Abstract:Two tourmaline samples occurring in quartz veinlets, which crosscut an amphibolite body at the Budniki camp near the Kowary town, in the south-west part of the Karkonosze Mountains (SW Poland), were studied through microprobe and single crystal X-ray diffraction. Samples were extracted from core and rim regions of crystals with a concentric zoning, respectively.Chemical and structural data revealed that the core tourmaline is characterized by a draviteoxy-dravite composition, with formula: X (Na0.82Ca0.07K0.01… Show more
“…Adjustment of the Y Al 3+ values to Y R 3+ (which considers Y Fe 3+ ) justifies their classification as oxy-dravite, at least in the case of the holotype described by Bosi and Skogby (2013). Sȩk et al (2022) correctly considered dravitic to oxy-dravitic compositions with significant Fe 3+ component.…”
Section: Comparison Of Reported Oxy-dravite Compositions and Structuresmentioning
confidence: 84%
“…The V- and W-sites are characterised by high OH (2.92–3.00 apfu) and O contents (0.80–0.95 apfu), with minor F (0.12–0.17 apfu) only. Figure 3.Composition of the Beluga oxy-dravite in several compositional spaces compared to compositions from other studies (Ertl et al , 2003; Čopjaková et al , 2012; Bosi and Skogby, 2013; Pieczka et al , 2018; Sȩk et al , 2022). Note the high miscibility with vacancy-, Fe- and OH-dominated species.…”
Section: Chemical Compositionmentioning
confidence: 91%
“…Occupancies of octahedral sites were refined using bond-valence optimisation (Table 3) which confirmed disorder of Mg and Al between the Y-and Z-sites, typical for Mg-rich tourmalines (e.g. Grice and Ercit, 1993;Hawthorne et al, 1993;Ertl et al, 2003;Bosi and Lucchesi, 2004;Bosi and Skogby, 2013;Bačík, 2015;Pieczka et al, 2018;Scribner et al, 2021;Bosi et al, 2022;Sȩk et al, 2022).…”
Section: Crystal Structure and Bond Valence Refinementmentioning
confidence: 94%
“…5). Data from studies of Bosi and Skogby (2013) and Sȩk et al (2022) plot in the oxy-dravite field (Fig. 5b); however, samples in both of those studies contain significant amounts of Fe 3+ (0.610 apfu and 0.565 apfu, respectively).…”
Section: Comparison Of Reported Oxy-dravite Compositions and Structuresmentioning
confidence: 99%
“…Implications for oxy-dravite occurrence Pieczka et al (2018) reported that the main petrogenetic environments of oxy-dravites are aluminous metapelites and metapsammites (e.g. Bosi and Skogby, 2013;Čopjaková et al, 2012;Ertl et al, 2003;Pieczka et al, 2018), low-Ca ultramafics (Sȩk et al, 2022), and (Cr,V)-rich metasediments (e.g. Bosi and Lucchesi, 2004;Cempírek et al, 2013).…”
Section: Petrogenesis Of Beluga Oxy-dravitementioning
Oxy-dravite, ideally Na(Al2Mg)(Al5Mg)(Si6O18)(BO3)3(OH)3(O), was found in a composition near its ideal end-member at the Beluga occurrence, Nunavut territory, Canada. It occurs in retrograde albite–muscovite–corundum–calcite domains in a calc-silicate rock. This uncommon oxy-dravite occurs as dark brown, equant to short-prismatic, idiomorphic crystals with vitreous lustre and up to ca. 4 × 3 cm in size. The oxy-dravite is optically uniaxial (–), with ω = 1.6453(5) and ɛ = 1.6074(18); its calculated density is 3.069 g.cm–3 with a compatibility index of 0.016. The Beluga oxy-dravite has trigonal symmetry, space group R3m with a = 15.9121(2) Å, c = 7.1788(10) Å, V = 1574.12(5) Å3 and Z = 3. The crystal structure was refined to R1 = 1.45 using 1613 unique reflections. The empirical crystal-chemical formula is X(Na0.88Ca0.08□0.03K0.01)Y(Al1.49Mg1.31Fe0.15Ti0.04Zn0.01)Z(Al5.42Mg0.58)T(Si5.84Al0.16O18)B(BO3)3V(OH2.95O0.05)W(O0.84OH0.01F0.15).
Oxy-dravite in nature commonly occurs in a solid solution with foitite, schorl and oxy-schorl. At the Beluga occurrence, its minor contents of Al, vacancy [□], and Ca are most likely compensated by (□Al)(NaR2+)–1 and (CaMg)(NaAl)–1 exchanges of the oxy-magnesio-foitite and magnesio-lucchesiite components. The Beluga occurrence of oxy-dravite is characterised by an Mg-rich environment related to a metamorphic overprint of the original sedimentary sequence. This sequence of marine dolomitic argillaceous marl was influenced by (B,Cl)-rich fluids, probably proximally-derived from mineral breakdown reactions in the calc-silicate during the retrograde stage of metamorphism. The locality is a rare example of a tourmaline + corundum assemblage.
