LA-ICP-MS zircon U-Pb dating of the Late Triassic-Early Jurassic granites in the eastern part of Qimantag area and its geological significance
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摘要:
祁漫塔格东段拉陵高里河地区晚三叠世—早侏罗世花岗岩组合为高SiO(2 72.18%~76.55%)、高K2O(4.08%~5.32%)的碱性花岗岩组合,具有明显的负Eu异常(δEu平均值为0.28)。岩石组合为二长花岗岩+正长花岗岩,采用LA-ICP-MS技术测得二长花岗岩和正长花岗岩的年龄分别为205.1±1.0 Ma和199.5±1.2 Ma。该套花岗岩组合与拉陵高里河地区的矽卡岩型多金属矿关系密切,初步确定祁漫塔格地区晚三叠世—早侏罗世花岗岩组合也是一期重要的成矿岩浆建造。
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关键词:
- 祁漫塔格 /
- 花岗岩 /
- 晚三叠世-早侏罗世 /
- LA-ICP-MS锆石U-Pb年龄
Abstract:The Late Triassic-Early Jurassic granitic assemblage in the eastern part of Qimantag area has high SiO2 content (72.18%~76.55%), high K2O content (4.08%~5.32%) and obvious negative Eu anomaly (average σEu value being 0.28).The granitic assem-blage is composed of monzogranite and syenogranite, whose ages were precisely redefined by the LA-ICP-MS zircon U-Pb meth-od, being 205.1±1.0 Ma and 199.5±1.2 Ma respectively.This granitic assemblage has close relationship with skarn-type polymetallic deposits in Lalinggaoli area.Therefore, the authors preliminarily hold that the Late Triassic-Early Jurassic granitic assemblage is proba-bly an important ore-forming magmatic formation in the eastern part of Qimantag area.
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Key words:
- Qimantag /
- granite /
- Late Triassic-Early Jurassic /
- LA-ICP-MS zircon U-Pb age
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图 7 稀土元素球粒陨石标准化配分曲线(标准化值据参考文献[11])
Figure 7.
表 1 二长花岗岩(10DQ9JD3312)和正长花岗岩(10DQ9JD3132)锆石U-Th-Pb同位素数据
Table 1. Zircon U-Th-Pb isotopic composition of the samples of monzogranite (10DQ9JD3312) and syenogranite (10DQ9JD3132) as measured by LA-ICP-MS technique
测点号 含量/10-6 207Pb/206Pb 207Pb/235U 206Pb/238U 207Pb/235U 206Pb/238U Th U 比值 1σ 比值 1σ 比值 1σ 年龄/Ma 1σ 年龄/Ma 1σ 10DQ9JD3312(二长花岗岩) 1 60.7 98.1 0.0515 0.0004 0.2259 0.0025 0.0323 0.0002 207.5 2.1 205.6 2.6 2 141.5 132.4 0.0507 0.0004 0.2238 0.0022 0.0325 0.0002 205.2 2.7 206.2 1.1 3 157.7 360.8 0.0513 0.0005 0.2273 0.003 0.0326 0.0003 208.1 3.4 207.3 2.1 4 152.8 396.2 0.0512 0.0003 0.2262 0.0022 0.0325 0.0003 207.3 2 206.3 2.3 5 110.5 281.5 0.0522 0.0005 0.2272 0.0036 0.0321 0.0004 208.3 3 203.5 3.5 6 88.5 204.7 0.0511 0.0003 0.2278 0.0022 0.0328 0.0002 208.6 2.1 208.1 1.8 7 123.2 290 0.0509 0.0003 0.2236 0.0019 0.0323 0.0002 205.1 2.9 205.1 1.2 8 21 23.8 0.0519 0.0009 0.2239 0.004 0.0319 0.0003 205.1 3.5 202.3 2.3 9 181.9 408.6 0.0513 0.0002 0.2244 0.0017 0.0322 0.0002 206.1 1.5 204.4 1.3 10 108.5 192.6 0.0516 0.0003 0.2251 0.0021 0.0322 0.0002 206.9 2.2 204.1 