Discovery of Late Devonian monzogranite from the Eastern Tianshan, and its constrains on the tectonic evolution of the Aqishan-Yamansu belt
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摘要:
阿奇山—雅满苏带位于东天山南部, 属于中亚造山带的重要组成部分, 其内发育大量岩浆岩, 形成时代主要为石炭纪—二叠纪。目前为止, 尚未有早期岩石的报道。对位于该区南缘的二长花岗岩进行了LA-MC-ICP-MS锆石U-Pb同位素测年研究。结果显示, 二长花岗岩中锆石呈自形—半自形, 具有明显的振荡环带, Th/U值均大于0.4, 显示岩浆锆石特征。这些锆石的206Pb/238U年龄加权平均值为374.7±4.0 Ma (MSWD=0.7, n=17), 代表岩浆结晶年龄。表明研究区存在晚泥盆世岩浆事件, 阿奇山—雅满苏带的形成至少开始于晚泥盆世。二长花岗岩的形成时代和中天山晚泥盆世岛弧环境岩浆岩形成时代一致, 表明其可能是古大洋板片向南俯冲的产物。
Abstract:The Aqishan-Yamansu belt, located at south of the Eastern Tianshan belt, is a pivotal part of the Central Asian orogenic belt.The most important feature of the Aqishan-Yamansu belt is the occurrence of voluminous igneous rocks, which mainly formed during Carboniferous and Permain with no pre-Carboniferous age has been reported.We present zircon LA-MC-ICP-MS U-Pb chronology of monzogranite, discovered on the southern margin of the Aqishan-Yamansu belt.The zircons from the monzogranite are mostly euhedral to subhedral, with oscillatory zoning and Th/U ratios more than 0.4, suggesting magmatic origin.Therefore, the obtained weighted mean 206Pb/238U age of 374.7±4.0 Ma (MSWD=0.7, n=17) can be used to represent the magma crystallization age.This result suggests that a magmatic event occurred during Late Devonian and formation of the Aqishan-Yamansu belt possibly began in Late Devonian at latest.Combined with the Late Devonian magmatism formed in arc environment in Central Tianshan, we concluded that the monzogranite may have been produced by the southward subduction of ancient oceanic plate beneath the Central Tianshan during Late Devonian.
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Key words:
- Aqishan-Yamansu belt /
- monzogranite /
- zircon U-Pb age /
- Late Devonian /
- tectonic evolution
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图 2 雅南二长花岗岩侵入体地质图(据参考文献①修改)
Figure 2.
表 1 雅南二长花岗岩锆石U-Th-Pb同位素测年结果
Table 1. Zircon U-Th-Pb dating results of Ya'nan monzogranite
测点号 含量/10-6 Th/U 同位素比值 年龄/Ma Pb Th U 207Pb/206Pb 1σ 207Pb/235U 1σ 206Pb/238U 1σ 207Pb/ 206Pb 1σ 206Pb/ 238U 1σ 207Pb/ 235U 1σ 1 34 306 475 0.64 0.055 26 0.001 08 0.455 65 0.011 04 0.060 55 0.001 37 433 41 379 8 381 8 2 109 1593 1170 1.36 0.055 51 0.001 03 0.455 44 0.015 00 0.060 01 0.002 19 432 44 376 13 381 10 3 35 439 494 0.89 0.054 67 0.000 68 0.452 83 0.009 56 0.060 82 0.001 36 398 28 381 8 379 7 4 36 349 571 0.61 0.053 89 0.001 66 0.455 50 0.026 21 0.060 69 0.002 55 365 69 380 16 381 18 5 35 408 502 0.81 0.054 79 0.000 72 0.452 09 0.009 31 0.060 09 0.001 19 467 30 376 7 379 7 6 31 330 465 0.71 0.051 22 0.000 89 0.418 15 0.010 69 0.061 62 0.001 96 250 40 385 12 355 8 7 30 301 435 0.69 0.051 94 