| 准噶尔盆地东部北三台地区石炭系火山岩的锆石U-Pb年代学、地球化学特征及其构造意义 |
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| 作者单位： | 中国石油新疆油田分公司准东采油厂 新疆阜康 831511；
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大陆动力学国家重点实验室，西北大学 西安 710069 |
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| 摘 要： | 准噶尔盆地北三台地区钻井岩心获得的巴塔玛依内山组火山岩主要由玄武岩、玄武安山岩、安山岩和英安岩及部分火山碎屑岩组成。地球化学研究结果显示，火山岩为低TiO2、高Na2O的钙碱性系列，具低到中度轻、重稀土分馏的谱型，相对富集大离子亲石元素，贫高场强元素，明显亏损Nb和Ta、富集Pb；由基性到中酸性火山岩。Sr、Ti和P的亏损逐渐增大，证明是与大洋俯冲相关的岛弧环境同源岩浆演化的产物。LA-ICP-MS锆石U-Pb定年分别获得安山岩和英安岩325～321Ma和310 Ma的形成年龄，结合前人同层位获得基性火山岩300 Ma的形成年龄认为，准噶尔洋在盆地东部的俯冲作用一直延续至晚石炭世，大洋闭合可能发生在晚石炭世末期。
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| 收稿时间： | 2017-10-20 |
Zircon U-Pb ages and geochemical characteristics of the Carboniferous volcanic rocks in the Beisantai area,eastern Junggar and their tectonic implications |
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| Abstract: | The volcanic rocks from the Batamayineishan Formation in the Beisantai area are mainly composed of basalt, basaltic andesite, andesite and dacite, with minor volcaniclastic rocks. These rocks have low TiO2 and high Na2O, indicating characteristics of calc-alkaline series. Geochemical research result shows that they are characterized by LREE-enriched patterns with slightly negative Eu anomalies. The rocks have high large ion lithophile element（LILE）, and low high field strength element（HFSE）concentrations with strong negative Nb, Ta and Ti anomalies. From basic through intermediate to felsic, the depletions in Sr, Ti and P of the studied volcanic rocks increase gradually. These geochemical characteristics indicate that the volcanic rocks are products of mantle-derived magma related to oceanic subduction in an island-arc setting. The LA-ICP-MS zircon U-Pb dating of the andesite and the dacite yielded ages at 325～321 Ma and 310 Ma, respectively. In combination with the published age（300 Ma）of basalts from this formation, it is inferred that subduction of the Junggar ocean in eastern Junngar Basin lasted to the Late Carboniferous. Consequently, the final closure of the Junggar ocean occurred most likely after 310 Ma. |
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