| 藏东纽多黑云母二长花岗岩锆石U-Pb年龄及成因 |
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| 引用本文： | 樊炳良,白涛,冯德新,张婷婷,汤勇,张力文,梁宏岩.藏东纽多黑云母二长花岗岩锆石U-Pb年龄及成因[J].地质通报,2018,37(7):1226-1235. |
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| 作者姓名： | 樊炳良 白涛 冯德新 张婷婷 汤勇 张力文 梁宏岩 |
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| 作者单位： | 西藏自治区地质矿产勘查开发局地热地质大队;成都理工大学地球科学学院 |
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| 基金项目： | 中国地质调查局项目《西藏卡贡地区1：5万四幅区域地质调查》（编号：DD20160016-21） |
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| 摘 要： | 通过对澜沧江北段卡贡地区出露的纽多黑云母二长花岗岩的岩石学、岩石地球化学及锆石U-Pb年龄的研究,分析了纽多黑云母二长花岗岩的地球化学和原岩特征。黑云母二长花岗岩中的锆石具有明显的振荡环带,较高的Th/U值(普遍大于0.4),属于典型的岩浆成因锆石,用LA-ICP-MS测得锆石~(206)Pb/~(238)U年龄为243.6±1.4Ma(MSWD=1.00,n=15),时代为中三叠世。岩石地球化学特征表明,该黑云母二长花岗岩具有较高的SiO_2、Al_2O_3及高钾富碱的特征,A/CNK值为1.05~1.08,为过铝质高钾钙碱性系列;稀土元素配分模式显示,配分曲线为右倾型,具有明显的负Eu异常和弱负Ce异常,表现为Nb、Ta、P、Zr、Ti等高场强元素相对亏损,相对富集Rb、K、Th、U等大离子亲石元素。岩石地球化学特征表明,纽多黑云母二长花岗岩为S型花岗岩,形成于地壳加厚增温环境下的深熔作用。
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| 关 键 词： | 黑云母二长花岗岩 地球化学 LA-ICP-MS锆石U-Pb测年 西藏纽多 |
| 收稿时间： | 2017/7/20 0:00:00 |
| 修稿时间： | 2017/10/9 0:00:00 |
Zircon U-Pb age and genesis of Niuduo biotite monzogranite in east Tibet |
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| FAN Bingliang,BAI Tao,FENG Dexin,ZHANG Tingting,TANG Yong,ZHANG Liwen and LIANG Hongyan.Zircon U-Pb age and genesis of Niuduo biotite monzogranite in east Tibet[J].Geologcal Bulletin OF China,2018,37(7):1226-1235. |
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| Authors: | FAN Bingliang BAI Tao FENG Dexin ZHANG Tingting TANG Yong ZHANG Liwen and LIANG Hongyan |
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| Institution: | Geothermal Geological Survey Party, Tibet Bureau of Geology and Mineral Exploration and Development, Lhasa 850000, Tibet, China,College of Earth Sciences, Department of Geology, Chengdu University of Technology, Chengdu 610059, Sichuan, China,Geothermal Geological Survey Party, Tibet Bureau of Geology and Mineral Exploration and Development, Lhasa 850000, Tibet, China,College of Earth Sciences, Department of Geology, Chengdu University of Technology, Chengdu 610059, Sichuan, China,Geothermal Geological Survey Party, Tibet Bureau of Geology and Mineral Exploration and Development, Lhasa 850000, Tibet, China,Geothermal Geological Survey Party, Tibet Bureau of Geology and Mineral Exploration and Development, Lhasa 850000, Tibet, China and Geothermal Geological Survey Party, Tibet Bureau of Geology and Mineral Exploration and Development, Lhasa 850000, Tibet, China |
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| Abstract: | This paper presents geochronological and whole-rock geochemical data of Niuduo biotite monzogranite exposed in the north of Lancang granitoids to discuss the origin of the Niuduo biotite monzogranite and its geochemical characteristics. Zircons of biotite monzogranite show no euhedral crystals and have clear oscillatory zones as well as high Th/U ratios, suggesting magmatic origin. Zircon LA-ICP-MS dating of the biotite monzogranite yielded an age of 243.6±1.4Ma(MSWD=1.00, n=15), implying that the crystallization of the biotite monzogranite body took place in Middle Triassic. Petrological and geochemical studies show that it is characterized by high silicon and aluminum as well as abundant alkali, with A/CNK being 1.05~1.08, thus belonging to high-K calc-alkaline series. The whole-rock geochemical characteristics such as strongly fractionated REE pattern, apparently negative Eu anomalies and Ce anomalies, depleted Nb, Ta, P, Zr, Ti, and high Rb, K, Th, U suggest that it belongs to S-type granite. The authors hold that the melting took place at about 25km in the middle crust due to extension of the thickened crust after the closure of the paleo-Lancang Ocean. The results obtained by the authors support the hypothesis that the Lancang River tectonic zone represents a remnant Paleo-Tethyan main ocean preserved in the collision suture along a Gondwana-derived microcontinent. |
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| Keywords: | biotite monzogranite geochemistry LA-ICP-MS zircon U-Pb dating Niuduo Tibet |
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