哈达门沟金矿床构造应力场演化及控矿规律分析

Evolution of the Tectonic Stress Field and Structural Controls on Ore Mineralization of the Hadamengou Gold Deposit in Inner Mongolia

以矿区构造节理统计分析为基础,结合矿区地质特征及区域构造演化,分析了哈达门沟金矿区构造控矿特征及应力场演化。认为山前"钾化带"与矿体就位直接相关,它沟通了复式褶皱核部的隐伏岩体与浅部节理,并成为流体运移的主要通道。与成矿控矿有关的构造应力场可分为四期:第一期变形在新太古代的乌拉山旋回,最大主应力σ1方位15°～195°,共轭节理为NNW和NE向;在成岩、变质作用同时进行下除形成了区内透入性的强塑性叠加小褶皱外还有整体上的大型复背斜。第二期构造应力场作用时间在晚古生代,σ1方位约在160°～340°,形成近SN和NE向共轭节理和西侧的大桦背岩体,这一期有局部的矿化现象;前两期应力场形成了轴向近EW向的叠加褶皱、断裂和两期共轭剪节理等成矿前主要构造。第三期应力场处于主成矿期,变形为燕山运动中、晚期构造,σ1在290°方位近水平扭压,形成EW和NW向共轭剪节理;张扭性应力场使近EW向的节理弯曲变形,并形成追踪张节理,这两类裂隙成为主要的矿液通道及容矿空间。第四期构造应力场应在晚燕山运动及以后,为成矿后构造变形,σ1近直立,整体抬升使矿脉遭受剥蚀而出露地表。

In order to study the characteristics of ore-controlling structures and the evolution processes of tectonic stress field in the Hadamengou area,the regional joints,combined with deposit geological features and regional tectonic evolution were investigated.The results show that the ore formation was directly related to the potassic alteration in the foreland structure zone,which connected underlying pluton in the core part of the complex fold with the shallow joints,and acted as the major channel of fluid migration.The evolution processes of the tectonic stress field can be divided into four periods：（1） The first period occurred in the Wulashan movement of Late Archean.The orientation of σ1（the maximal principal stress of the structurally deformed stress field） was 15°~195°,which formed conjugate joints with NNW and NE trending structures.In addition of the penetrative,small,strong ductile superposed folds,large complex anticlines were formed during the diagenesis and metamorphism periods.（2） The second period occurred in Late Paleozoic.The orientation of σ 1 was about 160°~340°,which led to the formation of the SN and NE-trending conjugate joints and the intrusion of the Dahuabei pluton.Local mineralization was formed in this period.The two periods of pro-mineralization deformation resulted in the nearly EW-trending superposition-folds,faults and conjugate shear joints.（3） The third period deformation was the main ore-forming period took place in the Middle to Late Yanshanian.With the σ 1 orientation of 290°,EW and NW-trending conjugate shear joints were formed by horizontal compresso-shear effect.Tenso-shear stress field made the early EW-trending joints bended,and formed tracking-expansion joints.These two kinds of fractures became the main ore-fluid channels and ore-forming spaces.（4） The fourth period post-mineralization deformation occurred during and after the Late Yanshanian.The nearly upright σ1 caused the tectonic uplift and resulted in the exposure and denudation of the mining area.