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

根据该合同，pi将测量地震速度、模态矿物学、含水量、矿物和岩石弹性特性，以了解是什么控制了海底地壳的地震速度随深度的变化。传统观点认为，在海洋地壳下部（地震层3）观测到的速度随深度变化，观测到的速度梯度受压力增加和蚀变（绿泥石）随深度减少的控制，但pi最近的证据表明，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量可能会控制地震速度。对ODP孔504B、735B、894G和923A样品的额外测量将用于验证这一假设，并扩展这一发现，以回答有关矿物学、裂缝、含水量和含水相之间关系的几个具体问题，以及下海洋地壳的地震速度和速度梯度。

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.