THE PETROLOGY, GEOCHEMICAL CHARACTERISTICS AND ORIGIN OF THE NAPENG GRANITE MASS FORMED IN INDO-CHINA PERIOD IN THE WEST OF GUANGDONG PROVINCE
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摘要: 那蓬岩体为混合岩化-花岗岩化作用的产物,主体岩性为中细粒(斑状)黑云母二长混合花岗岩、弱片麻状细粒黑云母二长混合花岗岩,富含堇青石、矽线石、红柱石等富铝矿物,靠近岩体边部为混合片麻岩、花岗片麻岩,逐渐过渡至围岩。对中细粒黑云母二长混合花岗岩进行LA-ICPMS锆石U-Pb同位素测年,锆石以变质锆石为主、岩浆锆石为辅,获得多期锆石U-Pb年龄,将最新的变质年龄252±1.9Ma作为成岩年龄,将那蓬岩体的成岩时代定为早三叠世。那蓬岩体形成于碰撞造山构造环境。Abstract: The Napeng granite mass is the product of migmatization and granitization, in which major lithologies are medium-fine grained (porphyritic) biotite monzonitic migmatitic granite and weak gneissic fine grained biotite monzonitic migmatitic granite, rich in a number of Al-rich minerals such as cordierite, fibrolite, bucholzite, andalusite and so on. The lithologies closed to the edge of Napeng granite mass are migmatitic gneiss and granitic gneiss, migrating to the surrounding rocks. By means of LA-ICP-MS Zircon U-Pb isotope dating on the medium-fine grained biotite monzonitic migmatitic granite, it is found that metamorphic zircons are the main zircons and few are magmatic zircons, and it is determined that the diagenetic age of the Napeng granite mass is 252±1.9Ma, the early Triassic age, in the tectonic environment of collision orogeny.
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图 4 那蓬岩体主体及围岩地质简图(据广东1:5万筋竹、连滩、泗纶、罗定幅区域地质图修编)
1.南华系2.云开岩群3.寒武系4.奥陶系5.志留系6.白垩系7.第四系8.早三叠世二长混合花岗岩9.白垩纪花岗岩10.白垩纪花岗斑岩11.(中)细粒(斑状)黑云母二长混合花岗岩12.细粒黑云母二长花岗岩13.花岗斑岩14.含矽线石片岩15.堇青石片岩16.二云母片岩17.糜棱岩带/脆性断层18.变质带界线19.不整合界线/整合或侵入界线20.混合交代界线1混合花岗岩带2混合岩化带3正常围岩带21.采样位置
Figure 4. The geological sketch map of the Napeng granite mass and its surrounding rocks
表 1 那蓬岩体主量元素分析结果(w%)
Table 1. The analysis results of the major elements in the Napeng granite mass (w%)
样号 SiO2 TiO2 Al2O3 Fe2O3 FeO MnO MgO CaO Na2O K2O P2O5 H2O+ 烧失量 总量 主量
元素(w%)D1005 70.13 0.55 14.31 1.01 2.52 0.042 1.37 2.17 2.59 3.71 0.20 0.72 1.02 100.34 D1736-1 73.58 0.55 12.63 1.03 2.75 0.032 1.30 0.64 1.12 3.35 0.17 1.60 1.76 100.51 D1062-1 72.42 0.55 13.92 1.10 2.73 0.022 1.51 0.52 0.79 3.38 0.14 1.70 1.96 100.74 C.I.P.W
标准
矿物
(w%)样号 Or Ab An C En Fs Hy Q ap il Mt D1005 22.16 22.17 9.69 2.55 3.46 2.99 6.45 33.70 0.44 1.06 1.48 D1736-1 20.33 9.73 2.27 6.53 3.34 3.44 6.78 51.21 0.37 1.08 1.54 D1062-1 20.51 6.85 1.81 8.55 3.86 3.30 7.16 51.81 0.31 1.08 1.64 特征指数 样号 σ A.R DI SI FL MF OX LI Na2O /K2O ALK AKI A/CNK D1005 1.46 1.92 78.27 12.23 74.38 72.04 0.60 20.08 0.70 6.30 0.44 1.69 D1736-1 0.65 2.02 81.40 13.61 87.48 74.41 0.64 22.23 0.33 4.47 0.35 2.47 D1062-1 0.59 1.81 79.40 15.88 88.91 71.72 0.65 21.75 0.23 4.17 0.30 2.97 表 2 那蓬岩体微量及稀土元素分析结果
