ZIRCON U-Pb AGES AND GEOCHEMICAL CHARACTERISTICS OF THE SUGAITILIKE LATE SILURIAN GRANITES IN SOUTHERN KUDI, XINJIANG AND ITS GEOTECTONIC SIGNIFICANCE
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摘要: 西昆仑地区早古生代原特提斯洋的后碰撞阶段划分存在分歧,通过对库地蛇绿岩南侧苏盖提力克花岗岩开展区域地质调查、岩石学、地球化学、锆石U-Pb年代学等方面研究,从而为原特提斯洋构造演化及闭合时限提供地质依据。研究表明,苏盖提力克花岗岩锆石U-Pb年龄(LA-ICP-MS)为(422.5±2.5)Ma,属于晚志留世岩浆活动产物。苏盖提力克花岗岩含有典型矿物白云母,A/CNK=1.07~1.11,刚玉分子含量为1.07%~1.56%,属于S型花岗岩。地球化学上,该岩体富硅、碱,贫钙、镁,富K、Rb、Nb、Th,贫Sr、Ti、P,Rb/Sr比值高;结合区域地质背景及地球化学特征综合分析表明,苏盖提力克花岗岩是原特提斯洋闭合后碰撞阶段的产物,因而晚志留世是原特提斯洋由消减闭合到陆陆碰撞—碰撞后伸展转换时期。Abstract: There are different opinions about the division of post-collisional stages of the Early Paleozoic Proto-Tethys Ocean in the West Kunlun area. In this paper, researches including regional geological survey, petrology, geochemistry, zircon U-Pb chronology, etc. were carried out on Sugaitilike granites, south side of Kudi ophiolite, which provide a geological basis for the tectonic evolution and closing time limit of the Proto-Tethys Ocean. The results show that, the age of zircon U-Pb(LA-ICP-MS) is 422.5±2.5 Ma, making granites products of the late Silurian magma activities. Sugaitilike granite contains typical mineral muscovite, A/CNK=1.07~1.11, and the content of corundum is 1.07~1.56%, belonging to S-type granite. Geochemically, the rock body is rich in silicon, alkali, calcium-depleted, magnesium-rich, rich in K, Rb, Nb, Th, lean in Sr, Ti, P, and high in Rb/Sr ratio. The comprehensive analysis of the geological background and geochemical characteristics of the Sugeitik granite area shows that granites are the products of the collision phase of the Proto-Tethys Ocean. Therefore, the late Silurian is the transition period from the closing of the Proto-Tethys Ocean to the collision of land and land-the period of post-collisional extension transformation.
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Key words:
- west Kunlun area /
- Proto-Tethys Ocean /
- zircon U-Pb age /
- Late Silurian granite /
- S-type granite
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表 1 二长花岗岩LA-ICP-MS锆石U-Pb分析结果
Table 1. LA-ICP-MS zircon U-Pb data of monzonite granite
