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引用本文:陈宣华,邵兆刚,熊小松,高锐,刘雪军,王财富,李冰,王增振,张义平. 祁连造山带断裂构造体系、深部结构与构造演化[J]. 中国地质, 2019, 46(5): 995-1020.
CHEN Xuanhua,SHAO Zhaogang,XIONG Xiaosong,GAO Rui,LIU Xuejun,WANG Caifu,LI Bing,WANG Zengzhen,ZHANG Yiping. Fault system, deep structure and tectonic evolution of the Qilian Orogenic Belt, Northwest China[J]. Geology in China, 2019, 46(5): 995-1020(in Chinese with English abstract).
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祁连造山带断裂构造体系、深部结构与构造演化
陈宣华1, 邵兆刚1, 熊小松1, 高锐2, 刘雪军3, 王财富3, 李冰1, 王增振1, 张义平1
1.中国地质调查局-中国地质科学院地球深部探测中心, 北京 100037;2.中国地质科学院地质研究所, 北京 100037;3.中国石油集团东方地球物理勘探有限责任公司综合物化探处, 河北 涿州 072751
摘要:
祁连造山带处在特提斯构造域的北缘,经历了早古生代原特提斯洋发育以来的构造演化,是青藏高原东北缘高原隆升与扩展的关键构造带。本文依据区域地质调查与构造地质填图,结合前人地球物理场资料,阐述了中国西北和祁连造山带断裂构造体系特征。通过超宽频大地电磁测深(MT)剖面数据采集处理,以及浅、中-深层电性剖面反演与构造解释,分析了祁连造山带全地壳深部结构特征与盆山耦合关系,揭示了原特提斯洋构造域北祁连洋板块向南和向北进行双向俯冲的化石俯冲带深部结构特征;俯冲消减的北祁连洋板块的宽度约在600 km以上。其中,北祁连洋向南在柴达木-祁连地块之下的俯冲作用角度较缓,俯冲带向南延伸的距离较远,其俯冲断离的板片可以达到现今柴达木盆地的北缘;北祁连洋向北的俯冲作用产状较陡,其俯冲断离的板片具有向南陡倾的产状倒转特征,可能与中生代以来、特别是印度-亚洲大陆碰撞的远程效应引起的挤压构造变形有关。大地电磁测深剖面的浅层反演与构造解释,验证了祁连山北缘断裂以北发育的榆木山逆冲推覆构造,榆木山构成飞来峰构造,将早白垩世酒泉盆地的一个分支掩盖在外来的逆冲推覆体之下;飞来峰之下具有油气勘查前景。根据早白垩世晚期普遍发育的伸展作用,限定榆木山逆冲推覆构造发育的时间在早白垩世早期,从而提供了青藏高原北缘早白垩世早期高原隆升与扩展的证据。综合前人资料和本研究成果,建立了祁连造山带自新元古代以来的构造演化概念模型。
关键词:  祁连山  断裂构造体系  超宽频大地电磁测深  深部结构  逆冲推覆构造  构造演化  深部地质调查工程
DOI:10.12029/gc20190504
分类号:
基金项目:中国地质调查局公益性基础地质调查项目“祁连—天山及周缘盆山结合带深部地质调查”(DD20160083)资助。
Fault system, deep structure and tectonic evolution of the Qilian Orogenic Belt, Northwest China
CHEN Xuanhua1, SHAO Zhaogang1, XIONG Xiaosong1, GAO Rui2, LIU Xuejun3, WANG Caifu3, LI Bing1, WANG Zengzhen1, ZHANG Yiping1
1.SinoProbe Center, Chinese Academy of Geological Sciences and China Geological Survey, Beijing 100037, China;2.Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;3.Department of Geophysical and Geochemical Exploration, BGP INC., China National Petroleum Corporation, Zhuozhou 072751, Hebei, China
Abstract:
The Qilian Orogenic Belt (QLOB), located on the northern margin of the Tethyan tectonic domain, suffered from the development and evolution of the Early Paleozoic Proto-Tethyan Ocean (i.e., the North Qilian Ocean, NQO), and was the key orogenic belt for the uplift and expansion of the Tibetan Plateau on its northeastern margin. Based on regional geological survey and structure geological mapping and combined with previous geophysical data and newly completed super-broadband magnetotelluric (MT) sounding, this paper expounds the characteristics of the fault system in Northwest China and the QLOB. Through superbroadband MT data acquisition, processing, and inversion, and structural interpretation of shallow, medium and deep electrical structures along the MT profile across the QLOB, the distribution of Mesozoic and Cenozoic basins related to the fault system, and the deep crustal structure underneath the QLOB are analyzed. The deep electrical structure of the QLOB reveals a fossil bidirectional subduction of the NQO plate in the Proto-Tethyan tectonic domain. According to deep electrical structure, the original width of the subducted North Qilian Ocean plate was over 600 km. The southward subducted NQO plate probably reached the north margin of the Qaidam Block (the present Qaidam Basin) in the south, with a gentle subduction angle underneath the Central and South Qilian Block. Then, the melting-broken plate (or slab) might have migrated downward to the depth. In the north, the subducted NQO plate probably reached the southern margin of the Yin'e Basin of the present position, with a steep subduction angle. The dumpling melting-broken NQO plate was separated from the crustal retention plate in the north, through the northward extrusion of the upper mantle. The authors hold that the folding deformation of the subducted ocean plate was probably caused by the compressional tectonics in the Mesozoic and the Cenozoic, especially during the Late Cimmerian orogeny of Early Cretaceous and the India-Asian continental collision in Neogene. The shallow part of the electrical structure proves that the Yumushan thrustnappe structure was developed northward to the North Qilian Fault, with the Yumushan as a klippe in the north. The concealed Early Cretaceous basin underneath the klippe should be a good area for oil and gas prospecting. According to the normal faulting developed in the Early Cretaceous, the authors constrain the main stage thrusting of the North Qilian Fault in the Early Cretaceous, which might provide the evidence for the uplift and expansion of the northern margin of the Tibetan Plateau in the Early Cretaceous. Based on combined data from previous researches and this study, the authors put forward a conceptual tectonic evolution model for the Qilian Orogenic Belt.
Key words:  Qilian Mountain  fault system  super-broadband MT sounding  deep structure  thrust  tectonic evolution  deep geological survey engineering