Table 2. The analysis results of trace and rare elements in the Napeng granite mass
样号 Co Ni Cr V W Au Ag Sb Sr Ba Li Be Zr Rb Nb Ta In Cs Th Rb/Sr Rb/Cs La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y ΣREE LREE HREE LREE/HREE (La/Yb)N δEu D1005 9.81 11.7 10 80.4 138 6.61 0.16 3.75 34.5 815 41.7 3.95 220 285 9.02 0.75 0.029 16 31.3 8.26 17.81 40.74 75.74 8.47 31.12 5.35 1.1 5.06 0.78 3.98 0.61 1.22 0.12 0.24 0.06 16.1 190.69 162.52 28.17 10.09 121.76 0.64 D1736-1 6.85 9.11 10.7 72.9 173 0.9 0.1 1.7 98.9 654 23.3 3.09 209 219 8.53 0.62 0.027 11.3 30.7 2.21 19.38 16.2 30.6 3.56 13.6 2.78 0.50 2.89 0.44 2.36 0.45 1.32 0.17 1.02 0.14 11.6 87.63 67.24 20.40 5.80 11.39 0.53 D1062-1 10 15.3 14.4 72.8 97.7 1.83 0.18 5.01 126.8 731 45.9 4.97 260 243 11.1 1.09 0.041 13.1 37.8 1.92 18.55 17.4 33.9 3.86 14.4 2.85 0.56 2.89 0.41 2.12 0.39 1.05 0.13 0.84 0.12 9.70 90.61 72.97 17.64 7.52 14.95 0.59 注:分析数据为质量分数, 单位除了w(Au)的单位是10-9外, 其余为10-6. 表 3 那蓬岩体LA-ICP-MS锆石U-Pb测年分析结果表
Table 3. The LA-ICP-MS Zircon U-Pb dating analysis results of the NaPeng granite mass
样号 232Th 238U Th/U 207Pb/206Pb 207Pb/235U 206Pb/238U 207Pb/206
Pb年龄(Ma)1σ 207Pb/235
U年龄(Ma)1σ 206Pb/238
U年龄(Ma)1σ D1005-01 144.8847 244.7661 0.591931 0.0534 0.4122 0.0559 346 42.6 350 5.9 351 3.6 D1005-02 231.0150 109.3941 2.111769 0.0592 0.7044 0.0867 576 54.6 541 11.1 536 5.0 D1005-03 73.5636 212.2713 0.346555 0.0621 0.5923 0.0682 676 55.6 472 11.1 426 4.2 D1005-05 64.4562 589.9296 0.109261 0.0614 0.6097 0.0713 654 27.8 483 6.2 444 4.5 D1005-06 207.1800 850.3097 0.243652 0.0673 1.2748 0.1363 856 22.2 835 8.7 824 8.8 D1005-07 249.0018 1201.2750 0.207281 0.0897 2.8481 0.2284 1420 20.7 1368 9.1 1326 9.4 D1005-08 45.7413 960.9404 0.047601 0.0795 1.7781 0.1592 1183 21.3 1037 12.5 952 10.8 D1005-09 268.8464 671.6712 0.400265 0.0929 2.5705 0.1989 1487 23.3 1292 9.5 1169 7.9 D1005-10 18.6586 486.3612 0.038364 0.0510 0.3101 0.0440 243 34.3 274 4.1 277 2.2 D1005-11 119.9550 297.8930 0.402678 0.0690 1.3684 0.1420 902 26.9 875 12.6 856 12.0 D1005-12 167.6638 562.8250 0.297897 0.0544 0.5372 0.0712 387 31.5 437 5.0 443 3.2 D1005-13 70.6485 127.8097 0.552763 0.0571 0.5630 0.0716 494 46.3 453 7.4 446 3.7 D1005-14 83.3724 306.9606 0.271606 0.0546 0.6001 0.0795 394 40.7 477 7.4 493 5.3 D1005-15 156.8107 200.2909 0.782915 0.0711 1.6902 0.1713 961 29.63 1005 