| 柴北缘赛坝沟增生杂岩组成与变形特征 |
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| 引用本文： | 曹泊,闫臻,付长垒,牛漫兰.柴北缘赛坝沟增生杂岩组成与变形特征[J].岩石学报,2019,35(4):1015-1032. |
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| 作者姓名： | 曹泊 闫臻 付长垒 牛漫兰 |
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| 作者单位： | 中国地质科学院地质研究所, 北京 100037,中国地质科学院地质研究所, 北京 100037,中国地质科学院地质研究所, 北京 100037,合肥工业大学资源与环境工程学, 合肥 230009 |
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| 基金项目： | 本文受国家自然科学基金项目（41672221、41702239、41872241）和中国地调局地质调查项目（DD20190006、DD20160201-4、DD20160022-2）联合资助. |
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| 摘 要： | 柴北缘构造带由高压-超高压变质岩、蛇绿岩、增生杂岩、火山-岩浆弧及前寒武纪中-高级变质岩共同构成。该构造带内的"滩间山群"岩石组合与构造属性复杂,其岩性包括中基性火山岩、碎屑沉积岩以及超基性岩和中酸性侵入岩,普遍遭受低绿片岩相变质作用和强烈构造变形。结合区域资料和地质填图结果,综合分析认为该构造带东段赛坝沟地区的"滩间山群"由火山-岩浆弧、增生杂岩、蛇绿岩三个不同构造单元岩石组成。其中增生杂岩主要是一套深海-半深海沉积组合,夹玄武岩、灰岩、硅质岩等块体,自南而北总体呈现出来自洋壳、海山和海沟环境的大洋板块地层的岩石组合特征,同时呈现与日本西南部增生杂岩极为相似的岩石组合类型。该套组合构造变形强烈,主要表现为2期构造变形。其中第一期构造变形(D1)主要表现为双冲构造和同斜紧闭褶皱,断层和褶皱轴面主体倾向为NE,形成于大洋俯冲阶段;第二期构造变形(D2)主要表现为不对称褶皱和S-C组构,可能是晚期柴达木与祁连地块发生陆-陆碰撞过程中形成的,形成时间为440～400Ma。空间上,该增生杂岩与出露于其北侧的蛇绿岩、火山-岩浆弧共同构成了相对完整的沟-弧系统,指示了寒武-奥陶纪时期,柴北缘地区曾发生古洋盆向北俯冲造山作用。
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| 关 键 词： | 增生杂岩 岩石组合 构造变形 赛坝沟 柴北缘构造带 |
| 收稿时间： | 2018/12/20 0:00:00 |
| 修稿时间： | 2019/2/24 0:00:00 |
Component and deformation of the Saibagou accretionary complex in the northern margin of the Qaidam block |
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| CAO Bo,YAN Zhen,FU ChangLei and NIU ManLan.Component and deformation of the Saibagou accretionary complex in the northern margin of the Qaidam block[J].Acta Petrologica Sinica,2019,35(4):1015-1032. |
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| Authors: | CAO Bo YAN Zhen FU ChangLei and NIU ManLan |
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| Institution: | Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China,Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China,Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China and School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China |
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| Abstract: | The northern margin of the Qaidam block is mainly composed of HP-UHP metamorphic rocks, ophiolite, accretionary complex, volcano-magmatic arc, and Precambrian metamorphic rocks. The so-called Tanjianshan Group is an important unit of this belt, which mainly consists of medium-mafic volcanic, siliciclastic, and ultramafic rocks. It was intruded by voluminous granitoids plutons, and generally experienced low-grade greenschist facies metamorphism. It was also seriously deformed and characterized by pervasive foliation. In combination with regional geological data, systemic analysis demonstrates that the Tanjianshan Group in Saibagou area of the eastern part of the northern margin of Qaidam block comprises Early Paleozoic volcano-magmatic arc, ophiolite, and accretionary complex. The Saibagou accretionary complex is dominated by abyssal-bathyal sedimentary matrix with blocks of basalt, limestone, and chert, representing the oceanic materials of normal oceanic crust, sea-mountain, and trench settings from south to north, respectively. They are similar to the rock assemblages of the accretionary complex of the Southwest Japan. The rocks of the Saibagou accretionary complex were strongly deformed and experienced two periods of deformations. The first deformation (D1) is characterized by duplex and syncline tight fold, which is closely related to oceanic plate subduction. The fault and axial plane of fold mainly trend to NE verging. The second deformation (D2) is characterized by asymmetric folds and S-C fabrics, which was probably formed by collision of the Qaidam block against Qilian block during 440~400Ma. Spatially, ophiolite was tectonically sandwiched between the volcano-magmatic arc and Sabagou accretionary complex, and underlain by Saibagou accretionary complex. Thus, these three different tectonic units constitute a trench-arc system, indicating northward subduction of ancient ocean basin along the northern margin of the Qaidam block during the Cambrian-Ordovician time. |
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| Keywords: | Accretionary complex Rock assemblage Deformation Saibagou Northern margin of the Qaidam block |
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