Collaborative Research: Dehydration Embrittlement of Serpentine at High Pressures: Implications for Intermediate and Deep Earthquakes

9726885 Reinen 30年来，人们已经知道，在低压脱水过程中，含水相受到应力会产生机械不稳定性，从而导致断层。这一现象被认为是解释地球30至300公里深处地震的主要候选现象，也是所有地震存在深度的可能机制。对这一现象的公认解释基于这样的假设，即在这种脱水反应中产生的流体体积大于脱水阶段的体积。现在我们知道，在非常高的压力下，这种反应产生的总体积实际上比母相的要小，这就提出了一个问题，即这种现象是否可以作为深层地震的一种机制而起作用。本项目将利用独特的高压仪器对反长岩蛇纹石在大于2.2 GPa的压力条件下进行变形实验，即产物组合的总体积小于脱水相的物理条件下，以测试在此条件下是否存在机械不稳定性。假设在这些条件下，主要破坏单元将从流体产生的拉伸微裂纹的形成转变为流体产生的压缩微裂纹的形成，并且不稳定性将保持。＊＊＊

9726885 Reinen It has been known for 30 years that hydrous phases subjected to stress during dehydration at low pressures can develop a mechanical instability leading to faulting. This phenomenon is considered to be the leading candidate to explain earthquakes at depths between 30 and 300km in Earth and a possible mechanism at all depths at which earthquakes exist. The accepted explanation of this phenomenon rests on the assumption that the volume of fluid produced in such dehydration reactions is greater than the volume of the dehydrating phase. It is now known that at very high pressure, the total volume produced by such reactions is actually smaller than that of the parent phase, raising the question as to whether this phenomenon can operate as an earthquake mechanism at depth. This project will utilize unique high pressure instrumentation to conduct deformation experiments on antigorite serpentine under pressures greater than 2.2 GPa, physical conditions such that the total volume of the product assemblage is smaller than that of the dehydrating phase, in order to test whether a mechanical instability can exist under these conditions. It is hypothesized that under these conditions, the primary failure unit will switch from formation of fluid-generated tensile microcracks to formation of fluid- generated compressive microanticracks and that the instability will be preserved. ***