东乌珠穆沁旗索纳嘎钼铅锌多金属矿床成岩成矿年代学

Chronology of Molybdenum-Lead-Zinc Polymetallic Deposit of Suo Naga,Dong Ujimqin Banner Region

索纳嘎钼铅锌多金属矿床是近些年继迪岩斑岩型钼矿床之后在二连-东乌珠穆沁旗多金属成矿带发现的又一个中型金属矿床,其以花岗斑岩岩浆热液体系的细网脉斑岩型钼矿化和热液脉型铅锌矿化的矿化组合为特点.采用锆石LA-ICP-MS U-Pb和辉钼矿ICP-MS Re-Os同位素精细测年技术,对成矿相关索纳嘎花岗斑岩的锆石和3个细网脉浸染型钼矿石的辉钼矿样品进行了同位素年代学测定,分别获得206Pb/238U加权平均年龄164.8±2.0Ma(MSWD=0.71)、谐和曲线的交点年龄167.8±2.6Ma(MSWD=1.4)和187Re-187Os模式年龄加权平均年龄166.9±2.3Ma.结果显示,索纳嘎钼铅锌多金属矿床成岩成矿年龄在误差范围内相一致,确立了二连一东乌珠穆沁旗成矿带早燕山期(167Ma左右)一次重要钼多金属成矿事件.该时限与内蒙北部地区中生代早期大规模火山喷发作用时限相一致.综合分析认为,东乌珠穆沁旗一带167Ma和140Ma左右的2次重要成矿事件与研究区乃至大兴安岭南部地区中生代2次大规模火山喷发和岩浆侵入作用密切相关.

Suo Naga molybdenum-lead-zinc ore deposit has been discovered in Erenhot-Dong Ujimqin Banner metal metallogenic belt in recent years following the discovery of Di Yan porphyry molybdenum deposit.It is characterized by vienlet-type porphyry molybdenum and vien-type lead-zinc mineralization.By using in situ zircon LA-ICP-MS U-Pb and molybdenite ICP-MS ReOs highly precise dating techniques,one zircon sample from Suo Nagagranite-porphyry related to mineralization,and three samples of molybdenum from Mo ores are determined.Zircon 206Pb/238U Weighted mean age of 164.8±2.0Ma（MSWD=0.71）,concordant curve intercepts at 167.8±2.6Ma（MSWD=1.4）Ma and molybenite 187 Re-187 Os weighted mean age of 127.82±0.87Ma are obtained respectively.The results show that the age of granitic magma intrusion corresponds to that of mineralization in the range of deviation.An important metallogenic event,which occurred during early Yanshanian（167Ma±） at Erenhot-Dong Ujimqin Banner metal metallogenic belt,was confirmed.The time limit corresponds to that of large scale volcanic eruption in northern region of Inner Mongolia at early stage during Mesozoic period.By comprehensive analysis,it is proposed that the two important metallogenic events are respectively related to twice large-scale volcanic eruptions and intrusions during Mesozoic period in Dong Ujimqin Banner region and even southern area of Hinggan mountains.