0 引言
1 剖面及烃源岩的发现
1.1 剖面实测
1.2 剖面特征
1.3 烃源岩初步评价
2 沉积时代分析
2.1 样品与实验方法
2.2 结果
表1 红柳沟剖面粉砂岩碎屑锆石U—Pb年龄测定结果(样品S17HL01)Table 1 U-Pb dating results of detrital zircon from siltstone of the Hongliugou section (sample S17HL01) |
测试点 | 含量/10-6 | Th/U | 同位素比值 | 年龄/Ma | 谐和度 /% | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Th | U | 207Pb /206Pb | ±1σ | 207Pb /235U | ±1σ | 206Pb /238U | ±1σ | 207Pb /206Pb | ±1σ | 207Pb /235U | ±1σ | 206Pb /238U | ±1σ | |||
S17HL01-1 | 381 | 480 | 0.79 | 0.121 5 | 0.003 1 | 6.124 2 | 0.145 9 | 0.360 2 | 0.005 0 | 1 988.9 | 51.1 | 1 993.7 | 20.8 | 1 983.0 | 23.7 | 99 |
S17HL01-2 | 35 | 38 | 0.90 | 0.063 3 | 0.003 4 | 1.244 6 | 0.072 2 | 0.142 2 | 0.003 7 | 716.7 | 114.8 | 820.9 | 32.7 | 856.9 | 20.7 | 95 |
S17HL01-4 | 95 | 319 | 0.30 | 0.069 7 | 0.002 0 | 1.479 6 | 0.038 4 | 0.152 9 | 0.002 1 | 920.4 | 57.9 | 922.1 | 15.7 | 917.4 | 12.0 | 99 |
S17HL01-5 | 216 | 336 | 0.64 | 0.078 7 | 0.002 4 | 1.661 0 | 0.048 9 | 0.151 5 | 0.002 0 | 1 164.8 | 65.7 | 993.8 | 18.7 | 909.1 | 11.0 | 91 |
S17HL01-8 | 148 | 636 | 0.23 | 0.071 6 | 0.001 8 | 1.355 4 | 0.036 2 | 0.135 6 | 0.002 2 | 973.8 | 56.0 | 869.9 | 15.6 | 819.8 | 12.5 | 94 |
S17HL01-9 | 340 | 998 | 0.34 | 0.073 9 | 0.002 1 | 1.397 4 | 0.039 7 | 0.135 8 | 0.002 2 | 1 038.9 | 57.1 | 887.9 | 16.8 | 821.0 | 12.7 | 92 |
S17HL01-10 | 129 | 128 | 1.01 | 0.072 3 | 0.002 6 | 1.479 2 | 0.056 4 | 0.147 3 | 0.002 9 | 995.4 | 73.0 | 921.9 | 23.1 | 885.5 | 16.4 | 95 |
S17HL01-11 | 275 | 657 | 0.42 | 0.073 0 | 0.001 8 | 1.481 7 | 0.035 4 | 0.145 7 | 0.001 9 | 1 013.0 | 49.2 | 922.9 | 14.5 | 876.6 | 10.5 | 94 |
S17HL01-12 | 256 | 276 | 0.92 | 0.074 0 | 0.002 2 | 1.567 4 | 0.050 5 | 0.151 7 | 0.002 3 | 1 042.6 | 56.5 | 957.4 | 20.0 | 910.4 | 12.8 | 94 |
S17HL01-13 | 99 | 547 | 0.18 | 0.065 4 | 0.001 6 | 1.256 3 | 0.031 9 | 0.137 6 | 0.002 1 | 787.0 | 51.1 | 826.3 | 14.4 | 831.0 | 11.8 | 99 |
S17HL01-14 | 377 | 499 | 0.75 | 0.099 2 | 0.001 8 | 3.999 1 | 0.078 8 | 0.288 9 | 0.003 9 | 1 609.3 | 33.3 | 1 634.0 | 16.0 | 1 636.0 | 19.7 | 99 |
S17HL01-15 | 98 | 636 | 0.15 | 0.075 6 | 0.001 5 | 1.746 3 | 0.042 3 | 0.165 0 | 0.002 8 | 1 087.0 | 40.7 | 1 025.8 | 15.7 | 984.6 | 15.2 | 95 |
