The solidus of carbonated eclogite in the system CaO–Al2O3–MgO–SiO2–Na2O–CO2 to 32 GPa and carbonatite liquid in the deep mantle
The solidus of carbonated eclogite in the system CaO–Al2O3–MgO–SiO2–Na2O–CO2 to 32 GPa and carbonatite liquid in the deep mantle
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DOI：
10.1016/j.epsl.2010.03.030
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发表时间：
2010-06
影响因子：
5.3
通讯作者：
K. Litasov;E. Ohtani
中科院分区：
文献类型：
--
作者：
K. Litasov;E. Ohtani
本文测定了碳酸盐榴辉岩（5 wt.%）的熔融相关系CO2）在10.5-32.0GPa和1300-1850°C下的压力。与部分熔体共存的硅酸盐矿物组合随压力的变化从10 GPa的石榴子石-绿辉石-蓝晶石-方石英，到16- 20 GPa的石榴子石-绿辉石-方石英，再到27- 32 GPa的Mg-钙钛矿-Ca-钙钛矿-CF相-方石英。菱镁矿是该系统中唯一稳定的碳酸盐，通过研究的压力范围。固相线温度由部分熔融的出现来定义。碳酸盐榴辉岩的固相线在10.5GPa下为1380-1460°C，在16.5GPa下为1460-1560°C，在20 GPa下为1530-1630°C，在27和32 GPa下为1600-1790°C。固相线曲线在10- 32 GPa范围内的斜率较低。无铁碳酸盐榴辉岩的固相线曲线与地幔平均地温曲线基本一致。碳酸盐榴辉岩在10.5-32.0GPa熔融形成的部分熔体具有镁碳酸盐成分，Ca/Mg比值高于橄榄岩组合中的同类熔体，并含有高Na_2 O。研究表明，碳酸盐榴辉岩在至少32 GPa的压力下（即下地幔深度）部分熔融可形成碳酸盐类熔体。
Melting phase relations have been determined in a model carbonated eclogite (5wt.% CO2) at 10.5–32.0GPa and 1300–1850°C. The assemblage of silicate minerals coexisting with partial melts changes with pressure from garnet–omphacite–kyanite–stishovite at 10GPa via garnet–corundum–stishovite at 16–20GPa to Mg–perovskite–Ca–perovskite–CF phase–stishovite at 27–32GPa. Magnesite is the only carbonate stable in this system through the studied pressure range. The solidus temperature was defined by the appearance of partial melt. The solidus of carbonated eclogite is bracketed at 1380–1460°C at 10.5GPa, 1460–1560°C at 16.5GPa, 1530–1630°C at 20GPa, and 1600–1790°C at 27 and 32GPa. The slope of solidus curve is less steep at 10–32GPa than at lower pressures. The solidus curve of Fe-free carbonated eclogite roughly coincides with an average mantle geotherm. Partial melts formed by melting of carbonated eclogite at 10.5–32.0GPa have magnesiocarbonatite compositions with Ca/Mg ratios higher than in similar melts in peridotite assemblages, and contain high Na2O-contents. It has been demonstrated that carbonatite-like melt can be generated by partial melting of carbonated eclogites at pressure up to at least 32GPa, i.e. to lower mantle depths.