| Shuangkoushan lead-zinc deposit is located in the Lvliangshan area of the northern margin of the Qaidam basin. The tectonic evolution in Qaidam basin has experienced a long history which experienced early Palaeozoic orogenic, late Paleozoic-early Mesozoic superposition composite orogenic, Mesozoic intraplate evolution process, and renew the different geological era and different structural properties of all kinds of geological body.Shuangkoushan lead-zinc deposit main exposed the ophiolite melange of Ordovician-Silurian Tanjianshan Group, Metabasite and Intermediate-basic volcanic rock are dominant, which extend in NWW direction.The ore of Shuangkoushan have variety types and complicated structure. The main ore minerals include galena, pyrite, chalcopyrite and sphalerite, they are shape-half shape granular textrue, disseminated structure, stockwork structure and Dense block structure.The near-ore wall rock alteration of mine are silication, limonitization, chloritization, actinolitization serpentinization and mylonitization. Among them the limonitization and silication are closely related to the mineralization which is the direct prospecting marks.Depending on the relationship of reolacement and filling between ore intersection and mineral, the ore-forming stage was divided into pyrite-chalcopyrite stage(pyrite. Chalcopyrite, sphalerite), galena stage(chalcopyrite, galena).The metallogenic element content include Au, Ag, Pb, Zn, As in Shuangkoushan lead-zinc mine are far higher than regional background value. Among them the content of Pb, As are higher than Crust abundance value.Fluid inclusion studies show that ore forming fluids is in the medium(201°～365°)-the medium-low salinity(3.8%-10.9%)-the medium-low density(0.75-0.87g/cm3) category. The ratio of3He/4He among0.28～0.57(Ra), The ratio of40Ar/36Ar among262.8～285.6, which reflect the ore-forming fluid contain the source of atmospheric precipitation and may also represent ore-forming fluid is mixed with saturated crustal fluids, mixing of mantle fluid compostion is not apparent.The range of the ratio of206Pb/204Pb、207Pb/204Pb、208Pb/204Pb is18.435～18.567(average18.472),15.564～15.773(average15.644),38.431～38.978(average38.595). They showed the characteristics of Shuangkoushan ore mineral are enrich Uranium-lead and Thorium-lead loss. Structural patterning of Pb displays that lead isotope values fall nearby tectonic evolution line, the eigenvalues of μ (238U/204Pb), ω (232Th/204Pb) are9.39～9.79(average9.55),36.39～39.51(average37.24) reveals the characteristics that lead source mixed the orogenic belt and the upper crust.The834S value of sulfide mine changes in the0.63%o-5.32%o, and the range is4.69%o, the average is1.68%o which reveals sulfur source is relatively single, mineralization environment and metallogenic physical and chemical conditions are more stable. Combined with mineral ore-forming geological background, we consider the sulfur of Shuangkoushan source mainly is the magma sulfur, mixing of surrounding rock of ultrabasic rock when ore-body formed.The rare earth element of sulfide in mining area showed the features that strong losses of Eu and weak losses of Ce. They may reflect the ore-body inherited the characteristic of acidic rock mass-orthophyre, moyite, and these rock mass output have the relationship with brittle-toughening brittle shearing tectonic activities. Among trace elements, LILE of Sr, Ba have strong losses state, anomaly characteristics of Rb is not obvious; HSFE such as Nb、Ta、Zr、Hf、 Ti of mining area are strong losses which are similar to the characteristics of volcanic island arc. These features are consistent with Tanjianshan group which possess the characteristic of island arc volcanic rocks. While Nb strong negative abnormal may also instruct crustal material participation in the process of diagenesis and mineralization.The metallogenic age of Shuangkoushan deposit is347-362Ma, which is responds to Qaidam basin occur the scale of acidic magma activity, and in the region it is respond to a mass acticity occurred in Tanjianshan, Xitieshan and Qinglongtan deposit of Late variscan. The determination of metallogenic epoch of Shuangkoushan lead-zinc deposit provide a powerful evidence for this large-scale metallogeny.In the Shuangkoushan deposit author discover a brittle-ductile transition structure aboveground, which instruct mineralization may relate to brittle-ductile shear structural deformation. We saw two period of shear structural deformation in Shuangkoushan deposit, the early stage is ductile shear structural deformation and the late stage is brittle-ductile shearing deformation. The mineralization main in relation to the late stage of brittle-ductile shearing deformation. The second period of mineralization in Tanjianshan gold deposit has also be considered with shear and large scale of magmatic activities of orogeny in Variscan-late Indosinian period. It is reflect that gold-lead-zinc mineralization is relate to the regional orogenic activities, and it is matallogenic response of two period orogenic activities. Indicate that Shuangkoushan lead-zinc deposit is formed by collision orogenic activities. To sum up in conclusion, we consider Shuangkoushan lead-znic deposit is composite hydrothermal vein type lead-zinc ore deposit. |
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