| 龙门山构造带北段构造变形特征——来自汶川科钻四号孔(WFSD-4)的证据 |
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| 关键词:Longmen Shan Wenchuan earthquake fault scientific drilling (WFSD) features of drilling cores tectonic deformation history foliation |
| 基金项目:国家自然科学基金项目(编号: 41602226; 41330211; 41620104006);中国地质调查局地质调查项目(编号: DD20160279; DD20190644) |
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| Characteristics of Tectonic Deformation in North Longmen Shan Tectonic Belt: Evidence from No. 4 Borehole of the Wenchuan Earthquake Fault Scientific Drilling (WFSD-4) |
| In 2008, the Wenchuan earthquake (MW7.9) struck the Longmen Shan tectonic belt, eastern Tibetan Plateau without warning, which produced surface ruptures 80 km and 275 km long co-seismic with different kinematics features along the Guanxian–Anxian and Yingxiu-Beichuan faults, respectively. The characteristics of Wenchuan earthquake are very rare in the earthquake history all over the world, which indicated that the Longmen Shan tectonic belt has experienced extremely complex tectonic evolution and deformation. As a rapid response to the large earthquake, the Wenchuan earthquake fault scientific drilling project provides new view for studying the essence of the movement and deformation of the Longmen Shan tectonic belt in the past. Bbased on the Wenchuan earthquake Fault Scientific Drilling project, the authors took the cores of the WFSD-4 as the principle study object and, in combination with the research on surface structural deformation, discussed the deformation features of the cores and tectonic deformation history of North Longmen Shan tectonic belt: The first tectonic deformation was characterized by foliation S1, which was developed along the composition layer, and was most injected by felsic veins later, indicating ductile deformation under extensional deformation mechanism, with the period probably in the formative period of Jiaoziding Complex; The second period of tectonic deformation was the time of foliation S2 formation, as shown by the obseration of sericite and other flaky minerals on the foliation S2. The boudinage indicates the ductile NW–SE compression. The phenomenon that S1 is incised by S2 can be seen both in the cores and on the surface; The third tectonic deformation was characterized by compressive thrusting, with local spaced cleavage S3 developed in cores. Cleavage S2 deformed and formed parallel fold whose axial plane trended NW; in addition NW dipping active faults were developed in this region and some became the seismic faults of Wenchuan earthquake. All these phenomena indicate that this activity occurred in the Himalayan period in north Longmen Shan tectonic belt, and also in the ultimate formation period of Tangwangzhai fold. The fourth tectonic deformation was characterized by partial cleavage S2 kinking both in cores and on the surface, and this kind of deformation was brittle. |
| ZHANG Jia-jia,LI Hai-bing,ZHENG Yong,WANG Huan,LI Cheng-long,ZHANG Zhao-rong.2019.Characteristics of Tectonic Deformation in North Longmen Shan Tectonic Belt: Evidence from No. 4 Borehole of the Wenchuan Earthquake Fault Scientific Drilling (WFSD-4)[J].Acta Geoscientica Sinica,40(1):93-105. |
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