海山的倾斜俯冲对上覆板块变形的影响  

Influence of oblique seamount subduction on the deformation of upper plate

作　　者：李付成[1,2] 孙珍[1] 张云帆[1] 徐子英[3] 谢辉[1,2] 

机构地区：[1]中国科学院边缘海地质重点实验室,中国科学院南海海洋研究所,广州510301 [2]中国科学院研究生院,北京100039 [3]广州海洋地质调查局,广州510760

出　　处：《地球物理学进展》2012年第4期1406-1415,共10页Progress in Geophysics

基　　金：国家重点基础研究发展计划(973计划)项目(2007CB41170405);国家基金项目(41076027)联合资助

摘　　要：伴随洋壳的俯冲,驼伏其上的海山会导致上覆板块的强烈变形.为解释该构造变形特征,本文运用物理模拟实验的方法,着重分析海山的斜向俯冲对上覆板块变形的影响,并将模拟结果与正向俯冲过程进行对比.实验结果显示:海山开始进入俯冲,前缘楔体的增生会被阻止,同时楔体被抬升并出现脱顶构造,未被海山破坏的楔体会出现后冲断层的激活,后冲断层轴平行于海山的俯冲方向.海山进一步俯冲,突起顶部发育一系列张扭性质的微断裂和走滑性质的共轭断裂,尾随突起之后的楔体由于重力会产生正断层系统.比起正向俯冲,斜向俯冲过程中所产生的后逆冲体、海山两侧的叠瓦状逆冲推覆构造都出现不对称分布,断裂和微断裂束的走向不规则散开,后冲断层的轴向及海山俯冲过后在楔体上产生的凹槽的轨迹都不断斜向迁移,且凹槽两侧的地势不一致等.最后利用文中的物理模拟结果,很好的解释了马尼拉海沟中段俯冲构造的构造特征,同时对其他俯冲大陆边缘的构造解释具有指导意义.With the subduction of the oceanic crust, the seamounts on the oceanic crust result in a vigorous deformation of the upper plate. To explain the tectonic characteristics, the paper have performed the physical modeling experiments to discuss the influence of oblique seamount subduction on the deformation of upper plate and compare the differences between oblique seamount suhduction experimental results and the process of orthogonal seamount subduction. This paper also focuses on the surface deformation directly comparable with seafloor morphology. The experimental results showed that the front of the margin is uplifted and form d6collement, the frontal part of the accretionary wedge stops accreting,meanwhile,some back thrusts reactivation can be observed in the undeformed wedge and the axial direction of these faults parallel to the direction of seamount suhduction in the initial stage. When the seamount is further subducted, ＂slip-line＇ fracture networks grow above the top of the subducting seamount and the characteristic of the networks is transtension. As the experiments continue, the networks will evolve into fractures which have strike-slip characters. The wedge in the wake of subducted seamount produces a series of normal faults due to the gravity; these faults are superimposed on the fracture networks. Comparing with the experimental results of orthogonal subduction,the back thrusts in the oblique subduction don^t symmetrically distributed with seamount as well as the imbricate thrust structures, the differences also include the strike of fractures and networks diverge irregularly; the axis direction of back thrusts that develop in front of the subducted seamount move obliquely; the trough, observed behind the crest of the subducted seamount, is elongated obliquely in the direction of the convergence; the relative relief on either side of the trough is differently and so on. The experimental results can explain the indentation tectonics in accretionary wedge of middle Manila Trench well; also they can g

关 键 词：海山斜向俯冲 物理模拟 不对称构造 板块变形 马尼拉海沟 

分 类 号：P738[天文地球—海洋地质]