Links between carbonatite and kimberlite melts in chloride-carbonate-silicate systems: experiments and application to natural assemblages

Safonov, O.G.; Kamenetsky, V.S.; Perchuk, L.L.

Авторы: Safonov O.G., Kamenetsky V.S., Perchuk L.L.
Журнал: Journal of Petrology
Том: 52
Номер: 7-8
Год издания: 2011
Издательство: Oxford University Press
Местоположение издательства: United Kingdom
Первая страница: 1307
Последняя страница: 1331
DOI: 10.1093/petrology/egq034
Аннотация: Recent data suggest an active role of alkali chloride-bearing carbonatitic melts in formation and evolution of kimberlites, while experiments indicate that chlorides could be responsible for liquid immiscibility during melting of the carbonated mantle rocks. Present study considers melting trends in the kimberlite-related chloride-carbonate-silicate systems at pressures 5.0-5.5 GPa. Direction of these trends largely depends on the chlorine concentration in the system. All trends start with the Cl-rich carbonatitic liquid coexisting with crystalline phases. Melting of peridotite-carbonate-chloride system containing 3-4 wt. % of chlorine results in a gradual transition from a carbonatitic melt (5-7 wt. % of SiO2, MgO/CaO = 0.5-0.6, ~2 wt. % of Cl) at 1000-1100OC through a Cl-rich carbonate-silicate melt (12-15 wt. % of SiO2, MgO/CaO = 0.6, and up to 14 wt. % of Cl) at 1360-1400OC toward Cl-bearing ultrabasic carbonate-silicate melt (UCSM), i.e. kimberlite-like (26-29 wt. % of SiO2, MgO/CaO = 1.5-2.8, and 6-4 wt. % of Cl), at 1500-1600OC. This trend results from a specific melting behavior of chlorides, which are found to be stable crystalline phases by about 300OC above solidus. In contrast, melting of the system with about 0.65 wt. % of chlorine proceeds along a simple trend from a carbonatitic melt (~5 wt. % of SiO2, MgO/CaO = 0.4-0.5, ~2 wt. % of Cl) at 1100-1150OC toward the UCSM (~25 wt. % of SiO2, MgO/CaO = 1.7-1.8, and 0.5-0.6 wt. % of Cl) at 1500-1600OC. At 17 wt. % of chlorine in the system, the melting trends involve the immiscibility gap and shows abrupt transition toward the UCSM equilibrated with the chloride-carbonate liquid at above 1500OC. Melting relations in the studied chloride-carbonate-silicate systems are exclusively regulated by peritectic reactions between the silicate phases and carbonate constituents (mostly, CaCO3) of the melts. Chlorides seem to be inert in these reactions. They decrease the solidus temperatures of carbonated peridotites, but do not reduce the temperature interval for transition from carbonate- to silicate-dominated melts. The experimental results are applied to the data on the Udachnaya-East kimberlite pipe (Yakutia). It is suggested that Cl-rich carbonatite liquids preserved in diamonds and Cl-rich kimberlites of this pipe could represent an interrelated system of chloride-rich liquids evolved within the wide temperature interval during incipience and evolution of kimberlite magmas from carbonated mantle source containing 3-4 wt. % of chlorine.
Добавил в систему: Сафонов Олег Геннадьевич

	ИСТИНА	Войти в систему Регистрация
	ИПМех РАН
	Главная Поиск Статистика О проекте Помощь

ИСТИНА

ИПМех РАН

Links between carbonatite and kimberlite melts in chloride-carbonate-silicate systems: experiments and application to natural assemblagesстатья

Прикрепленные файлы