| 内蒙古阿拉善地区前寒武纪变质基底阿拉善群的再厘定 |
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| 引用本文： | 耿元生,王新社,沈其韩,吴春明.内蒙古阿拉善地区前寒武纪变质基底阿拉善群的再厘定[J].中国地质,2006,33(1):138-145. |
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| 作者姓名： | 耿元生 王新社 沈其韩 吴春明 |
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| 作者单位： | 中国地质科学院地质研究所,北京,100037 |
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| 基金项目： | 中国地质调查局地质调查项目 |
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| 摘 要： | 原划分的阿拉善群包含了时代、成因各异、构造样式有别、变质程度不同的变质地层和变形深成片麻岩体。作为一个岩石地层单元已不合适,应予解体并重新厘定。根据目前的研究,原阿拉善群可划分成3套变质地层单元和两个变形深成片麻岩杂岩。本区最古老的岩石地层单元为迭布斯格岩群,由深变质的变质表壳岩系组成,是区内的基底岩系。初步的锆石SHRIMPU-Pb年代学研究表明,它们形成于27亿年左右,属于新太古代。新建立的巴彦乌拉山岩组主要由变质火山岩组成,是区内的火山岩系。目前获得的年龄为2264Ma和2271Ma,属于古元古代。重新厘定的阿拉善岩群主要由变质碎屑岩和变质碳酸盐岩组成,是陆缘沉积岩系,形成于古元古代晚期或更晚。波罗斯坦庙英云闪长质-花岗质片麻岩杂岩,由早期的英云闪长质片麻岩和晚期的花岗质片麻岩组成。早期英云闪长质片麻岩形成于18亿年左右,晚期的花岗质片麻岩大致形成于古生代期间。毕及格台花岗闪长质片麻岩杂岩主要由角闪斜长片麻岩、黑云斜长片麻岩等组成,初步的同位素年龄测定结果显示它们的主期形成于8￣10亿年的晋宁期。
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| 关 键 词： | 阿拉善岩群 前寒武纪 再厘定 内蒙古阿拉善地区 |
| 文章编号： | 1000-3657（2006）01-0138-08 |
| 收稿时间： | 2005-07-07 |
| 修稿时间： | 2005-07-072005-08-26 |
Redefinition of the Alxa Group-complex (Precambrian metamorphic basement) in the Alxa area, Inner Mongolia |
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| GENG Yuan-sheng,WANG Xin-she,SHEN Qi-han,WU Chun-ming.Redefinition of the Alxa Group-complex (Precambrian metamorphic basement) in the Alxa area, Inner Mongolia[J].Chinese Geology,2006,33(1):138-145. |
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| Authors: | GENG Yuan-sheng WANG Xin-she SHEN Qi-han WU Chun-ming |
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| Institution: | Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | The original Alxa Group-complex consists of metamorphic strata and deformed orthogneisses of different ages, geneses, tectonic styles and metamorphic grades;so it is not suitable for a lithostratigraphic unit and should be disintegrated and redefined. Based on recent studies, the original Alxa Group-complex may be divided into three metamorphic stratigraphic units and two deformed orthogneiss complexes. The oldest lithostratigraphic unit in the area is the Diebusige Group-complex, which consists of high-grade metamorphic supracrustal rocks and is the basement rock series in this area. Preliminary zircon SHRIMP U-Pb dating suggests that the Diebusige Group-complex formed at ~2700 Ma and is considered to be of Neoarchean age. The newly established Bayan Ul Formation-complex, which is principally composed of metavolcanic rocks, is a volcanic rock series in this area. Its newly obtained ages are 2264 and 2271 Ma, indicating a Paleoproterozoic age. The redefined Alxa Group-complex, which consists predominantly of meta-clastic rocks and meta-carbonate rocks, is a continental-margin sedimentary series and formed in the late Paleoproterozoic or still later. The Boluosutanmiao tonalitic-granitic gneiss complex is composed of early-stage tonalitic gneiss and late-stage granitic gneiss. The early-stage tonalitic gneiss formed at ~1.8 Ga and the late-stage granitic gneiss formed approximately during the Paleozoic. The Bijigetai granodioritic gneiss complex is mainly composed of hornblende-plagioclase gneiss and biotite-plagioclase gneiss and the preliminary isotopic dating indicates that the main stage of this complex occurred in the Jinningian at 0.8-1 Ga. |
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| Keywords: | Alxa Group-complex Precambrian redefinition Alxa area Inner Mongolia |
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