A widely accepted explanation for deep-focus earthquakes is that they are caused by the delayed transformation kinetics of dry olivine, which would seem to require dry subducting slabs. However, many geochemical and geophysical observations and mineral physics data indicate that water is present within both hydrous and nominally anhydrous minerals, implying hydrated subducting slabs. The presence of metastable olivine in wet slabs is therefore paradoxical, and the hydration state of the slabs remains an open question. Here, we report results of water-partitioning experiments between olivine, wadsleyite and a major dense hydrous magnesium silicate in slabs, hydrous phase A, under water-undersaturated conditions. We show that olivine and wadsleyite coexisting with hydrous phase A are kinetically dry and contain less than 1 ppm and approximately 300 ppm water, respectively. Our results suggest that olivine and wadsleyite show dry transformation kinetics even in wet slabs. It is therefore possible that olivine transformation as a cause of deep-focus earthquakes and large slab deformation creating stagnant slabs could occur in the water-undersaturated wet slabs. These processes could be caused jointly by dehydration of hydrous minerals and the subsequent rapid phase transformation when the dehydration starts at lower temperatures than the phase transformation.

对深源地震的一个广泛接受的解释是，它们是由干橄榄石的延迟转变动力学引起的，这似乎需要干俯冲板片。然而，许多地球化学和地球物理观测以及矿物物理数据表明水存在于含水矿物和名义上无水矿物中，这意味着水合俯冲板片。因此，湿板中亚稳态橄榄石的存在是自相矛盾的，板的水合状态仍然是一个悬而未决的问题。在这里，我们报告了在水不饱和条件下，橄榄石、wadsleyite 和主要致密含水硅酸镁在水合相 A 中的水分配实验结果。我们表明，与含水相 A 共存的橄榄石和硅镁石在动力学上是干燥的，并且分别含有小于 1 ppm 和大约 300 ppm 的水。我们的结果表明，即使在湿板中，橄榄石和硅钙石也表现出干转变动力学。因此，橄榄石转变可能是深源地震和大板变形产生停滞板的原因，可能发生在水欠饱和湿板中。这些过程可能是由含水矿物的脱水和随后的快速相变共同引起的，当脱水在比相变低的温度下开始时。因此，橄榄石转变可能是深源地震和大板变形产生停滞板的原因，可能发生在水欠饱和湿板中。这些过程可能是由含水矿物的脱水和随后的快速相变共同引起的，当脱水在比相变低的温度下开始时。因此，橄榄石转变可能是深源地震和大板变形产生停滞板的原因，可能发生在水欠饱和湿板中。这些过程可能是由含水矿物的脱水和随后的快速相变共同引起的，当脱水在比相变低的温度下开始时。