| Инд. авторы: | Sharygin I.S., Shatskiy A., Litasov K.D., Golovin A.V., Ohtani E., Pokhilenko N.P. |
| Заглавие: | Interaction of peridotite with Ca-rich carbonatite melt at 3.1 and 6.5 GPa: Implication for merwinite formation in upper mantle, and for the metasomatic origin of sublithospheric diamonds with Ca-rich suite of inclusions |
| Библ. ссылка: | Sharygin I.S., Shatskiy A., Litasov K.D., Golovin A.V., Ohtani E., Pokhilenko N.P. Interaction of peridotite with Ca-rich carbonatite melt at 3.1 and 6.5 GPa: Implication for merwinite formation in upper mantle, and for the metasomatic origin of sublithospheric diamonds with Ca-rich suite of inclusions // Contributions to Mineralogy and Petrology. - 2018. - Vol.173. - Iss. 3. - Art.22. - ISSN 0010-7999. - EISSN 1432-0967. |
| Внешние системы: | DOI: 10.1007/s00410-017-1432-3; WoS: 000427307200008; |
| Реферат: | eng: We performed an experimental study, designed to reproduce the formation of an unusual merwinite + olivine-bearing mantle assemblage recently described as a part of a Ca-rich suite of inclusions in sublithospheric diamonds, through the interaction of peridotite with an alkali-rich Ca-carbonatite melt, derived from deeply subducted oceanic crust. In the first set of experiments, we studied the reaction between powdered Mg-silicates, olivine and orthopyroxene, and a model Ca-carbonate melt (molar Na:K:Ca = 1:1:2), in a homogeneous mixture, at 3.1 and 6.5 GPa. In these equilibration experiments, we observed the formation of a merwinite + olivine-bearing assemblage at 3.1 GPa and 1200 degrees C and at 6.5 GPa and 1300-1400 degrees C. The melts coexisting with this assemblage have a low Si and high Ca content (Ca# = molar 100 x Ca/(Ca + Mg) > 0.57). In the second set of experiments, we investigated reaction rims produced by interaction of the same Ca-carbonate melt (molar Na:K:Ca = 1:1:2) with Mg-silicate, olivine and orthopyroxene, single crystals at 3.1 GPa and 1300 degrees C and at 6.5 GPa and 1400 degrees C. The interaction of the Ca-carbonate melt with olivine leads to merwinite formation through the expected reaction: 2Mg(2)SiO(4) (olivine) + 6CaCO(3) (liquid) = Ca3MgSi2O8 (merwinite) + 3CaMg(CO3)(2) (liquid). Thus, our experiments confirm the idea that merwinite in the upper mantle may originate via interaction of peridotite with Ca-rich carbonatite melt, and that diamonds hosting merwinite may have a metasomatic origin. It is remarkable that the interaction of the Ca-carbonate melt with orthopyroxene crystals does not produce merwinite both at 3.1 and 6.5 GPa. This indicates that olivine grain boundaries are preferable for merwinite formation in the upper mantle.
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| Ключевые слова: | ECLOGITE; TRANSPORT; HIGH-PRESSURE; TRANSITION ZONE; EARTHS INTERIOR; PHASE-RELATIONS; DEEP MANTLE; UDACHNAYA-EAST KIMBERLITE; CONTINENTAL LITHOSPHERIC MANTLE; Carbonatite melt; Subduction; Mantle; Merwinite; Diamond; EXTRACTION; |
| Издано: | 2018 |
| Физ. характеристика: | 22 |