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| 青藏高原北缘阿尔金东段中生代南北向伸展作用 | |
| 引用本文： | 陈宣华,An Yin,George E. Gehrels,Eric S. Cowgill,Marty Grove,T. Mark Harrison,王小凤,杨农,刘健.青藏高原北缘阿尔金东段中生代南北向伸展作用[J].地质力学学报,2004,10(3):193-212. |
| 作者姓名： | 陈宣华 An Yin George E. Gehrels Eric S. Cowgill Marty Grove T. Mark Harrison 王小凤 杨农 刘健 |
| 作者单位： | 1. 中国地质科学院地质力学研究所,北京,100081 2. Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics,University of California,Los Angeles,CA,90095-1567 3. Department of Geosciences,University of Arizona,Tucson,AZ,85721 |
| 基金项目： | 国家自然科学基金(编号:40342015)，美国国家科学基金委员会大陆动力学计划资助项目。 |
| 摘 要： | 青藏高原北缘的阿尔金山脉东段发育了延伸大于300km、东西走向的拉配泉断裂,为南倾的正断层,局部倾角可以低至30°以下。断层中段表现为30～50m厚的韧性剪切带,发育有较好的糜棱岩组构和矿物伸展线理;东段和西段以碎裂变形为特征。断裂带内运动学标志,如不对称香肠构造、不对称褶皱和次级脆性和韧性断裂,都指示了上盘向南的正滑移剪切方式。两方面证据控制了拉配泉断裂的活动时代。首先,拉配泉断裂上盘局部产出早 中侏罗世沉积地层。侏罗系地层中的砾石,特别是其中的含叠层石硅质灰岩和紫色石英岩,可以与断裂下盘的岩石相对比。早 中侏罗世地层可能为拉配泉断裂之上的伸展盆地沉积。其次,拉配泉断裂下盘岩石的40Ar 39Ar热年代学分析给出2个明显的冷却事件。较老的事件出现在约220～187Ma之间的三叠纪末期至侏罗纪早期,而年轻的事件出现在早白垩世的晚期(约100Ma)。约220～187Ma之间的冷却年龄在拉配泉断裂下盘岩石中普遍存在,代表了拉配泉断裂正断作用的主要阶段。约100Ma时,断裂东段的正断作用再次活动,该事件可能被南倾的恰什坎正断层运动所叠加而增强,并与拉配泉断裂的东段合并。这2条断裂具有共同的上盘向南的正滑移运动方式。青藏高原和东亚其它地区的中生代伸展作用可以归结为特提斯洋向北和太平 |
| 关 键 词： | 青藏高原 阿尔金山 伸展构造 |
| 文章编号： | 1006-6616(2004)03-0193-20 |
| 收稿时间： | 2004/6/18 0:00:00 |
| 修稿时间： | 2004年6月18日 |
MESOZOIC N-S EXTENSION IN THE EASTERN ALTYN TAGH RANGE ON THE NORTHERN MARGIN OF THE QINGHAI-TIBET PLATEAU |
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| CHEN Xuan-hu,AN Yin,George E. GEHRELS,Eric S. COWGILL,Marty GROVE,T. Mark HARRISON,WANG Xiao-Feng,YANG Nong and LIU Jian.MESOZOIC N-S EXTENSION IN THE EASTERN ALTYN TAGH RANGE ON THE NORTHERN MARGIN OF THE QINGHAI-TIBET PLATEAU[J].Journal of Geomechanics,2004,10(3):193-212. | |
| Authors: | CHEN Xuan-hu AN Yin George E GEHRELS Eric S COWGILL Marty GROVE T Mark HARRISON WANG Xiao-Feng YANG Nong and LIU Jian |
| Institution: | CHEN Xuan-hua~1,AN Yin~2,George E.GEHRELS~3,Eric S.COWGILL~2,Marty GROVE~2,T.Mark HARRISON~2,WANG Xiao-Feng~1,YANG Nong~1,LIU Jian~1 |
| Abstract: | Lying in the eastern Altyn Tagh Range along the northern margin of the Qinghai-Tibet Plateau, the >300-km long, E-W-trending Lapeiquan fault is a south-dipping normal fault, with its dip angle as low as <30°.The central segment of the fault is a 30~50 m thick ductile shear zone with a well-developed mylonitic fabric and stretching mineral lineation, whereas the eastern and western segments are characterized by cataclastic deformation.The kinematic indicators such as asymmetric boudinage structure, asymmetric folds and minor brittle and ductile faults within the fault zone all indicate a hanging wall-south normal-slip sense of shear.The age of the Lapeiquan fault is constrained by two lines of evidence.First, a sequence of Early-Middle Jurassic sediments is locally present in the hanging wall of the Lapeiquan fault.The clasts of the Jurassic strata, particularly the stromatolite-bearing, cherty limestone and purple quartzite, can be correlated with those in the footwall of the fault.The Early-Middle Jurassic strata were probably deposited in an extensional basin above the Lapeiquan fault.Second, 40Ar 39Ar thermochronological analyses indicate two prominent cooling events in the Lapeiquan footwall.The older event occurred in the latest Triassic-earliest Jurassic between~220 and 187 Ma, while the younger event occurred in the late Early Cretaceous at~100 Ma.Because the 220~187 Ma cooling ages are prevalent in the Lapeiquan footwall, they represent the main stage of faulting.The authors interpret the younger phase of fault motion at~100 Ma to have been related to fault reactivation.The deformation was aided by motion along the south-dipping Qiashikan normal fault that merges with the eastern Lapeiqaun fault. The Mesozoic extension in the Qinghai-Tibet Plateau and other parts of East Asia may be summarized as back-arc extension resulting from northward subduction of the Tethyan oceanic plate and the westward subduction of the Pacific plate. |
| Keywords: | Qinghai-Tibet Plateau Altyn Tagh extensional tectonics |
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