| 湖南常德-安仁断裂印支期构造运动分段性: 来自花岗岩的约束 |
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| 引用本文： | 柏道远,李彬,李银敏,陈迪,凌跃新.湖南常德-安仁断裂印支期构造运动分段性: 来自花岗岩的约束[J].地质科技通报,2021,40(5):173-187. |
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| 作者姓名： | 柏道远 李彬 李银敏 陈迪 凌跃新 |
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| 基金项目： | 湖南省地勘局科研项目201901湖南省地质调查院科研项目201917中国地质调查局项目DD20160031-04 |
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| 摘 要： | 常德-安仁断裂是湖南东部一条NW向大断裂。以大量的基础地质资料为基础，对该断裂的分段性特征进行了总结；基于断裂带印支期花岗岩成因及分布规律，提出其在中三叠世晚期印支运动主幕中的活动具有分段性。根据断裂带及其两侧地区构造特征以及出露地层和岩浆岩等方面的差异，将常德-安仁断裂分为安仁-衡山段（Ⅰ）、湘乡段（Ⅱ）、桃江段（Ⅲ）、常德-石门段（Ⅳ）4段，各段间以穿切深部地壳乃至地幔的NE向深大断裂为界。NE向深大断裂主要形成于加里东运动并具左行走滑，其将常德-安仁断裂切错为互不连通的多段，导致后者在中生代的构造运动具分段性。区域上晚三叠世花岗岩主要为后碰撞环境下深部地壳熔融形成的S型花岗岩。常德-安仁断裂带上晚三叠世花岗岩的分布特征指示该断裂在印支运动主幕中的活动具有明显的分段性:中三叠世印支运动主幕中断裂湘乡段深部发生剪切活动，在端部受限的条件下其运动幅度、剪切强度及相应的增温效应自该段中部向端部减小，导致晚三叠世的深部地壳减压熔融仅发生于湘乡段中段，相应的花岗岩体则出露于湘乡段中段和北段。这一构造-岩浆机制在安仁-衡山段和桃江段得到同样反映。常德-安仁断裂在印支期的分段运动，是先期贯通断裂被NE向深大断裂切错为多段后产生的"被动性"分段运动，有别于-般的多条小断裂发生、扩展并最终连接为一条大断裂的"主动性"断裂分段运动或分段生长。
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| 关 键 词： | 常德-安仁断裂 NE向深大断裂 S型花岗岩 分段特征 “被动性”分段运动 印支期 |
| 收稿时间： | 2020-12-22 |
Segmentation of the movement in Indosinian of the Changde-Anren fault in Hunan: Constraints from granite |
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| Abstract: | Changde-Anren fault is a large NW-trending fault in eastern Hunan Province.Based on a large number of basic geological data, this paper summarized the segmental characteristics of the fault; according to the oringin and distribution of Indosinian granite in the fault zone, the paper suggests that the activity of the fault in the main episode of Indosinian movement in the Late Middle Triassic was segmented.According to the structural characteristics of the fault and its two sides, the exposed strata and magmatic rocks, the Changde-Anren fault can be divided into four segments such as Anren-Hengshan segment (Ⅰ), Xiangxiang segment (Ⅱ), Taojiang segment (Ⅲ) and Changde-Shimen segment (Ⅳ), between which are NE-trending deep faults that cut through the deep crust and even the mantle.The NE-trending deep faults were mainly formed in Caledonian movement with sinistral strike-slipping, and cut the Changde-Anren fault into several disconnected segments, which resulted in the segmentation of the movement in Mesozoic of the Changde-Anren fault.In the region, the Late Triassic granites are mainly S-type granites formed by deep crustal melting in a post-collisional environment.The distribution characteristics of Late Triassic granites in the Changde-Anren fault indicate that the activity of the fault in the main episode of Indosinian movement is obviously segmented: there occurred shearing of the Xiangxiang segment of Changde-Anren fault in the deep part in Middle Triassic Indosinian movement, when the movement amplitude, shear strength and corresponding warming effect decreased from the middle to the end of the segment for the end restriction, which caused that the decompression-melting of deep crustal in Late Triassic only occurred in the middle part of Xiangxiang segment, and the corresponding granites were exposed in the middle and northern sections of Xiangxiang segment.This structural-magmatic mechanism is also reflected in Anren-Hengshan segment and Taojiang segment.The segmental movement of the Changde-Anren fault in Indosinian is a "passive" segmental movement after the first penetrating fault was divided into several segments by the NE-trending deep fault, which is different from the general "active" fault segmental movement or segmental growth with many small faults occurring, expanding and finally being connected into a large fault. |
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