2.7 11 67.5 215.5 0.0525 0.0004 0.2289 0.0022 0.0321 0.0002 209.2 2.1 204.6 1.1 12 97.7 278.9 0.0527 0.0003 0.2324 0.0021 0.0324 0.0002 212.4 2.3 206.8 2.6 13 157.3 486 0.0512 0.0002 0.2244 0.0015 0.0323 0.0002 206.2 1.77 205.8 1.9 14 99.7 249.6 0.05 0.0003 0.2195 0.0024 0.0323 0.0003 201 2.1 205.5 2.8 15 169.4 210.4 0.0508 0.0003 0.222 0.0018 0.0322 0.0002 204.7 1.6 204.5 1.1 10DQ9JD3132(正长花岗岩) 1 158.9 374.4 0.0496 0.0006 0.2185 0.0035 0.0319 0.0003 200.6 3.2 202.7 2 2 68.6 188 0.0519 0.001 0.2294 0.0057 0.0321 0.0005 209.7 5.2 203.5 3.3 3 179.4 222 0.0514 0.0011 0.2262 0.005 0.0319 0.0003 207 4.6 202.5 2 4 187.5 514.6 0.0513 0.0004 0.2248 0.0036 0.0318 0.0005 205.9 3.3 201.6 2.9 5 118.3 154.6 0.0522 0.0016 0.2287 0.0071 0.0318 0.0003 209.1 6.5 202 1.8 6 299.1 571.2 0.0513 0.0015 0.2251 0.0067 0.0318 0.0004 206.1 6.1 201.8 2.4 7 134.9 227.6 0.05 0.0011 0.2203 0.0051 0.0319 0.0003 202.1 4.7 202.7 2 8 300.4 327.4 0.0489 0.0011 0.2102 0.005 0.0312 0.0003 193.7 4.6 198 1.8 9 149.9 270.4 0.0489 0.0014 0.2108 0.0059 0.0313 0.0004 194.2 5.4 198.5 2.3 10 327.8 257.8 0.0476 0.0012 0.2094 0.0057 0.0319 0.0004 193.1 5.2 202.2 2.2 11 163.5 149.7 0.0523 0.0018 0.2312 0.0085 0.032 0.0003 211.2 7.8 203.1 1.8 12 386.7 560.9 0.0503 0.0009 0.2227 0.0045 0.0321 0.0003 204.1 4.1 203.8 1.7 13 100.4 223.4 0.0494 0.001 0.2171 0.0044 0.0319 0.0002 199.5 4.1 202.3 1.6 14 387.1 461.2 0.0511 0.0014 0.2194 0.0066 0.0311 0.0002 201.5 6.1 197.7 1 15 46.3 121.3 0.0522 0.0007 0.2284 0.0062 0.0317 0.0007 208.9 5.7 201.2 4.4 16 85.9 330 0.051 0.0003 0.2242 0.0028 0.0319 0.0003 205.4 2.5 202.4 2.2 17 80.2 121.4 0.0501 0.0009 0.2161 0.005 0.0313 0.0003 198.7 4.6 198.7 1.7 18 131.7 249.1 0.0499 0.0007 0.2174 0.0032 0.0316 0.0002 199.7 3 200.5 1.1 19 216.6 249.7 0.0503 0.0009 0.2175 0.0042 0.0314 0.0003 199.8 3.9 199.2 1.6 20 85.3 166.8 0.0521 0.0006 0.2264 0.0033 0.0315 0.0003 207.2 3 200.1 1.6 21 146.6 381.4 0.0518 0.0009 0.2205 0.0045 0.0309 0.0002 202.3 4.2 196 1.1 22 105.5 294.8 0.0514 0.0004 0.2194 0.0024 0.031 0.0002 201.4 2.2 196.8 1.3 23 190.8 332.3 0.0518 0.0013 0.217 0.0049 0.0304 0.0002 199.4 4.5 193 1.5 24 103.6 232.3 0.05 0.0005 0.2174 0.0025 0.0315 0.0002 199.8 2.3 200 1.2 25 99.4 202.4 0.0528 0.0013 0.229 0.0058 0.0315 0.0003 209.4 5.3 200 1.8 表 2 拉陵高里河地区晚三叠世—早侏罗世花岗岩主量、微量和稀土元素含量
Table 2. Composition of major, trace and rare earth elements of Late Triassic -Early Jurassic granites in Lalinggaoli area
序号
