内蒙古哈达门沟金矿构造演化及成矿控矿构造特征

Tectonic evolution and metallogenic ore-controlling tectonic characteristics of Hadamengou gold deposit in Inner Mongolia

哈达门沟金矿是内蒙古迄今最大的金矿床,具有超大型金矿床规模。金的成矿作用对岩性没有明确的选择性,而主要是受褶皱-断裂构造的控制。成矿流体主要来自深源,在有利的构造扩容带中聚积成矿。研究表明,该区的构造变形从早到晚,力学性质往往从塑性到脆性,构造规模从小到大,构造类型则是褶皱与剪切带同时形成,或相间发育。该区主要经历了4个期次的强烈褶皱-剪切作用,并形成了主要的成矿控矿构造。第一期构造变形时岩石的流变性较强,褶皱幅度较小,一般多表现为小规模的塑性流变褶皱,并产生了小规模韧性剪切带;第二期(主期)褶皱以乌拉山主峰为主的东西向区域规模的复式背、向斜(形),并在主期褶皱的倒转翼发育了一系列与褶皱同向延伸的脆韧性剪切带,它们构成了区域性构造薄弱带;第三期为横跨叠加褶皱,使近东西向褶皱发生了南北向蛇形弯曲,伴随该期褶皱作用形成了低绿片岩相韧脆性剪切带,为深源成矿流体的贯入与集聚成矿提供了很好的赋存空间,是主要的成矿控矿构造;第四期构造变形则以区域性隆升作用为主,使早期褶皱发生横弯褶皱的同时,还将深部形成的金矿体抬升至浅部。文中在成矿控矿构造研究的基础上,探讨了矿床成矿规律,提出了找矿远景。

The Hadamengou Gold Deposit in Inner Mongolia is so far the largest gold deposit,with superlarge scale.The gold mineralization has no definite selectivity on lithology,however,it is mainly controlled by fold and fault structures.Ore-forming fluids are mainly originated from the deep source,and are accumulated within the favorable zones of tectonic expansion forming the ore-deposit.Research shows that,the mechanical property of the structural deformation in this area had been evolved from plastic to brittle since the beginning,and the scale of deformation is from small to large.Folding and shearing deformations were formed simultaneously or alternatively during the tectonism.There are four periods（or times）of intensive folding and shearing in this area,and the main ore-forming and ore-controlling structures are formed during these periods.During the first period,the rocks showed strong rheological property.So the foldings developed are characterized by low amplitude and small scale plastic rheomorphic folds.They are thickened in hinge zone and thinned in the limbs,even appeared a series of ptygmatic folds,and small scale ductile shear zones are developed.Second period of deformation formed the major regional fold which takes the Wulashan main peak antiform as a backbone forming east-west trending anticlinoria and synclinoria,and developing a series of brittle ductile shear zones in the overturned limbs of the major folds,they constitute the regional tectonically weak zones.In the third period developed the crossover superimposed fold,which makes the nearly E-Wtrending folds turned to be North-South snake-like bending,accompanying with low greenschist facies ductilebrittle shear zone,which provides the favorable space for the occurrence of ores formed by penetration and accumulation of the deep sourced ore-forming fluids and is the main ore-forming and ore-controlling structure.The fourth stages of tectonic deformation is mainly of regional uplift,together with the bending of the earlier folds the gold ore bodies formed in the depth are uplifted to the shallower part,and makes them easier to be found and exploited.In the present paper on the basis of research on the metallogenic and ore-controlling structures,the metallogeny of ore-deposits is discussed and the perspective of ore-prospecting is put forward.