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首页> 外文期刊>Contributions to Mineralogy and Petrology >H_2O storage Capacity of MgSiO_3 clinoenstatite at 8-13 GPa, l,100-l,400 deg C
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H_2O storage Capacity of MgSiO_3 clinoenstatite at 8-13 GPa, l,100-l,400 deg C

机译：MgSiO_3斜长辉石在8-13 GPa，1,100-1,400摄氏度下的H_2O储存容量

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摘要

We present H_2O analyses of MgSiO_3 pyroxene crystals quenched from hydrous conditions in the presence of olivine or wadsleyite at 8-13.4 GPa and l,100-l,400 deg C. Raman spectroscopy shows that all pyroxenes have low clinoenstatite structure, which we infer to indicate that the crystals were high clinoenstatite (C2/c) during conditions of synthesis. H_2O analyses were performed by secondary ion mass spectrometry and confirmed by unpolarized Fourier transform infrared spectroscopy on randomly oriented crystals. Measured H_2O concentrations increase with pressure and range from 0.08 wt. percent H_2O at 8 GPa and 1,300 deg C up to 0.67 wt. percent at 13.4 GPa and l,300 deg C. At fixed pressure, H_2O storage capacity diminishes with increasing temperature and the magnitude of this effect increases with pressure. This trend, which we attribute to diminishing activity of H_2O in coexisting fluids as the proportion of dissolved silicate increases, is opposite to that observed previously at low pressure. We observe clinoenstatite 1.4 GPa below the pressure stability of clinoenstatite under nominally dry conditions. This stabilization of clinoenstatite relative to orthoenstatite under hydrous conditions is likely owing to preferential substitution of H_2O into the high clinoenstatite polymorph. At 8-11 GPa and 1,200-1,400 deg C, observed H_2O partitioning between olivine and clinoenstatite gives values of D~(ol/CEn) between 0.65 and 0.87. At 13 GPa and l,300 deg C, partitioning between wadsleyite and clinoenstatite, D~(wd/CEn), gives a value of 2.8 + - 0.4.
机译：我们介绍了在8-13.4 GPa和1,100-1,400摄氏度下在橄榄石或沃兹利特石存在下从含水条件淬灭的MgSiO_3辉石晶体的H_2O分析。拉曼光谱表明，所有辉石都具有低斜云母辉石结构，我们推断表明在合成条件下晶体为高斜发钙辉石（C2 / c）。 H_2O分析是通过二次离子质谱进行的，并通过无极化傅里叶变换红外光谱对随机取向的晶体进行了确认。测得的H_2O浓度随压力而增加，范围为0.08 wt。％。在8 GPa和1,300℃时高达0.67 wt。％的H_2O百分比。在13.4 GPa和1300℃时，H_2O的百分含量降低。在固定压力下，H_2O的存储容量随温度的升高而减小，并且这种影响的程度随压力的升高而增加。这种趋势归因于随着溶解硅酸盐比例的增加，共存流体中H_2O的活性降低，这一趋势与以前在低压下观察到的趋势相反。在标称干燥条件下，我们观察到斜发钙辉石的压力稳定性低于其1.4 GPa。在含水条件下，斜长辉石相对于正长辉石的这种稳定可能是由于优先将H_2O置换为高斜长辉石多晶型物。在8-11 GPa和1,200-1,400摄氏度下，观察到的H_2O在橄榄石和斜辉石之间的分配使D〜（ol / CEn）的值介于0.65和0.87之间。在13 GPa和1300摄氏度下，沃兹利石和斜发钙石之间的分配D〜（wd / CEn）值为2.8 +-0.4。

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