The Geological Features And Evolution Of Metallogenic Tectonics Of The Ore Bearing Quartz Veins At Hukeng Tungsten Deposit, Jiangxi Province

Hukeng tungsten deposit is a large scale tungsten deposit which locates at the Wugong Mountain in the west of Jiangxi Province. Ore bearing quartz veins are mainly at the inner contact zone of the rock body which are different from the topical five-layer model in the southern Jiangxi Province. The main direction of the ore-bearing quartz veins are NW striking and EW striking. Some are NWW striking and NE striking. The mode of veins'motion is lefe-lateral nomal fault.According to their structure,we can differentiate them as massive quartz veins, banded quartz veins and complex quartz veins. The petrological study shows that banded ore belongs to mylonite, which has abundant microstructure feature of plastic deformation.Using magnetic fabric analysis to research the ore-bearing quartz veins of Hukeng tungsten deposit. The mean degree of magnetic anisotropy is 1.279,which meas that the ore-bearing quartz veins experienced intensity ductile deformation. Magnetic foliation and lineation well developed in the ore-bearing quartz veins with the E value was either above one or below one.The samples with the E value above one distributed alone the line of E=1,indicationg that the mining area were subjected to compressional and shear deformation.The dominant orientation of minimum magnetic susceptibility shows that the direction of maximum compressive stress is SSW-SW with the dip of 30°-60°.The kinematic model of the ductile deformation is left-lateral shear in the horizonal direction and normal slip in vertical direction.Petrofabric of quartz C-axis is characterized by monoclinic and triclinic symmetry. Deformation model is non-coaxial shearing and had resulted from the combined action of underside slide system and cylinder slide system. Deformation environment is that tempreture was a little bit lower than 550℃and low strain rate.40Ar-39Ar dating of new-generated sericites from mylonite in the NW-trending shear zone yields a plateau age of 140.3±1.0Ma and an isochron age at 139.6±2.4Ma respectively. Whereas, the plateau ages of EW-trending shear zone are more complicated,in which the high-temperature stage plateau age may be affected by muscovite remnant phenocryst which formed in mineralization stage and the medium-temperature stage total gas age and apparent age are more close to the age of plateau age of sample HK121.It is concluded that the age of ductile shearing is about 140Ma, which indicated that ductile shearing deformation occurred after petrogenesis and mineralization.Structural analysis reveals that most primary joints related to magmatic rocks are synchronogenic. The quartz veins which intruded into the joints underwent long-term and multi- tectonic movements, thereby formed complicated quartz veins and ore types. The evolution series of structure in the mining area are as follows: formation of the primary joints→filled by the quartz veins→ductile shear→filled by the quartz veins at second stage→formation of brittle fracture.