| 兴安地块南段乌兰复合岩体年代学、地球化学及其地质意义 |
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| 作者姓名： | 郝书清 贾士影 戎秀伟 |
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| 作者单位： | 1.山西省第三地质工程勘察院有限公司,山西 晋中 030620;2.山西省 自然资源事业发展中心,山西 太原 030024 |
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| 摘 要： | 兴蒙造山带北缘晚古生代的构造格局,尤其是洋盆的闭合时限一直存在争议,兴安地块南的乌兰复合岩体为解决这一问题提供了一个良好的研究窗口。对乌兰复合岩体进行了锆石U-Pb测年与地球化学特征研究,确定了其形成时代与岩石成因,进而揭示了区域构造背景。乌兰复合岩体由细粒二长花岗岩和斑状二长花岗岩组成,前者构成了岩体的主体,成岩年龄为(312±2) Ma,形成时代为晚石炭世早期。地球化学特征显示: 细粒二长花岗岩和斑状二长花岗岩均具有全碱含量中等、富钾、过铝质的特征,为高钾钙碱性系列的高分异S型花岗岩,且细粒二长花岗岩的稀土含量偏低,负Eu异常更明显,显示了更高的分异演化特征; 细粒二长花岗岩和斑状二长花岗岩均富集大离子亲石元素(Rb、Th及K),显著亏损Ba、Sr、Ti等元素,弱亏损Ta、Nb等元素,具有相似的微量元素与稀土元素分布特征,指示二者来自于同一源区。乌兰复合岩体的形成与古亚洲洋的演化有关,形成于洋盆闭合后的造山晚期伸展环境。
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| 关 键 词： | 乌兰复合岩体 S型花岗岩 地球化学 兴安地块 古亚洲洋 |
| 收稿时间： | 2021-04-13 |
Geochronology,geochemistry and geological significance of the Wulan composite pluton in the southern Xing'an block |
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| Authors: | HAO Shuqing JIA Shiying RONG Xiuwei |
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| Institution: | 1. Shanxi Third Geological Engineering Investigation Institute Co., ltd, Shanxi Jinzhong 030620, China;2. Natural Resources Development Center of Shanxi Province, Shanxi Taiyuan 030024, China |
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| Abstract: | There are some existing debates about the Late Paleozoic tectonic framework of the northern margin of the Xing'an-Mongolian orogenic belt, especially the final closing time of oceanic basin. Wulan composite Pluton in the southern Xing'an block provides a good medium to address this problem. In this paper, the Zircon LA-ICP-MS U-Pb ages and geochemical characteristics of Wulan composite Pluton were studied to determine its formation epoch and petrogenesis, and to reveal the regional tectonic setting. Wulan composite Pluton is composed of fine grained monzogranite and porphyritic monzogranite, the former constitutes the main body of the rock mass, with the diagenetic age of (312±2) Ma, which was formed in early Late Carboniferous. Geochemical analyses indicates that both of the fine grained monzogranite and porphyritic monzogranite have the characteristics of medium total alkali content, rich in K and peraluminous, belonging to highly fractionated S-type granite of high-K calc-alkaline series. The total REE contents of main rock mass of fine grained monzogranite are relatively low, with obvious negative Eu anomalies, showing high differential evolution character. Both the fine grained monzogranite and porphyritic monzogranite are rich in large ion lithophylic elements (Rb, Th and K), and obviously depleted in Ba, Sr and Ti, with slightly depleted in Ta and Nb. These two types of rocks have characterastics of similar trace and rare earth elements distribution, indicating that they come from the same source region. The formation of the rock mass is related to the evolution of the ancient Asian ocean and was formed in the late orogenic extensional environment after the oceanic basin was closed. |
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| Keywords: | Wulan composite pluton S-type granite geochemistry Xing'an Block Paleo-Asian Ocean |
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