0.000 81 0.445 31 0.011 81 0.062 65 0.001 57 283 36 392 10 374 8 8 28 260 426 0.61 0.053 99 0.000 79 0.450 18 0.012 82 0.060 98 0.001 66 372 33 382 10 377 9 9 67 787 940 0.84 0.054 63 0.000 67 0.449 71 0.011 84 0.060 00 0.001 59 398 27 376 10 377 8 10 29 306 438 0.70 0.055 74 0.000 72 0.444 97 0.012 35 0.058 50 0.001 57 443 29 366 10 374 9 11 54 550 814 0.68 0.055 19 0.000 65 0.453 58 0.010 96 0.059 64 0.001 33 420 27 373 8 380 8 12 95 883 1452 0.61 0.055 65 0.001 10 0.444 23 0.012 25 0.059 20 0.001 77 439 44 371 11 373 9 13 88 730 1353 0.54 0.053 13 0.000 53 0.436 74 0.010 07 0.060 02 0.001 41 345 25 376 9 368 7 14 58 644 825 0.78 0.055 86 0.001 22 0.446 45 0.011 44 0.058 63 0.001 28 456 49 367 8 375 8 15 25 245 337 0.73 0.052 02 0.001 84 0.426 84 0.014 40 0.060 72 0.001 46 287 79 380 9 361 10 16 89 971 1314 0.74 0.057 04 0.000 73 0.448 73 0.007 39 0.057 81 0.001 09 494 29 362 7 376 5 17 23 219 327 0.67 0.052 38 0.001 49 0.430 94 0.014 41 0.059 57 0.000 75 302 65 373 5 364 10 表 2 阿奇山—雅满苏带岩浆侵入体侵位年龄
Table 2. Age data for magmatic intrusions in the Aqishan-Yamansu belt
岩体名称 岩性 测年方法 年龄/Ma 资料来源 岩体名称 岩性 测年方法 年龄/Ma 资料来源 西凤山 钾长花岗岩 锆石LA-ICPMS U-Pb 349±3 [10] 多头山 二长花岗岩
英安玢岩锆石LA-ICPMS U-Pb
锆石LA-ICPMS U-Pb318±3
197±4[17]
[17]石英滩 钾长花岗岩 锆石LA-ICPMS U-Pb 342±11 [10] 红云滩 花岗闪长岩 锆石LA-ICPMS U-Pb 329±9 [34] 赤龙峰 黑云闪长岩
花岗闪长岩
正长岩锆石LA-ICPMS U-Pb
锆石LA-ICPMS U-Pb
锆石LA-ICPMS U-Pb317±1
306±2
253±1[38]
[38]
[38]长条山 石英闪长岩 锆石LA-ICPMS U-Pb 337±3 [10] 百灵山 花岗闪长岩 锆石LA-ICPMS U-Pb 318±4 [10] 花岗闪长岩 锆石LA-ICPMS U-Pb 318±2 [35] 红山梁 花岗斑岩
花岗闪长岩
二长花岗岩锆石LA-ICPMS U-Pb
锆石LA-ICPMS U-Pb
锆石LA-ICPMS U-Pb343±2
250±4
236±2[6]
[6]
[6]二长花岗岩 锆石LA-ICPMS U-Pb 314±2 [35] 花岗岩 锆石LA-ICPMS U-Pb 307±2 [35] 闪长岩包体 锆石LA-ICPMS U-Pb 329±2 [5] 维权 花岗岩 锆石SHRIMP U-Pb 297±3 [39] 闪长岩 锆石LA-ICPMS U-Pb 323±3 [5] 陇东 二长花岗岩 锆石LA-ICPMS U-Pb 276±3 [10] 二长花岗岩 锆石LA-ICPMS U-Pb 313±2 [5] 土墩 钾长花岗岩 锆石LA-ICPMS U-Pb 246±3 [10] 花岗闪长岩 锆石LA-ICPMS U-Pb 308±2 [5] 雅满苏 花岗岩 锆石LA-ICPMS U-Pb 227~230 [18] 阿奇山 花岗闪长岩 锆石LA-ICPMS U-Pb 336±3 [36] 雅满苏北 钾长花岗岩 锆石LA-ICPMS U-Pb 230±1 [1] 钠长斑岩 锆石LA-ICPMS U-Pb 333±3 [36] 花岗岩 锆石LA-ICPMS U-Pb 223±1 [40] 钾长花岗岩 锆石LA-ICPMS U-Pb 292±3 [36] 黑峰山 闪长岩 锆石LA-MC-ICPMS U-Pb 274±2 [16] 二长花岗岩 锆石LA-ICPMS U-Pb 281±2 [36] 花岗岩 锆石LA-MC-ICPMS U-Pb 274±3 [16] 鄯善采石场 正长花岗岩 锆石LA-MC-ICPMS U-Pb 272±3 [22] 突出山 花岗岩 锆石LA-MC-ICPMS U-Pb 317±2 [16] 二长花岗岩 锆石LA-MC-ICPMS U-Pb 251±4 [22] 闪长岩 锆石LA-MC-ICPMS U-Pb 326±2 [16] 钾长花岗岩 单颗粒锆石U-Pb 230±2 [37] 沙泉子 闪长岩 锆石LA-MC-ICPMS U-Pb 276±1 [16] 多头山 钾长花岗岩 锆石LA-ICPMS U-Pb 272±6 [10] 闪长岩 锆石LA-ICPMS U-Pb 299±5 [23] 花岗斑岩 锆石LA-ICPMS U-Pb 316±8 [17] 白石泉 钾长花岗岩 锆石LA-ICPMS U-Pb 303±18 [10] -
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① 新疆维吾尔自治区地质矿产勘查开发局第一区域地质调查大队,雅满苏镇幅(K46C003003幅)1:25万区域地质调查报告.2013.
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