| Precise Timing of Caledonian Structural Deformation Chronology and Its Implications in Southeast Qilian Mountains, China |
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| 作者姓名： | 樊光明 雷东宁 |
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| 作者单位： | Faculty of Earth Sciences China University of Geosciences，Faculty of Earth Sciences China University of Geosciences，Wuhan 430074 China，Wuhan 430074 China |
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| 基金项目： | This paper is financially supported by the projects of 1：250 000 Scale Regional Geological Survey of Linxia, and Dingxi （No. 200413000007） from Ministry of Land and Resources of China. |
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| 摘 要： | The middle Qilian orogenic belt and Lajishan orogenic belt, both of which were formed in the Caledonian, strike NW-SE direction across southeast Qilian Mountains and their basement consists of pre-Caledonian metamorphic rocks with lozenge-shaped ductile shear zones in the crystalline base- ment. The blunt angle between the conjugated ductile shear zones ranges from 104° to 114°, indicating approximate 210° of the maximum principal stress. The plateau ages of muscovite 40Ar/39Ar obtained from the mylonitized rocks in the ductile shear zones of Jinshaxia-Hualong-Keque massif within the middle Qilian massif are (405.1±2.4) Ma and (418.3±2.8) Ma, respectively. The chronology data confirm the formation of ductile shear zones in the Caledonian basement metamorphic rocks during the Cale- donian orogeny. Furthermore, on the basis of basement rock study, precise timing for the closing of the Late Paleozoic volcanic basin (or island-arc basin) and Lajishan ocean basin is determined. This pro- vides us a new insight into the closing of ocean basin in the structural evolution of orogenic belt.
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| 关 键 词： | 祁连山东南部 加里东期 构造形变 年代学 精确定年 造山带 |
| 收稿时间： | 2006-09-05 |
| 修稿时间： | 2006-11-29 |
Precise Timing of Caledonian Structural Deformation Chronology and Its Implications in Southeast Qilian Mountains, China |
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| Fan Guangming,Lei Dongning.Precise Timing of Caledonian Structural Deformation Chronology and Its Implications in Southeast Qilian Mountains, China[J].Journal of China University of Geosciences,2007,18(1):11-18. |
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| Authors: | Fan Guangming Lei Dongning |
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| Institution: | Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China |
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| Abstract: | The middle Qilian orogenic belt and Lajishan orogenic belt, both of which were formed in the Caledonian, strike NW-SE direction across southeast Qilian Mountains and their basement consists of pre-Caledonian metamorphic rocks with lozenge-shaped ductile shear zones in the crystalline basement. The blunt angle between the conjugated ductile shear zones ranges from 104° to 114°, indicating approximate 210° of the maximum principal stress. The plateau ages of muscovite 40Ar/39Ar obtained from the mylonitized rocks in the ductile shear zones of Jinshaxia-Hualong-Keque massif within the middle Qilian massif are (405.1±2.4) Ma and (418.3±2.8) Ma, respectively. The chronology data confirm the formation of ductile shear zones in the Caledonian basement metamorphic rocks during the Caledonian orogeny. Furthermore, on the basis of basement rock study, precise timing for the dosing of the Late Paleozoic volcanic basin (or island-arc basin) and Lajishan ocean basin is determined. This provides us a new insight into the closing of ocean basin in the structural evolution of orogenic belt. |
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| Keywords: | southeast Qilian Mountains Caledonian orogenic belt ductile shear zones metamor- phic and deformational events tectono-thermochronology |
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