Geochronology,Fluid Inclusions and Isotopic Characteristics of the Dongjun Pb-Zn-Ag Deposit,Inner Mongolia,NE China  

作　　者：XIE Wei WEN Shouqin ZHANG Guangliang TANG Tieqiao 

机构地区：[1]Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines,Department of Geology,Northeastern University,Shenyang 110819,China

出　　处：《Acta Geologica Sinica(English Edition)》2021年第5期1611-1633,共23页地质学报（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Grant No.41372098)。

摘　　要：The Dongjun Pb-Zn-Ag deposit in the northern part of the Great Xing’an Range(NE China)consists of quartzsulfide vein-type and breccia-type mineralization,related to granite porphyry.Hydrothermal alteration is well-developed and includes potassic-silicic-sericitic alteration,phyllic alteration and propylitic alteration.Three stages of mineralization are recognized on the basis of field evidence and petrographic observation,demarcated by assemblages of quartz-pyritearsenopyrite(early stage),quartz-polymetallic sulfide(intermediate stage)and quartz-carbonate-pyrite(late stage).Zircon LA-ICP-MS U-Pb dating indicates that the granite porphyry was emplaced at 146.7±1.2 Ma(Late Jurassic).Microthermometry and laser Raman spectroscopy shows that ore minerals were deposited in conditions of intermediate temperatures(175-359℃),low salinity(0.5-9.3 wt% Na Cl eqv.)and low density(0.60-0.91 g/cm^(3)).Ore-forming fluids were derived largely from magmatic hydrothermal processes,with late-stage addition of meteoric water,belonging to a H_(2)O-NaCl-CO_(2)±CH_(4) system.The δ^(34)SV-CDT values range from 0.75‰ to 4.70‰.The ^(206)Pb/^(204)Pb,^(207)Pb/^(204)Pb,and ^(208)Pb/^(204)Pb values of the ore minerals are in the ranges of 18.240-18.371,15.542-15.570,and 38.100-38.178,respectively.Data for the S and Pb isotopic systems indicate that the ore-forming metals and sulfur were derived from Mesozoic magma.Based on the geological characteristics and geochemical signatures documented in this study,we conclude that the Dongjun deposit is a mesothermal magmatic hydrothermal vein-type Pb-Zn-Ag deposit controlled by fractures and related to granite porphyry,in response to Late Jurassic tectonic-magmatic-hydrothermal activity.We further conclude that fluid immiscibility,fluid mixing and fluid-rock interactions were the dominant mechanisms for deposition of the ore-forming materials.

关 键 词：zircon U-Pb dating fluid inclusions H-O-S-Pb isotopes mesothermal Pb-Zn-Ag deposit Dongjun northern Great Xing’an Range 

分 类 号：P597[天文地球—地球化学] P618.2[天文地球—地质学]