| 内蒙古乌兰浩特地区正长花岗岩LA-ICP-MS锆石U-Pb年龄及其地质意义 |
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| 作者姓名： | 邱锦雄 杨亮 陈萌超 王文义 高勇 |
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| 作者单位： | 内蒙古地质矿产勘查院,呼和浩特 010010 |
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| 基金项目： | 中国地质调查局“内蒙古1:5万哈尔居日和(L51E009008)、巴达荣贵(L51E010007)、西巴达嘎(L51E010008)幅区域地质矿产调查(编号: 12120114013101)”项目资助 |
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| 摘 要： | 为探讨乌兰浩特地区正长花岗岩形成时代及其构造环境,对其进行锆石U-Pb年龄和岩石地球化学研究。结果表明: LA-ICP-MS锆石U-Pb年龄为(219.7±1.2) Ma,代表了其成岩年龄; 岩石高硅、高碱,贫铝、钙、镁、铁; 岩石稀土含量偏高,轻重稀土分馏不明显,Eu负异常明显; 在微量元素上,富集大离子亲石元素Rb、K,贫Sr、Eu、Ba,富高场强元素U、Th、Hf、HREE,贫Ti; 10 000×Ga/Al值(3.53~5.09)均大于A型花岗岩的下限值(2.6),明显高于I型和S型花岗岩的平均值(分别为2.10和2.28)。因此,晚三叠世正长花岗岩为A型花岗岩,推断其形成于古亚洲洋闭合后的造山后岩石圈伸展构造环境。
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| 关 键 词： | 乌兰浩特 锆石U-Pb年龄 岩石地球化学 A型花岗岩 伸展构造环境 |
| 收稿时间： | 2018-05-09 |
LA-ICP-MS zircon U-Pb age of the syengranite in Ulanhot region of Inner Mongolia,and its geological significance |
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| Authors: | QIU Jinxiong YANG Liang CHEN Mengchao WANG Wenyi GAO Yong |
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| Institution: | Inner Mongolia Institute of Geological Survey and Mineral Exploration, Hohhot 010010, China |
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| Abstract: | In order to investigate the formation age and tectonic background of the syengranite in Ulanhot region, the authors have studied its zircon U-Pb age and geochemical characteristics. The results show that LA-ICP-MS zircon U-Pb age is (219.7±1.2)Ma, which represents its formation age. The syengranite is rich in silicon and alkali, while the content of aluminum, calcium, magnesium and iron is low. These rocks also have high rare-earth elements content, inapparent fractional distillation between light rare-earth elements and heavy rare-earth elements, and obvious negative abnormal Eu. For the trace elements, these rocks are rich in large ion lithophile elements (Rb and K) and high field strength elements( U, Th, Hf and HREE), while they are poor in Sr, Eu, Ba and Ti. The 10 000×Ga/Al value (3.53 ~ 5.09) is higher than the lower limit value (2.6) of A-type granite, and significantly higher than the average value of the I-type and S-type granites (2.10 and 2.28, respectively). Therefore, the authors concluded that Triassic syenogranite is A-type granite, and the formation environment belongs to post-orogenic lithospheric extension tectonic setting after the closure of Paleo-Asian Ocean. |
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| Keywords: | Ulanhot zircon U-Pb age rock geochemistry A-type granite extension tectonic setting |
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