东天山板块缝合带石炭纪火山岩地球化学和Sr-Nd同位素特征及其大地构造意义

J4 ›› 2012, Vol. 42 ›› Issue (2): 400-409.

东天山板块缝合带石炭纪火山岩地球化学和Sr-Nd同位素特征及其大地构造意义

曹锐¹|木合塔尔·扎日²|陈斌^2,3|李德威¹|曹福根⁴|刘德民¹

1.中国地质大学地球科学学院|武汉430074;
2.新疆大学地质与勘查工程学院|乌鲁木齐830046;
3.北京大学地球与空间科学学院|北京100871;
4.新疆地矿局第一区域地质调查大队|乌鲁木齐830000

收稿日期:2011-07-10 出版日期:2012-03-26 发布日期:2012-03-26
通讯作者: 陈斌（1964-），男，教授，博士生导师，主要从事岩浆作用与成矿机制方面研究 E-mail:binchen@pku.edu.cn
作者简介:曹锐(1984-)|男|博士|主要从事构造地质学和岩石地球化学方面研究|E-mail:rcao318@gmail.com
基金资助:
国家自然科学基金项目(41162006,40862006)；新疆大学天山学者启动基金(陈斌)；新疆中亚造山带大陆动力学与成矿预测实验室开放基金项目(XJDX1102201107)

Geochemistry and Sr-Nd Isotopic Characteristics of the Carboniferous Volcanic Rocks from the Eastern Tianshan Suture Zone and Tectonic Implications

Cao Rui¹,Muhetaer Za-ri²,Chen Bin^2,3,Li De-wei¹,Cao Fu-gen⁴,Liu De-min¹

1.College of Earth Sciences, China University of Geosciences, Wuhan430074,China;
2.Institute of Geology and Exploration Engineering, Xinjiang University, Urumqi830046, China;
3.School of Earth and Space Sciences, Peking University, Beijing100871, China;
4.The No.1 Institute of Geological Survey, Geological Bureau of Xinjiang, Urumqi830000, China

Received:2011-07-10 Online:2012-03-26 Published:2012-03-26

摘要/Abstract

摘要：

对东天山沿康古尔塔格缝合带分布的企鹅山群和梧桐窝子组火山岩的地球化学特征及Rb-Sr和Sm-Nd同位素进行了系统研究。结果显示：企鹅山群火山岩富集LREE，Eu异常变化较大（从明显负异常到微弱正异常），富集Sr、Ba和U等大离子亲石元素，相对亏损Nb、Zr、Ti等高场强元素,Sr-Nd同位素特征是I_Sr=0.703 97~0.704 26，ε_Nd(t)=5.61~6.99，具有亏损地幔性质，表明其岩浆源区可能来自古生代期间被古亚洲洋俯冲板片释放的流体/熔体交代过的岩石圈地幔楔;梧桐窝子组玄武岩富集轻稀土元素(LREE)和大离子亲石元素，而高场强元素没有明显负异常，样品的ε_Nd值都在9以上，I_Sr(330 Ma)为0.704 71~0.705 33，表明梧桐窝子组玄武岩可能来自亏损的软流圈地幔的部分熔融。企鹅山群和梧桐窝子组火山岩在Zr-Zr/Y判别图解中分别落在岛弧拉斑玄武岩（IAB）和板内玄武岩（WPB）范围内，表明企鹅山群可能为准噶尔洋盆向南俯冲形成的石炭纪岛弧火山岩，而梧桐窝子组火山岩可能形成于在弧后盆地的基础上拉张为裂陷槽的伸展环境。

关键词: 玄武岩, 微量元素, Sr-Nd同位素, 东天山

Abstract:

Geochemistry, Rb-Sr and Sm-Nd isotopic compositions of the volcanic rocks, from the Qi’eshan Group and Wutongwozi Formation in the eastern Tianshan plate suture zone have been studied in this paper. The basalt from the Qi’eshan Group is highly enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) such as Sr, Ba and U, and depleted in high field strength elements (Nb, Ti and Zr), with variable Eu anomalies (varying from significant negative Eu anomalies to minor positive Eu anomalies) in the chondrite-normalized REE patterns. It is charactered by isotopic signatures of depleted mantle source, with ε_Nd(t)=5.61-6.99, and I_Sr(330 Ma)=0.703 97-0.704 26. All these geochemical characteristics suggest that the basalt in Qi’eshan Group probably was derived from the lithospheric mantle wedge previously metasomatized by fluids/melts released from the down-going paleo-Asian oceanic slab in the Paleozoic period. The basalt from the Wutongwozi Formation is characterized by enrichment of LREEs and LILEs, without obvious negative anomalies of high field strength elements. High and positive Nd values (>+9) and relatively low ISr ratios (0.704 71-0.705 33) suggest that the basalt in the Wutongwozi Formation was derived from partial melting of the depleted asthenospheric mantle. In the Zr-Zr/Y discrimination diagram, samples from the Qi’eshan Group are mainly plotted in the field of island arc basalt (IAB), while, those from the Wutongwozi Formation in the field of within plate basalt (WPB). It’s suggested that the Qi’eshan Group formed in an island arc setting owing to the southward subduction of the Junggar oceanic slab, while the Wutongwozi Formation formed in a rifting setting that was developed upon the extensional back-arc basin.

Key words: basalt, trace elements, Sr-Nd isotopes, eastern Tianshan Mts

中图分类号:

P595

曹锐, 木合塔尔·扎日, 陈斌, 李德威, 曹福根, 刘德民. 东天山板块缝合带石炭纪火山岩地球化学和Sr-Nd同位素特征及其大地构造意义[J]. J4, 2012, 42(2): 400-409.

CAO Rui, MUHETAER Za-ri, CHEN Bin, LI De-wei, CAO Fu-gen, LIU De-min. Geochemistry and Sr-Nd Isotopic Characteristics of the Carboniferous Volcanic Rocks from the Eastern Tianshan Suture Zone and Tectonic Implications[J]. J4, 2012, 42(2): 400-409.

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