| 东天山巴里坤地区晚石炭世双峰式火山岩年代学、地球化学及其构造意义 |
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| 引用本文： | 罗婷,陈继平,廖群安,王国灿,胡朝斌,王良玉.东天山巴里坤地区晚石炭世双峰式火山岩年代学、地球化学及其构造意义[J].地球科学,2018,43(9):3018-3035. |
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| 作者姓名： | 罗婷 陈继平 廖群安 王国灿 胡朝斌 王良玉 |
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| 作者单位： | 1.陕西省地质调查实验中心, 陕西西安 710054 |
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| 基金项目： | 中国地质调查局项目1212011120509中国地质调查局项目DD20160006中国地质调查局项目12120114042801中国地质调查局项目1212011120503 |
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| 摘 要： | 新疆东天山博格达-哈尔里克造山带巴里坤地区晚石炭世双峰式火山岩很好地记录了中亚造山带西南缘晚古生代时期洋陆转换阶段复杂的岩浆作用过程，对该过程的详细剖析能更好地理解中亚造山带的地质历史.通过对晚石炭统二道沟组火山岩详细的岩石学、地球化学、锆石U-Pb年代学和Sr-Nd同位素组成的研究，结合区域上已有的研究成果，获得了如下认识:（1）东天山博格达-哈尔里克造山带晚石炭统二道沟组火山岩形成于晚石炭世早期（308~312 Ma），为陆相喷发的产物.火山岩具明显的双峰式组合特征，基性火山岩端元由高钾-钾玄岩系列的玄武岩、粗面玄武岩、玄武粗安岩及同成分的火山碎屑岩组成；酸性火山岩端元由粗面岩、流纹岩组成.（2）岩石地球化学和同位素特征显示，该套双峰式火山岩具有相似的地球化学特征，是相同源区岩浆演化的产物，为深部受到俯冲流体交代的软流圈上涌（尖晶石-石榴石橄榄岩5%~25%部分熔融）形成具有明显Nb、Ta亏损的基性火山岩，岩浆经过结晶分异作用形成酸性火山岩，进而形成晚石炭世双峰式火山岩组合.（3）该套双峰式火山岩是早石炭世双峰式火山岩的延续，代表了该区域弧后盆地基础上的持续裂开.
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| 关 键 词： | 双峰式火山岩 晚石炭世 东天山 地球化学 岩石学 |
| 收稿时间： | 2018-01-06 |
Geochronology,Geochemistry and Geological Significance of the Late Carboniferous Bimodal Volcanic Rocks in the Balikun Area,Eastern Tianshan |
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| Abstract: | The bimodal volcanic rocks distributed in the Balikun area are important to study on the timing of oceanic closure and the tectonic transition process of the Central Asian orogenic belt (CAOB), which are critical to deciphering the geological history of CAOB. In this paper, data on major and trace elements and Sr-Nd isotopes of whole rocks, and in-situ U-Pb age of zircons are reported for Carboniferous volcanic rocks in the Balikun area, in order to investigate their sources, petrogenesis and implications for the Carboniferous evolution of study area. The main results are obtained as follows:(1) Late Carboniferous volcanic rocks from Erdaogou Formation, mainly basalts, trachybasalts, basaltic-trachyandesite, trachyte rhyolitic and volcaniclastics, are bimodal volcanic rocks. The zircon U-Pb age of the Erdaogou basaltic-trachyandesite and trachybasalt and rhyolite yield a early Late Carboniferous age (312±4 Ma, 312±3 Ma and 308±3 Ma respectively). (2) The basaltic volcanic rocks and the acidic volcanic rocks from Erdaogou Formation show the same magma source. The Erdaogou basaltic volcanic rocks were derived from mantle which were modified by slab fluids at an rifting stage. The magma was derived by partial melting (5%-25%) of asthenosphere mantle. The acid rocks were generated from the direct fractional crystallization of basaltic magma. (3) Two episodes of Late Paleozoic bimodal suites have been identified and it is proposed that the essentially bimodal character of the complex reflects the features of back-arc rifting magmatism in Balikun area. |
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