STRUCTURAL AND CHEMICAL INVESTIGATION OF A ZONED SYNTHETIC Cu-RICH TOURMALINE

Ertl, Andreas; Vereshchagin, Oleg S.; Giester, Gerald; Тиллманнс, Е.; Meyer, Hans‐Peter; Ludwig, Thomas; Rozhdestvenskaya, I. V.; Frank-Kamenetskaya, O. V.

doi:10.3749/canmin.1400078

Cited by 16 publications

(10 citation statements)

References 42 publications

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“…The ideal Al-O bond length for octahedral coordination, which is calculated using the bond-valence approach (Brown 2006 The situation gets more complicated for d elements, whose internal structure with unfilled d orbitals allows for the reduction of symmetry due to Jahn-Teller distortion (Jahn et al 1937). This was observed for Fe 2+ , Mn 3+ , and Cu 2+ in similar silicates, such as epidote, gadolinite-hingganite, chlorite and mica, as well as in tourmaline (Burns and Strens 1967;Faye 1968;Ito and Hafner 1974;Burns and Hawthorne 1996;Bačík et al 2014Bačík et al , 2017Ertl et al 2015;Fridrichová et al 2018). However, this distortion can be described in the second approximation.…”

Section: Determination Of the "Goldilocks Zone" For Crystallographic mentioning

confidence: 85%

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Cation partitioning among crystallographic sites based on bond-length constraints in tourmaline-supergroup minerals

Bačík

Fridrichová

2021

American Mineralogist

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Theoretical bond-length calculations from ideal bond valences for each ion and coordination allow for the prediction of ion site preference and partitioning in tourmaline structures at low-pressure conditions. A comparison of calculated data with published bond-length values enables the determination of the range of structurally stable bond lengths with a minimal induced distortion—the “Goldilocks zone.” The calculations provided the following conclusions: the B-site occupancy is strictly limited to B3+; the T site can freely accommodate not only Si4+ but also B3+ and Al3+, although these substituents require shrinkage and expansion of the TO4 tetrahedron, respectively; and the Be2+ substitution results in a significant difference in charge. Satisfactory bond lengths for octahedral sites were calculated for Al3+ (Z-site preference), Ti4+, Mn3+, Ga3+, V3+, Fe3+ (mixed preference), Mg2+, Fe2+, Li+, Mn2+, Ni2+, Zn2+, Cu2+, Sc3+, and Zr4+ (Y-site preference). Another group of cations, which includes U4+, Th4+, Y3+, and lanthanoids from Tb to Lu and Ce4+, have significantly longer bonds than typical Y-O and very short bonds for the X site; therefore, it is likely they would prefer an octahedron. The empirical bond length for the X site is met with Na+, Ca2+, Sr2+, Pb2+, and lanthanoids from La to Gd, while K, Rb, and Cs are too large in the low-pressure conditions. However, the final tourmaline composition results from the interaction of the structure with the genetic environment in terms of P-T-X and geochemical conditions. This results in structural and environmental constraints that limit the incorporation of elements into the structure. Consequently, major elements, such as Si, Al, B, Mg, Fe, Na, and Ca usually occur in abundance, whereas other elements (V, Cr, Mn, Ti, Pb) could form end-member compositions, but rarely do because of their low abundance in the environment. The elements with contents limited to trace amounts have either structural (Be, C, REE, Rb, Cs, U, Th) or geochemical (Zr4+, Sc3+, and Sr2+) limits. However, environmental properties, such as high pressure or specific local structural arrangements, can overcome structural constraints and enable the incorporation of elements (K).

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Section: Determination Of the "Goldilocks Zone" For Crystallographic mentioning

confidence: 85%

“…DOI: https://doi.org/10.2138/am-2021-7804. http://www.minsocam.org/ Vereshchagin et al 2013;Ertl et al 2015), Ni 2+ (up to 3.96 wt % NiO; Baksheev and Kudryavtseva 2004), and Zn 2+ (up to 7.37 wt % ZnO; Pieczka et al 2018).…”

Section: Crystal Chemistry Vs Genetic Environmentmentioning

confidence: 99%

Cation partitioning among crystallographic sites based on bond-length constraints in tourmaline-supergroup minerals

Bačík

Fridrichová

2021

American Mineralogist

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“…Over the last 20 years many examples of substitution of Si by B have been found in natural and synthetic tourmalines (Ertl et al, 1997(Ertl et al, , 2005(Ertl et al, , 2006(Ertl et al, , 2007(Ertl et al, , 2008(Ertl et al, , 2012a(Ertl et al, , 2012b(Ertl et al, , 2015Hughes et al, 2004;Kutzschbach et al, 2016Kutzschbach et al, , 2017Lussier et al, 2008Lussier et al, , 2009Schreyer et al, 2000Schreyer et al, , 2002. Using the crystallographic and analytical techniques that are most commonly employed today it is difficult to verify the presence of B at the T site.…”

Section: Boron At the T Sitementioning

confidence: 99%

Tetrahedral substitutions in tourmaline: a review

Ertl

Henry

Тиллманнс

2018

ejm

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The Si 4þ cation, typically the overwhelming occupant of the tetrahedral site of the tourmaline structure, can be partially replaced by Al 3þ , B 3þ , and Be 2þ. Tetrahedrally coordinated Al (up to ∼0.9 [4] Al atom per formula unit, apfu) has been found in different Mg-and/or Fe 2þ-rich tourmalines from high-temperature aluminous lithologies as well as in Li-rich pegmatites. It is relatively common for Li-and [4] Al-bearing tourmalines to also contain some [4] B. While the highest boron content (∼0.8 [4] B apfu) in a natural tourmaline was found in an Al-rich tourmaline (olenite) from the Eastern Alps, Austria, much higher contents of up to ∼2.8 apfu have been reported for synthetic Al-rich tourmalines. Natural tourmalines with a higher total Al content (> 7.2 Al apfu) can also contain significant [4] B. The highest verified beryllium content in a tourmaline is still below 100 ppm, but current data show that in pegmatitic tourmaline crystals the Be content is positively correlated with the overall Al content. Therefore Li-rich tourmalines can contain higher Be contents in pegmatites that originated from differentiated granitic magma, than in pegmatites that have evolved as granitic pegmatitic melts from the surrounding country-rocks during decompression.

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“…This suggests that the usually used rigid-sphere model is insufficient, not only in the case of the Jahn-Teller distortion (e.g. Goodenough 1964;Burns and Strens 1967;Faye 1968;Ito and Hafner 1974;Burns and Hawthorne 1996;Kyono et al 2012;Bačík et al 2014;Ertl et al 2015;Fridrichová et al 2017), but short-range bond-valence effects also influence the geometry of ions and coordination bodies in the interaction between "spherical" ions.…”

Section: Octahedral Metricsmentioning

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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STRUCTURAL AND CHEMICAL INVESTIGATION OF A ZONED SYNTHETIC Cu-RICH TOURMALINE

Cited by 16 publications

References 42 publications

Cation partitioning among crystallographic sites based on bond-length constraints in tourmaline-supergroup minerals

Cation partitioning among crystallographic sites based on bond-length constraints in tourmaline-supergroup minerals

Tetrahedral substitutions in tourmaline: a review

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

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