Study On The Geoglogical Characteristics And Regularity Of Structural Ore-controlling Of Sidaogou Gold Deposit, Dandong City, Liaoning Province

Sidaogou gold deposit is one of the important gold deposit in Dongdan city , which discovered earlier in the Southeast area of Liaoning province,and its administrative division is subordinated to Dandong City, Liaoning Province,which away from the city just about 7Km. This gold deposit located in the southern of Yingkou-Kuandian ouplift of Liaodong anticline ,which to lie in west side of the Yalu River deep faults of North China platform.The exposed strata were relatively simple,in addition,the metamorphic rocks of Liaohe group was most widely distributed within the region。Ore-bearing strata were mainly Gaixian group of Liaohe group,which mainly developed in the mining,and the ore bodies were mainly produced in the central rock section,major rocks as sandstone,gneiss and so on.Overall,the mining located in the western of Yalu River deep faults,away from about 2 Km, under its control and influence, the role of tectonic deformation within the mining area is also relatively strong, the main structural features as folds and faults. Showing from the observations and studies of geological characteristics for surface mining and the openingupbyroadways in existing 12 mining level, the mining area developed the main faults,as F1, F2, F3and F4, which were the the secondary structure of Yalu River deep faults, moretheless,the folds in the mining mainly developed in the area between F2 and F3.Magmatic rocks are not well developed in the mining area, but showing a certain number of dykes, which include granite porphyry, lamprophyre, diorite porphyry and so on., are filling a mostly along the NE trending fault. Over all, diorite porphyry veins more concentrated in the F 1 fault zone and it's both sides in the mining area, and lamprophyre veins are developed in the whole mining. Gold mining is divided into the following three main types: disseminated - fine vein-disseminated type tectonic schist; gold-bearing silicified alteration (sand) rock type; quartz - pyrite veins. And gold ores can be divided into four main types namely: graphite schist-type structure, gold-bearing silicified altered rock type, quartz veins type and massive pyrite type. Hydrothermal alteration grows within the near-ore mining rock, so the main alteration can be divided into five types, as silicification, pyrite, sericite, chlorite-based, and carbonation.According to the ore mineral assemblage, texture , structure and the cutting relationship between different mineral composition veins, the characteristics of epithermal gold mineralization of this area are divided into four stages namely:Ⅰpoor sulfide - milky white quartz vein stage;Ⅱpyrite-quartz stage;Ⅲquartz-polymetallic sulfide stage;Ⅳ(chalcopyrite) -quartz - calcite stage.Geochemical results show more complex mineral sources in Sidaogou gold deposits. Showing from REE and magmatic rock ore analysis, various types of magmatic rocks and the dykes all have potential to provide the material sources for gold mineralization, especially are the Sanguliu granodiorite, diabase, lamprophyre rocks , granitic porphyry or other types of rock and dykes, these ore-forming elements were higher than other types of igneous rocks and dykes, and more closely related to mineralization. Sowing from the results of sulfur ,lead isotope analysis and stratum ore analysis ,the Liaohe Group metamorphic rocks, in particular the Gaixian group and Dashiqiao group, have potential to provide the material sources for gold mineralization. Therefore, we believe that the main material sources are provided from the Gaixian group ,Sanguliu granodiorite, diabase, lamprophyre and granite porphyry dikes in Sidaogou gold deposit.Showing from comprehensive study of fluid inclusions ,we can see the poor white gold quartz veins forming in early mineralization, mainly native CO2, containing CO2 and gas-liquid two-phase inclusions in quarz veins,and the homogenization temperature of containing CO2 inclusions is 296.8-310.6℃, and salinity is 2.22-4.55 wt% NaCl, the homogenization temperature of gas-liquid two-phase inclusions is 168-259.8℃, and salinity is 3.55~4.96 wt% NaCl, in the word, they indicates the ore-forming fluid is belonged to hydrothermal system.,which be rich of CO2, mesothermal and low salinity .And the origin, geochemistry Characteristics are similar with Wulong gold deposit, but occurred the phase separation obviously in these mineralization process each other. Combined with previous research, we can suggest that the ore sources related with magmatic differentiation effect of Sanguliu rock, fine diorite and granite porphyry dikes.Pyrite - quartz vein is the main ore mining stage, and also the main ore bodies are formed in this mineralization stage. This type quartz veins mainly contain three-phase inclusions with NaCl Sub-grain and gas-liquid two-phase primary fluid inclusions, homogeneous temperature of the former is 253.4-335.9℃,the salinity is 34.83~40.45 wt% NaCl, and then the temperature of the latter is 164.3~291.6℃, the salinity is 18.8-21.96 wt% NaCl, in a word, these characteristic reflect the hydrothermal of mesothermal and higher salinity, so analyzing the sources may be related with the intrusive body ( veins) of late events in this mining areas; quartz-calcite veins stand for mining products of late hydrothermal mineralization, these veins are developed in the primary fluid inclusions of gas-liquid two-phase, showing of temperature measurement results ,the homogenization temperatures is 132.5~225.6℃, the salinity is 3.22-8.41 wt% NaCl, reflecting the hydrothermal of low temperature ,low salinity fluid in the late stage, and Integrated analyzing the sources may be from mainly precipitation.Therefore,Sidaogou gold deposit formedby mass-sources ,mass-fluids and multi-period, but the main hydrothermal of ore stage should be from the magma, in addition to, the main metallogenic epoch is Yanshanian.Mining lithologic and structural form control of mineralization types in this mining, although showing the Gaixian group is the main host rock, because of some differences of lithology between upper, middle and under layers, leading to unequal tectonic deformation behavior forming in these lithologic layers. Generally, the upper layers and under layers mainly were the metamorphic schist, compared to the middle layers dominated by metamorphic sandstone. As the difference of rock intensity, the upper stratum and lower stratum of Gaixian group grow the ductile-brittle schistosity structure, and grows folds and Interlayer fracture zone controlled by the folds in the middle metamorphic sandstone;the former structures mainly control the mineralization of fine vein-disseminated tectonic schist type, while the latter controls the most important mineralization of strong silicification type. Gold metallogenic in space mainly focus in the region between F2 faults and F3 faults ,which mainly formed by metamorphic sandstone; in this space, Mineralized region be distributed as a belt from north to south, we classified the ores into four zones asⅠ-Ⅳ,which distributed as"broom"from east to west, showing the mineralization of the western of shaft plunging anticline axis is better than the Eastern, while made the shaft Anticline as the center; and spread gradually to the western belt, compared with Weaken gradually to the eastern belt.The four NW large-scale faults were the major host structures in this mining, moretheless, the shaft anticline and interlayer fracture zones of sandstone layers ,which bound by the former to structure ,were the main ore structure. The favorable combination between lead ore structures and host structures was good for Ore-bearing hydrothermal riching in interlayer fracture zones ,which rising along cracks and fractures from the deep faults, then depositing as ore bodies by metasomatism with host rocks. Showing by structural characteristics analysis,the tectonic movement patterns and coordination restricted the forming of favorable structural space and spatial distribution regularity ,which hosted in the interlayer fracture zones. The F2 and F3 structures were mainly as right-lattral thrust, which resulting the hanging wall rocks of F3 dislocated to western, compare to the the lower plate rocks, which dislocated to eastern, and the east of shaft anticline was relatively extrusive, which located on the hanging wall of F3 ,compared to, the west is relatively tensile. therefore, the west of shaft anticline was benifited for a better depositing space of ore structural, while the east side do not have such conditions, so which explains better that the main ore mining were developed in the hinge zone and the west wing of shaft anticline, compared to the less ore bodies in the east wing.