Gase Andrew C, Bangs Nathan L, Saffer Demian M, Han Shuoshuo, Miller Peter K, Bell Rebecca E, Arai Ryuta, Henrys Stuart A, Kodaira Shuichi, Davy Richard, Frahm Laura, Barker Daniel H N
Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA.
Department of Earth Science and Engineering, Imperial College London, London, UK.
Sci Adv. 2023 Aug 18;9(33):eadh0150. doi: 10.1126/sciadv.adh0150. Epub 2023 Aug 16.
Recurring slow slip along near-trench megathrust faults occurs at many subduction zones, but for unknown reasons, this process is not universal. Fluid overpressures are implicated in encouraging slow slip; however, links between slow slip, fluid content, and hydrogeology remain poorly known in natural systems. Three-dimensional seismic imaging and ocean drilling at the Hikurangi margin reveal a widespread and previously unknown fluid reservoir within the extensively hydrated (up to 47 vol % HO) volcanic upper crust of the subducting Hikurangi Plateau large igneous province. This ~1.5 km thick volcaniclastic upper crust readily dewaters with subduction but retains half of its fluid content upon reaching regions with well-characterized slow slip. We suggest that volcaniclastic-rich upper crust at volcanic plateaus and seamounts is a major source of water that contributes to the fluid budget in subduction zones and may drive fluid overpressures along the megathrust that give rise to frequent shallow slow slip.
许多俯冲带的近海沟巨型逆冲断层会反复发生缓慢滑动，但不知为何，这一过程并不普遍。流体超压被认为会促使缓慢滑动；然而，在自然系统中，缓慢滑动、流体含量和水文地质之间的联系仍鲜为人知。希库朗伊边缘的三维地震成像和海洋钻探揭示，在俯冲的希库朗伊高原大火成岩省广泛水化（高达47%体积的水）的火山上地壳中，存在一个广泛且此前未知的流体储层。这个约1.5公里厚的火山碎屑上地壳在俯冲过程中很容易脱水，但在到达具有典型缓慢滑动特征的区域时，仍保留了一半的流体含量。我们认为，火山高原和海山上富含火山碎屑的上地壳是水的主要来源，它有助于俯冲带的流体收支平衡，并可能导致沿巨型逆冲断层的流体超压，从而引发频繁的浅层缓慢滑动。
