| 龙门山陆内复合造山带的四维结构构造特征 |
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| 引用本文： | 刘树根,李智武,曹俊兴,刘顺,邓宾,王国芝,邓斌.龙门山陆内复合造山带的四维结构构造特征[J].地质科学,2009,44(4):1151-1179. |
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| 作者姓名： | 刘树根 李智武 曹俊兴 刘顺 邓宾 王国芝 邓斌 |
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| 作者单位： | 成都理工大学油气藏地质及开发工程国家重点实验室成都 ,610059 |
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| 基金项目： | 中国石化海相前瞻性课题"扬子西缘龙门一川滇构造系统及成藏效应研究"项目 |
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| 摘 要： | 位于扬子陆块和松潘陆块过渡带上的龙门山造山带，是在印支期中国大陆主体拼合和秦岭造山带形成过程中开始发育、燕山期陆内构造活动中继承发展、喜马拉雅期印-亚碰撞和青藏高原隆升过程中遭受改造并定型的。现今构造面貌是扬子陆块向北漂移过程中产生的北西向推挤力、源自秦岭造山带的南北向推挤力和源自青藏高原的东西向推挤力三者联合作用的结果，因此是一个典型的陆内复合造山带。其陆内复合结构构造特征具有下列特点。 1）倾向上，龙门山造山带由茂县-汶川断裂、北川-映秀断裂、安县-灌县断裂和广元-大邑（隐伏）断裂4条主干断裂分隔显示出明显的分带变形特征，由北西向南东具有层次渐浅、强度递减、卷入层位变新的趋势，总体上呈前展式扩展。 2）走向上，龙门山造山带呈现北、中、南段三分格局，它们在基底性质及展布、地层发育及演化历史、变形特征、沉降与隆升特征、活动构造等多个方面具有差异。 3）垂向上，龙门山造山带发育多层次滑脱构造，最重要的滑脱界面是15～20 km深处的低速层和中下三叠统富膏盐岩层，由此控制了深浅构造不一致的变形幅度和变形样式。 4）时间演化上，龙门山造山带表现出倾向上的前展式扩展和走向上的分段式递进性或序次性演化的趋势：印支期，龙门山中北段活动较强，由北东向南西逐渐扩展，主要为挤压逆冲和左旋走滑作用； 燕山期，构造活动总体上趋于相对平静，具有南北分段、由北东向南西迁移的特征； 喜马拉雅山期，龙门山中南段活动较强，由南西向北东逐渐扩展和递进，主要为挤压逆冲、隆升和右旋走滑作用。
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| 关 键 词： | 四维结构构造 倾向分带性 走向分段性 垂向分层性 演化序次性 造山带 龙门山 |
| 收稿时间： | 2009-06-10 |
| 修稿时间： | 2009-07-02 |
4-D textural and structural characteristics of Longmen intracontinental composite orogenic belt,southwest China |
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| Liu Shugen|Li Zhiwu|Cao Junxing|Liu Shun,Deng Bin|Wang Guozhi|Deng Bin.4-D textural and structural characteristics of Longmen intracontinental composite orogenic belt,southwest China[J].Chinese Journal of Geology,2009,44(4):1151-1179. |
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| Authors: | Liu Shugen|Li Zhiwu|Cao Junxing|Liu Shun Deng Bin|Wang Guozhi|Deng Bin |
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| Institution: | State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation|;
Chengdu University of Technology| Chengdu |610059 |
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| Abstract: | Located in the boundary between Yangtze Block and Songpan Block，the NE trending Longmen orogenic belt initiated in the Indosinian amalgamation between North China Block and South China Block and the formation of Qinling orogenic belt，developed successively during the Yanshanian intracontinental tectonic activity，and was finally formed during the Cenozoic India Asia collision and the uplift of Tibetan Plateau. The present structural and tectonic features of Longmen orogenic belt were resulted in the interactions among the following three processes，ie. the SN directed compression and sinistral shearing from Qinling orogenic belt，the EW directed compression and dextral shearing from Tibet Plateau，and the SE directed compression owing to the northwest drift of Yangtze Block. All the processes are intracontinental，and Longmen orogenic belt is a typical intracontinental composite orogenic belt. The textural and structural characteristics of Longmen intracontinental composite orogenic belt are as follows.(i)In the dip direction，Longmen orogenic belt is composed up of thrust sheets bounded by four major NE strike thrusting faults，ie. Maoxian Wenchuan Fault，Beichuan Yingxiu Fault，Anxian Guanxian Fault and Guangyuan Dayi(blind)Fault. From northwest to southeast across Lomgmen orogenic belt，the deformation changed from ductile to ductile brittle to brittle with the distinct structural dip zonation.(ii)Along the strike of Longmen orogenic belt，there are structural and tectonic segmentations with the difference in basement，stratigraphy，deformation，subsidence，uplift，tectonic evolution and activity.(iii)Vertically，the lithosphere of Longmen orogenic belt and its adjacent area is multi layered，and multi layered detachment structures were developed. The most important decollement layers are the low velocity zone at the depth of 15～20 km in the crust and the middle and lower Triassic anhydrite and gypsum beds in the sedimentary covers，which controlled the inconsistent deformation and showed obvious structural delamination.(iv)Temporally，there is a progressive or sequential evolution tendency from NE to SW during late Triassic to Cretaceous，and from SW to NE during Cenozoic along Longmen orogenic belt. The main tectonics is compressing，thrusting and sinistral shearing during late Triassic，and compressing，uplifting and dextral shearing during Cenozoic in Longmen orogenic belt. The deformation was more intense during Indosinian stage and weaker during Himalayan stage in the northern segment，and weaker during Indosinian stage and more intense during Himalayan stage in the southern segment. During Yanshanian stage，though the tectonic activity became quiet relatively，there was a sharp deformation strength migration from northern segment to southern segment of Longmen orogenic belt.
Therefore，the 4 D textural and structural characteristics of Longmen intracontinental composite orogenic belt are dip structural zonation； strike structural segmentation； vertically structural delamination； and temporally sequential evolution. The formation and evolution of the middle northern segment of Longmen orogenic belt is mainly controlled by Qinling Orogenic belt，and the formation and uplifting of Tibetan Plateau chiefly resulted in the formation and evolution of its middle southern segment. However，the hardness and the western margin shape are the foundation to the formation and evolution of Longmen orogenic belt. |
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| Keywords: | 4 D textural and structural characteristics Dip structural zonation Strike structural segmentation Vertically structural delamination Temporally sequential evolution Orogenic belt Longmen Mountains |
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