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首页> 外文期刊>Contributions to Mineralogy and Petrology >Carbonate melts in the hydrous upper mantle
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Carbonate melts in the hydrous upper mantle

机译：碳酸盐熔化在湿润的上部罩上

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Carbonatite compositions resulting from melting of magnesian calcite + olivine + clinopyroxene were experimentally determined in the system CaO-MgO-SiO2-CO2-H2O as a function of temperature and bulk H2O contents at 1.0 and 1.5 GPa. The melting reaction and melt compositions were found to be highly sensitive to H-loss or -gain during experiments. We hence designed a new hydrogen-trap technique, which provided sufficient control to obtain consistent results. The nominally dry solidus temperatures at 1.0 and 1.5 GPa are 1225-1250 degrees C and 1275-1300 degrees C, respectively. At 1.0 GPa, the solidus temperature decreases with H2O increasing to 3.5 wt% (1025-1050 degrees C), then remains approximately constant at higher H2O concentrations. Our nominally dry solidus temperatures are up to 140 degrees C higher than in previous studies that did not take measures to limit hydrogen infiltration and hence suffered from H2O formation in the capsule. The near-solidus anhydrous melts have 7-8 wt% SiO(2)and molar Ca/(Ca + Mg) of 0.78-0.82 (X-Ca). Melting temperatures decrease by as much as 200 degrees C with increasing X-H2O in the coexisting COH-fluid. Concomitantly, near-solidus melt compositions change with increasing bulk H2O from siliceous Ca-rich carbonate melts to Mg-rich silico-carbonatites with up to 27.8 wt% SiO2 and 0.55 X-Ca. The continuous compositional array of Ca-Mg-Si carbonatites demonstrates the efficient suppression of liquid immiscibility in the alkali-free system. Diopside crystallization was found to be sensitive to temperature and bulk water contents, limiting metasomatic transformation of carbonated upper mantle to wehrlite at 1.0-1.5 GPa to < 1175 degrees C and < 7 wt% bulk H2O.
机译：通过在1.0和1.5GPa下的温度和本体H 2 O含量的函数，在系统CaO-MgO-SiO 2-CO 2-H 2 O中实验确定由镁方解石+橄榄石+临床+ Clinococococexene的碳酸盐盐组合物。发现熔融反应和熔融组合物对实验期间对H损伤的高度敏感。因此，我们设计了一种新的氢捕集技术，提供了足够的控制来获得一致的结果。 1.0和1.5GPa的标称干燥固体温度分别为1225-1250摄氏度和1275-1300℃。在1.0GPa下，固相温度随H2O增加到3.5wt％（1025-1050℃），然后在较高的H 2 O浓度下保持近似恒定。我们名义上干燥的固体温度高达140℃，高于先前的研究，这些研究没有采取措施限制氢气渗透，因此在胶囊中遭受H2O形成。近固体无水熔体具有7-8wt％SiO（2）和摩尔Ca /（Ca + Mg），0.78-0.82（X-Ca）。熔化温度随着共存COH流体中的X-H 2 O而减小多达200摄氏度。伴随着，近似固溶熔体组合物随着从含有硅的Ca的碳酸盐熔化至Mg富含Mg的二氧化硅 - 碳酸盐，近似固体熔体组合物变化，可达27.8wt％SiO 2和0.55×Ca。 Ca-Mg-Si Carbonatites的连续组成阵列显示出在无碱系统中有效抑制液体不混溶性。发现偶极旁泡结晶对温度和体积水含量敏感，限制碳酸化上垫片的偏畴转化为1.0-1.5GPa至<1175℃和<7wt％的体积H 2 O。

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