Assembling North China Craton within the Columbia supercontinent: The role of double-sided subduction
Assembling North China Craton within the Columbia supercontinent: The role of double-sided subduction
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DOI：
10.1016/j.precamres.2010.02.003
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发表时间：
2010-04
影响因子：
3.8
通讯作者：
M. Santosh
中科院分区：
文献类型：
--
作者：
M. Santosh
通过对华北地区不同剖面沿着横波接收函数、横波速度和两种不同的纵波层析成像结果的分析，为研究古元古代哥伦比亚超大陆内部不同地壳块体的俯冲-碰撞历史及其最终融合提供了一些线索。克拉通南北向地震剖面的解释表明，厚板状碎屑沉降到地幔的不同深度。西-东向地震走廊显示了鄂尔多斯地块之下厚（> 200 km）的岩石圈根（构造圈）的保存及其向燕辽地块（东部地块）的变化和广泛的侵蚀。该带的特征是具有明显的速度对比的层，并建议重复叠加的底侵和增生的古元古代海洋岩石圈的残余物。现今该区域下方的岩石圈-软流圈边界可能标志着“侵蚀面”，沿该侵蚀面沿着，通过从东部的俯冲-侵蚀以及从下方上涌的软流圈的热侵蚀和物质侵蚀，发生了去角质化作用，导致构造圈的部分破坏和向东变薄。燕辽地块下方的软流圈内，以较年轻、较薄的板片为主，没有任何明显的厚高速层。这些较年轻的板片定义了一个向西的极性，并构成了一个巨型双相体，该双相体是通过中生代俯冲过程，特别是太平洋板块从东部俯冲而形成的底侵作用形成的。内蒙古缝合带内的岩性组合将阴山地块划分为北部和南部鄂尔多斯地块，对应于一个增生的洋板块地层序列，英云闪长岩-奥长花岗岩-花岗闪长岩（TTG）片麻岩、紫苏花岗岩和钙碱性花岗岩代表了一个由北部俯冲形成的大陆弧。地震剖面显示了两个板块俯冲机制的对比性，阴山地块的俯冲方向是由东向南倾斜，燕辽地块的俯冲方向是向西倾斜。在这里，我提出了一个双面俯冲历史的NCC，类似于正在进行的俯冲过程在西太平洋。这种双面俯冲作用被认为促进了超大陆内部大陆碎片的快速融合，因此，NCC的俯冲极性和地幔动力学被认为是评估古元古代超大陆哥伦比亚最终组装的关键。
An evaluation of recent S-wave receiver functions, S-wave velocities and two versions of P-wave tomographic images along various transects in the North China Craton provides some clues on the subduction-collision history of the different crustal blocks and their final amalgamation within the Paleoproterozoic Columbia supercontinent. Interpretation of a N–S seismic section of the craton suggests thick slab debris sinking to various depths in the mantle. The W–E seismic corridors show the preservation of a thick (>200km) lithospheric root (tectosphere) beneath the Ordos Block and its variable and extensive erosion towards the Yanliao Block (Eastern Block). This zone is characterized by layers with marked velocity contrast and suggests repeated stacking of the remnants of underplated and accreted Paleoproterozoic oceanic lithosphere. The present day lithosphere-asthenosphere boundary beneath this region probably marks the ‘erosional plane’ along which decratonization occurred through subduction-erosion from the east and thermal and material erosion by upwelling asthenosphere from below resulting in the partial destruction of the tectosphere and its thinning towards the east. Within the asthenosphere below the Yanliao Block, younger and thinner slabs predominate, in the absence of any prominent thick high velocity layers. These younger slabs define a westward polarity and constitute a mega-scale duplex formed by underplating through Phanerozoic subduction process, particularly the Pacific plate subduction from the east. The lithologic associations within the Inner Mongolia Suture Zone dividing the Yinshan Block to the north and Ordos Block to the south correspond to an accreted ocean plate stratigraphic sequence, with the tonalite-trondhjemite-granodiorite (TTG) gneisses, charnockites and calc-alkaline granites representing a continental arc built up through subduction from the north. The seismic transects bring out a contrasting polarity in the subduction regime with an oblique east- to southward subduction of the Yinshan Block and a westward subduction of the Yanliao Block. Here I propose a double-sided subduction history for the NCC, similar to the ongoing subduction process in the Western Pacific. Such double-sided subduction is considered to promote rapid amalgamation of continental fragments within supercontinents and the subduction polarities and mantle dynamics of NCC are therefore considered to be critical in evaluating the final assembly of the Paleoproterozoic supercontinent Columbia.