“…Adjustment of the Y Al 3+ values to Y R 3+ (which considers Y Fe 3+ ) justifies their classification as oxy-dravite, at least in the case of the holotype described by Bosi and Skogby (2013). Sȩk et al (2022) correctly considered dravitic to oxy-dravitic compositions with significant Fe 3+ component.…”
Section: Comparison Of Reported Oxy-dravite Compositions and Structuresmentioning
confidence: 84%
“…The V- and W-sites are characterised by high OH (2.92–3.00 apfu) and O contents (0.80–0.95 apfu), with minor F (0.12–0.17 apfu) only. Figure 3.Composition of the Beluga oxy-dravite in several compositional spaces compared to compositions from other studies (Ertl et al , 2003; Čopjaková et al , 2012; Bosi and Skogby, 2013; Pieczka et al , 2018; Sȩk et al , 2022). Note the high miscibility with vacancy-, Fe- and OH-dominated species.…”
Section: Chemical Compositionmentioning
confidence: 91%
“…Occupancies of octahedral sites were refined using bond-valence optimisation (Table 3) which confirmed disorder of Mg and Al between the Y-and Z-sites, typical for Mg-rich tourmalines (e.g. Grice and Ercit, 1993;Hawthorne et al, 1993;Ertl et al, 2003;Bosi and Lucchesi, 2004;Bosi and Skogby, 2013;Bačík, 2015;Pieczka et al, 2018;Scribner et al, 2021;Bosi et al, 2022;Sȩk et al, 2022).…”
Section: Crystal Structure and Bond Valence Refinementmentioning
confidence: 94%
“…5). Data from studies of Bosi and Skogby (2013) and Sȩk et al (2022) plot in the oxy-dravite field (Fig. 5b); however, samples in both of those studies contain significant amounts of Fe 3+ (0.610 apfu and 0.565 apfu, respectively).…”
Section: Comparison Of Reported Oxy-dravite Compositions and Structuresmentioning
confidence: 99%
“…Implications for oxy-dravite occurrence Pieczka et al (2018) reported that the main petrogenetic environments of oxy-dravites are aluminous metapelites and metapsammites (e.g. Bosi and Skogby, 2013;Čopjaková et al, 2012;Ertl et al, 2003;Pieczka et al, 2018), low-Ca ultramafics (Sȩk et al, 2022), and (Cr,V)-rich metasediments (e.g. Bosi and Lucchesi, 2004;Cempírek et al, 2013).…”
Section: Petrogenesis Of Beluga Oxy-dravitementioning
Oxy-dravite, ideally Na(Al2Mg)(Al5Mg)(Si6O18)(BO3)3(OH)3(O), was found in a composition near its ideal end-member at the Beluga occurrence, Nunavut territory, Canada. It occurs in retrograde albite–muscovite–corundum–calcite domains in a calc-silicate rock. This uncommon oxy-dravite occurs as dark brown, equant to short-prismatic, idiomorphic crystals with vitreous lustre and up to ca. 4 × 3 cm in size. The oxy-dravite is optically uniaxial (–), with ω = 1.6453(5) and ɛ = 1.6074(18); its calculated density is 3.069 g.cm–3 with a compatibility index of 0.016. The Beluga oxy-dravite has trigonal symmetry, space group R3m with a = 15.9121(2) Å, c = 7.1788(10) Å, V = 1574.12(5) Å3 and Z = 3. The crystal structure was refined to R1 = 1.45 using 1613 unique reflections. The empirical crystal-chemical formula is X(Na0.88Ca0.08□0.03K0.01)Y(Al1.49Mg1.31Fe0.15Ti0.04Zn0.01)Z(Al5.42Mg0.58)T(Si5.84Al0.16O18)B(BO3)3V(OH2.95O0.05)W(O0.84OH0.01F0.15).
Oxy-dravite in nature commonly occurs in a solid solution with foitite, schorl and oxy-schorl. At the Beluga occurrence, its minor contents of Al, vacancy [□], and Ca are most likely compensated by (□Al)(NaR2+)–1 and (CaMg)(NaAl)–1 exchanges of the oxy-magnesio-foitite and magnesio-lucchesiite components. The Beluga occurrence of oxy-dravite is characterised by an Mg-rich environment related to a metamorphic overprint of the original sedimentary sequence. This sequence of marine dolomitic argillaceous marl was influenced by (B,Cl)-rich fluids, probably proximally-derived from mineral breakdown reactions in the calc-silicate during the retrograde stage of metamorphism. The locality is a rare example of a tourmaline + corundum assemblage.
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