The formation age and tectonic significance of Yemuqi granite in West Junggar, Xinjiang
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摘要:
对新疆西准噶尔南部地区与早古生代蛇绿岩紧密伴生的业姆奇花岗岩体岩石学、岩石地球化学、同位素年代学进行研究,认为业姆奇花岗岩为低钾(拉斑)系列,岩石地球化学特征具板内靠近岛弧区域特征。通过对二长花岗岩LA-ICP-MS锆石U-Pb测年,获得比较准确的年龄数据539.7±2.6Ma,表明其形成时代为早寒武世,该侵入岩作为西准噶尔地区最老的岩浆活动产物,代表了在诺丁尼亚统一大陆形成之后早期裂解阶段古洋盆初期的地质记录。
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关键词:
- 西准噶尔 /
- 花岗岩 /
- LA-ICP-MS锆石U-Pb年龄 /
- 构造意义
Abstract:In this paper, the petrology, lithogeochemistry, and isotope chronology of Yemuqi granite closely associated with Early Paleozoic granite in the southern part of West Junggar, Xinjiang, were studied in detail. It is considered that the granite belongs to low potassium (tholeiitic) series. The rock geochemistry shows the characteristics of the intraplate close to island arc region. The authors obtained accurate age data of 539.7±2.6Ma by LA-ICP-MS zircon U-Pb dating of the monzonite granite. It is shown that the age of its formation was Early Cambrian. The intrusive rock is the oldest product of magmatic activity in the West Junggar area, which represents the geological record of the early stage of the splitting in the Early Paleoceanic Basin after the formation of the united continent of Nodingnia.
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Key words:
- West Junggar /
- granite /
- LA-CP-MS zircon U-Pb age /
- tectonic significance
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图 1 新疆西准噶尔巴尔鲁克山一带地质简图①
Figure 1.
图 2 新疆西准噶尔业姆奇一带地质图②
Figure 2.
图 5 业姆奇侵入体微量元素原始地幔蛛网图(a)和稀土元素球粒陨石配分型式图(b)[10]
Figure 5.
图 8 (Y+Nb)-Rb(a)和Yb-Ta图解(b)[14]
Figure 8.
表 1 业姆奇侵入岩主量、微量和稀土元素分析结果
Table 1. Major, trace element and REE content of Yemuqi granite
样号 D0209/1 D0209/2 D0222/1 D1013/1 D3047/1 D3047/6 D3047/10 D1333/1 SiO2 56.1 71.74 73.17 66.41 48.59 66.9 57.5 62.31 TiO2 0.45 0.23 0.2 0.37 0.68 0.35 0.57 0.45 Al2O3 11.69 13.45 12.57 14.77 16.28 13.67 14.51 15.52 Fe2O3 8.45 3.07 2.48 4.59 11.05 4.63 8.56 3.06 FeO 5.36 2.17 1.91 2.52 6.84 3.06 5.2 3.88 MnO 6.49 1.83 3.27 2.61 5.31 3.12 4.78 0.15 MgO 7.11 1.12 0.82 1.88 5.77 2.1 3.75 3.1 CaO 0.18 0.08 0.08 0.1 0.19 0.11 0.17 6.48 Na2O 0.15 0.07 0.09 0.16 0.32 0.18 0.24 4.35 K2O 0.5 1.46 0.65 1.38 0.52 0.71 0.62 0.56 P2O5 3.51 4.79 4.75 5.2 4.45 5.15 4.12 0.17 Pb 2.9 3.5 2 2.6 / 0.9 4.5 4.3 Co 33 5.58 4.24 8.41 / 8.16 19.5 24.3 Ni 43.6 11 4.19 5.03 / 5.17 13.1 14 Cr 235 7 4.8 4.3 / 3.2 16.1 9.1 Ga 13.7 12.5 11.9 15.7 / 14.5 16.1 18 Sc 31.9 7 3.3 10.9 / 9.7 27.8 30.5 Sr 285 255 187 203 / 284 303 544 Ba 255 657 297 368 / 468 521 407 Rb 8.98 13.8 13.1 17.4 / 10.7 11.7 7.2 Cs 0.54 0.46 0.8 0.87 / 0.77 0.98 0.79 Nb 2.75 2.93 10.6 9.26 / 4.64 11.6 3.49 Ta 0.25 0.22 0.45 0.86 / 0.46 0.39 0.24 Zr 26.4 33.3 36.4 21.4 / 22.8 13.2 11 Hf 2.2 2.38 2.31 1.68 / 1.82 1.31 1.06 U 1.72 1.06 1.16 1.62 / 1.77 1.23 1.25 Th 11.1 9.06 8.74 6.27 / 4.45 4.37 3.87 Ti 2491 1067 1162 2005 / 2030 3219 3460 La 14 34.4 30.2 23.1 15.7 / / / Ce 28.1 65 53.8 46.2 38.1 / / / Pr 3.42 6.53 5.6 5.37 5.14 / / / Nd 14.4 22.4 19.6 21.3 23.4 / / / Sm 3.05 3.24 3.13 4.05 5.22 / / / Eu 0.96 0.89 0.84 1.15 1.49 / / / Gd 2.92 2.84 2.73 3.47 4.49 / / / Tb 0.42 0.29 0.3 0.46 0.61 / / / Dy 2.62 1.4 1.67 2.58 3.58 / / / Ho 0.51 0.28 0.33 0.52 0.69 / / / Er 1.56 0.87 1.08 1.56 2 / / / Tm 0.23 0.14 0.17 0.23 0.28 / / / Yb 1.47 0.98 1.12 1.59 1.82 / / / Lu 0.24 0.17 0.2 0.27 0.27 / / / Y 13.3 7.68 9.28 13.4 16.5 / / / ΣREE 73.9 139.43 120.77 111.85 102.79 / / / LREE/HREE 6.41 19 14.89 9.47 6.48 / / / LaN/YbN 6.83 25.18 19.34 10.42 6.19 / / / 表 2 业姆奇侵入岩样品(D0222-1) LA-ICP-MS锆石U-Th-Pb同位素分析结果
Table 2. LA-ICP-MS zircon U-Th-Pb composition of Yemuqi granite (D0222-1)
测点 含量/10-6 同位素比值 年龄/Ma Pb Th U 207Pb/206U 1σ 207Pb/235U 1σ 206Pb/238U 1σ 207Pb/206U 1σ 206Pb/238U 1σ 207Pb/235U 1σ 1 4.63 58.7 52.3 0.05861 0.0024 0.7079 0.0280 0.08760 0.00105 553 87 541 6 543 17 2 0.80 4.75 12.0 0.05753 0.0009 0.6922 0.0092 0.08726 0.00052 512 35 539 3 534 6 3 2.73 49.2 43.6 0.05919 0.0013 0.7119 0.0135 0.08722 0.00061 574 45 539 4 546 8 4 1.55 20.5 22.2 0.0578 0.0011 0.6967 0.0112 0.08741 0.00056 522 41 540. 3 537 7 5 0.45 7.44 7.15 0.05846 0.0013 0.7041 0.0139 0.08733 0.00062 547 47 539 4 541 8 6 0.64 2.73 6.19 0.05809 0.0010 0.6997 0.0101 0.08735 0.00053 533 38 539 3 539 6 7 9.04 42.8 47.7 0.05858 0.0014 0.7035 0.0147 0.08709 0.00064 552 49 538 4 541 9 8 2.19 25.8 30.0 0.06026 0.0011 0.7273 0.0119 0.08752 0.00057 613 40 540 3 555 7 -
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