Crust–mantle boundaries in the Taiwan–Luzon arc-continent collision system determined from local earthquake tomography and 1D models: Implications for the mode of subduction polarity reversal
Crust–mantle boundaries in the Taiwan–Luzon arc-continent collision system determined from local earthquake tomography and 1D models: Implications for the mode of subduction polarity reversal
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DOI：
10.1016/j.tecto.2011.12.029
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发表时间：
2012-11
期刊：
影响因子：
2.9
通讯作者：
K. Ustaszewski;Yih‐Min Wu;J. Suppe;Hsin‐Hua Huang;Chien‐Hsin Chang;S. Carena
中科院分区：
文献类型：
--
作者：
K. Ustaszewski;Yih‐Min Wu;J. Suppe;Hsin‐Hua Huang;Chien‐Hsin Chang;S. Carena
为了更好地了解台湾-吕宋弧-陆碰撞带的俯冲极性反转模式，我们利用局部地震层析成像技术绘制了该带的壳幔边界。通过绘制Vp=7.5kms−1的等值面，我们确定了三个莫霍面不连续面和欧亚下地壳与菲律宾海板块地幔岩石圈并置的板块界面。板块界面在台湾东南部下方向东倾斜，并逐渐向北变陡，直到在23.7°N处垂直。从那里它继续向北在垂直方向，直到限制层析成像模型禁止进一步映射。对于莫霍面，额外的深度限制来自于使用当地地震的P波到达的一维模型。欧亚板块和菲律宾海板块的莫霍面在板块交界面上是不连续的。在台湾南部之下，欧亚莫霍面以50-60°的倾角向东倾斜，遵循板块边界的方向，并与贝尼奥夫带连续。向北，欧亚莫霍面变陡，接近垂直，再次与板块边界一起。菲律宾海板块莫霍面表现出一个类似于向斜的地壳根，解释为岩浆吕宋弧的基础。向北，这个根在琉球海沟下面30到70公里处加深。在台湾最北端，垂直俯冲的欧亚板块的枢纽向西走出冲断带，使东部的变形锋不活跃，让位于北倾的菲律宾海板块。一个30- 35 km深度的近水平莫霍面覆盖在北倾的菲律宾海板块之上，被解释为一个新形成的莫霍面，是俯冲欧亚板块向西回滚和拆沉后形成的。结合起来，这些数据支持一个渐进俯冲极性反转的模型，其中欧亚岩石圈内的撕裂向西南传播，使变形锋失活。
In order to better understand the mode of subduction polarity reversal in the Taiwan–Luzon arc-continent collision zone, we mapped its crust–mantle boundaries using local earthquake tomography. By contouring surfaces of constant Vp=7.5kms−1, we identified three Moho discontinuities and the plate interface that juxtaposes Eurasian lower crust against mantle lithosphere of the Philippine Sea plate. The plate interface dips to the east under southeastern Taiwan and steepens progressively towards north until it becomes vertical at 23.7°N. From there it continues northward in a vertical orientation, until the limit of the tomographic model inhibited further mapping. For the Moho, additional depth constraints were derived from 1D models using P-wave arrivals of local earthquakes. The Mohos of the Eurasian and Philippine Sea plates are disconnected across the plate interface. Beneath southern Taiwan, the Eurasian Moho dips to the east at 50–60°, following the orientation of the plate boundary and continuous with the Benioff zone. Towards north, the Eurasian Moho steepens into subvertical, again together with the plate boundary. The Philippine Sea plate Moho exhibits a synform-like crustal root, interpreted as the base of the magmatic Luzon arc. Towards the north, this root deepens from 30 to 70km underneath the Ryukyu trench. In northernmost Taiwan, the hinge of the vertically subducting Eurasian slab steps westward out of the thrust belt, leaving the deformation front to the east inactive and giving way to the north-dipping Philippine Sea plate. A subhorizontal Moho at 30–35km depth overlies the north-dipping Philippine Sea slab and is interpreted as a newly formed Moho, established after westward rollback and delamination of the subducting Eurasian slab. In combination, these data support a model of progressive subduction polarity reversal, in which a tear within the Eurasian lithosphere propagated southwestward, deactivating the deformation front.