内蒙古敖汉旗八家锌多金属矿床物化探特征及发现意义

Geophysical and Geochemical Characteristics and Discovery Significance of the Bajia Zinc Polymetallic Deposit in Aohan Banner,Inner Mongolia

随着我国经济和高新技术产业的快速发展,对铅锌银矿产资源的需求量不断增加,因此该类矿种的找矿勘查进展备受关注。近年来在内蒙古赤峰敖汉旗境内的黄土覆盖区新发现的八家大型锌多金属矿床(总金属量大于70万吨),标志着该区域铅锌银地质找矿活动的重大突破。八家矿床位于华北克拉通北缘与天山-兴蒙造山带东段贴合部位的造山带南侧,其矿体主要赋存于晚石炭世酒局子组变质长石石英砂岩、变质细砂岩、变质粉砂岩夹碳质板岩层内构造裂隙中,晚二叠世二长花岗岩体中有少量产出。八家覆盖区的找矿勘探综合应用了多尺度物化探找矿方法,并取得突破性进展,土壤测量结果显示Ag、Pb、Zn、As、Sb、Hg异常规模大、强度高,呈现出明显的浓度分带特征和多处异常浓集中心,元素套合程度好。进一步的1∶1万激电中梯测量结果显示,矿体具有相对中高阻、高极化的异常特征。最后通过钻探工程对深部激电异常进行查证发现大型锌多金属矿体。综合成矿地质分析认为,矿体的形成严格受NW向张扭性断裂构造的控制,成矿与晚二叠世二长花岗岩浆热液活动关系密切,含矿热液沿NNW、NNE及近SN向次级断裂带及构造裂隙交代充填形成脉状矿体,属于岩浆热液脉型矿床。八家锌多金属矿床的发现不仅提升了区域矿产资源的开发潜力,也为区域内同类型金属矿产勘探提供了重要的勘查思路和新的找矿方向,具有重要的理论和勘查意义。

With the rapid development of China's economy and high-tech industries,the demand for lead,zinc,and silver mineral resources has been continuously increasing,thus attracting significant attention to the exploration progress of such mineral types.In recent years,the discovery of Bajia large zinc-polymetallic deposit(with a total metal quantity exceeding 700,000 tons)in the loess-covered area of Aohan Banner,Chifeng,Inner Mongolia,marks a significant breakthrough in geological exploration activities for lead,zinc,and silver in this region.This deposit is located on the southern margin of the orogenic belt at the junction of the North China Craton's northern margin and the eastern section of the Tianshan-Xingmeng Orogenic Belt.The orebodies were primarily hosted within structural fractures of metamorphosed feldspar-quartz sandstone,fine sandstone,and siltstone interbedded with carbonaceous slate from the late Carboniferous Jiujuzi Formation,with minor occurrences in the late Permian monzonite body.The exploration in the Bajia area has comprehensively applied multi-scale geophysical and geochemical exploration methods,and has achieved breakthrough results.Soil geochemical survey indicates that significant anomalies of Ag,Pb,Zn,As,Sb,and Hg have a large scale and high intensity,and display distinct concentration zonation and multiple anomaly concentration centers,with good element combination.Further 1∶10,000 induced polarization(IP)measurements reveal that the ore bodies exhibit relatively high to medium resistivity and high polarization anomalies.Finally,drilling operations have confirmed the deep-seated induced polarization anomalies,leading to the discovery of the Bajia large Zn-polymetallic deposit.Comprehensive metallogenic geological analysis suggests that the formation of the Bajia deposit is strictly controlled by NW-trending extensional and torsional fault structures,closely related to the magmatic hydrothermal activities of late Permian monzonite.The mineralized hydrothermal fluids filled and replaced structures along secondary fault zones trending NNW,NNE,and nearly NS,forming vein-type ore bodies,which are classified as magmatic hydrothermal vein deposits.The discovery of the Bajia Zn-polymetallic deposit not only enhances the development potential of regional mineral resources but also provides important exploration insights and new directions for the exploration of similar types of metallic minerals in the area,holding significant theoretical and exploration value.