S17HL01-16 | 486 | 510 | 0.95 | 0.076 1 | 0.002 1 | 1.482 0 | 0.042 5 | 0.139 6 | 0.002 3 | 1 098.2 | 55.6 | 923.1 | 17.4 | 842.6 | 12.7 | 90 |
S17HL01-17 | 397 | 824 | 0.48 | 0.078 0 | 0.001 9 | 1.609 9 | 0.041 1 | 0.147 6 | 0.002 0 | 1 146.3 | 48.1 | 974.1 | 16.0 | 887.6 | 11.3 | 90 |
S17HL01-18 | 234 | 410 | 0.57 | 0.090 1 | 0.001 8 | 3.334 4 | 0.063 3 | 0.264 9 | 0.003 3 | 1 428.7 | 37.8 | 1 489.2 | 14.8 | 1 514.8 | 16.6 | 98 |
S17HL01-19 | 161 | 263 | 0.61 | 0.105 0 | 0.002 2 | 3.791 5 | 0.079 4 | 0.259 1 | 0.004 1 | 1 713.9 | 37.8 | 1 591.0 | 16.8 | 1 485.5 | 20.8 | 93 |
S17HL01-20 | 52 | 122 | 0.43 | 0.079 5 | 0.002 2 | 2.119 0 | 0.062 4 | 0.191 9 | 0.003 2 | 1 187.0 | 54.2 | 1 155.0 | 20.3 | 1 131.5 | 17.5 | 97 |
S17HL01-21 | 156 | 229 | 0.68 | 0.169 2 | 0.003 0 | 11.202 3 | 0.192 1 | 0.476 0 | 0.006 1 | 2 550.3 | 29.3 | 2 540.1 | 16.0 | 2 509.8 | 26.7 | 98 |
S17HL01-23 | 62 | 133 | 0.47 | 0.180 6 | 0.003 5 | 11.850 0 | 0.290 1 | 0.469 8 | 0.007 9 | 2 658.3 | 31.0 | 2 592.6 | 22.9 | 2 482.7 | 34.7 | 95 |
S17HL01-24 | 225 | 331 | 0.68 | 0.066 5 | 0.001 6 | 1.296 2 | 0.030 4 | 0.140 6 | 0.001 6 | 821.9 | 50.0 | 844.0 | 13.4 | 848.3 | 9.1 | 99 |
S17HL01-25 | 145 | 176 | 0.82 | 0.068 1 | 0.002 4 | 1.268 5 | 0.044 2 | 0.134 4 | 0.002 3 | 872.2 | 72.2 | 831.7 | 19.8 | 813.0 | 13.1 | 97 |
S17HL01-27 | 273 | 206 | 1.32 | 0.091 9 | 0.002 6 | 3.123 1 | 0.096 7 | 0.244 7 | 0.004 1 | 1 464.8 | 53.4 | 1 438.4 | 23.8 | 1 411.3 | 21.4 | 98 |
S17HL01-29 | 94 | 244 | 0.38 | 0.069 6 | 0.002 1 | 1.303 8 | 0.040 9 | 0.135 1 | 0.002 8 | 916.7 | 67.6 | 847.4 | 18.0 | 817.2 | 16.1 | 96 |
S17HL01-30 | 72 | 107 | 0.68 | 0.074 9 | 0.003 0 | 1.509 7 | 0.058 7 | 0.144 8 | 0.002 3 | 1 065.7 | 80.4 | 934.3 | 23.8 | 871.7 | 13.0 | 93 |
S17HL01-31 | 240 | 493 | 0.49 | 0.073 8 | 0.001 5 | 1.509 8 | 0.031 3 | 0.147 5 | 0.001 7 | 1 036.7 | 42.6 | 934.4 | 12.7 | 887.1 | 9.5 | 94 |
S17HL01-33 | 290 | 260 | 1.11 | 0.155 7 | 0.003 8 | 8.122 4 | 0.249 6 | 0.374 5 | 0.009 1 | 2 409.6 | 41.0 | 2 244.7 | 27.8 | 2 050.7 | 42.9 | 90 |
S17HL01-36 | 171 | 250 | 0.68 | 0.077 2 | 0.002 8 | 1.925 1 | 0.063 5 | 0.179 5 | 0.003 3 | 1 127.8 | 72.2 | 1 089.8 | 22.0 | 1 064.4 | 17.9 | 97 |
