| 新疆南天山开都河火山岩地球化学特征、锆石 LA-ICP-MS年代学及其意义 |
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| 引用本文： | 高睿,肖龙,王绘清,王国灿,罗彦军,刘函.新疆南天山开都河火山岩地球化学特征、锆石 LA-ICP-MS年代学及其意义[J].岩石矿物学杂志,2012,31(4):541-553. |
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| 作者姓名： | 高睿 肖龙 王绘清 王国灿 罗彦军 刘函 |
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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
2. 天津华北地质勘查局,天津,300170 |
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| 基金项目： | 中石化海相油气勘探前瞻性项目“中国西北地区构造-岩相古地理研究与编图资助项目”(07370502000130)之子项目《塔里木区块构造-岩相古地理研究与编图》 |
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| 摘 要： | 位于塔里木-卡拉库姆板块与伊犁-哈萨克斯坦板块之间的南天山造山带是最具代表性的造山带之一,其中发育一条不完整的蛇绿岩带——南天山南缘库勒湖-科克铁克达坂蛇绿岩带,暗示古缝合线的存在。该蛇绿岩带北面的开都河水电站泥盆纪地层中发育一套中酸性火山岩(包括熔结凝灰岩、含晶屑酸性玻璃质熔岩和安山岩等),属于碱性-钙碱性系列,A/CNK值在0.82~1.31之间;该套岩石整体REE含量较高,轻重稀土元素分异显著,轻稀土元素相对富集,重稀土元素亏损,并具强烈的Eu负异常。对熔结凝灰岩中岩浆锆石进行LA-ICP-MS U-Pb定年,获得其结晶年龄为393.1±3.4 Ma,与中泥盆统(D2)萨阿尔明组一致。岩石地球化学研究表明,安山岩可能来自于玄武岩分离结晶;熔结凝灰岩、含晶屑酸性玻璃质熔岩来自于上地壳部分熔融。推测其形成机制是:库勒洋盆在中泥盆世向北俯冲消减过程中释放出流体,导致地幔楔发生部分熔融并形成玄武质岩浆,部分玄武质岩浆结晶分异形成安山岩,随着俯冲持续和地壳不断加厚,玄武质岩浆对上部地壳加热使得其发生部分熔融形成酸性母岩浆,并最终喷发至地表形成熔结凝灰岩和含晶屑酸性玻璃质熔岩。
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| 关 键 词： | 南天山 熔结凝灰岩 LA-ICP-MS 锆石年龄 俯冲消减 |
| 收稿时间： | 2011/3/20 0:00:00 |
| 修稿时间： | 2012/5/14 0:00:00 |
Geochemical characteristics and LA-ICP-MS U-Pb zircon ages of volcanic rocks in Kaidu River, South Tianshan, Xinjiang, and their geological significance |
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| GAO Rui,XIAO Long,WANG Hui-qing,WANG Guo-can,LUO Yan-jun and LIU Han.Geochemical characteristics and LA-ICP-MS U-Pb zircon ages of volcanic rocks in Kaidu River, South Tianshan, Xinjiang, and their geological significance[J].Acta Petrologica Et Mineralogica,2012,31(4):541-553. |
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| Authors: | GAO Rui XIAO Long WANG Hui-qing WANG Guo-can LUO Yan-jun and LIU Han |
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| Institution: | 1(1.Faculty of Earth Science,China University of Geosciences,Wuhan 430074,China;2.Tianjin North China Geological Exploration Bureau,Tianjin 300170,China) |
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| Abstract: | South Tianshan orogeny is a typical orogenic belt between Tarim-Kalakumu plate and Yili-Kazakhstan plate.Kulehu-Keketiekedaban ophiolitic mélange is exposed in the south margin of the South Tianshan.Kaidu River section is located on the northern margin of Kulehu-Keketiekedaban ophiolite mélange in South Tianshan.In the section,Devonian volcanic rocks composed of ignimbrite,crystal pyroclastic-bearing felsic glassy lava and andesite were discovered.The Devonian volcanic rocks are of alkaline to calc-alkaline series,with A/CNK being 0.82～1.31.The ignimbrite is characterized by high content of REE and strongly enriched and highly-fractionated LREE,with low fractionated HREE and strong negative Eu anomalies.The LA-ICP-MS U-Pb age of zircons from ignimbrite is 393.1±3.4 Ma,suggesting that Saerming Formation belongs to Middle Devonian indeed. The age 393.1 Ma restricts the subduction time of the Kule Ocean basin.Kule Ocean basin started subduction in Middle Devonian(393.1 Ma),which released fluids and resulted in melting of mantle wedge to form basaltic magma.Thus,andesite was formed by fractionation and crystallization of the basaltic magma.When the crust was thickened,the basaltic magma continually ascended upward to cause the melting of the upper crust.Finally,the ignimbrite and crystal pyroclastic-bearing felsic glassy lava were erupted. |
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| Keywords: | South Tianshan ignimbrite LA-ICP-MS zircon age subduction |
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