Nominally Anhydrous Minerals and Earth's Deep Water Cycle
Nominally Anhydrous Minerals and Earth's Deep Water Cycle
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DOI：
10.1029/168gm02
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发表时间：
2013-03
期刊：
影响因子：
--
通讯作者：
J. Smyth;S. Jacobsen
中科院分区：
文献类型：
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作者：
J. Smyth;S. Jacobsen
地球内部的固体硅酸盐矿物中含有羟基的深层水库可能包含了地球上大部分的氢，并在地质时期起到了保持海洋体积和大陆干舷的缓冲作用。在俯冲的海洋地壳物质中，一重量%的h2o的十分之二随后从洋中脊玄武岩释放到水圈，这足以在45亿年的时间里循环一次海洋总量。实际的通量可能是这个量的几倍。过渡带（410-660公里深）名义上的无水矿物可作为大型内部储层。关于摩尔体积和弹性性质的最新数据表明，在各自的不确定性范围内，水合作用对剪切速度的影响比温度的影响更大。根据这些新数据，该地区的地震速度与显著的水化作用相一致（在由辉石岩组成的地幔中，按重量计h2o占0.5%或更多）。数据表明，至少在远离俯冲带的地区，过渡带（TZ）的横向速度变化可能反映的是水化作用的变化，而不是温度的变化。
Deep reservoirs of water incorporated as hydroxyl into solid silicate minerals of the Earth's interior may contain the majority of the planet's hydrogen and have acted as buffers to maintain ocean volume and continental freeboard over geologic time. Two tenths of one weight percent H 2 O in subducted oceanic crustal material and subsequently released to the hydrosphere from mid-ocean ridge basalt is sufficient to recycle the total ocean volume once over 4.5 billion years. It is possible that actual fluxes are several times this amount. The nominally anhydrous minerals of the transition zone (410-660 km depth) may serve as a large internal reservoir. New and recent data on molar volumes and elastic properties indicate that hydration has a larger effect on shear velocities than does temperature within their respective uncertainties. Based on these new data, seismic velocities ill this region are consistent with significant hydration (one-half percent or more H 2 O by weight in a pyrolite-composition mantle). The data indicate that lateral velocity variations in the Transition Zone (TZ) may reflect variations in hydration rather than variations in temperature, at least in regions distant from subduction zones.