表2 红柳沟剖面粉砂岩碎屑锆石U—Pb年龄测定结果(样品S17HL04)Table 2 U-Pb dating results of detrital zircon from siltstone of the Hongliugou section (sample S17HL04) |
测试点 | 含量/10-6 | Th/U | 同位素比值 | 年龄/Ma | 谐和度 /% | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Th | U | 207Pb/206Pb | ±1σ | 207Pb/235U | ±1σ | 206Pb/238U | ±1σ | 207Pb/206Pb | ±1σ | 207Pb/235U | ±1σ | 206Pb/238U | ±1σ | |||
S17HL04-1 | 341 | 584 | 0.58 | 0.064 9 | 0.002 2 | 1.207 3 | 0.040 6 | 0.133 8 | 0.002 6 | 772.2 | 72.2 | 803.9 | 18.7 | 809.6 | 14.7 | 99 |
S17HL04-2 | 102 | 187 | 0.54 | 0.076 8 | 0.004 7 | 1.485 6 | 0.082 5 | 0.139 1 | 0.002 9 | 1 116.7 | 122.2 | 924.5 | 33.7 | 839.5 | 16.5 | 90 |
S17HL04-3 | 72 | 169 | 0.43 | 0.146 8 | 0.003 5 | 9.177 4 | 0.233 0 | 0.448 1 | 0.007 0 | 2 308.3 | 8.3 | 2 355.9 | 23.2 | 2 386.7 | 31.3 | 98 |
S17HL04-4 | 138 | 167 | 0.83 | 0.077 6 | 0.002 9 | 1.779 2 | 0.060 8 | 0.166 0 | 0.003 7 | 1 136.1 | 75.2 | 1 037.9 | 22.2 | 990.1 | 20.4 | 95 |
S17HL04-5 | 138 | 258 | 0.54 | 0.076 9 | 0.002 7 | 1.729 6 | 0.061 8 | 0.161 5 | 0.003 1 | 1 117.6 | 65.7 | 1 019.6 | 23.0 | 964.9 | 17.3 | 94 |
S17HL04-7 | 189 | 236 | 0.80 | 0.078 6 | 0.004 2 | 1.579 7 | 0.083 9 | 0.144 6 | 0.002 7 | 1 162.7 | 107.4 | 962.3 | 33.0 | 870.8 | 15.4 | 90 |
S17HL04-8 | 186 | 242 | 0.77 | 0.065 4 | 0.002 4 | 1.245 0 | 0.045 8 | 0.136 6 | 0.002 5 | 787.0 | 75.9 | 821.2 | 20.7 | 825.6 | 14.3 | 99 |
S17HL04-12 | 86 | 115 | 0.75 | 0.127 7 | 0.003 1 | 6.227 9 | 0.170 3 | 0.349 0 | 0.005 9 | 2 066.4 | 38.1 | 2 008.4 | 23.9 | 1 929.9 | 28.1 | 96 |
S17HL04-13 | 349 | 387 | 0.90 | 0.073 1 | 0.002 1 | 1.285 2 | 0.037 7 | 0.126 3 | 0.002 0 | 1 016.7 | 53.2 | 839.2 | 16.7 | 766.5 | 11.4 | 90 |
S17HL04-14 | 216 | 381 | 0.57 | 0.068 1 | 0.001 8 | 1.193 6 | 0.032 3 | 0.125 7 | 0.001 9 | 872.2 | 53.7 | 797.6 | 14.9 | 763.4 | 10.8 | 95 |
S17HL04-15 | 630 | 602 | 1.05 | 0.073 3 | 0.002 1 | 1.242 4 | 0.037 9 | 0.122 6 | 0.002 7 | 1 033.3 | 57.4 | 820.0 | 17.2 | 745.3 | 15.6 | 90 |
S17HL04-16 | 509 | 455 | 1.12 | 0.068 4 | 0.001 7 | 1.189 7 | 0.030 3 | 0.125 2 | 0.001 8 | 879.6 | 51.9 | 795.8 | 14.1 | 760.4 | 10.1 | 95 |
