| 滇西勐海西定地区南段组褶叠层构造及其研究意义 |
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| 引用本文： | 于远山,张斌辉,陈敏华,王宏,牛浩斌,董其升,任希杰,曹聪.滇西勐海西定地区南段组褶叠层构造及其研究意义[J].沉积与特提斯地质,2022,42(4):626-641. |
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| 作者姓名： | 于远山 张斌辉 陈敏华 王宏 牛浩斌 董其升 任希杰 曹聪 |
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| 作者单位： | 中国地质调查局成都地质调查中心, 四川 成都 610081;四川省地质矿产勘查开发局攀西地质大队, 四川 西昌 615000 |
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| 基金项目： | 中国地质调查局地质调查项目(DD20190053) |
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| 摘 要： | 滇西勐海西定地区，在大地构造上位于西南“三江”造山带南段昌宁-孟连结合带东侧的双江-澜沧俯冲增生杂岩带内。该区分布有一套晚古生代的浅变质碎屑岩系--南段组(DCn)。该套地层既显示层型面状构造型式，又发育有顺层片理、顺层掩卧褶皱、粘滞型石香肠及顺层韧性剪切带等构造形迹，具明显的分层剪切变形、横向构造置换和顺层固态流变特点，构成较典型的褶叠层构造。本文对其构造变形特征进行了系统分析与总结，结合区域构造背景研究成果认为，南段组褶叠层构造总体形成于昌宁-孟连古特提斯洋闭合后同碰撞造山收缩挤压背景下的伸展剪切机制。同时指出，南段组是经过构造改造重建而形成的构造地层单元，应称其为南段岩组；现今露头剖面所见南段岩组岩性组合及厚度只代表改造后构造地层的岩性组合特征及褶叠层的露头厚度，不能完全代表南段组原沉积地层的韵律组合及沉积地层厚度；应按构造地层单位进行划分、填图和研究。褶叠层构造作为浅变质岩区一种普遍的构造型式，是对岩石变形组合特征的客观认识，其构造型式、形成机制、形成层次以及形成时间的研究对分析造山带构造演化过程和深化大陆动力学机制的认识具有科学意义。
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| 关 键 词： | 勐海西定地区 南段组 褶叠层构造 分层剪切变形 横向构造置换 |
| 收稿时间： | 2020/5/18 0:00:00 |
| 修稿时间： | 2020/9/23 0:00:00 |
Folding Layers of Nanduan Formation, Xiding, Menghai, Western Yunnan |
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| YU Yuanshan,ZHANG Binhui,CHEN Minhu,WANG Hong,NIU Haobin,DONG Qisheng,REN Xijie,CAO Cong.Folding Layers of Nanduan Formation, Xiding, Menghai, Western Yunnan[J].Sedimentary Geology and Tethyan Geology,2022,42(4):626-641. |
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| Authors: | YU Yuanshan ZHANG Binhui CHEN Minhu WANG Hong NIU Haobin DONG Qisheng REN Xijie CAO Cong |
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| Institution: | Chengdu Center, China Geological Survey, Chengdu 610081, China;Panxi Geological Team, Bureau of Geology and Mineral Exploration and Development of Sichuan Province, Xichang 615000, China |
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| Abstract: | The Upper Paleozoic Nanduan Formation, a set of epimetamorphic clastic rocks, occurs in the accretionary complex of the Shuangjiang-Lancang subduction belt in Xiding area of Menghai, western Yunnan.Previously, the Nanduan Formation is thought to be a suite of normall stratigraphic sequences. In this paper, based on detailed geological investigation and research, it is believed that the Nanduan Formation is actually a tectonic-stratigraphic unit which is composed of folding layers. A lot of typical structures of folding layers, such as bedding schistosities, recumbent folds, viscous sausages and bedding ductile shear zones, have been identified in the Nanduan Formation. The folding layer structures in Nanduan Formation are with obvious characteristics such as stratified shear deformation, transverse structural replacement, and solid-state rheology. Considering regional tectonic background, it is suggested that the folding layer structures of the Nanduan Formation are formed by the extensional shear mechanism under the background of orogenic collisional contraction and compression after the closure of Changning-Menglian Paleo Tethys Ocean. At the same time, it is pointed out that the Nanduan Formation is a structural stratigraphic unit formed by structural reconstruction and reconstruction, and it should be called the Nanduan Rock Formation. The lithologic assemblage and thickness of the Nanduan Formation seen in present outcrops can only represent the reconstructed lithologic assemblage and thickness of folding layers, which are not the rhythmic assemblage of the original sedimentary strata and the thickness of the sedimentary strata. The Nanduan Formation should be divided, mapped and studied according to structural stratigraphic units. |
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| Keywords: | Xiding area of Menghai Nanduan Formation folding layer structure stratified shear deformation transverse tectonic replacement |
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