Tetrahedrally coordinated boron in tourmalines from the liddicoatite-elbaite series from Madagascar: Structure, chemistry, and infrared spectroscopic studies

Ertl, Andreas; Hughes, John M.; Prowatke, Stefan; Ludwig, Thomas; Prasad, P. B. V.; Brandstätter, F.; Körner, Wilfried; Schuster, Ralf; Pertlik, F.; Marschall, Horst R.

doi:10.2138/am.2006.2245

Cited by 59 publications

(49 citation statements)

References 39 publications

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“…It is well established that boron in aqueous fluids of low pH that are suitable for tourmaline stability occurs in trigonal B(OH) 3 complexes (Palmer and Swihart, 1996), and Raman spectroscopy in diamond anvil cell experiments confirm the dominance of trigonal coordination at high temperatures and pressures (Schmidt et al, 2005). Boron in tourmaline also occurs almost exclusively as trigonal BO 3 groups although cases of tourmaline have been reported with minor amounts of "excess" boron (>3 cations pfu) that was shown to occupy tetrahedral sites in place of Si (e.g., Hughes et al 2001;Marschall et al 2004;Ertl et al, 2006). As mentioned above, our chemical analyses of tourmaline…”

Section: Boron Isotope Fractionation Among Tourmaline Fluids and Gramentioning

confidence: 59%

“…5b) whereas F contents are considerably higher in the granite-hosted samples than the basement tourmalines (Fig. 5d) Recent attention has been paid to the presence of "excess" boron in tourmaline(> 3 cations pfu), which substitutes for Si in tetrahedral sites Marschall et al, 2004;Ertl et al, 2006). This can be significant for boron isotope behavior, since isotopic fractionation depends on the coordination environment of boron (see section 7.1).…”

Section: General Observationsmentioning

confidence: 96%

“…Tourmaline is therefore at the center of interest in boron isotope geochemistry and its applications to fluid-related processes including hydrothermal ore formation, subduction zone dehydration and arc magma-genesis, crustal metamorphism and anatexis (e.g., Smith and Yardley, 1996;Chaussidon and Appel, 1997;Tonarini et al, 1998;Dyar et al, 1999;Jiang et al, 1999;Taylor et al, 1999;Trumbull and Chaussidon, 1999;Kasemann et al, 2000;Altherr et al, 2004;Pesquera et al, 2005). In-situ microanalysis of B-isotope composition in tourmaline by SIMS has the great advantage over bulk techniques that contamination with mineral inclusions can be largely avoided and variations in isotope ratios at the sub-grain scale can be resolved, which allows direct coupling of isotopic and chemical composition with important petrographic features such as mineral zoning, replacement or overgrowth textures (Nakano and Nakamura, 2001;Chaussidon and Appel, 1997;Matthews et al, 2003;Altherr et al, 2004;Marschall et al, 2006). This paper reports in-situ B-isotope and chemical compositions in tourmaline from samples that represent different stages in a sequence of crustal anatexis, granitic differentiation and post-magmatic metasomatism in the Neoproterozoic Damara Belt of Namibia.…”

Section: Introductionmentioning

confidence: 99%

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Chemical and boron-isotope variations in tourmalines from an S-type granite and its source rocks: the Erongo granite and tourmalinites in the Damara Belt, Namibia

Trumbull

Krienitz

Gottesmann

et al. 2007

Contrib Mineral Petrol

129

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Tourmaline is widespread in metapelites and pegmatites from the Neoproterozoic Damara Belt, which form the basement and potential source rocks of the Cretaceous Erongo granite. This study traces the B-isotope variations in tourmalines from the basement, from the Erongo granite and from its hydrothermal stage. Tourmalines from the basement are alkali-deficient schorl-dravites, with Bisotope ratios typical for continental crust (δ 11 B average -8.4‰ ±1.4, n=11; one sample at -13‰, n=2).Virtually all tourmaline in the Erongo granite occurs in distinctive tourmaline-quartz orbicules. This "main-stage" tourmaline is alkali-deficient schorl (20-30% X-site vacancy, Fe/(Fe+Mg) 0.8 to 1), with uniform B-isotope compositions (δ 11 B -8.7‰ ±1.5, n=49) that are indistinguishable from the basement average, suggesting that boron was derived from anatexis of the local basement rocks with no significant shift in isotopic composition. Secondary, hydrothermal tourmaline in the granite has a bimodal B-isotope distribution with one peak at about -9‰, like the main-stage tourmaline and a second at -2‰. We propose that the tourmaline-rich orbicules formed late in the crystallization history from an immiscible Na-B-Fe-rich hydrous melt. The massive precipitation of orbicular tourmaline nearly exhausted the melt in boron and the shift of δ 11 B to -2‰ in secondary tourmaline can be explained by Rayleigh fractionation after about 90% B-depletion in the residual fluid.2