样品号 含量/×10-6 同位素比值 年龄/Ma P1TW1 Pb U 206Pb/238U 1σ 207Pb/235U 1σ 207Pb/206Pb 1σ 208Pb/232Th 1σ 232Th/238U 1σ 206Pb/238U 1σ 207Pb/235U 1σ 207Pb/206Pb 1σ P1TW1.1 18 247 0.0686 0.0005 0.5196 0.0096 0.0549 0.0010 0.0211 0.0002 0.6024 0.0032 427 3 425 8 410 39 P1TW1.2 90 1380 0.0694 0.0004 0.5285 0.0044 0.0553 0.0004 0.0204 0.0002 0.0922 0.0007 432 2 431 4 423 17 P1TW1.3 15 204 0.0691 0.0004 0.5201 0.0110 0.0546 0.0011 0.0192 0.0001 0.7381 0.0025 431 3 425 9 395 46 P1TW1.4 42 631 0.0687 0.0004 0.5205 0.0049 0.0550 0.0005 0.0198 0.0001 0.2140 0.0012 428 3 425 4 411 20 P1TW1.5 23 321 0.0686 0.0004 0.5360 0.0068 0.0566 0.0007 0.0197 0.0001 0.5574 0.0022 428 3 436 6 477 26 P1TW1.6 21 274 0.0687 0.0004 0.5333 0.0075 0.0563 0.0008 0.0199 0.0001 0.7047 0.0062 428 3 434 6 464 30 P1TW1.7 23 340 0.0682 0.0005 0.5264 0.0070 0.0560 0.0007 0.0201 0.0001 0.3738 0.0055 425 3 429 6 452 27 P1TW1.8 38 313 0.1244 0.0008 1.1077 0.0103 0.0646 0.0005 0.0385 0.0003 0.1954 0.0016 756 5 757 7 761 18 P1TW1.9 9 136 0.0633 0.0006 0.4739 0.0245 0.0542 0.0027 0.0219 0.0005 0.5397 0.0022 396 4 394 20 379 114 P1TW1.10 24 342 0.0671 0.0005 0.5157 0.0074 0.0557 0.0007 0.0224 0.0001 0.4178 0.0019 419 3 422 6 439 29 P1TW1.11 19 276 0.0666 0.0004 0.5077 0.0094 0.0553 0.0010 0.0232 0.0002 0.4425 0.0016 416 3 417 8 424 39 P1TW1.12 43 357 0.1230 0.0009 1.0890 0.0104 0.0642 0.0005 0.0393 0.0002 0.2244 0.0029 748 5 748 7 748 18 P1TW1.13 43 576 0.0676 0.0005 0.5270 0.0052 0.0566 0.0005 0.0199 0.0001 0.7179 0.0040 421 3 430 4 475 20 P1TW1.14 34 402 0.0664 0.0004 0.5257 0.0062 0.0574 0.0006 0.0206 0.0002 1.2851 0.1485 414 2 429 5 508 25 P1TW1.15 35 481 0.0670 0.0005 0.5238 0.0058 0.0567 0.0006 0.0195 0.0001 0.7089 0.0039 418 3 428 5 482 23 P1TW1.16 40 570 0.0669 0.0005 0.5219 0.0051 0.0566 0.0005 0.0199 0.0001 0.5597 0.0052 417 3 426 4 476 20 P1TW1.17 26 326 0.0670 0.0004 0.5514 0.0084 0.0596 0.0009 0.0202 0.0001 1.0436 0.0036 418 3 446 7 590 31 P1TW1.18 22 270 0.0681 0.0005 0.5311 0.0076 0.0566 0.0008 0.0216 0.0001 0.9443 0.0093 425 3 433 6 474 30 P1TW1.19 24 340 0.0676 0.0004 0.5281 0.0076 0.0567 0.0008 0.0211 0.0001 0.4940 0.0028 422 3 431 6 478 30 P1TW1.20 16 215 0.0675 0.0004 0.5278 0.0101 0.0567 0.0011 0.0196 0.0001 0.8569 0.0048 421 3 430 8 481 41 P1TW1.21 13 357 0.0351 0.0002 0.2554 0.0061 0.0528 0.0012 0.0115 0.0001 0.4664 0.0062 222 1 231 5 321 53 P1TW1.22 29 416 0.0672 0.0004 0.5150 0.0063 0.0556 0.0006 0.0225 0.0001 0.3992 0.0214 419 2 422 5 437 26 P1TW1.23 29 388 0.0671 0.0004 0.5312 0.0072 0.0575 0.0007 0.0208 0.0002 0.6723 0.0297 418 2 433 6 509 29 P1TW1.24 13 184 0.0670 0.0005 0.5380 0.0106 0.0583 0.0011 0.0196 0.0002 0.5327 0.0020 418 3 437 9 540 43 P1TW1.25 31 437 0.0683 0.0004 0.5208 0.0070 0.0553 0.0007 0.0190 0.0002 0.5053 0.0065 426 2 426 6 425 29 表 2 苏盖提力克花岗岩主量元素(%)和微量元素(×10-6)及相关参数
