Late Paleoproterozoic breakup events of North China: Evidence from LA-ICP-MS zircon U-Pb ages of basaltic andesite from the Daqingshan area in Inner Mongolia
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摘要:
在内蒙古大青山地区1∶5 万矿产资源调查中,采用LA-ICP-MS 锆石U-Pb 同位素测年,在一套侏罗纪火山岩中获得锆石U-Pb 年龄加权平均值为1863±10Ma。经野外实测,认为其被上二叠统脑包沟组不整合覆盖。结合岩石主量、稀土和微量元素测试结果进行构造环境分析,认为其为陆内裂谷环境的产物,反映了华北古元古代末—中元古代多期裂谷事件中的一次裂解事件,对华北古元古代末多期裂谷事件的研究具有重要意义,为华北克拉通进入地台型演化的时间提供了重要依据。
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关键词:
- LA-ICP-MS 锆石U-Pb 年龄 /
- 多期裂谷事件 /
- 华北克拉通 /
- 大青山地区 /
- 内蒙古
Abstract:During the 1∶50000 regional geological survey in Daqingshan area of Inner Mongolia, the authors used LA-ICP-MS zircon U-Th-Pb isotopic dating method and obtained weighted average zircon U-Pb age of 1863±10Ma from the Jurassic volcanic rock. The contact relation is considered to be unconformably covered by Upper Permian Naobaogou Formation, as shown by field survey. According to the major, trace and rare earth elements analytical results of the rock, the basaltic andesite was formed in an intracontinental rift. This was a breakup event between multi -stage rifting in the Late Paleoproterozoic to Neoproterozoic in North China. It is of great significance for studying multi-stage rifting and provides an important basis for the North China Craton (NCC) evolution as a stable platform or para-platform.
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Key words:
- LA-ICP-MS zircon U-Pb age /
- multi-stage rifting /
- NCC /
- Daqingshan area /
- Inner Mongolia
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表 1 安山岩(D0501)LA-ICP-MS 锆石U-Th-Pb 同位素分析结果
Table 1. U-Th-Pb composition of zircons from basalticandesite (D0501) measured by LA-ICP-MS
样品
号含量/10-6 206Pb/238U 1σ 同位素比值 年龄/Ma 谐和
度Pb U 207Pb/235U 1σ 207Pb/206Pb 1σ 208Pb/232Th 1σ 232Th/238U 1σ 206Pb/238U 1σ 207Pb/235U 1σ 207Pb/206Pb 1σ 01 48 135 0.3302 0.0033 5.318 0.080 0.1168 0.0016 0.1098 0.0010 0.4246 0.0053 1839 18 1872 28 1909 25 104 02 32 93 0.3294 0.0031 5.153 0.077 0.1134 0.0016 0.1124 0.0008 0.3237 0.0045 1835 18 1845 28 1855 25 101 0323720.29430.00294.6020.0720.11340.00160.10360.00100.44270.005416631617502718552611204 46 131 0.3296 0.0032 5.177 0.077 0.1139 0.0016 0.1036 0.0006 0.3859 0.0041 1837 18 1849 27 1863 25 101 05 71 199 0.3317 0.0032 5.169 0.076 0.1130 0.0015 0.1084 0.0004 0.4057 0.0035 1847 18 1848 27 1849 25 100 06152000.07000.00070.5470.0120.05670.00120.02280.00030.49790.00684364443104804610207 36 99 0.3241 0.0031 5.069 0.077 0.1134 0.0016 0.0996 0.0005 0.6337 0.0052 1810 18 1831 28 1855 25 102 08 23 64 0.3167 0.0031 4.960 0.076 0.1136 0.0016 0.0912 0.0005 0.7023 0.0137 1774 17 1813 28 1858 26 105 09381070.31240.00305.3520.0820.12430.00180.12550.00080.45350.003817531718772920182511510 75 223 0.3156 0.0030 4.919 0.072 0.1130 0.0015 0.0897 0.0004 0.3871 0.0030 1768 17 1806 27 1849 25 105 11 40 118 0.3104 0.0030 4.859 0.073 0.1135 0.0016 0.0856 0.0004 0.5102 0.0041 1743 17 1795 27 1857 25 107 12 44 125 0.3138 0.0030 4.924 0.073 0.1138 0.0016 0.0778 0.0003 0.7157 0.0058 1760 17 1806 27 1861 25 106 13 77 228 0.3175 0.0030 4.934 0.072 0.1127 0.0015 0.0760 0.0002 0.4833 0.0038 1778 17 1808 26 1843 25 104 14 25 73 0.3154 0.0030 4.980 0.077 0.1145 0.0017 0.0760 0.0006 0.5316 