The formation of the Dabashan orocline, central China: Insights from high-resolution 3D crustal shear-wave velocity structure
The formation of the Dabashan orocline, central China: Insights from high-resolution 3D crustal shear-wave velocity structure
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中国中部大巴山斜坡的形成：高分辨率三维地壳剪切波速度结构的见解
DOI：
10.1016/j.tecto.2019.228244
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发表时间：
2020-01
期刊：
影响因子：
2.9
通讯作者：
Huajian Yao
中科院分区：
文献类型：
--
作者：
Song Luo;Rong Huang;Lupei Zhu;Huajian Yao
大巴山造山带是中国中部的一条大型逆冲带。测定其高分辨率的地壳三维剪切波(S波)速度结构，可以加深对南中国板块和北中国板块陆内演化的认识。在这项研究中，我们估计了5-50个S周期的瑞雷波相位和群速度、P波接收函数和P波和SPS走时，并建立了大巴山造山斜及邻区的3DS波速度模型和地壳厚度和Vp/Vs比值图。地壳厚度和Vp/Vs比值图显示了明显的厚壳(50-55公里)和高的Vp/Vs比值(1.8-1.85)，表明大巴山造山斜为镁铁质下地壳。3DS波速度结构显示，大巴山造山斜上地壳存在北东向倾斜的低速异常，汉南-米仓和神农-黄陵穹隆的高速度从近地表向下地壳延伸，反映了两个穹隆的深部。我们认为这两个穹隆作为刚性压痕，与南中国板块一起顺时针旋转，进入秦岭-大别造山带。大巴山造山斜上地壳的弱沉积物受到两个穹隆和秦岭-大别刚性造山带的挤压和阻挡，造成沉积物和地壳的垂直堆积，进而形成北东向倾斜的低速异常和大巴山造斜带下的厚地壳。
The Dabashan orocline is a large thrust belt in central China. Determination of its high-resolution three-dimensional (3D) crustal shear-wave (S-wave) velocity structure can enhance our understanding of the intracontinental evolution of the South China plate and North China plate. In this study, we estimated the Rayleigh wave phase and group velocities at periods of 5–50 s,P-wave receiver functions, andPsandSsPmptravel times from 63 permanent stations and 29 portable stations; we also constructed a 3DS-wave velocity model and crustal thickness andVp/Vsratio maps of the Dabashan orocline and adjacent areas. The crustal thickness andVp/Vsratio maps show prominent thick crust (50–55 km) and highVp/Vsratios (1.8–1.85), suggesting a mafic lower crust in the Dabashan orocline. The 3DS-wave velocity structure shows northeast-dipping low-velocity anomalies in the upper crust of the Dabashan orocline, and high velocities extended from near the surface to the lower crust in the Hannan-Micang and Shennong-Huangling domes, suggesting deep roots of the two domes. We propose that the two domes acted as rigid indenters and rotated clockwise together with the South China plate, penetrating into the Qinling-Dabie orogenic belt. Weak sediments in the upper crust of the Dabashan orocline were compressed and blocked by the two domes and the rigid Qinling-Dabie orogenic belt, resulting in vertical accretion of the sediments and crust and subsequent formation of the northeast-dipping low-velocity anomalies and the thick crust beneath the Dabashan orocline.
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