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Megacrysts of “Bubbly” Kaersutite in Neogene–Quaternary Volcanic Rocks of Northwestern Syria: Evidence for Crystallization in a Boiling Melt/Fluidстатья
- Авторы: Sharkov E.V., Prokofiev V.Yu, Chistyakov A.V., Bogina M.M., Gornostaeva T.A.
- Журнал: Journal of Volcanology and Seismology
- Том: 16
- Номер: 3
- Год издания: 2022
- Издательство: Springer Verlag
- Местоположение издательства: Germany
- Первая страница: 221
- Последняя страница: 238
- DOI: 10.1134/S0742046322030046
- Аннотация: The paper addresses megacrysts of “bubbly” kaersutite found among mantle xenoliths in the AlGhab plateau basalts, northwestern Syria. The xenoliths as all xenoliths worldwide are represented by two series: green spinel peridotites (mainly lherzolites) and cross-cutting veins rocks of “black series” (mainly kaersutite hornblendites and kaersutite clinopyroxenites). It is believed that the parental melts/fluids of the “black series” were formed under decompressional fluid-assisted melting of the plume’s spinel peridotites at the late stages of development of the plume-related magmatic systems. “Bubbly” kaersutite megacrysts are fragments of pegmatoid varieties of the “black series” rocks. They represent monocrystals up to 10 cm long, which contain numerous relatively large cavities partially filled with volcanic dust. It is shown that the “bubbly” structure of these megacrysts is explained by their crystallization during retrograde boiling of parental melt/fluid in the mantle plume head at a pressure of 9–10 kbar. The oval cavities initially represented bubbles of high-density carbon dioxide entrapped by growing crystals. These bubbles were likely degassed during eruption and CO2 has been partially preserved only in some microscopic bubbles. It was also shown that the parental melt contained small suspended drops of fluid-saturated high-Fe liquid, which were likely derived through liquid immiscibility before retrograde boiling of the melt/fluid.
- Добавил в систему: Прокофьев Всеволод Юрьевич