S17HL04-18 | 365 | 413 | 0.88 | 0.073 0 | 0.002 7 | 1.253 9 | 0.045 3 | 0.125 2 | 0.002 1 | 1 013.0 | 75.2 | 825.2 | 20.4 | 760.6 | 12.2 | 91 |
S17HL04-19 | 217 | 581 | 0.37 | 0.080 7 | 0.002 1 | 1.798 4 | 0.059 6 | 0.160 8 | 0.003 9 | 1 213.0 | 51.8 | 1 044.9 | 21.6 | 961.1 | 21.5 | 91 |
S17HL04-20 | 340 | 175 | 1.95 | 0.079 7 | 0.003 5 | 2.212 6 | 0.086 2 | 0.202 2 | 0.005 2 | 1 190.7 | 87.0 | 1 185.0 | 27.3 | 1 187.3 | 27.8 | 99 |
S17HL04-21 | 323 | 377 | 0.86 | 0.065 2 | 0.003 1 | 1.143 6 | 0.050 0 | 0.127 8 | 0.002 4 | 783.3 | 98.9 | 774.2 | 23.7 | 775.4 | 13.7 | 99 |
S17HL04-22 | 523 | 644 | 0.81 | 0.074 7 | 0.002 0 | 1.313 0 | 0.035 4 | 0.127 1 | 0.002 1 | 1 061.1 | 57.6 | 851.5 | 15.6 | 771.5 | 12.2 | 90 |
S17HL04-23 | 7 | 243 | 0.03 | 0.144 5 | 0.003 4 | 7.819 8 | 0.198 1 | 0.388 8 | 0.005 8 | 2 283.3 | 39.7 | 2 210.5 | 22.8 | 2 117.1 | 26.9 | 95 |
S17HL04-24 | 286 | 356 | 0.80 | 0.066 8 | 0.002 1 | 1.165 6 | 0.036 5 | 0.125 6 | 0.001 9 | 831.5 | 66.7 | 784.6 | 17.1 | 762.6 | 10.7 | 97 |
S17HL04-25 | 92 | 88 | 1.04 | 0.072 5 | 0.003 6 | 1.232 5 | 0.060 9 | 0.123 0 | 0.002 9 | 999.1 | 101.9 | 815.5 | 27.7 | 747.7 | 16.6 | 91 |
S17HL04-27 | 165 | 231 | 0.71 | 0.067 9 | 0.002 0 | 1.304 8 | 0.036 8 | 0.138 2 | 0.001 8 | 877.8 | 60.0 | 847.9 | 16.2 | 834.5 | 10.3 | 98 |
S17HL04-28 | 54 | 229 | 0.24 | 0.067 6 | 0.001 5 | 1.305 1 | 0.029 5 | 0.138 6 | 0.001 8 | 857.4 | 46.3 | 848.0 | 13.0 | 836.6 | 10.1 | 98 |
S17HL04-30 | 272 | 345 | 0.79 | 0.065 2 | 0.001 8 | 1.124 5 | 0.031 1 | 0.123 4 | 0.001 6 | 783.3 | 57.4 | 765.1 | 14.9 | 750.2 | 8.9 | 98 |
表3 红柳沟剖面粉砂岩碎屑锆石U-Pb年龄测定结果(样品S17HL07)Table 3 U-Pb dating results of detrital zircon from siltstone of the Hongliugou section (sample S17HL07) |
测试点 | 含量/10-6 | Th/U | 同位素比值 | 年龄/Ma | 谐和度 /% | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Th | U | 207Pb/ 206Pb | ±1σ | 207Pb/ 235U | ±1σ | 206Pb/ 238U | ±1σ | 207Pb/ 206Pb | ±1σ | 207Pb/ 235U | ±1σ | 206Pb/ 238U | ±1σ | |||
S17HL07-1 | 69 | 62 | 1.12 | 0.078 0 | 0.005 0 | 1.531 3 | 0.091 9 | 0.143 3 | 0.003 7 | 1 146.3 | 128.2 | 943.0 | 36.9 | 863.5 | 20.9 | 91 |
S17HL07-2 | 211 | 349 | 0.60 | 0.067 5 | 0.001 6 | 1.327 0 | 0.035 4 | 0.141 4 | 0.001 9 | 853.7 | 48.1 | 857.6 | 15.5 | 852.6 | 10.8 | 99 |
