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- 2017
马里亚纳海沟Challenger Deep的岩石圈流变结构与动力学分析
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Abstract:
摘要 马里亚纳海沟是西太平洋板块边缘沟-弧-盆体系构造演化的关键地区，其南端的Challenger Deep不仅是地球表面最深点，也是马里亚纳海沟、马里亚纳岛弧、马里亚纳海槽、西马里亚纳洋脊和帕里西维拉海盆的构造汇聚点。开展岩石流变结构与动力学过程研究对于认识Challenger Deep的形成演化具有重要的科学意义。利用综合地球物理资料，通过对重、磁数据的计算分析，研究马里亚纳沟-弧-槽-盆系统的等效黏滞系数和岩石圈强度等流变学特征。利用地震资料，勾绘海沟之下贝尼奥夫带随深度变化的特征以及陡变形态。计算结果表明：对应马里亚纳海沟-岛弧-海槽系统，自由空气重力异常向东凸出，形成弧型异常区；区内异常表现为串珠状线性特征，异常值中间高，两侧低。不同深度岩石圈累积强度比值表明，海沟南北两侧地壳上硬下软，海沟中部地壳上软下硬。在给定应变速率条件下计算的等效黏滞系数东高西低，说明西侧构造体地壳比东侧构造体地壳更容易变形。Challenger Deep岩石圈强度较大，等效黏滞系数较高，具有上硬下软的流变学特征，为板块俯冲在该区的弯曲、撕裂与快速翻转提供了重要条件。地震与重力剖面分析表明，Challenger Deep处的岩石圈累积应力强度和有效粘滞系数条件，可以使马里亚纳海沟俯冲带在重力作用下弯曲、开裂，或部分向南翻转、变陡。
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