| The Zn-Pb potential of the Sayram Massif has drawn significant attention since the discovery of the adjacent large Tekeli SEDEX Zn-Pb deposit in Kazakhstan in 1950s.A series of Zn-Pb deposit was discovered in the Proterozoic strata in the Sayram Massif in recent years,indicating a great potential for Zn-Pb prospecting.Tuokesai,Hardaban,and Sitai-Haiquan deposits are characterized by their typical mineralization styles with substantial reserves.In this contribution,based on detailed investigation of regional and local geology,these three deposits were selected to decipher the ore-forming geological setting,ore geological characteristics,source of ore-forming material and characteristics of ore-forming fluid.The Zn-Pb mineralization process was discussed.Furthermore,with the comparison of other Zn-Pb deposits in the Sayram area,the regional metallogenetic regularity and controlling factors of ore-forming were also summaried to help with the Zn-Pb prospecting in the Sayram area in the future.The main achievements of this study have been listed as below:(1)The Proterozoic clastic-carbonate strata in the Sayram massif were formed in the continental margin basin during Neoproterozoic,and are the host strata of SEDEX-type Zn-Pn mineralization.Tuokesai is hosted in the marble of the Wenquan Group,while Hardaban is hosted in the dolostone,carbonaceous-calcareous slate and chert of the Hardaban Group.Sitai-Haiquan is hosted in the clayey-carbonaceous limestone of the Kusongmuqieke Group.The lens-shaped Zn-Pb orebodies of these deposits are stratiform and conformable with the host strata.The ore minerals are mainly with laminated or banded textures.These features indicate the Zn-Pb mineralization probably have syn-sedimentary genesis.(2)The chert in the Tuokesai Zn-Pb ore district is conformably interlayered with the ore-bearing marble,and have relatively high ?30Si values(1.3?2.2‰),with light LREE depletion and negative Ce anomalies show a seawater signature.However,the slightly Eu anomalies and relatively low Y/Ho ratios(concentrated from 30.48 to 48.57)of the chert indicating a contribution from hydrothermal fluids sourced from regional submarine hydrothermal activities.The chert's Fe-Al-Ti compositions and La/Ce ratios indicate that the Zn-Pb mineralization was formed in a continental margin environment.(3)The fluid inclusion studies of Hardaban deposit's sphalerite reveal that the homogenization temperatures are 60?263?,and the salinities are estimated to be 0.18?18.22 wt.%NaCl equivalent.These results indicate that the ore-forming fluid is characterized by medium-low temperature and medium-low salinity.Furthermore,the C-O isotopic compositions of hydrothermal dolomite,ankerite and calcite(which are intergrowth with stockwork sphalerite)have features of the resolution of marine carbonate rocks,which indicating that the source of ore-forming fluid may be related to concentrated seawater.(4)The S isotopic compositions of the ore minerals of Tuokesai(?34S=8.10?20.42‰)and Hardaban(?34S=2.6?15.9‰)imply that the sulfur was mainly derived from the thermal sulfate reduction(TSR)of seawater sulfate;The Pb compositions of the ore minerals indicate that the ore metals of these two deposits may have been derived from the detrital and mafic volcanic rocks with minor carbonate rocks of the host strata.The oxidized ores of Sitai-Haiquan deposit are probably derived from the supergenesis of primary sulfide ores.The carbonaceous bands in the ore district possibly help with the reduction of primary ores,(5)In combination with the regional and ore geological characteristics,we suggested that the Sayram Massif may represent the eastern extension of the Tekeli metallogenic belt.We believed that the Ertuosaier,Aoertake,Akekuocuo,Kaladaban and Eastern Karbayi deposits in the Sayram Massif are important targets for SEDEX Zn-Pb prospecting.Carbonate-clastic rocks with high carbon contents in the Meso-Neoproterozic strata,syn-sedimentary fault,chert and hydrothermal breccia rocks are good indicators for potential Zn-Pb mineralization. |
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