0.0042 1767 17 1816 28 1872 26 106 15 53 162 0.3106 0.0029 4.927 0.072 0.1151 0.0016 0.0731 0.0004 0.4487 0.0036 1744 16 1807 26 1881 25 108 16 24 69 0.3139 0.0030 5.007 0.079 0.1157 0.0018 0.0791 0.0006 0.6614 0.0052 1760 17 1820 29 1892 27 107 17 49 148 0.3153 0.0030 4.896 0.072 0.1126 0.0015 0.0702 0.0003 0.4757 0.0038 1767 17 1802 26 1842 25 104 18 27 80 0.3150 0.0030 4.954 0.075 0.1141 0.0016 0.0731 0.0006 0.4089 0.0038 1765 17 1812 27 1865 26 106 20 22 63 0.3148 0.0030 5.017 0.079 0.1156 0.0017 0.0752 0.0005 0.6736 0.0053 1764 17 1822 29 1889 27 107 21 63 187 0.3197 0.0030 5.009 0.073 0.1136 0.0016 0.0777 0.0003 0.4313 0.0034 1788 17 1821 27 1858 25 104 22 42 123 0.3187 0.0030 4.982 0.074 0.1134 0.0016 0.0799 0.0004 0.4771 0.0037 1784 17 1816 27 1854 25 104 23 28 82 0.3167 0.0030 4.896 0.074 0.1121 0.0016 0.0904 0.0006 0.5422 0.0052 1774 17 1802 27 1834 26 103 24 27 73 0.3460 0.0033 5.695 0.088 0.1194 0.0017 0.1138 0.0010 0.4040 0.0036 1915 18 1931 30 1947 26 102 25 51 147 0.3291 0.0031 5.222 0.077 0.1151 0.0016 0.1065 0.0005 0.3318 0.0026 1834 17 1856 27 1881 25 103 26 49 141 0.3274 0.0031 5.104 0.075 0.1131 0.0016 0.1053 0.0005 0.3386 0.0027 1826 17 1837 27 1850 25 101 27 61 168 0.3367 0.0033 5.385 0.080 0.1160 0.0016 0.1227 0.0007 0.3250 0.0026 1871 18 1883 28 1896 25 101 28 22 61 0.3270 0.0031 5.039 0.078 0.1118 0.0016 0.1099 0.0008 0.4327 0.0034 1824 17 1826 28 1829 27 100 29 75 211 0.3325 0.0032 5.218 0.076 0.1138 0.0016 0.1179 0.0004 0.3396 0.0027 1851 18 1856 27 1861 25 101 3028890.28430.00314.4540.0710.11370.00160.13110.00080.30440.0028161317172327185926115注:标注删除线的点号在本次统计分析中均未被采用,具体原因见文中描述 表 2 安山岩主量、稀土及微量元素分析结果
Table 2. Analytical results of major elements, REEand trace elements of the basaltic andesite
主量元素 SiO2 TiO2 Al2O3 Fe2O3 FeO TFe2O3 MnO MgO CaO Na2O K2O P2O5 SO3 CO2 LOI(烧失量) D0501/2 54.96 1.58 15.23 6.88 0.98 7.97 0.08 1.89 5.51 4.67 3.44 0.89 0.29 1.59 3.18 稀土元素 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y D0501/2 78.9 159 17.7 6.36 9.84 2.26 8.87 0.69 3.44 0.45 1.07 0.13 1.05 0.11 15.0 微量元素 Rb Ba Th U K Ta Nb Sr P Zr Hf Ti Sc V Cr Co Ni Sb D0501/1 49.9 1810 6.61 1.37 2.34 2.75 19.4 917 3862 440 2.35 9781 9.9 89.2 67.5 17.5 27.3 0.16 D0501/2 62.6 1959 5.56 1.42 2.11 4.17 24.5 1540 3665 433 3.87 9173 9.6 84.6 52.8 18.9 29.7 0.27 D0501/3 65.0 2087 8.14 1.12 2.71 4.26 26.0 1140 4176 454 7.28 10318 7.4 105 63.8 17.5 27.4 0.10 D0501/4 51.2 2304 4.52 1.23 2.55 4.70 14.6 1501 4286 453 3.41 10012 12.0 98.8 63.4 20.9 32.5 0.12 D0501/5 52.8 2275 4.88 1.14 2.88 4.02 18.9 799 3361 409 4.36 9859 7.5 59.0 47.2 14.7 21.5 0.14 D0501/6 62.6 1912 6.70 1.50 2.56 5.75 23.6 1295 3551 467 7.37 9625 10.9 58.0 57.8 22.3 31.1 0.15 D0501/7 59.3 2196 7.44 1.28 2.55 3.54 13.9 1244 3532 447 2.81 9029 11.1 91.7 51.7 20.0 29.3 0.16 D0501/8 62.4 2143 7.49 1.44 2.62 3.05 20.2 1195 3543 438 5.75 9113 9.1 86.2 53.2 18.0 28.7 0.17 D0501/9 68.6 1971 6.90 1.57 2.76 3.50 25.2 987 3449 439 6.99 9749 9.0 88.9 57.8 19.2 29.4 0.13 D0501/10 67.4 2010 6.63 1.42 2.74 2.67 22.8 1109 3442 436 6.01 9005 11.6 87.4 53.8 19.7 30.2 0.091 D0501/11 73.2 2512 5.74 1.63 3.11 2.20 18.7 1118 3550 454 5.56 9458 11.1 93.3 52.8 16.6 26.5 0.17 注:主量元素含量单位为%,微量、稀土元素为10-6 -
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