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Section: Boron Isotope Fractionation Among Tourmaline Fluids and Gramentioning

confidence: 59%

Section: General Observationsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Chemical and boron-isotope variations in tourmalines from an S-type granite and its source rocks: the Erongo granite and tourmalinites in the Damara Belt, Namibia

Trumbull

Krienitz

Gottesmann

et al. 2007

Contrib Mineral Petrol

129

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“…The tetrahedron can also be occupied by B (e.g. Ertl et al 2002a, 2006, 2007, 2015Hughes et al 2004;Lussier et al 2008Lussier et al , 2009Kutzschbach et al 2016Kutzschbach et al , 2017.…”

Section: Cationic Sitesmentioning

confidence: 99%

The crystal-chemical autopsy of octahedral sites in Na-dominant tourmalines: octahedral metrics model unconstrained by the Y,Z-site disorder assignment

Bačík¹

2018

J. Geosci.

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The structure of tourmaline-supergroup minerals includes two types of octahedral sites: the ZO 6 octahedron is smaller and more distorted than the YO 6 octahedron. The octahedral sites metrics were studied and their dependency on the chemical composition unconstrained by Y,Z-site disorder assignment. Published chemical and structural data were collected from American Mineralogist Crystal Structure Database for tourmaline samples belonging to dravite-schorl, schorl-elbaite (including tsilaisites) and schorl (± dravite)-olenite series. Correlation analysis of this dataset provided the evidence of cation distribution between sites -Al and Mg are disordered between Z and Y sites, while Fe (mostly ferrous), Li and Mn strongly prefer Y site. Irregular cation distribution results in the variable metrics of both octahedra in tourmalines. It is the function of well-balanced relations between cations at octahedral and neighbouring sites based on bond-valence variations due to different ionic charges. Considering Z and Y cations, there is a dependence of the cation charge difference and the octahedral metrics. The most pronounced irregularity of both octahedra was observed in elbaite samples with the largest charge difference between Li and Al. In contrast, "buergerite" samples with trivalent Fe and Al at both octahedral sites have both octahedra almost isometric. Schorl and dravite samples display an increasing metric irregularity related to the Al and Mg content; increase in Mg reduces irregularity because Mg is distributed between both octahedral sites balancing charge difference. In contrast, Fe-rich and Al-rich schorl samples display larger irregularity which may result from selective incorporation of Fe 2+ to the Y site. In olenite samples, the irregularity of both octahedra decreases with an increasing Al content. These variations are related to the shared edge of ZO 6 and YO 6 octahedra including both O3 and O6 site where bonds of both anions are balancing bond-valence requirements of the stable electroneutral structure. In addition to the bond-valence relations, effects of the internal geometry of atomic shells should be also considered, i.e. Jahn-Teller distortion that can be decisive factor in cation occupancy. Especially Fe 2+ can strongly prefer YO 6 octahedron whose prolonged tetragonal dipyramidal geometry is more favourable for Fe 2+ in (t 2g ) 4 (e g ) 2 configuration. Received: 6 October 2017; accepted: 31 May 2018; handling editor: J. Cempírek The online version of this article (doi: 10.3190/jgeosci.260) contains supplementary electronic material. Keywords: tourmaline supergroup, octahedral metrics, bond-valence theory, Jahn-Teller effectvacancies (Henry et al. 2011), although Ti structural position is not clear yet.Although the site occupancy usually follows Goldschmidt rules (ionic radii of cations occupying the Z site are lower and therefore the ZO 6 octahedron is smaller), local structural and bond-valence requirements may result in various cation disorder. Along with the Al-Mg disorder (Hawthorne ...

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“…The presence of Β inside T0 4 is debatable, some authors assert there is no evidence for its occupation of Si tetrahedral site, whereas recently Erti et al (2006) describe ttourmaline containing IVB from several localities. The presence of substantial IV Β is limited to, or more common in, Al-rich tourmalines.…”

Section: Introductionmentioning

confidence: 99%

An Unusual Tourmaline Composition From Sithonia Peninsula (Northern Greece)

et al. 2007

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Tetrahedrally coordinated boron in tourmalines from the liddicoatite-elbaite series from Madagascar: Structure, chemistry, and infrared spectroscopic studies

Cited by 59 publications

References 39 publications

Chemical and boron-isotope variations in tourmalines from an S-type granite and its source rocks: the Erongo granite and tourmalinites in the Damara Belt, Namibia

Chemical and boron-isotope variations in tourmalines from an S-type granite and its source rocks: the Erongo granite and tourmalinites in the Damara Belt, Namibia

The crystal-chemical autopsy of octahedral sites in Na-dominant tourmalines: octahedral metrics model unconstrained by the Y,Z-site disorder assignment

An Unusual Tourmaline Composition From Sithonia Peninsula (Northern Greece)

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