8.7 1019 6.7 D1005-16 293.6312 2016.8631 0.145588 0.0676 1.3254 0.1410 855 24.1 857 7.3 850 6.2 D1005-17 44.2500 1235.4359 0.035817 0.0679 1.3351 0.1414 865 30.6 861 7.1 853 5.2 D1005-18 292.9549 452.1747 0.64788 0.0698 1.5891 0.1637 924 25.9 966 9.2 977 8.9 D1005-19 17.1559 710.9974 0.024129 0.0491 0.2712 0.0399 150 34.3 244 3.5 252 1.9 D1005-20 182.2593 588.5203 0.309691 0.2243 11.2669 0.3607 3012 14.7 2545 9.8 1985 11.5 D1005-21 24.8185 554.8114 0.044733 0.0512 0.2857 0.0402 250 45.4 255 3.8 254 1.7 D1005-22 25.1176 409.3433 0.061361 0.0546 0.3559 0.0472 394 44.4 309 5.5 297 3.6 D1005-23 55.6929 176.4427 0.315643 0.0593 0.8415 0.1025 576 8.3 620 8.4 629 4.6 D1005-24 272.4864 562.0899 0.484774 0.1000 3.8874 0.2791 1625 -176.1 1611 11.2 1587 13.2 D1005-25 270.4372 341.2244 0.792549 0.1002 3.8810 0.2783 1628 23.8 1610 10.3 1583 9.3 D1005-26 162.7956 453.2374 0.359184 0.1117 4.7259 0.3040 1828 20.4 1772 9.2 1711 8.6 D1005-28 116.5688 655.1016 0.17794 0.0598 0.7064 0.0848 594 25.9 543 6.4 525 5.2 D1005-29 636.2001 1821.8654 0.349203 0.0593 0.8108 0.0983 576 22.2 603 4.4 605 3.1 D1005-30 901.7205 739.8623 1.218768 0.0701 1.3143 0.1347 931 22.2 852 9.3 815 10.0 D1005-31 328.9760 784.4476 0.419373 0.0704 1.5224 0.1555 940 21.9 939 6.4 932 4.6 D1005-32 88.4910 438.9295 0.201606 0.0511 0.3357 0.0474 256 48.1 294 6.0 299 3.5 D1005-33 84.8064 405.0169 0.20939 0.0544 0.5444 0.0722 387 41.7 441 6.0 450 3.8 D1005-36 113.9015 281.7185 0.404309 0.0551 0.4909 0.0643 417 46.3 406 9.3 402 7.5 D1005-37 120.5885 95.9502 1.256781 0.0581 0.7122 0.0893 600 53.7 546 10.1 551 5.4 D1005-38 127.5920 281.8625 0.452675 0.0948 2.9591 0.2241 1524 22.2 1397 12.3 1303 13.0 D1005-39 161.7950 274.3461 0.589748 0.0986 3.6945 0.2701 1598 22.2 1570 9.3 1541 9.4 D1005-40 235.1231 1606.6881 0.14634 0.0685 1.4007 0.1471 883 25.9 889 7.4 885 5.7 D1005-41 254.4262 1720.1636 0.147908 0.0690 1.2615 0.1316 898 24.8 829 7.3 797 5.5 D1005-42 275.4897 625.2869 0.440581 0.0975 4.0388 0.2974 1577 15.7 1642 11.1 1678 13.1 D1005-43 170.7003 418.1114 0.408265 0.0962 3.8217 0.2854 1551 22.2 1597 13.3 1619 17.2 D1005-44 778.8945 985.6139 0.790263 0.1607 10.4727 0.4680 2465 16.1 2478 12.9 2475 21.5 D1005-45 385.7968 1099.1755 0.350987 0.0613 0.9094 0.1066 650 22.2 657 5.5 653 4.0 D1005-46 62.8590 538.1486 0.116806 0.0567 0.5472 0.0686 480 26.9 443 9.3 428 8.2 D1005-47 107.8264 435.3079 0.247701 0.0886 2.9118 0.2353 1395 22.1 1385 12.3 1362 13.9 -
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