíba tourmaline" is found in the most evolved parts of the pegmatites.sommAiRe De diverses espèces de tourmaline sont présentes comme accessoires dans les pegmatites granitiques de Boqueirão, Capoeira et Quintos, enrichies en éléments rares (Li-Be-Ta-Nb) et de type LCT, situées dans la province pegmatitique de Borborema (BPP), nord-est du Brésil. Dans les zones de bordure et de paroi des pegmatites, la tourmaline est enrichie en Mg et Fe; les compositions sont des membres magnésiens de la solution solide entre dravite et schorl. Dans la zone intermédaire, la tourmaline est enrichie en Fe et Al + Li, et correspond à la composition de schorl. L'elbaïte dépourvue de Fe-Mg et enrichie en Li-Al est typique de transition entre la zone intermédiaire et le noyau de quartz, et des poches de remplacement. L'elbaïte bleu turquoise connue sous le nom de "tourmaline de Paraíba" se rencontre dans les pegmatites de Capoeira 2 et Quintos, et se distingue par des teneurs élevées en Cu, atteignant jusqu'à 1.07% de CuO (poids). Dans d'autres indices de ce genre d'elbaïte dans la ceinture BPP, on a signalé jusqu'à 2.37% de CuO. Des différences dans les tracés géochimiques évolutifs des tourmalines parmi les massifs de pegmatites étudiés, par exemple dans la proportion de lacunes au site X, et de...

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Section: Methodsmentioning

confidence: 99%

Section: Major and Trace Elementmentioning

confidence: 97%

Section: Comments On the Occurrence Of The "Electric Blue "Paraíba Tomentioning

confidence: 98%

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Compositional Variation of Tourmaline-Group Minerals in the Borborema Pegmatite Province, Northeastern Brazil

Soares¹,

Beurlen²,

Barreto³

et al. 2008

The Canadian Mineralogist

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“…All known tourmalines with elevated Zn contents are elbaite or fluor-elbaite ( [10][11][12][13][14][15][16]; present study). The excesses of Al over Li and high amounts of X-site vacancies or W O 2− could favor the formation of Zn-tourmaline with dominance of the end-members (Zn 2 Al)Al 6 B 3 Si 6 O 27 (OH) 3 (OH) or Na(Zn 2 Al)Al 6 B 3 Si 6 O 27 (OH) 3 O.…”

Section: Discussion: Is Natural Zn-dominant Tourmaline Possible?mentioning

confidence: 99%

“…Zinc is found in numerous tourmalines, although commonly at amounts not exceeding a few tenths of wt %. Rare findings of tourmalines with ZnO > 1 wt % have been reported, for instance, from Cross Lake, MB, Canada (1.24 wt %; [9]), Minas Gerais (1.72 wt %; [10]; 1.88 wt %; [11]) and Rio Grande do Norte (2.15 wt %; [12]; 2.43 wt %; [13]; 3.01 wt %; [14]) in Brazil, and from Congo (2.85 wt %; [15]). The most Zn-enriched tourmaline (3.83 wt % ZnO) has been described from Russia [16].…”

Section: Introductionmentioning

confidence: 99%

Towards Zn-Dominant Tourmaline: A Case of Zn-Rich Fluor-Elbaite and Elbaite from the Julianna System at Piława Górna, Lower Silesia, SW Poland

et al. 2018

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Tourmalines are a group of minerals which may concentrate various accessory components, e.g., Cu, Ni, Zn, Bi, Ti, and Sn. The paper presents fluor-elbaite and elbaite from a dyke of the Julianna pegmatitic system at Piława Górna, at the NE margin of the Bohemian Massif, SW Poland, containing up to 6.32 and 7.37 wt % ZnO, respectively. Such high amounts of ZnO are almost two times higher than in the second most Zn-enriched tourmaline known to date. The compositions of the Zn-rich tourmalines from Piława Górna, studied by electron micropropy and Raman spectroscopy, correspond to the formulae: X (Na 0.733 Ca 0.013 0.254) Σ1 Y (Al 1.033 Li 0.792 Zn 0.755 Fe 2+ 0.326 Mn 0.094) Σ3 Z Al 6 (T Si 6 O 18)(BO 3) 3 V (OH) 3 W (F 0.654 OH 0.344), and X (Na 0.779 Ca 0.015 0.206) Σ1 Y (Al 1.061 Li 0.869 Zn 0.880 Fe 2+ 0.098 Mn 0.094) Σ3 Z Al 6 (T Si 6 O 18)(BO 3) 3 V (OH) 3 W (OH 0.837 F 0.163), respectively, with Zn as one of the main octahedral occupants. A comparison with other tourmalines and associated Zn-rich fluor-elbaite and elbaite from the pegmatite indicates that atypically high Zn-enrichment is not a result of Zn-Fe fractionation, but dissolution and reprecipitation induced by a late (Na,Li,B,F)-bearing fluid within the assemblage of gahnite spinel and primary schorl-type tourmaline. This strongly suggests Na-Li-B-F metasomatism of gahnite-bearing mineral assemblages as that is the only environment that can promote crystallization of a hypothetical Zn-dominant tourmaline. The compositions of the Zn-rich fluor-elbaite and elbaite suggest three possible end-members for such a hypothetical tourmaline species: NaZn 3 Al 6 (Si 6 O 18)(BO 3) 3 (OH) 3 (OH), (Zn 2 Al)Al 6 (Si 6 O 18)(BO 3) 3 (OH) 3 (OH) and Na(Zn 2 Al)Al 6 (Si 6 O 18)(BO 3) 3 (OH) 3 O by analogy with other tourmalines with divalent Y occupants, such as schorl/foitite/oxy-schorl and dravite/magnesio-foitite/oxy-dravite.

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Developing a lateral topographic density model for Brazil

Medeiros

Marotta

Yokoyama

et al. 2021

Journal of South American Earth Sciences

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Chemical and mineralogical characterization of elbaites from the Alto Quixaba pegmatite, Seridó province, NE Brazil

Cited by 6 publications

References 14 publications

Compositional Variation of Tourmaline-Group Minerals in the Borborema Pegmatite Province, Northeastern Brazil

Compositional Variation of Tourmaline-Group Minerals in the Borborema Pegmatite Province, Northeastern Brazil

Towards Zn-Dominant Tourmaline: A Case of Zn-Rich Fluor-Elbaite and Elbaite from the Julianna System at Piława Górna, Lower Silesia, SW Poland

Developing a lateral topographic density model for Brazil

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