岩性1 2 3 4 5 6 7 8 9 10 11 12 13 14 正长花岗岩 二长花岗岩 正长花岗岩 样号 9GS 9GS 9GS 9GS 9GS 9GS Pm28 Pm25 Pm25 Pm25 10DQ9 10DQ9 PM21 PM2 6467 3400 3405 3605 Jan-85 3205 Gs5-1 GS3-3 GS3-4 GS3-5 GS3132 GS3603 GS1-1 1GS6-1 SiO2 76.2 75.93 76.02 76.55 75.37 75.09 72.18 76.09 76.17 76.15 76.16 76.43 75.77 73.13 TiO2 0.07 0.14 0.13 0.08 0.22 0.18 0.33 0.07 0.1 0.08 0.14 0.16 0.17 0.22 Al2O3 12.57 12.59 12.48 12.04 13.05 12.79 13.75 12.35 12.3 12.49 12.67 12.44 12.41 13.51 Fe2O3 0.42 0.85 0.5 0.61 0.01 0.72 0.3 0.58 0.94 0.8 0.26 0.4 0.94 0.75 FeO 0.67 0.5 0.82 1.1 1.15 0.87 1.82 0.5 0.42 0.33 1.13 1.03 0.68 1 MnO 0.02 0.03 0.04 0.05 0.03 0.04 0.06 0.02 0.03 0.03 0.04 0.04 0.03 0.04 MgO 0.06 0.23 0.23 0.13 0.34 0.37 0.85 0.2 0.17 0.15 0.29 0.33 0.37 0.56 CaO 0.76 0.92 0.95 0.67 0.64 1.37 1.73 0.64 0.65 0.65 0.74 0.8 0.99 1.52 Na2O 3.62 3.73 3.75 3.9 3.74 3.72 2.75 3.44 3.25 3.54 3.09 3.18 3.8 3.88 K2O 4.77 4.31 4.38 4.1 4.57 4.08 4.81 5.32 5.18 5.14 4.73 4.44 4.22 4.12 P2O5 0.01 0.02 0.02 0.01 0.05 0.03 0.12 0.02 0.03 0.03 0.07 0.07 0.05 0.06 H2O+ 0.61 0.52 0.4 0.55 0.58 0.5 1.03 0.43 0.45 0.32 0.44 0.45 0.38 0.54 CO2 0.13 0.08 0.13 0.06 0.04 0.06 0.07 0.21 0.16 0.16 0.09 0.09 0.06 0.51 总量 99.91 99.85 99.85 99.85 99.79 99.82 99.8 99.87 99.85 99.87 99.85 99.86 99.87 99.84 alk 8.39 8.04 8.13 8 8.31 7.8 7.56 8.76 8.43 8.68 7.82 7.62 8.02 8 La 12.94 27.9 40.73 25.62 27 33.66 29.7 29.5 29 22.3 34.6 32.4 46.5 43.4 Ce 37.8 50.93 74.11 46.38 49.68 59.06 58.2 57.8 58.6 47.7 66.5 63.5 98.4 90.3 Pr 5.95 6.22 8.96 5.54 6.5 7.16 6.91 6.01 6.07 5.29 7.55 7.36 10.4 8.88 Nd 31.61 19.37 29.01 18.07 21.38 23.6 25.5 19.1 19.1 17.6 24.8 24.7 35.2 29.1 Sm 12.15 3.55 5.33 3.37 3.87 4.22 6.12 3.32 3.08 3.54 4.51 4.71 6.64 4.93 Eu 0.38 0.36 0.3 0.25 0.55 0.46 0.838 0.319 0.418 0.262 0.304 0.279 0.284 0.531 Gd 16.26 2.58 3.98 2.86 3.25 3.36 6.17 3.27 2.77 3.19 3.74 3.93 5.9 4.24 Tb 3.07 0.38 0.6 0.5 0.53 0.52 1.05 0.486 0.395 0.491 0.529 0.599 0.858 0.594 Dy 20 2.04 3.32 2.74 2.95 2.8 6.57 2.76 1.95 2.83 2.78 3.43 4.75 3.18 Ho 4.17 0.44 0.68 0.57 0.62 0.62 1.29 0.551 0.367 0.542 0.515 0.632 0.879 0.59 Er 11.87 1.14 1.68 1.43 1.66 1.47 3.7 1.61 1.08 1.54 1.68 2.08 2.52 1.77 Tm 1.78 0.17 0.25 0.22 0.26 0.23 0.545 0.262 0.183 0.247 0.237 0.304 0.397 0.288 Yb 11.5 1.1 1.45 1.35 1.73 1.37 3.46 1.78 1.1 1.68 1.65 1.95 2.67 1.9 Lu 1.69 0.17 0.22 0.2 0.28 0.22 0.455 0.258 0.166 0.248 0.239 0.29 0.388 0.275 Y 104 11.34 17.37 15.55 16.24 14.46 16.8 11.4 15.6 24.3 33.9 28.3 17.9 Zr 61.9 59.2 66.1 112 135 Nb 8.8 1.89 6.75 14 12.3 Ba 278 370 258 227 492 Hf 3.3 2.66 3.4 4.84 5.12 Ta 1.55 1.13 1.43 1.82 1.4 Sc 2.55 2.15 2.43 4.19 3.78 Rb 128 112 140 187 171 Th 18.1 16 16.2 26.4 24 Sr 101 82.5 53.7 81.1 195 注:主量元素含量单位为%,微量和稀土元素含量为10-6,8~14号样品据参考文献① -
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