青藏高原东北缘碧口地块逆冲推覆构造结构与运动学研究

发布时间：2018-02-12 13:06

本文关键词： 碧口地块逆冲推覆构造变形期次边界断裂　出处：《中国地质大学(北京)》2015年硕士论文　论文类型：学位论文

【摘要】：碧口地块位于青藏高原东北缘、龙门山逆冲构造带北段,西秦岭造山带、松潘-甘孜造山带和扬子板块汇聚部位。碧口地块呈楔形形态,轴向NEE向,北侧以近E-W向勉略缝合带为界与西秦岭造山带相隔,西侧以近S-N向虎牙断层为界与松潘-甘孜造山带相邻,南侧以近NEE向青川-平武断层为界与龙门山构造带相隔,东侧在青川-平武断层与勉略缝合带渐变交汇处呈楔形构造尖灭。前人曾长期将碧口地块作为龙门山逆冲构造带北段,认为其形成与新生代晚期龙门山向SE逆冲有关,但近期有关岩石学和区域构造的研究表明,其形成可能与晚三叠世南秦岭前陆逆冲作用和挤出构造有关。造成上述认识分歧的根本原因在于缺少对碧口地块及其边界断裂的构造样式和运动学的系统性解析。本文在前人研究的基础上,对碧口地块逆冲推覆构造结构与运动学进行研究,并且厘定了三期构造变形。D1期是向S的逆冲推覆,以发育间隔劈理(S1),线理构造(L1),中等紧闭褶皱(f1)和活动断层(F1)为特征,大多被后期构造叠加;D1期变形发生在中-晚三叠世,与印支期华北和华南板块的碰撞有关。D2期是向SSE的正向剪切,以发育有区域性透入性劈理(S2),矿物线理(L2),平卧褶皱(f2),以及拆离断层(F2),不同尺度的韧性变形为特征,透入性面理S2∥S0,指示了顺层剪切作用;D2期伸展作用发生在早-中侏罗世,与印支造山后期区域上的伸展作用有关。D3期变形是向SE的逆冲和走滑作用,以发育有间隔劈理(S3),线理构造(L3),褶皱(f3)和逆冲断层(F3)为特征。D3期变形存在三个不同的阶段:第一阶段是沿青川-平武断层向SE的活化逆冲推覆作用,发生在晚侏罗世-早白垩世;第二阶段逆冲推覆作用减弱,沿青川-平武断层发生左行走滑作用,碧口地块沿虎牙断层向西逆冲推覆,发生在晚白垩世-渐新世;第三阶段走滑方向反转为右行走滑,主要体现在青川-平武断层对现今水系和地貌的改造,此阶段自中新世开始并持续至今;D3期变形与青藏高原隆升有关。青川-平武断层与虎牙断层在不同变形期有不同的构造属性,D1期青川-平武断层作为主逆冲断层,沿其发生逆冲推覆作用,虎牙断层还未形成,或仅发育张性破裂面;D3期时青川-平武断层早期具有逆冲断层性质,后期表现为走滑断层性质,虎牙断层早期具有走滑断层性质,晚期具有逆冲断层性质。
[Abstract]:The Bikou block is located in the northeast margin of the Qinghai-Xizang Plateau, the northern section of the Longmenshan thrust tectonic belt, the West Qinling orogenic belt, the Songpan-Ganzi orogenic belt and the converging site of the Yangtze plate. The northern side is separated from the west Qinling orogenic belt by the near E-W direction Mianluo suture belt, the west side by the near S-N direction Tiger tooth fault as the boundary and the Songpan-Ganzi orogenic belt as the boundary, the south side by the near NEE direction Qingchuan-Pingwu fault boundary and the Longmenshan tectonic belt, the south side is separated from the Longmenshan tectonic belt by the near NEE direction Qingchuan-Pingwu fault boundary. The east side of Qingchuan-Pingwu fault and Mianliao suture zone is wedge-shaped structural pinnacle. The Pikou block was regarded as the northern segment of Longmenshan thrust belt for a long time, and its formation is related to the SE thrust in the late Cenozoic Longmen Mountain. But recent studies on petrology and regional tectonics suggest that. Its formation may be related to the late Triassic Foreland thrust and extrusion tectonics in the South Qinling Mountains. The fundamental reason for the above differences lies in the lack of systematic analysis of the tectonic style and kinematics of the Bikou Block and its boundary faults. On the basis of previous studies, The tectonic structure and kinematics of thrust nappe in Bikou block have been studied, and it has been determined that the three tectonic deformations. D1 are thrusting nappe to S, characterized by the development of interval cleavage (S1), linear tectonics (L1), moderately closed fold (f1) and active fault (F1). Most of the deformation occurred in the Middle-Late Triassic by the late tectonic superimposition of D 1, which is related to the collision of the North and South China plates in the Indosinian period. The D 2 period is a positive shear to SSE. It is characterized by the development of regional permeable cleavage (S _ 2), mineral cleavage (L _ 2), horizontal fold (F _ 2), and ductile deformation at different scales (S _ 2 / S _ 0), indicating that the extension of the D _ 2 stage occurred in the early and middle Jurassic. The deformation of phase D3 is related to the extension in the late Indosinian orogenic region, and the thrust and strike-slip to SE are involved in the deformation. There are three different stages in the deformation of stage D _ 3, characterized by the development of spaced cleavage S3, linear tectonics, L3, fold f3) and thrust fault F3. The first stage is the active thrust nappe along the direction of Qingchuan-Pingwu fault, the first stage is the active thrust nappe along the Qingchuan-Pingwu fault. It occurred in late Jurassic-early Cretaceous, the second stage of thrusting nappe weakened, along Qingchuan-Pingwu fault occurred left strike-slip, the Bikou block thrust west along the Tianyao fault, occurred in the late Cretaceous to Oligocene; In the third stage, the direction of strike-slip is reversed to right-strike-slip, which is mainly reflected in the transformation of the present drainage system and geomorphology by the Qingchuan-Pingwu fault. The deformation of Qingchuan Pingwu fault and Huya fault have different tectonic attributes in different deformation periods. Qingchuan Pingwu fault in D1 period is the main thrust fault, and Qingchuan-Pingwu fault is related to the uplift of the Qingchuan plateau since the Miocene epoch, which is related to the uplift of Qinghai-Xizang Plateau. Along the thrusting nappe, the Tiger tooth fault has not been formed, or the Qingchuan-Pingwu fault has the character of thrust fault in the early stage of tensional fracture plane D 3, and the strike-slip fault in the later period, and the strike-slip fault in the early stage of the Tiger tooth fault, and the fault has the character of strike-slip fault in the early stage of the Tiangyao fault. The late stage has the property of thrust fault.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P542

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