| 北山北带新元古代岩浆记录:来自内蒙古哈珠地区片麻状花岗岩的证据 |
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| 引用本文： | 牛文超,任邦方,任云伟,段霄龙,段连峰,孙立新,李敏,张家辉.北山北带新元古代岩浆记录:来自内蒙古哈珠地区片麻状花岗岩的证据[J].地球科学,2019,44(1):284-297. |
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| 作者姓名： | 牛文超 任邦方 任云伟 段霄龙 段连峰 孙立新 李敏 张家辉 |
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| 作者单位： | 1.中国地质调查局天津地质调查中心, 天津 300170 |
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| 基金项目： | 中国地质调查局项目DD20179382国家自然科学基金项目41572172中国地质调查局项目12120114064601中国地质调查局项目DD20160039中国地质调查局项目DD20160039-17 |
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| 摘 要： | 北山造山带位于中亚造山系中段，带内各古老陆块的前寒武纪演化历史是了解北山造山带形成和演化的关键问题.本文选取北山北带哈珠地区片麻状花岗岩进行了锆石U-Pb年代学和地球化学分析.结果显示哈珠地区片麻状花岗岩形成于885±4 Ma，首次揭示了北山北带存在新元古代岩浆活动.哈珠片麻状花岗岩主量元素具有高SiO2、低CaO、高K2O+Na2O的特征，铝饱和指数A/CNK>1，属过铝质高钾钙碱性花岗岩.稀土元素球粒陨石标准化曲线呈现出轻稀土富集，重稀土亏损，铕强烈负异常的右倾海燕型；微量元素显示岩石富集Rb、K、Th、U等大离子亲石元素，亏损Nb、Sr、P、Ti等高场强元素.岩石成因分析表明其为S型花岗岩，岩浆来源于变质杂砂岩部分熔融的源区，且初始熔融温度较高（777~798℃）.构造环境判别图解显示其形成于碰撞后由挤压转向伸展的背景，为大陆碰撞的产物.通过与北山南带和东天山地块前寒武纪资料的对比，结果表明北山南带、北山北带和天山造山带中各古老陆块在前寒武纪可能具有一致的演化历史，其共同参与了新元古代Rodinia超大陆的聚合，构成了Rodinia超大陆的一部分.哈珠地区新元古代岩浆事件即为Rodinia超大陆聚合在北山地区的响应.
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| 关 键 词： | 新元古代 片麻状花岗岩 S型花岗岩 Rodinia超大陆 北山北带 地球化学 |
| 收稿时间： | 2018-08-31 |
Neoproterozoic Magmatic Records in the North Beishan Orogenic Belt: Evidence of the Gneissic Granites from the Hazhu Area,Inner Mongolia |
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| Abstract: | The Beishan orogenic belt is located in the middle of the Central Asian orogenic belt (CAOB) and the tectonic history of its Precambrian basement rocks is the key to understand the formation and evolution of the Beishan orogenic belt. In this study, we select the gneissic granites in the North Beishan orogenic belt (NBOB) for zircon U-Pb chronology and geochemical analysis. The results show that the gneissic granites formed in the 885±4 Ma, which reveals the Neoproterozoic magmatic events in the NBOB for the first time. The gneissic granites belong to the peraluminous, high-K, calc-alkaline series and are characterized by high SiO2 and K2O+Na2O, low CaO. The gneissic granites show an enrichment of light rare earth elements (LREE) with Europium negative anomaly and are characterized by enrichment of large ion lithophile elements (LILE) such as Rb, K, Th, U, but depletion in high field strength elements (HFSE) such as Nb, Sr, P, Ti. The petrography and geochemical signatures reveal a possible S-type granite affinity and are derived from the partial melting of metamorphic complex sandstone of source area with initial melt temperature (777-798℃). The gneissic granites were likely generated in a continental collision tectonic setting. By comparing our new data with previous results from the Precambrian basement in the South Beishan orogenic belt and the Tianshan block (microcontinent in the Chinese Tianshan), we suggest that the Precambrian microcontinents in the northern Beishan have similar crustal evolutionary history to the South Beishan orogenic belt (SBOB) and Central Tianshan block. They participated in the Rodinia supercontinent aggregation together and formed a part of Rodinia during the Neoproterozoic period. The Neoproterozoic magmatic events in the Beishan area are the response of the Rodinia supercontinent aggregation. |
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