| 喀拉昆仑火烧云一带早侏罗世双峰式火山岩的发现及意义 |
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| 引用本文： | 周能武,陈邦学,邓中飞,桑明帅,白权金.喀拉昆仑火烧云一带早侏罗世双峰式火山岩的发现及意义[J].现代地质,2019,33(5):990-1002. |
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| 作者姓名： | 周能武 陈邦学 邓中飞 桑明帅 白权金 |
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| 作者单位： | 新疆地质矿产勘查开发局 第十一地质大队,新疆 昌吉 831100 |
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| 基金项目： | 中国地质调查局西安地质调查中心项目(K15-1-LQ09) |
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| 摘 要： | 喀拉昆仑火烧云北火山岩发育在乔尔天山断裂附近,玄武岩体和安山岩体在时空上紧密伴生。主量元素测试结果显示,其中玄武岩和英安岩的Si O2含量分别为48.84%~52.44%和62.22%~65.63%,具有明显的Daly间断面,属于典型的双峰式火山岩。玄武岩Al2O3含量较低,MgO、Ca O、Ti O2含量较高,Sr、Ba、K等微量元素强烈亏损,高场强元素Ta、Nb、Ti、Zr无亏损。英安岩具有相对较高的Al2O3、Na2O、K2O含量,较低的MgO、Ca O、Ti O2含量;微量元素具富集大离子亲石元素(Rb、Th、U、K)、亏损高场强元素(Ta、Nb、Ti),显示典型岛弧环境特征。岩石地球化学特征表明二者同属钙碱系列,形成于弧后盆地,属同源演化,英安岩为玄武岩结晶分异的产物。通过对英安岩进行LA-ICP-MS锆石U-Pb方法测年,获得流纹岩形成年龄为(195.5±1.1)Ma,属于早侏罗世。通过对该区域构造演化进行分析讨论,认为乔尔天山一带盆地整体可能处于弧后盆地的发育阶段,盆地形成过程中岩石圈地幔未被拉断,没有洋壳形成。
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| 关 键 词： | 喀拉昆仑火烧云 双峰式火山岩 玄武质岩石 英安岩 |
| 收稿时间： | 2018-12-23 |
| 修稿时间： | 2019-05-22 |
Discovery and Significance of Early Jurassic Bimodal Volcanic Rocks in Huoshaoyun,Karakoram |
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| ZHOU Nengwu,CHEN Bangxue,DENG Zhongfei,SANG Mingshuai,BAI Quanjin.Discovery and Significance of Early Jurassic Bimodal Volcanic Rocks in Huoshaoyun,Karakoram[J].Geoscience——Journal of Graduate School,China University of Geosciences,2019,33(5):990-1002. |
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| Authors: | ZHOU Nengwu CHEN Bangxue DENG Zhongfei SANG Mingshuai BAI Quanjin |
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| Institution: | No.11 Geological Party, Xinjiang Bureau of Geology and Mineral Exploration and Development, Changji, Xinjiang 831100, China |
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| Abstract: | The Karakoram volcanic rocks are close to the Qiao’er Tianshan Fault, and the two are closely space-time related. The SiO2 contents of the basalt and dacite are of 48.84%-52.44% and 62.22%-65.63%, respectively. They have obvious Daly intercepts and are typically bimodal. Basalt has a low content of Al2O3, and high contents of MgO, CaO, TiO2. Some trace elements (Sr, Ba) are strongly depleted, whereas the high field strength elements (HFSEs, e.g.Ta, Nb, Ti, Zr) are not depleted. Dacite has relatively high Al2O3, Na2O and K2O contents, but low MgO, CaO and TiO2 contents, and are enriched in large ion lithophile elements (LILEs, e.g.Rb, Th, U, K), depleted of HFSEs, showing typical island arc geochemical affinity. Both the basalt and dacite are calc-alkaline, co-magmatic and likely formed in back-arc basins. Dacite may have formed from the fractionation of basaltic magma. LA-ICP-MS zircon U-Pb dating of the dacite yielded Early Jurassic age of (195.5±1.1) Ma. Considering the regional tectonic evolution, it is concluded that the Qiao’er Tianshan area may have been a developing backarc basin. We suggest that the lithospheric mantle of the basin during the volcanism had not been broken off and no oceanic crust was formed. |
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| Keywords: | Karakoram bimodal volcanism basaltic rock dacite |
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