Partitioning of H₂O between olivine and carbonate-silicate melts at 6.3 GPa and 1400鈥壜癈: Implications for kimberlite formation

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• 作者：Alex ; er G. Sokol ; Igor N. Kupriyanov ; Yuri N. Palyanov
• 关键词：olivine water storage capacity ; kimberlite ; hydrous partial melting ; IR spectroscopy
• 刊名：Earth and Planetary Science Letters
• 出版年：1 December, 2013
• 年：2013
• 卷：383
• 期：Complete
• 页码：58-67
• 全文大小：954 K

文摘

Partitioning of H₂O between olivine and carbonate-silicate melts has been studied at 6.3 GPa and 1400鈥壜癈 using a split-sphere multianvil apparatus. Olivine was synthesized in equilibrium with hydrous silicate and hydrous carbonate-silicate卤chloride melts saturated with respect to one of Opx, Grt, Ms or a harzburgitic (Ol+Opx+Grt) residue and had CO₂/(CO₂+SiO₂) molar ratios from 0 to 0.8. The concentration of H₂O in olivine was determined using FTIR spectroscopy. We found that depending on the melt carbonation and saturation in equilibrium silicate phases the H₂O content in olivine varied from 100 to 1500 ppm. The obtained results and data reported in indicate that H₂O content in olivine becomes approximately two times lower as CO₂/(CO₂+SiO₂) molar ratios in the equilibrium melt increases from 0 to 0.4-0.8 and the crystallization media transform from hydrous silicate to hydrous carbonate-silicate (kimberlite like) melt. The estimated water partitioning between carbonate-silicate melt and nominally anhydrous mantle minerals indicates that carbonatitic melt can effectively extract water once it invades H₂O-poore the peridotite. We suggest that extraction of H₂O owing to the freezing point depression may provide the necessary melting degree of metasomatized peridotite source and formation of kimberlitic magma.