Water storage in cratonic mantle
Water storage in cratonic mantle
复制标题
DOI：
10.1111/ter.12599
复制
发表时间：
2022-04
期刊：
影响因子：
2.4
通讯作者：
E. Chin;R. Palin
中科院分区：
文献类型：
--
作者：
E. Chin;R. Palin
了解深层岩石圈的水容量对于验证克拉通生长模型和限制地质时期固体地球挥发循环至关重要。然而，关于水溶性和分配的实验约束往往与天然岩石数据不一致。我们提出了一个在岩石圈地幔压力和温度范围内的软锰矿储水能力的体积成分依赖模型。将模型与已公布的捕虏体名义无水矿物（NAM）含水量进行比较，并利用同一样品中共存的辉石含水量重新计算以反映地幔岩石圈的最后含水量。我们的主要发现是：(1)无论构造背景如何，橄榄石记录了相似的重新计算水含量，表明岩石圈地幔中存在共同的水欠饱和水平；(2)斜辉石和正辉石之间的平衡水分配（Dcpx/opx）随着温度的降低而增加。我们认为这些趋势可以通过克拉通地幔在合并早期的再水化/再受精来解释，随后随着克拉通变厚和稳定，正辉石和石榴石形成的水被冷却诱导析出。
Knowledge of the water capacity of the deep lithosphere is crucial for validating models of craton growth and for constraining solid earth volatile cycles over geologic time. However, experimental constraints on water solubility and partitioning often disagree with natural rock data. We present a bulk compositionally dependent model of water storage capacity in pyrolite over a range of lithospheric mantle pressures and temperatures. Models are compared against published xenolith nominally anhydrous mineral (NAM) water contents, which have been recalculated to reflect the last water content of the mantle lithosphere by using coexisting pyroxene water contents in the same samples. Our main findings are that (1) regardless of tectonic setting, olivine records similar recalculated water contents, suggesting a common level of water undersaturation in the lithospheric mantle, and (2) equilibrium water partitioning between clinopyroxene and orthopyroxene (Dcpx/opx) increases down‐temperature. We propose these trends may be explained by re‐hydration/re‐fertilization of cratonic mantle early during coalescence, followed by cooling‐induced water exsolution from orthopyroxene and garnet formation as cratons thicken and stabilize.