S17HL07-3 | 153 | 164 | 0.93 | 0.067 6 | 0.001 9 | 1.396 1 | 0.039 5 | 0.150 0 | 0.002 5 | 855.2 | 63.1 | 887.3 | 16.7 | 901.1 | 14.1 | 98 |
S17HL07-5 | 79 | 149 | 0.53 | 0.064 8 | 0.001 8 | 1.267 0 | 0.033 2 | 0.142 2 | 0.001 8 | 768.5 | 62.0 | 831.1 | 14.9 | 856.8 | 10.4 | 96 |
S17HL07-6 | 158 | 191 | 0.83 | 0.067 1 | 0.001 8 | 1.414 3 | 0.040 7 | 0.152 5 | 0.002 0 | 838.9 | 56.3 | 895.0 | 17.1 | 914.8 | 11.4 | 97 |
S17HL07-11 | 215 | 97 | 2.22 | 0.065 0 | 0.005 1 | 1.123 2 | 0.086 8 | 0.125 8 | 0.004 0 | 775.9 | 166.7 | 764.5 | 41.5 | 764.1 | 22.8 | 99 |
S17HL07-12 | 232 | 391 | 0.59 | 0.167 8 | 0.003 5 | 10.674 6 | 0.238 2 | 0.457 7 | 0.006 6 | 2 535.5 | 33.8 | 2 495.2 | 20.7 | 2 429.5 | 29.3 | 97 |
S17HL07-13 | 171 | 169 | 1.01 | 0.076 6 | 0.003 2 | 1.482 8 | 0.057 0 | 0.141 9 | 0.002 3 | 1 110.2 | 79.5 | 923.4 | 23.3 | 855.3 | 13.2 | 92 |
S17HL07-14 | 119 | 131 | 0.91 | 0.071 6 | 0.002 8 | 1.452 6 | 0.050 1 | 0.149 3 | 0.002 7 | 975.9 | 76.9 | 910.9 | 20.7 | 897.0 | 15.3 | 98 |
S17HL07-16 | 156 | 177 | 0.88 | 0.073 3 | 0.002 9 | 1.495 9 | 0.056 9 | 0.148 0 | 0.002 7 | 1 033.3 | 79.6 | 928.7 | 23.2 | 889.6 | 15.2 | 95 |
S17HL07-17 | 270 | 329 | 0.82 | 0.077 2 | 0.003 2 | 1.459 1 | 0.066 5 | 0.136 9 | 0.002 8 | 1 127.8 | 83.3 | 913.6 | 27.5 | 827.0 | 16.1 | 90 |
S17HL07-18 | 139 | 164 | 0.85 | 0.067 7 | 0.003 3 | 1.289 1 | 0.048 9 | 0.142 6 | 0.002 8 | 858.9 | 106.5 | 840.9 | 21.7 | 859.3 | 15.9 | 97 |
S17HL07-20 | 144 | 284 | 0.51 | 0.107 1 | 0.002 4 | 4.586 9 | 0.103 5 | 0.306 6 | 0.004 2 | 1 750.9 | 41.0 | 1 746.9 | 18.8 | 1 724.1 | 20.5 | 98 |
S17HL07-21 | 132 | 163 | 0.81 | 0.075 6 | 0.003 9 | 1.395 7 | 0.060 7 | 0.134 8 | 0.002 9 | 1 087.0 | 99.1 | 887.1 | 25.7 | 815.1 | 16.4 | 91 |
S17HL07-22 | 125 | 145 | 0.86 | 0.070 8 | 0.002 5 | 1.433 5 | 0.051 6 | 0.145 8 | 0.002 2 | 950.9 | 78.7 | 903.0 | 21.5 | 877.4 | 12.6 | 97 |
S17HL07-23 | 303 | 465 | 0.65 | 0.068 5 | 0.001 8 | 1.224 6 | 0.033 3 | 0.128 1 | 0.001 7 | 883.3 | 55.6 | 811.9 | 15.2 | 777.0 | 9.9 | 95 |
S17HL07-24 | 286 | 233 | 1.23 | 0.125 5 | 0.002 7 | 6.480 5 | 0.148 5 | 0.369 6 | 0.005 0 | 2 036.1 | 37.8 | 2 043.3 | 20.2 | 2 027.6 | 23.6 | 99 |
