Fingerprinting the water site in mantle olivine
Fingerprinting the water site in mantle olivine
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DOI：
10.1130/g21759.1
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发表时间：
2005-11-01
期刊：
影响因子：
5.8
通讯作者：
Foran, GJ
中科院分区：
文献类型：
--
作者：
Berry, AJ;Hermann, J;Foran, GJ
橄榄石等名义上无水的矿物含有微量的水，可以容纳上地幔的全部水收支。在这里，我们首次报道了在上地幔条件下实验结晶的合成橄榄石，它再现了在尖晶石橄榄岩地幔橄榄石中观察到的最常见和最强烈的红外羟基伸展带(3572和3525厘米(-1))。这些带来自与微量元素钛有关的点缺陷处容纳的水，我们认为这是上地幔浅层最重要的缺陷位置。在较高的压力下可能会出现额外的水合缺陷。我们还发现了与Fe3+有关的与水有关的条带；这些条带不太可能反映与地幔的平衡，并表明在折返或退变过程中水的参与。水必须存在于适合地幔的缺陷位置，在感兴趣的条件下，才能进行相关的划分、地震波速和含水橄榄石的变形实验。
Nominally anhydrous minerals such as olivine contain trace amounts of water and may accommodate the entire water budget of the upper mantle. Here we report for the first time synthetic olivines, crystallized experimentally under upper mantle conditions, that reproduce the most common and intense infrared hydroxyl stretching bands (at 3572 and 3525 cm(-1)) observed in spinel peridotite mantle olivines. These bands arise from water accommodated at point defects associated with the trace element Ti, and we suggest that this is the most important defect site in the shallow upper mantle. Additional hydrated defects may occur at higher pressures. We also identify bands related to water associated with Fe3+; these are unlikely to reflect equilibrium with the mantle, and indicate water incorporation during exhumation or retrogression. Water must be present at the defect site appropriate for the mantle, at the conditions of interest, for partitioning, seismic wave speed, and deformation experiments on hydrous olivine to be relevant.