The habitat of slow slip phenomena in the Hikurangi subduction zone

俯冲带是地球上最具地质动力的系统之一。俯冲带是指大洋板块俯冲到大陆板块之下的区域。在过去的十年里，随着地震学和大地测量仪器的进步，我们对这一领域的断层滑动行为的了解大大增加了。新发现的断层滑动模式可以持续数月，因此被称为慢地震。控制这种滑动行为的地质因素仍然存在争议。375探险计划从2018年3月8日至2018年5月5日，由R/V JOIDES分辨率对新西兰近海Hikurangi俯冲边缘北部浅层慢滑地震的栖息地进行采样和记录，以采集和记录前缘推力、上板块和传入沉积物以及洋壳。前缘逆冲和上板块上的钻探地点以断裂带为目标，预计流体将在这些断裂带迁移到海底，这将为慢滑源区提供一个窗口。这项研究旨在通过成岩作用、粘土脱水过程和流体运移来识别和描述重要的成岩过程及其对俯冲推覆的流体力学状态的影响。这项研究将采用流体和全岩地球化学的协调战略，结合硼和锂同位素分析来识别水-岩相互作用过程，通过热液压实试验确定所识别过程的地球化学指纹的温度依赖性，并将地球化学数据与反应-输运模型相结合，以限制俯冲带弧前的水-岩相互作用和流体迁移的时空发生。

Subduction zones - where an oceanic plate is subducting beneath a continental plate – are among the most geologically dynamic systems on earth. In the last decade our knowledge of fault slip behavior in this realm has tremendously increased in response to advances in seismological and geodetic instruments. The newly discovered fault slip modes can last for months and thus are termed slow earthquakes. The geological factors that control such slip behavior is still subject to debate. Expedition 375 has been scheduled from March 8th, 2018, to May 5th, 2018, for R/V JOIDES Resolution to sample and log the frontal thrust, upper plate and incoming sediment plus oceanic crust in order to characterize the habitat that hosts shallow slow slip earthquakes in the northern Hikurangi subduction margin offshore New Zealand. Drill sites at the frontal thrust and on the upper plate target fault zones where fluid migration to the seafloor is expected, which will provide a window to the slow slip source region. The proposed research aims at the identification and spatio-temporal characterization of important diagenetic processes and their influence on the hydro-mechanical state of the subduction thrust through diagenesis, clay dehydration processes and fluid migration. The research will be implemented by a coordinated strategy of fluid and whole rock geochemistry in combination with boron and lithium isotope analysis to identify water-rock interaction processes, hydrothermal compaction tests to determine the temperature-dependence of the geochemical fingerprints from the identified processes and integration of the geochemical data with reaction-transport models to constrain the spatio-temporal occurrence of water-rock interaction and fluid migration in the subduction zone forearc.