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引用本文:张耀阳,方慧,仇根根,艾印双,赵亮. 利用S波接收函数研究下扬子及其邻区的岩石圈结构[J]. 中国地质, 2019, 46(4): 786-794.
ZHANG Yaoyang,FANG Hui,QIU Gengen,AI Yinshuang,ZHAO Liang. The lithospheric structure of the lower Yangtze Craton and its adjacent regions by S receiver function imaging[J]. Geology in China, 2019, 46(4): 786-794(in Chinese with English abstract).
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利用S波接收函数研究下扬子及其邻区的岩石圈结构
张耀阳1,2, 方慧1, 仇根根1, 艾印双2, 赵亮2
1.中国地质科学院地球物理地球化学勘查研究所, 河北 廊坊 065000;2.中国科学院地质与地球物理研究所, 北京 100029
摘要:
下扬子及其邻区位于欧亚板块、太平洋板块和菲律宾海板块的交汇地带,自中生代以来经历了广泛的伸展变形和岩浆活动,其岩石圈结构和性质对深入认识华南块体乃至整个中国东部的显生宙构造演化以及相关动力学过程都具有重要意义。本文使用中国科学院地质与地球物理研究所地震台阵实验室在合肥—金华沿线布设的流动地震台阵数据,通过S波接收函数偏移成像方法对下扬子及其邻区岩石圈的速度间断面结构进行了研究。成像结果显示,主测线下方Moho面深度为32~42 km,岩石圈底界面深度为84~112 km,总体表现为西深东浅,且速度间断面结构与区域构造特征变化趋势相一致。这为下扬子及其邻区岩石圈中生代以来的改造和减薄提供了新的观测证据:华北南部盆地区下方Moho面结构复杂,岩石圈较厚(90~112 km),表明该区域的改造程度相对较低;下扬子克拉通与华夏块体北缘岩石圈结构特征相似,仅在江南造山带附近Moho面和岩石圈底界面有小尺度变化,表明它们自新元古代拼合以来可能作为一个整体被改造。进一步结合同剖面南段大地电磁测深成像结果,文章对研究区的岩石圈改造提出了与华北地区相似的地幔流模型,郯庐断裂带和江南造山带两侧断裂带等薄弱带在太平洋板块俯冲的作用下,可能成为软流圈物质上涌的通道。
关键词:  下扬子及邻区  接收函数  速度间断面  岩石圈改造  深部资源工程
DOI:10.12029/gc20190409
分类号:P622+.2
基金项目:中国地质科学院基本科研项目(AS2017J05),国家自然科学基金项目(41574068)及中国地质调查局项目(121201108000160913、12120114005801、DD20160082、DD20190012)联合资助。
The lithospheric structure of the lower Yangtze Craton and its adjacent regions by S receiver function imaging
ZHANG Yaoyang1,2, FANG Hui1, QIU Gengen1, AI Yinshuang2, ZHAO Liang2
1.Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences, Langfang 065000, Hebei, China;2.Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100061, China
Abstract:
The lower Yangtze Craton, Located at the triple junction area of the Eurasian Plate, Pacific Plate, and Philippine Sea Plate, has undergone intensive extension and magmatic activities ever since the Mesozoic. The lithospheric structure and property of the lower Yangtze Craton and its adjacent regions could throw new insight into the tectonic evolution and dynamic process of the South China Block or even the whole eastern China in the Phanerozoic. In this paper, the authors collected data from the NCISP-Ⅲ arrays deployed by the Institute of Geology and Geophysics, Chinese Academy of Sciences, and used the wave equation-based migration technique of S-receiver function to image the lithospheric structure. The results show that the Moho depth and lithosphere-asthenosphere boundary (LAB) depth along the profile is~32-42 km and~84-112 km, respectively. Both of the discontinuities deepen from east to west, and the variation of them corresponds well to the tectonic features. The results support the argument that the lower Yangtze Craton and its adjacent regions may have undergone extensive lithospheric modification and thinning since the Mesozoic:The Hefei Basin of the southern NCC is characterized by a complicated Moho and thick lithosphere, indicating that the modification in this region is of less extent. The lower Yangtze Craton and the Cathysia Block may have behaved coherently in the Mesozoic modification, because the lithospheric structures of this two blocks are alike, only characterized by subtle undulation of the velocity discontinuities beneath the Jiangnan Orogen. Combined with the magnetotelluric results in the southern part of this profile, the authors propose a similar mantle flow model as in the NCC to explain the modification in the lower Yangtze Craton and its adjacent regions. The lithosphere beneath the Tanlu Fault and the Jiangnan Orogen is mechanically weak, and may act as the upwelling channel of the asthenospheric material under the subduction of the Pacific Plate to facilitate the modification.
Key words:  Lower Yangtze Craton and adjacent regions  receiver function  velocity discontinuities  lithospheric modification  deep resources engineering