The dynamics of laterally variable subductions: laboratory models applied to the Hellenides
The dynamics of laterally variable subductions: laboratory models applied to the Hellenides
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DOI：
10.5194/se-4-179-2013
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发表时间：
2013-07
期刊：
影响因子：
3.4
通讯作者：
Benjamin Guillaume;L. Husson;F. Funiciello;C. Faccenna
中科院分区：
文献类型：
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作者：
Benjamin Guillaume;L. Husson;F. Funiciello;C. Faccenna
抽象的。我们设计了三维动力学自洽的实验室俯冲模型，以分析上地幔俯冲动力学与上覆板块变形之间的关系。我们研究了横向可变浮力的岩石圈俯冲对海沟运动学和形状的时间演化、软流圈顶部的水平流动、动态地形和覆盖板块的变形的影响。两个俯冲单元，这对应于一个负浮力的海洋板块和正浮力的大陆板块，并置通过一个沟槽垂直界面（类似于撕裂断层），这是完全耦合或剪切应力自由。两个板块之间的海沟后退速率差异超过6 cm/年，在大洋板片板块上方触发的地幔流比在大陆板片板块上方更强烈。由此产生的不对称的岩石圈下流动剪切撕裂断层前的覆盖板块，变形逐渐从伸展转换为扭张。我们的模型的结果和地质观测之间的一致性表明，晚新生代变形的爱琴海域，包括北爱琴海海槽和中央希腊剪切带的形成，俯冲岩石圈的浮力的空间变化的结果。特别是，俯冲制度的横向变化所造成的上新世早期俯冲的古老的海洋爱奥尼亚板块重新设计地幔流和激励下的覆盖板越来越有力的右旋剪切。该模型表明，这是凯法利尼亚断层的开始，导致之间的过渡延伸为主的构造体制transtension，在北爱琴海，希腊大陆和伯罗奔尼撒半岛。撕裂断层的俯冲也可能有助于北安纳托利亚断层向爱琴海域的传播。
Abstract. We designed three-dimensional dynamically self-consistent laboratory models of subduction to analyse the relationships between overriding plate deformation and subduction dynamics in the upper mantle. We investigated the effects of the subduction of a lithosphere of laterally variable buoyancy on the temporal evolution of trench kinematics and shape, horizontal flow at the top of the asthenosphere, dynamic topography and deformation of the overriding plate. Two subducting units, which correspond to a negatively buoyant oceanic plate and positively buoyant continental one, are juxtaposed via a trench-perpendicular interface (analogue to a tear fault) that is either fully-coupled or shear-stress free. Differential rates of trench retreat, in excess of 6 cm yr−1 between the two units, trigger a more vigorous mantle flow above the oceanic slab unit than above the continental slab unit. The resulting asymmetrical sublithospheric flow shears the overriding plate in front of the tear fault, and deformation gradually switches from extension to transtension through time. The consistency between our models results and geological observations suggests that the Late Cenozoic deformation of the Aegean domain, including the formation of the North Aegean Trough and Central Hellenic Shear zone, results from the spatial variations in the buoyancy of the subducting lithosphere. In particular, the lateral changes of the subduction regime caused by the Early Pliocene subduction of the old oceanic Ionian plate redesigned mantle flow and excited an increasingly vigorous dextral shear underneath the overriding plate. The models suggest that it is the inception of the Kefalonia Fault that caused the transition between an extension dominated tectonic regime to transtension, in the North Aegean, Mainland Greece and Peloponnese. The subduction of the tear fault may also have helped the propagation of the North Anatolian Fault into the Aegean domain.