Opal-CT in chert beneath the toe of the tohoku margin and its influence on the seismic aseismic transition in subduction zones
Opal-CT in chert beneath the toe of the tohoku margin and its influence on the seismic aseismic transition in subduction zones
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东北边缘趾部燧石中的蛋白石-CT及其对俯冲带地震地震转变的影响
DOI：
10.1002/2016gl071784
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发表时间：
2017
影响因子：
5.2
通讯作者：
G.
中科院分区：
文献类型：
--
作者：
Kameda;J.;Okamoto;A.;Sato;K.;Fujimoto;K.;Yamaguchi;A.;Kimura;G.
燧石的厚积是古老大洋板块会聚边缘的普遍特征。在这项研究中，我们调查了综合大洋钻探计划第343次考察队在2011年东北冲地震（Mw9.0）发生的日本海沟发现的燧石碎片。该样品提供了一个独特的机会，研究在一个活跃的俯冲边缘的燧石成岩作用及其对巨型逆冲断层运动学的影响。我们的矿物学分析表明，燧石的特征是含水蛋白石-CT，因此可能通过压力溶液蠕变高度变形，并在千帕斯卡量级的驱动应力下容易适应会聚板之间的剪切应变。随着硅质岩成岩作用的进展，任何进一步的变形都需要大于100 MPa的应力，因为陆地上硅质岩中溶质的迁移距离越来越长。因此，燧石成岩作用与该边缘从弱耦合到强耦合的板块界面的机械过渡有关。
Thick accumulation of chert is a ubiquitous feature of old oceanic plates at convergent margins. In this study, we investigate chert fragments recovered by the Integrated Ocean Drilling Program expedition 343 at the Japan Trench where the 2011 Tohoku‐Oki earthquake (Mw9.0) occurred. This sample provides a unique opportunity to investigate in situ chert diagenesis at an active subduction margin and its influence on the kinematics of megathrust faulting. Our mineralogical analyses revealed that the chert is characterized by hydrous opal‐CT and may therefore be highly deformable via pressure solution creep and readily accommodate shear strain between the converging plates at driving stresses of kilopascal order. As chert diagenesis advances, any further deformation requires stresses of >100 MPa, given the increasing transport distances for solutes as represented in cherts on land. The chert diagenesis is thus related to the mechanical transition from a weakly to strongly coupled plate interface at this margin.