|
ИСТИНА |
Войти в систему Регистрация |
ИСТИНА ЦЭМИ РАН |
||
Ti4+ and Sn4+-bearing tourmalines - pressure control and comparison of synthetic and natural counterpartsстатья
- Авторы: Vereshchagin O.S., Wunder B., Baksheev I.A., Wilke F.D.H, Vlasenko N.S., Frank-Kamenetskaya O.V.
- Журнал: Journal of Geosciences
- Том: 67
- Номер: 2
- Год издания: 2022
- Издательство: Czech Geological Society
- Местоположение издательства: Czech Republic
- Первая страница: 163
- Последняя страница: 171
- DOI: 10.3190/jgeosci.345
- Аннотация: Me4+-bearing (Me4+ = Sn, Ti) dravite analogs were synthesized in the system MeO2–MgO–Al2 O3–B2 O3–SiO2–NaO–H2 O at 700 °C and 4 / 0.2 GPa in four hydrothermal experiments. Tourmalines form rosette-like aggregates and needle-like crystals that are chemically homogeneous. Tourmaline crystals obtained in high-pressure runs (4 GPa) are much smaller (up to 0.1 × 2 μm) and have lower Me4+ (0.27 wt. % SnO2 , 0.57 wt. % TiO2 ) than those from the low-pressure (0.2 GPa) runs (up to 1 × 5 μm; 1.77 wt. % SnO2 , 2.25 wt. % TiO2 ). Synthetic analogs of rutile, quartz and coesite were obtained in the system TiO2–MgO–Al2 O3–B2 O3–SiO2–NaO–H2 O, whereas synthetic analogs of cassiterite, tin-rich (up to ~19.55 wt. % SnO2 ) Na-pyroxene, MgSn(BO3 )2 (Mg-analogue of tusionite), quartz and coesite were synthesized in the system SnO2–MgO–Al2 O3–B2 O3–SiO2–NaO–H2 O. We suggest that at a high temperature (≥ 700 ºC), the pressure negatively affects the Ti incorporation into the tourmaline structure. In contrast, at relatively low pressures, the Ti incorporation in tourmaline structures is governed by the Ti content in the mineral-forming medium. Low-pressure conditions are feasible for Sn incorporation in the tourmaline structure. The presence of Ti4+ and Sn4+ cations in structures of the synthesized tourmalines (probably at octahedrally coordinated sites), is also indicated by changes in the unit-cell parameters.
- Добавил в систему: Бакшеев Иван Андреевич