| Hua’aobaote Ag-Pb-Zn ore deposit is a large polymetallic deposit, located in the region of Xi Ujimqin Qi in Inner Mongolia, and belongs to the Xilinhot-Huolin Gol metallogenic sub-belt in the middle-southern of Greater Higgnan Mountains, which is an important part of the circum-Pacific polymetallic metallogenic belt. This area had experienced the transformation and intense superimposition from Paleo-Asian tectonic- metallogenic domain to the Circum-Pacific tectonic-metallogenic domain during the Paleozoic era to Mesozoic era, with the advantageous mineralizing geological background. By studying the regional geology, the characteristics of ore (body), fluid inclusion and isotopes, some results could be obtained as follows:(1) By studying the spatial occurrence of the ore body, the mineralization of this deposit was controlled by tectonic and magmatic bodies. The microscopic observation results of the ore indicate that the formation of this deposit had undergone three metallogenic stages, they were Quartz-Pyrite stage、Sphalerite- Galena stage and Arsenopyrite-Pyrite stage.(2) In the stratum of Shoushangou Group, the background values of the main ore-forming elements (Pb, Zn, Ag, As, Hg, Sb) are about n×10-n×100 times higher than the abundance values of the continental crust,east China, which indicates that this stratum of Shoushangou group probably provide some ore-forming materials for the mineralization. Additionally, this area could be considered to be a strongly mineralized one, with a lot of mineralization potential.(3) The factor analysis result shows that:the Fl factor is Cd, Hg, In, Zn main mineralizing factor, mainly medium-low temperature elements assemblage, which confirrmmed the Zn mineralization here. The F2 factor is Ag, Cu, Pb, Sb assemblage, the variance contribution is 22.27%, which also confirmmed the Pb, Ag mineralization. The F3 factor is Bi, Cu, Mo, Sn assemblage, F4 factor is As, W assemblage, both are mainly high temperature elements assemblage. Meanwhile, the elements assemblages of F2, Fl are basicly corresponding with Sphalerite-Galena stage, and the element assemblages of F3, F4 may represent the early-stage of high temperature mineralization.(4) Through the study of microthermometry of primary liquid-riched fluid inclusions in the mineralized quartz veins and sphalerite, we can find that the ore-forming temperature is 146.7-274.3 ℃, belonging to the medium-low temperature type deposit. The ore-forming fluid had the characteristics of low salinity(w(NaCleq) =0.54～8.52ωt%), low density(0.790-0.943g/cm3) and unsaturation. The metallogenic pressure is between 9.60-20.26MPa, the caculated ore-forming depths are between 0.96-2.03km, mainly concentrated between 1.20-1.70km, which indicates a mesogene-hypergene environment.(5) The S, Pb isotopes analysis result of the metal sulfides indicates that the source of the ore-forming materials had the characteristics of crust-mantle mixed type. The H-O isotopic compositions of the fluid inclusions in the quartz show that the near-isothermal mixed Early Cretaceous magmatic water and the infiltrated meteoric water composed the ore-forming fluid.(6) Combining with the regional geological characteristics and tectonic evolution, this deposit is considered to be a hydrothermal-type veined Pb-Zn-Ag deposit, formed under the background of the south Greater Higgnan Mountains stretching tectonic system, the deposit was controlled by multiple geological factors of the deep fault, neutral-acidic subvolcanic-intrusive complexes of the Early Cretaceous and so on.(7) By studying the regional metallogenic regularity of this area, the Cu (Au), Pb, Zn, Ag, Sn, Mo, W polymetallic deposits were mainly controlled by the faults, and had the characteristics of zonation; Regionally, the eary stage mineralization of this area was primarily Cu, the Cu (the late stage), Pb, Zn, Ag, Au, Sn, W, Mo mineralization were relatively late, and the metallogenic strength were more significant, the metalllogenic series were different. Comprehensively considered the S, Pb isotopes composition of Bairendaba, Weilasituo and other polymetallic deposits, their ore-forming materials were mainly from the mantle, some of them from the mixture of the crust and the mantle (magma).(8) Finally, through the comprehensive study of geological, geophysical, geochemical characteristics and the corresponding relationship between ore bodies and geologic bodies, the synthetical prospecting model of this deposit has been formed. |
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