Horizontal shortening versus vertical loading in accretionary prisms
Horizontal shortening versus vertical loading in accretionary prisms
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吸积棱柱中的水平缩短与垂直载荷
DOI：
10.1029/2008gc002279
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Kimura
中科院分区：
文献类型：
--
作者：
Raimbourg;H.;Shibata;T.;Yamaguchi;A.;Yamaguchi;H. and G;Kimura
对日本九州四万十带内俯冲浊积岩的两期变形的分析表明，早期的非同轴“褶皱-逆冲”型阶段和晚期的变质同轴垂直缩短阶段之间存在强烈的运动学对比。深部变形的特征是近水平的白云母-白云母变质叶理的发展，与纯剪切变形有关，它覆盖了早期继承的构造。我们将变质变形阶段与增生棱柱体向陆段（内楔）的较低水平相关联，因此，该阶段是通过垂直加载和水平伸展变形的，这与棱柱体向沟段（外楔）形成鲜明对比，后者通常显示褶皱和逆冲构造，表明水平缩短。基于Wang和Hu（2006）的模型，对棱柱体变形运动学的这些纵向变化的一个可能的解释可能在于其基底表面的对比流变学，内部楔形体下方地震部分的应变减弱，而外部楔形体下方地震部分的应变加强。这项研究揭示的垂直缩短活动的内部楔可能代表了一个大的贡献，更深层次的增生棱柱体的折返。
The analysis of two‐phased deformation of subducted turbidites within the Shimanto Belt on Kyushu (Japan) shows strongly contrasted kinematics between an earlier, noncoxial “fold‐and‐thrust”‐type stage and a later, metamorphic, coaxial vertical shortening stage. The deep deformation is characterized by the development of a subhorizontal muscovite‐chlorite metamorphic foliation, associated with pure shear deformation, which overprinted the structures inherited from the earlier stage. We associate the metamorphic deformation stage with the lower levels of accretionary prism landward segment (inner wedge), which was therefore deformed by vertical loading and horizontal extension, much in contrast with prism trenchward segment (outer wedge), which often shows fold‐and‐thrust structures indicative of horizontal shortening. A possible explanation, based on Wang and Hu's (2006) model, for these longitudinal variations in deformation kinematics of the prism may lie in the contrasted rheology of its basal surface, strain weakening in the seismic portion below the inner wedge while strain strengthening in the aseismic portion below the outer wedge. The vertical shortening active within the inner wedge revealed by this study possibly represents a large contribution to the exhumation of the deeper levels of accretionary prisms.