S17HL07-25 | 193 | 242 | 0.80 | 0.068 0 | 0.002 8 | 1.202 1 | 0.050 2 | 0.127 4 | 0.002 2 | 877.8 | 81.0 | 801.6 | 23.1 | 773.0 | 12.6 | 96 |
S17HL07-26 | 108 | 281 | 0.39 | 0.068 8 | 0.002 1 | 1.482 8 | 0.051 4 | 0.154 1 | 0.002 7 | 894.4 | 69.4 | 923.4 | 21.0 | 924.1 | 15.2 | 99 |
S17HL07-27 | 310 | 224 | 1.39 | 0.073 4 | 0.002 7 | 1.302 8 | 0.048 9 | 0.127 7 | 0.002 2 | 1 025.0 | 74.1 | 847.0 | 21.6 | 774.8 | 12.4 | 91 |
S17HL07-28 | 111 | 124 | 0.90 | 0.068 4 | 0.003 9 | 1.317 9 | 0.068 1 | 0.141 8 | 0.003 8 | 879.6 | 113.9 | 853.6 | 29.8 | 854.9 | 21.3 | 99 |
S17HL07-29 | 46 | 100 | 0.46 | 0.091 3 | 0.003 4 | 3.083 7 | 0.106 5 | 0.245 2 | 0.004 1 | 1 453.7 | 70.4 | 1 428.6 | 26.5 | 1 413.6 | 21.2 | 98 |
S17HL07-30 | 322 | 377 | 0.85 | 0.066 3 | 0.002 2 | 1.276 8 | 0.044 2 | 0.137 6 | 0.002 1 | 816.7 | 69.3 | 835.4 | 19.7 | 831.1 | 11.7 | 99 |
S17HL07-31 | 114 | 164 | 0.70 | 0.126 0 | 0.003 2 | 6.487 4 | 0.167 4 | 0.369 7 | 0.005 4 | 2 042.9 | 44.6 | 2 044.2 | 22.7 | 2 028.1 | 25.5 | 99 |
S17HL07-32 | 214 | 147 | 1.45 | 0.067 2 | 0.004 6 | 1.158 6 | 0.073 6 | 0.127 2 | 0.003 6 | 855.6 | 143.4 | 781.3 | 34.6 | 771.7 | 20.4 | 98 |
S17HL07-33 | 268 | 249 | 1.08 | 0.077 3 | 0.004 1 | 1.476 2 | 0.070 7 | 0.138 1 | 0.002 7 | 1 129.3 | 105.6 | 920.7 | 29.0 | 833.9 | 15.5 | 90 |
S17HL07-35 | 37 | 102 | 0.36 | 0.086 0 | 0.003 2 | 2.597 3 | 0.098 0 | 0.219 1 | 0.003 8 | 1 338.9 | 71.8 | 1 299.9 | 27.7 | 1 277.1 | 20.1 | 98 |
S17HL07-36 | 357 | 516 | 0.69 | 0.063 1 | 0.002 0 | 1.128 4 | 0.035 3 | 0.128 3 | 0.002 1 | 709.3 | 68.5 | 767.0 | 16.9 | 778.3 | 11.9 | 98 |
S17HL07-37 | 58 | 122 | 0.47 | 0.087 2 | 0.003 0 | 3.086 9 | 0.096 4 | 0.256 9 | 0.004 1 | 1 364.8 | 65.6 | 1 429.4 | 24.0 | 1 473.9 | 21.0 | 96 |
图4 红柳沟剖面新元古界样品碎屑锆石CL图像和年龄Fig.4 Representative cathodoluminescence images and ages of zircons from the Neoproterozoic samples of the Hongliugou section |
图5 红柳沟剖面新元古界样品碎屑锆石U—Pb谐和图与年龄频谱图(a) 样品S17HL01碎屑锆石U—Pb谐和图;(b) 样品S17HL01年龄频谱图;(c) 样品S17HL04碎屑锆石U—Pb谐和图;(d) 样品S17HL04年龄频谱图;(e) 样品S17HL07碎屑锆石U—Pb谐和图;(f) 样品S17HL07年龄频谱图 Fig. 5 Zircon U-Pb concordia diagram and age spectrum histogram from the Neoproterozoic samples of the Hongliugou section |