Simultaneous Measurements of Elastic Wave Velocity and Porosity of Epidosites Collected From the Oman Ophiolite: Implication for Low Vp/Vs Anomaly in the Oceanic Crust
Simultaneous Measurements of Elastic Wave Velocity and Porosity of Epidosites Collected From the Oman Ophiolite: Implication for Low Vp/Vs Anomaly in the Oceanic Crust
复制标题
同时测量从阿曼蛇绿岩采集的绿帘岩的弹性波速度和孔隙度：对大洋地壳中低 Vp/Vs 异常的影响
DOI：
10.1029/2022gl098234
复制
发表时间：
2022
影响因子：
5.2
通讯作者：
Katayama Ikuo
中科院分区：
文献类型：
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作者：
Nagase Kumpei;Hatakeyama Kohei;Okazaki Keishi;Akamatsu Yuya;Abe Natsue;Michibayashi Katsuyoshi;Katayama Ikuo
海洋地壳的地球物理调查表明，地震2层普遍存在热液循环，由于裂缝的存在，导致地震速度低，VP/ vs高。然而，在2/3层过渡处观察到的异常低的VP/ vv不能用裂纹模型来解释，因为有效介质理论预测由于裂纹的发展，VP/ vv会增加。在本研究中，我们首次提出了海洋地壳中低VP/ vv是由热液系统中流体向上流动引起的绿石化引起的证据。阿曼钻探项目收集的绿帘石的弹性波速和孔隙度的同时测量表明，石英沉淀和球形孔隙导致了低VP/VS，而辉绿岩则含有薄裂缝。CT成像支持了附着石中球形孔隙的存在，并且与有效介质模型的预测相一致。
Geophysical surveys of the oceanic crust indicate that hydrothermal circulation universally occurs in seismic layer 2, which results in a low seismic velocity and high VP/VSdue to the occurrence of cracks. However, the anomalously low VP/VSobserved at the layer 2/3 transition cannot be explained by the crack model, because the effective medium theory predicts an increase in VP/VSdue to crack development. In this study, we present the first evidence that shows the low VP/VSin the oceanic crust is caused by epidotization due to upward fluid flow in hydrothermal systems. Simultaneous measurements of elastic wave velocity and porosity of epidosites collected by the Oman Drilling Project show that quartz precipitation and spheroidal pores results in low VP/VS, in contrast to diabases that contain thin cracks. The presence of spheroidal pores in epidosites is supported by CT imaging, and is consistent with predictions from the effective medium model.