Collaborative Project: Seismic Petrology of the Lower Oceanic Crust: An Investigation of Seismic Velocity, Modal Mineralogy and Water Content in Oceanic Diabase and Gabbro

根据这一奖项，PI将测量地震速度、模式矿物学、水含量以及矿物和岩石的弹性性质，以了解是什么控制了海洋下部地壳中地震速度随深度的变化。传统观点认为，大洋下部地壳(地震层3)的观测速度随深度变化，观测到的速度梯度受控于随深度增加的压力和减少的蚀变(绿泥石)，而PI的最新证据表明，这些因素不太可能起主要控制作用。相反，初步数据表明，含水矿物的存在和岩石的总体含水率可能控制着地震速度。对ODP504B、735B、894G和923A孔样品的额外测量将用于验证这一假设，并扩大发现，以回答几个具体问题，即矿物学、裂缝、含水率和含水阶段之间的关系，以及对下部洋壳地震速度和速度梯度的影响。

Under this award, the PIs will measure the seismic velocities, modal mineralogy, water content, and mineral and rock elastic properties in order to understand what controls the seismic velocity variation with depth in the lower ocean crust. Whereas conventional wisdom suggests that the observed velocity changes with depth in lower ocean crust (seismic layer 3) and the observed velocity gradients are controlled by increasing pressure and decreasing alteration (chlorite) with depth, recent evidence by the PIs indicates these factors are unlikely to exert major control. Instead, preliminary data suggest that the presence of hydrous minerals and the overall water content of the rocks may control the seismic velocities. The additional measurements for samples from ODP holes 504B, 735B, 894G, and 923A will be used to test this hypothesis and extend the findings to answer several specific questions about the relationships between mineralogy, cracks, water content, and hydrous phases, on the seismic velocities and velocity gradients in the lower ocean crust.