Table 2. Major elements (%) and trace elements (%) in sugaitlike granites and related parameters
样号 SiO2 TiO2 Al2O3 Fe2O3 FeO MnO MgO CaO Na2O K2O P2O5 Los La Ce Pr Nd Sm Eu P1YQ1 74.14 0.21 13.91 0.29 0.91 0.04 0.27 1.26 3.3 4.87 0.055 0.67 48.17 92.74 10.23 34.05 5.82 0.76 P1YQ2 73.53 0.25 14.08 0.84 0.57 0.028 0.23 1.29 3.22 4.86 0.085 0.93 63.76 118.7 13.12 43.92 7.64 0.86 P1YQ3 74.97 0.11 13.89 0.41 0.41 0.021 0.15 0.89 2.89 5.59 0.046 0.59 38.47 70.86 7.88 27.07 5.67 0.59 P1YQ4 73.61 0.19 14.09 0.32 1.08 0.035 0.35 1.35 3.18 4.74 0.069 0.9 48.23 91.21 9.95 33.12 6.08 0.7 P1YQ5 74.37 0.19 13.6 0.45 0.84 0.032 0.25 1.07 2.86 5.21 0.069 0.95 52.03 98.09 10.72 36.21 6.61 0.7 P1YQ6 72.53 0.3 14.23 0.49 1.34 0.038 0.48 1.73 3 4.82 0.08 0.85 65.54 122.4 12.67 41.38 6.56 0.93 样号 Gd Tb Dy Ho Er Tm Yb Lu Y Rb Sr Ba Ga Nb Ta Zr Hf Th P1YQ1 4.96 0.84 4.72 0.9 2.52 0.46 3.02 0.35 24.87 300.8 79.9 502.3 17.17 37.81 5.38 140.9 3.98 27.06 P1YQ2 6.2 0.91 4.25 0.73 1.95 0.3 2.38 0.28 20.21 313.8 63.2 472.7 20.15 46.07 4.85 183.8 5.16 21.61 P1YQ3 5.06 1.01 6.18 1.26 3.53 0.66 3.87 0.46 39.28 317.5 60.1 278.4 16.26 29.61 3.78 94.9 2.87 19.58 P1YQ4 5.01 0.82 4.32 0.82 2.23 0.38 2.22 0.29 24.72 240 98.1 658.9 17.75 28.87 3.9 130.5 3.26 26.6 P1YQ5 5.32 0.83 4.2 0.76 2.02 0.34 2.06 0.24 22.6 302.3 50.3 361.1 18.39 37.2 5.43 121.9 2.86 20.32 P1YQ6 5.47 0.77 4.02 0.78 2.13 0.36 2.04 0.23 22.69 268.2 135.1 1618 17.54 35.46 3.38 184.9 5.21 26.67 样号 V Cr Sc U AR K2O/Na2O A/CNK C Mg# ∑REE (La/Yb)N δEu (La/Sm)N (Gd/Yb)N (Ho/Yb)N Rb/Sr Rb/Ba Y/Yb P1YQ1 8.9 3.5 3.86 2.68 2.54 1.48 1.07 1.07 29 209.53 10.77 0.42 5.2 1.33 0.87 3.77 0.6 8.24 P1YQ2 14.7 4.9 3.4 4.94 2.44 1.51 1.09 1.39 25 265.04 18.07 0.37 5.25 2.1 0.9 4.97 0.66 8.5 P1YQ3 4.4 4.4 2.76 5 2.28 1.93 1.11 1.56 25 172.56 6.7 0.33 4.27 1.05 0.95 5.29 1.14 10.15 P1YQ4 11.7 5.3 3.47 2.02 2.4 1.49 1.1 1.42 32 205.37 14.64 0.38 4.99 1.82 1.07 2.45 0.36 11.12 P1YQ5 8.2 4.7 2.96 3.66 2.28 1.82 1.11 1.46 25 220.13 17.02 0.35 4.95 2.08 1.07 6.01 0.84 10.96 P1YQ6 20.3 5 3.77 2.39 2.2 1.61 1.08 1.1 32 265.27 21.66 0.46 6.29 2.16 1.12 1.99 0.17 11.12 -
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