| 东准噶尔南缘两套泥盆纪火山岩地球化学特征对比及其地质意义 |
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| 引用本文： | 赵浩,廖群安,罗婷,田锦明,张孟,王良玉,刘鸿飞.东准噶尔南缘两套泥盆纪火山岩地球化学特征对比及其地质意义[J].地球科学,2018,43(2):371-388. |
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| 作者姓名： | 赵浩 廖群安 罗婷 田锦明 张孟 王良玉 刘鸿飞 |
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| 作者单位： | 1.中国地质大学地球科学学院, 湖北武汉 430074 |
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| 基金项目： | 中国地质调查局项目DD20179607中国地质调查局项目12120114042801 |
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| 摘 要： | 东准噶尔一直以来都是研究新疆北部古生代洋陆格局和构造演化热点地区之一.前人对东准噶尔南缘火山岩的研究较为薄弱, 关注点多在石炭纪火山岩源区及构造属性上, 对泥盆纪火山岩构造背景和岩浆演化过程缺乏认识.对卡拉麦里蛇绿岩北侧的泥盆系北塔山组和乌鲁巴斯套组火山岩的岩石学、地球化学和年代学特征进行了详细研究, 结果表明:卡拉麦里北塔山组火山岩形成于早泥盆世晚期-中泥盆世早期(404 Ma), 具中-高钾、中钛、中铁和低铝的特征, 微量元素显示其富集LREE、LILE和亏损Nb、Ta, 推测其形成于洋壳俯冲的陆缘弧环境, 源区为受过俯冲沉积物熔体和流体交代的亏损地幔楔; 而莫钦乌拉中泥盆统乌鲁巴斯套组火山岩具贫碱、低钾、低钛、高铝等特征, 显示为典型的岛弧火山岩特征, 同位素和微量元素特征显示其来源于俯冲消减板片流体交代的亏损地幔楔.综合两套火山岩的差异特征和区域地质背景, 推测中泥盆纪卡拉麦里洋北向俯冲经历了由陆缘弧到岛弧的转变过程.
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| 关 键 词： | 东准噶尔 卡拉麦里 莫钦乌拉 泥盆纪 岛弧火山岩 陆缘弧 地球化学 地质年代学 |
| 收稿时间： | 2017-10-13 |
Geochemistry and Geological Implications of Two Sets of Devonian Volcanic Rocks in South Margin of East Junggar |
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| Abstract: | The East Junggar has always been one of study hotspots on the Paleozoic ocean-continent transformation and tectonic evolution of the northern Xinjiang.However, studies of volcanic rocks in the south margin of the East Junggar are relatively weak since studies focus more on the origin and structural attributes of Carboniferous volcanic rocks, resulting in a lack of understanding of the tectonic setting and magmatic evolution of the Devonian volcanic rocks.Here we report a detailed petrologic, geochemical and geochronologic analyses on the Devonian volcanic rocks from the Beitashan and Wulubasitao Formations in the northern of the Karamaili ophiolite, to examine its formation environment and magma origin.Combining with the previous works in this region, our study reveals that the volcanic rocks of the Beitashan Formation from the Karamaili formed during the Early Devonian to Middle Devonian (404 Ma), which is characterized by intermediate-high K, Ti and Fe, low Al2O3 levels, enriched in LREE and LILE, and relatively depleted in HFSE (Nb, Ta).These rocks was probably formed in a continental marginal arc construction environment and the magma is originated from a depleted mantle wedge metasomatismed by melt and fluid from subduction sediment.For the Wulubasitao Formation, the volcanic rocks formed during the Middle Devonian (MoQinulla), characterized by poor alkali, low K, Ti, Fe and high Al, indicating typical island arc volcanic rocks.Isotope and trace element characteristics show it was derived from depleted mantle wedge metasomatismed by fluid from subducted plate.According to the differences of two volcanic rocks features as well as regional geology, we speculate that the subduction of the Karamaili ocean transformed from continental marginal arc to island arc during the Middle Devonian. |
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