Tourmaline from the Solnechnoe tin deposit, Khabarovsk Krai, Russia

Abstract

Tourmaline from the Solnechnoe hydrothermal granitoid-related tin deposit in the Khabarovsk Krai, Russian Far East has been studied with electron microprobe, infrared and Mössbauer spectroscopy. Tourmaline formed in three distinct stages with different types of chemical substitution. Tourmaline from the first unmineralised stage is classified as dravite or schorl, which could be enriched locally in Ca, the X-site vacancy and F. This tourmaline is characterised by the Fe ↔ Mg and X vacancy + Al ↔ Na + Fe substitutions. The second, molybdenum-stage tourmaline, is schorl–dravite and fluor-schorl–fluor-dravite enriched in Ca, and a few compositions belong to the calcic group. The predominant substitution is Ca + Mg ↔ Na + Al. The third, tin-stage tourmaline, is classified as schorl–dravite with some tourmalines being fluor-schorl, oxy-schorl, foitite and magnesio-foitite. The tin-stage tourmaline is characterised by the substitutions Fe2+ ↔ Mg, Altot + O2– ↔ Fe2+ + OH–, and Fe3+ ↔ Altot. An increase of the Fe3+/Fetot value from 3–9% in the molybdenum stage to 12–16% in the tin-stage tourmalines indicates an increase in oxidation potential, which possibly contributed to cassiterite deposition. Comparison of tourmalines from greisen, porphyry and intrusion-related tin deposits worldwide shows they differ in primary chemical substitutions so can be characterised by this mechanism. The Fe3+/Fetot value in tourmaline also appears to be one of the indications for the tin deposit type. The Fe3+/Fetot value increases from <10% in greisen tourmaline through 15% in tourmaline from intrusion-related deposits to 20% in tourmaline from porphyry deposits.

Ti4+ and Sn4+-bearing tourmalines - pressure control and comparison of synthetic and natural counterparts

“…Our data on tin-tourmaline and tin-pyroxene (Tab. 2), data on tin-tourmaline (Baksheev et al 2020), and coexisting tin-free melilite and tin-enriched pyroxene (Butler 1978), suggest that Sn 4+ occupies octahedral sites in the tourmaline and pyroxene crystal structures. Baksheev et al (2020) pointed out that, despite the Si content variation in Sn-bearing schorl, no correlation between Si and Sn was found and suggested the substitution scheme for the Sn-bearing schorl as follows: (Baksheev et al 2020).…”

“…% SnO 2 (Drivenes 2021); in Solnechnoe in Russia -1.02 wt. % SnO 2 ; (Baksheev et al 2020); in Pridorozhnoe in 3-1; Tab. 2), we found out that a pressure increase influences the titanium content negatively in our synthetic tourmalines.…”

“…%; Vereshchagin et al 2018). However, as natural tourmalines could contain up to 10 different cations at the same crystallographic site simultaneously (e.g., Ertl et al 2019), data on synthetic tourmaline analogs are needed to determine (1) preferable crystallographic sites for each element, (2) maxi-of porphyry-style and granitoid-related Sn deposits (e.g., Mlynarczyk and Williams-Jones 2006;Baksheev et al 2012Baksheev et al , 2020.…”

Sn-rich tourmaline from the Land’s End granite, SW England

“…The data in Bosi et al (2017) plot from oxy-schorl towards dravite composition, concerning Al-Fe-Mg, until it reaches the line connecting oxydravite and povondraite, which the data plot neatly along towards povondraite. The data in this study differ from those reviewed in Bosi et al (2017) in that the change in the direction of the trend towards Fe-rich compositions happens before the oxy-dravite-povondraite line and that the exchange vector controlling the composition with increasing Fe involves Mg, although as Bosi et al (2017) concluded, there is no evidence for a direct solid solution between oxy-schorl and bosiite or povondraite (e.g., a Mg 2 Fe 1 Al -3 exchange vector) Previously suggested substitution schemes for Sn in tourmaline include X Na + + YZ Fe 2+ + YZ Sn 4+ ↔ X Ca 2+ + YZ Mg 2+ + YZ Al 3+ , 2 XY Al 3+ ↔ YZ Sn 4+ + YZ Mg 2+ , YZ Al 3+ + VW OH -↔ YZ Sn 4+ + VW O 2-, and 2 YZ Mg 2+ ↔ YZ Sn 4+ + YZ ☐ (Baksheev et al 2020;Vereshchagin et al 2022). The Sn-rich tourmalines in this study are Fe-rich, and the latter three substitution reactions were derived from synthesized dravite.…”

Iron-bearing to iron-rich tourmalines from granitic pegmatites of the Murzinka pluton, Central Urals, Russia

“…Tourmaline is stable over the wide range of pressure-temperature conditions, from lowtemperature hydrothermal to magmatic and high-pressure metamorphic (Henry and Dutrow 1996; https://doi.org/10.1180/mgm.2022.104 Published online by Cambridge University Press Selway et al, 1999;Marks et al, 2013;Baksheev et al, 2019) and therefore is a good indicator of the mineral-forming environment. The major and trace element composition, substitution mechanisms, and spectroscopic features may help to understand the fractionation degree and the evolution of a pegmatite melt in general (Čerńy et al, 1985;Jolliff et al, 1986;Tindle et al, 2002;Roda-Robles et al, 2004).…”