Chronology of Molybdenum-Lead-Zinc Polymetallic Deposit of Suo Naga, Dong Ujimqin Banner Region
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摘要: 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±2.0 Ma(MSWD=0.71)、谐和曲线的交点年龄167.8±2.6 Ma(MSWD=1.4)和187Re-187Os模式年龄加权平均年龄166.9±2.3 Ma.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(167 Ma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167 Ma和140 Ma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.Abstract: 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 Re-Os highly precise dating techniques,one zircon sample from Suo Naga granite-porphyry related to mineralization,and three samples of molybdenum from Mo ores are determined. Zircon 206Pb/238U Weighted mean age of 164.8±2.0 Ma (MSWD=0.71),concordant curve intercepts at 167.8±2.6 Ma (MSWD=1.4) Ma and molybenite 187Re-187Os weighted mean age of 127.82±0.87 Ma 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(167 Ma ±) 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.
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图 1 索纳嘎地区地质简图(据内蒙古地质局,中华人民共和国1∶200 000巴颜毛都、塔日根敖包幅地质调查报告,1978编制)
1.第三-第四系;2.上侏罗统流纹岩和流纹质凝灰角砾岩、英安质晶屑岩屑凝灰岩;3.中下侏罗统阿拉坦合力群角岩化砂质板岩及变质砂砾岩;4.下二叠统宝力格庙组安山玢岩、安山质凝灰岩;5.上泥盆统安格尔音乌拉组泥质板岩夹砂质粉砂质火山碎屑岩、斑点板岩;6.上志留统板岩、变质砂岩夹结晶灰岩透镜体;7.中奥陶统多宝山组细碧角斑岩、板岩、大理岩及矽卡岩铁锌矿层及锰矿层;8.燕山早期黑云母花岗岩;9.花岗斑岩;10.断层.Ⅰ.南蒙古早古生带构造岩浆岩带;Ⅱ.奥尤特-朝不楞早古生带构造岩浆岩带;Ⅲ.东乌珠穆沁旗晚古生代构造-岩浆岩带;Ⅳ.二连浩特-贺根山晚古生代蛇绿混杂岩带;Ⅴ.阿尔善图-查干淖尔晚古生代构造-岩浆岩带; Ⅵ.艾力格庙-锡林浩特前寒武纪中间地块;Ⅶ.白乃庙-温都尔庙前寒武纪-早古生代构造-岩浆岩带; 图中方框标示外框图的大致位置
Fig. 1. Simplified geological map of Suo Naga district
表 1 索纳嘎花岗斑岩锆石LA-ICP-MS U-Pb年代学分析结果
Table 1. Zircon U-Pb dating data by LA-ICP-MS for granitic porphyry from Suo Naga Mo-Pb-Zn deposit
样号 组成(10-6) Th/U 207Pb/206Pb 207Pb/235U 206Pb/238U 208Pb/232Th 207Pb/235U 206Pb/238U 208Pb/232Th ρr 232Th 238U 比值 1σ 比值 1σ 比值 1σ 比值 1σ 年龄(Ma) ±1σ 年龄(Ma) 1σ 年龄(Ma) 1σ ZK204-01 279 345 0.81 0.053 5 0.001 8 0.402 0 0.015 8 0.055 2 0.001 3 0.019 4 0.000 3 343 11 346 8 388 7 99% ZK204-02 130 220 0.59 0.051 6 0.002 7 0.189 2 0.009 9 0.026 9 0.000 4 0.008 5 0.000 4 176 8 171 2 170 7 97% ZK204-03 377 457 0.82 0.051 9 0.002 5 0.173 3 0.007 5 0.024 6 0.000 3 0.007 4 0.000 2 162 6 157 2 149 4 96% ZK204-04 174 318 0.55 0.052 2 0.002 7 0.181 9 0.008 9 0.025 9 0.000 3 0.007 