| Xiaohongshi-lazi lead-znic deposit is located in the southeast of JilinProvince, north margin of north China craton. Hitherto, this mining area has delineated 58 ore bodies. There are 24 ore bodies in these two mining belts(Ⅰ、Ⅱ) have been estimated, total mineral is 3063510t, metal Ag74082kg, Pb19969t, Zn 1049416t.The geotectonic position of Xiaohongshi-lazi lead-znic deposit is in east rim of Xing-Meng orogenic belt, among the Siberian plate, the north China craton and the Pacific plate, characterized by multiple plates’jointing. The distribution of ore boides controls by structures which stretch SN. Meanwhile, these structural features also control the later stage of the scope of superposition mineralization.This paper base on systematically presenting the regional tectonic background combines with geochemistry of wall rocks, to clarify the conditions of rock formation. Furthermore, this paper also study on geologic feature of ore-forming fluid, to illuminate the source and evolution characters of mineralizing material, and clarify the genesis of this deposit, built up the metallogenic model.There are 2 mineralization alteration zones in this mining area, faulting tectonics developed, most of them are SN & NW. ore bodies expended along with these faults. The major wall rocks are marine volcanic-sedimentary rocks, daheshen fm. Main lithology are andesite tuff with alteration, and volcanin breccia. These rocks formed under the circumstance of collision of plate caused by subduction of the north China plate.Chloritization, silicification, kaolinization, and carbonation are widely-distributed in the wall rocks, with a small quantity of epidotization. The alteration of mineral in ore bodies is more intensive, and wears off in wall rocks. Alterations of this deposit are characterized by both VMS-type and medium-low temperature hydrothermal type. Minerals from primary zone of this deposit are sulfide ore. The major metallic minerals are sphalerite, galena, pyrite, pyrrhoite,chalcopyrite, etc. The main noble metal minerals are pyrargyrite and native silver, gold is rare. Most of gangue minerals are quartz and calcite. The main texture of ore is crumby of sulfide metal. Affected by hydrothermal superposition, a large amount of veinlet-disseminated mineralization was formed. At the same time, these ore bodies are characterized by bedding structure, output as stratiform and lentoid, and conformity with wall rocks. Veinlet like ore bodies are widely spread in mining area.The study on mineralization related fluid inclusions in quartz gangue shows the ore-forming temperature varies from99.5 to 250.1℃, fluid salinity 5.99-21.5wt%, fluid density 0.88～1.06g/cm3 which can be classified as medium-low temperature and salinity, and low density. The estimated matollogenic pressure is 28.21-69.88MPa, and depth is 4.16-6.77km. The laser-raman spedtrum of fluid inclusions shows that the chief constituents are H2O, CO2, and contain a little N2, CH4. The S isotopes show that the ores are rich in light S, and go through a bacterial reduction. H-O isotopes indicate that the source of ore-forming fluid is magmatic water. Meanwhile, Pb isotopes’analytic results infer that the source of Pb is upper crust. Xiaohongshi-lazi lead-znic deposit has the features of submarine volcano plume-hydrothermal sedimentation, and the hydrothermal activity joins the mineralization in later stage.To sum up, this paper considers Xiaohongshi-lazi lead-znic deposit as a hydrothermal vein type deposit, formed during Late Paleozoic through early Mesozoic. The initial enrichment of this deposit was affected by hot water jet flow. In the afterwards regional tectonic, hydrothermatism was more intensive, and overlays the former mineralization. |
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