Synthetic hypersilicic Cl-bearing mica in the phlogopite-celadonite join: a multimethodical characterization of the missing link between di- and tri-octahedral micas at high pressures

Nazzareni, S.; Comodi, P.; Bindi, L.; Safonov, O.G.; Litvin, Y.A.; Perchuk, L.L.

Авторы: Nazzareni S., Comodi P., Bindi L., Safonov O.G., Litvin Yu A., Perchuk L.L.
Журнал: American Mineralogist
Том: 93
Год издания: 2008
Издательство: Mineralogical Society of America
Местоположение издательства: United States
Первая страница: 1429
Последняя страница: 1436
DOI: 10.2138/am.2008.2802
Аннотация: A hypersilicic Cl-rich mica was synthesized at 4 GPa and 1200-1250°C close to the solidus of the join diopside-jadeite-KCl, in association with diopside-jadeite pyroxene, K-rich aluminosilicate glass and/or sanidine and (K,Na)Cl. The mica shows negative correlation between tetrahedral Si and octahedral (Al+Mg), suggesting an Al-celadonitic substitution (Si+VIAl+VI[]=IVAl+VIMg) and a chemical formula: K1.01(Mg2.45Al0.19[]0.35)Σ=3(Si3.52Al0.48)Σ=4O10[(OH,O)1.66Cl0.34)]Σ=2. The presence of hydroxyl was confirmed by OH stretching modes at 3731 and 3604 cm-1 in the Raman spectra. Single-crystal X-ray diffraction data provides the unit-cell parameters (space group C2/m, 1M polytype): a = 5.299(4), b = 9.167(3), c = 10.226(3) Å, β =100.06(4)°, V = 489.1(4) Å3. The structural refinement shows the presence of vacancies on the octahedral sites (15% for M1 and 6.5% for M2), moreover chlorine split of about 0.5 Å from O4 with partial occupancy (0.39 a.p.f.u). Crystal-chemical mechanism seems to rule chlorine incorporation in mica, since a large A site is necessary to locate the anion in the structure. This configuration resulted when the six tetrahedral ring is hexagonal and the tetrahedral rotation angle  is 0°. Such a geometry is achieved either by increasing the annite component in biotite or by the hypersilicic character of phlogopite through the Al-celadonite substitution. The present Si-rich mica shows a partial dioctahedral character due to the Al-celadonite substitution which lowers the angle and expands its stability field at high-pressure. High aK2O conditions, like in potassium-rich brine or potassic carbonatitic melts, increase the Al-celadonite component in the phlogopite solid solution, explaining the association of Si-rich micas with inclusions of potassic liquids in kimberlitic diamonds.
Добавил в систему: Сафонов Олег Геннадьевич

	ИСТИНА	Войти в систему Регистрация
	Интеллектуальная Система Тематического Исследования НАукометрических данных
	Главная Поиск Статистика О проекте Помощь

ИСТИНА

Интеллектуальная Система Тематического Исследования НАукометрических данных

Synthetic hypersilicic Cl-bearing mica in the phlogopite-celadonite join: a multimethodical characterization of the missing link between di- and tri-octahedral micas at high pressuresстатья

Прикрепленные файлы