Abstract:

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-W-trending folds turned to be North-South snake-like bending, accompanying with low greenschist facies ductile-brittle 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.

Key words: structural deformation；folding, ductilebrittle shear zone, metallogenetic and orecontrolling processes, orecontrolling model, Wulashan region