| 江南造山带北部早中生代岳阳—赤壁断褶带构造特征及变形机制研究 |
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| 引用本文： | 柏道远 倪艳军 李送文 马铁球 王先辉 彭云益 李,纲.江南造山带北部早中生代岳阳—赤壁断褶带构造特征及变形机制研究[J].中国地质,2009,36(5):996-1009. |
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| 作者姓名： | 柏道远 倪艳军 李送文 马铁球 王先辉 彭云益 李 纲 |
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| 作者单位： | 1. 湖南省地质调查院,湖南,长沙,410011
2. 湖南省地勘局418队,湖南,娄底,417100 |
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| 基金项目： | 中国地质调查局地质大调查项目 |
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| 摘 要： | 早中生代(晚印支-早燕山期)岳阳-赤壁断褶带位于江南造山带与中扬子前陆盆地交界地带.作者对该构造带进行了地表地质调查,以此为基础探讨了构造剖面结构及构造变形动力机制.岳阳-赤壁断褶带自南而北可分为岳阳-临湘基底滑脱-逆冲带,桃花泉-肖家湾盖层滑脱褶皱带,以及赤壁-嘉鱼前陆盆地断-褶-盆构造带.岳阳-临湘基底滑脱-逆冲带自南而北依次有郭镇向斜、官山背斜、临湘倒转向斜和聂市背斜,组成隔槽式褶皱组合.褶皱轴面多向南倾,褶皱变形面为南华系盖层与冷家溪群褶皱基底间的角度不整合面和顺界面的滑脱断裂面.桃花泉-肖家湾盖层滑脱褶皱带主要发育轴面南倾倒转褶皱,褶皱波长较小,卷入地层为南华系-志留系以及上石炭统-中三叠统沉积盖层.赤壁-嘉鱼前陆盆地断-褶-盆构造带以南倾蒲圻断裂(江南断裂)为南部边界,发育T3-J2前陆盆地沉积,带内褶皱与断裂卷入地层包括沉积盖层以及T3-J2地层:南部断裂与褶皱轴面南倾.北部轴面近直立.自南西至北东,研究区内构造线走向由EW向渐变为NEE-NE向.上述构造分带及变形特征反映出自南向北的运动指向,表明岳阳-赤壁断褶带具前陆冲断带构造性质.从断裂相关褶皱理论出发,以地表构造特征为依据,厘定了岳阳-赤壁地质剖面结构并进行了变形动力机制分析,认识如下:①自南而北、自下而上的多个滑脱层及其间的南倾逆断裂或断坡(主要为江南断裂)组成近似台阶状的逆冲断裂系统,从总体上控制了构造块体的滑移、逆冲以及相应的构造格架或变形分区.②郭镇向斜为基底滑脱褶皱,官山背斜具滑脱褶皱和断裂传播褶皱双重成因,聂市背斜为断裂转折褶皱;临湘向斜为受两侧背斜控制的被动向斜,由于弯滑褶皱作用在其两翼沿不整合界面形成滑脱断裂.③岳阳-临湘基底滑脱-逆冲带隔槽式褶皱的形成主要受控于褶皱基底的滑脱和基底整体的水平压缩,其形成机制类似于肿缩式褶皱.最后讨论认为湘东北-鄂东南地区不存在大规模、长距离的逆冲推覆构造.
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| 关 键 词： | 早中生代 岳阳-赤壁断褶带 江南造山带 构造特征 变形机制 |
A geometrical and kinematic analysis of the Early-Mesozoic Yueyang-Chibi fold-thrust belt in southern Jiangnan orogen |
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| BAI Dao-yuan,NI Yan-jun,LI Song-wen,MA Tie-qiu,WANG Xian-hui,PENG Yun-yi,LI Gang.A geometrical and kinematic analysis of the Early-Mesozoic Yueyang-Chibi fold-thrust belt in southern Jiangnan orogen[J].Chinese Geology,2009,36(5):996-1009. |
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| Authors: | BAI Dao-yuan NI Yan-jun LI Song-wen MA Tie-qiu WANG Xian-hui PENG Yun-yi LI Gang |
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| Institution: | 1. Hunan Institute of Geological Survey, Changsha 410011, Hunan, China; 2. No. 418 Geological Party, Hunan Bureau of Geology and Mineral Exploration and Development, Loudi 417100, Hunan, China |
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| Abstract: | The Early Mesozoic (Late Indosinian-Early Yanshanian) Yueyang-Chibi fold-thrust belt is located in the border area between the Jangnan orogen and the middle Yangtze foreland basin. Detailed geological mapping was conducted to reveal the structural geometry and kinematics of the belt. From south to north, the Yueyang-Chibi fold -thrust belt is composed of Yueyang -Linxiang basement detachment -thrust belt, Taohuaquan -Xiaojiawan cover rock detachment fold belt and Chibi-Jiayu fault-fold-basin. The Yueyang-Linxiang basement detachment-thrust belt is composed of Guozhen syncline, Guanshan anticline, Linxiang overturned syncline and Nieshi anticline in northward direction, making up trough -like folds. Most axial planes of the folds dip south. The unconformity surface between Nanhuan cover rock and Lengjiaxi Group and the detachment fault along the unconformity surface have been folded. In Taohuaquan-Xiaojiawan cover rock detachment fold belt, there occur mainly overturned folds composed of Nanhuan -Silurian and Late Carboniferous -Middle Triassic strata, whose axial planes dip south, with small crosswise sizes. The Chibi-Jiayu fault-fold-basin has a southern boundary fault, namely south-dipping Puqi fault (Jiangnan fault). In the fault-fold-basin there occur Late Triassic-Middle Jurassic sediments, which, together with cover layers, are involved into folds and faults. The faults and the axial planes of the folds dip south in the south of the fault-fold-basin, and the axial planes are vertical in the north. The EW-trending lineament changes to NEE～NE from southwest to northeast of the study area. These structural zonation and deformation characteristics indicate a northward movement direction and the properties of a foreland fold -thrust belt. According to the theory of fault -related folding and on the basis of near -surface geological characteristics, the geotectonic section structure and the deformation dynamic mechanism of the the Yueyang-Chibi fold-thrust belt are considered to be as follows:① Several detachment faults and south-dipping thrust faults from the south and the lower part to the north and the upper part make up a step-shaped thrust-fault system, which controls the slip -thrust of tectonic blocks, structural framework and deformation zones. ② The Guozhen syncline is a basement -detachment fold; the Guanshan anticline has characteristics of a double detachment fold and a fault-propagation fold; the Nieshi anticline is a fault-bending fold; the Linxiang syncline is a passive fold controlled by anticlines on both sides, with detachment faults along the unconformity on the two wings of the syncline.③ The trough-like folds of the Yueyang-Linxiang basement detachment-thrust belt are mainly controlled by fold -basement detachment and horizontal compression, with its formation mechanism similar to that of the pinch and swell fold. The authors hold that there exists no long distance thrust nappe in northeastern Hunan and southeastern Hubei. |
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| Keywords: | Early Mesozoic Yueyang -Chibi fold -thrust belt Jiangnan orogen tectonic characteristics deformation mechanism |
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