湖南东安锑矿构造应力场的演化与成矿分析

Relation of tectonic stress field evolution to mineralization of Dong'an antimony deposit,Hunan province

文章通过对东安锑矿区的共轭节理进行统计分析,结合矿区地质特征和区域构造演化历史,确定了矿区构造应力场演化和构造控矿特征。矿区构造应力场可以划分为五期。第一期为加里东期近SN向挤压,形成牛头寨NE向基底褶皱和同期NE-NNE向断裂,以及近SN向F_1断裂的雏形。第二期为印支期近EW向水平挤压,共轭节理为NE和NNW向,形成了以近SN向的牛头寨复式背斜和区域性F_1断裂为主体的构造格架,以及小牛头寨NW向断裂和继承早期NNE向断裂发育的断裂构造。第三期为燕山早期近SN向水平挤压,共轭节理为NE和NW向;F_1、NNE向断裂整体处于挤压状态。前述三期构造形成了矿区近SN向构造骨架,以及配套的断裂、节理等成矿前构造。第四期为燕山晚期NW-SE向伸展,共轭节理为NE和NWW向;NE向组继承前期节理;F_1、NNE、NNW、NW向断裂此时成为矿液运移通道和容矿场所。第五期构造变形发生在第四纪,为NW-SE向水平挤压,共轭剪节理为NWW和NNW向;此期断裂为成矿后断裂,它们错断矿脉、矿脉被抬升剥蚀后出露地表。

Based on statistical analysis of conjugate joints and geological characteristics and regional tectonic evolution history of the deposit are conformed characteristics of the tectonic stress field evolution and the structure control on ore.The evolution of tectonic stress field can be divided into period（1）the nearly SN compression during Caledonian epoch which led to Niutouzhai NE basement folds and the contemporary NE-NNE faults and rudiment of SN F_1;（2）the nearly horizontal compression during Indo-Chinese epoch to NE and NW joints,the tectonic frame of the nearly SN anticlinorium and regional fault F_1 and NW Xiaoniutouzhai fault and NNE succeeding fault of former fault;（3）the nearly SN Yanshanian horizontal compression to NE,NW joint and the compressional F_1、NNE faults;during the above mentioned epochs were formed the SN fault and sub-fault and joint which are the pre-ore structure;（4）the late Yanshanian NW-SE extensional movement to the NE-NWW conjugate joint（the NE joint,succeeding the former joint）,F_1、NNE、NNW、NW faults which together are the feeder of ore fluid and host structure of the ore;（5）NW-SE compression during Quaternary to NWW-NNW conjugate joint and the post-ore faults which displace ore veins and the uplifted segment was exposed to erosion and outcropped at surface.