8 0.000 3 170 8 165 2 158 6 97% ZK204-05 197 348 0.56 0.051 7 0.002 9 0.183 6 0.010 4 0.026 2 0.000 4 0.007 4 0.000 3 171 9 166 2 148 5 97% ZK204-06 248 413 0.60 0.049 5 0.002 4 0.172 2 0.008 1 0.025 3 0.000 3 0.007 8 0.000 2 161 7 161 2 158 5 99% ZK204-07 309 528 0.59 0.049 7 0.002 2 0.179 3 0.008 0 0.026 1 0.000 3 0.008 0 0.000 2 167 7 166 2 162 4 99% ZK204-08 110 230 0.48 0.048 4 0.002 8 0.170 2 0.009 8 0.025 4 0.000 4 0.008 1 0.000 4 160 9 162 3 163 8 98% ZK204-09 2 558 1 695 1.51 0.052 8 0.001 6 0.188 7 0.005 6 0.025 6 0.000 2 0.007 8 0.000 2 176 5 163 2 157 4 92% ZK204-10 32.8 67 0.49 0.082 4 0.006 0 0.321 0 0.023 2 0.028 0 0.000 8 0.010 5 0.000 7 283 18 178 5 211 14 54% ZK204-11 265 492 0.54 0.043 1 0.002 4 0.155 8 0.008 3 0.026 4 0.000 3 0.008 0 0.000 3 147 7 168 2 161 6 96% ZK204-12 186 325 0.57 0.049 4 0.003 3 0.186 6 0.011 4 0.027 7 0.000 4 0.008 8 0.000 4 174 10 176 3 177 7 98% ZK204-13 107 1 359 0.08 0.059 2 0.001 4 0.663 9 0.016 1 0.080 4 0.000 8 0.019 2 0.000 8 517 10 499 5 385 16 96% ZK204-14 237 486 0.49 0.048 1 0.002 2 0.182 1 0.008 1 0.027 4 0.000 4 0.008 2 0.000 3 170 7 175 3 164 6 97% ZK204-15 363 657 0.55 0.055 0 0.002 5 0.193 7 0.008 4 0.025 4 0.000 3 0.007 5 0.000 3 180 7 162 2 151 5 89% ZK204-16 227 356 0.64 0.053 1 0.003 4 0.187 1 0.011 8 0.025 4 0.000 4 0.007 3 0.000 3 174 10 162 3 147 6 92% ZK204-17 76 137 0.55 0.065 2 0.005 5 0.229 7 0.014 0 0.027 9 0.000 6 0.008 1 0.000 4 210 12 178 4 163 8 83% 表 2 内蒙东乌旗索纳嘎和迪岩钼多金属矿床中辉钼矿Re-Os同位素测试结果
Table 2. Re-Os isotopic age of molybdenite from Suo Naga and Diyan deposit
矿床 样号 样重(g) Re(μg·g-1) 普Os(ng·g-1) 187Re(μg·g-1) 187Os(ng·g-1) 模式年龄(Ma) 测定值 不确定度 测定值 不确定度 测定值 不确定度 测定值 不确定度 测定值 不确定度 索纳嘎 ZK601-1 0.020 45 12.78 0.10 0.013 2 0.059 1 8.032 0.065 22.33 0.19 166.7 2.4 ZK601-2 0.050 06 13.57 0.13 0.088 1 0.029 6 8.530 0.085 24.02 0.19 168.8 2.5 迪岩 ZK204-1 0.050 46 27.45 0.25 0.032 4 0.012 3 17.260 0.160 47.63 0.43 165.4 2.5 DY-SHK 0.050 53 17.68 0.17 0.003 6 0.020 3 11.120 0.110 29.57 0.27 159.5 2.5 注:Re,Os含量的不确定度包括样品和稀释剂的称量误差、稀释剂的标定误差、质谱测量的分馏校正误差、待分析样品同位素比值测量误差,置信度95%.Re-Os模式年龄t按下式计算:t=1/λ(ln(1+187Os/187Re), 其中λ(187Re衰变常数)=1.666×10-11 a-1( Smoliar et al., 1996 ),模式年龄的不确定度还包括衰变常数的不确定度(1.02%), 置信度95%. -
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