| 藏东吉塘复式花岗岩成因——来自锆石U-Pb年龄和地球化学的证据 |
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| 引用本文： | 樊炳良,张鑫利,于涛,白涛,冯德新.藏东吉塘复式花岗岩成因——来自锆石U-Pb年龄和地球化学的证据[J].地质通报,2019,38(8):1274-1286. |
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| 作者姓名： | 樊炳良 张鑫利 于涛 白涛 冯德新 |
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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, 西藏 拉萨 850000,青海省青藏高原北部地质过程与矿产资源重点实验室, 青海 西宁 810012;青海省地质调查院, 青海 西宁 810012,西藏大学理学院, 西藏 拉萨 850000,成都理工大学地球科学学院, 四川 成都 610059,西藏自治区地质矿产勘查开发局地热地质大队, 西藏 拉萨 850000 |
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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： | 吉塘复式花岗岩位于澜沧江岩浆岩带北段,是研究澜沧江结合带演化过程的重要窗口。对澜沧江北段卡贡地区吉塘复式花岗岩中的黑云母二长花岗岩和花岗闪长岩开展了LA-ICP-MS锆石U-Pb年代学、岩石地球化学研究。研究结果表明,所选锆石样品均具有明显的生长环带,Th/U值普遍大于0.4,为典型的岩浆锆石,分别获得锆石~(206)Pb/~(238)U年龄加权平均值为222.8±1.5Ma(MSWD=1.60,n=16)、213.6±1.1Ma(MSWD=0.98,n=20)和221.1±1.5Ma(MSWD=1.30,n=15),时代均属于晚三叠世。岩石地球化学特征表明,吉塘黑云母二长花岗岩和花岗闪长岩具有较一致的主量、微量元素含量,其变化特征也具有一致性,反映这2类岩石可能为同一期岩浆演化而来;吉塘复式花岗岩属于过铝质S型花岗岩,与临沧花岗岩、纽多花岗岩具有一致的岩石地球化学性质,为澜沧江花岗岩带的重要组成部分,具有统一的构造岩浆活动模式;吉塘复式花岗岩的成因与碰撞造山导致地壳加厚增温及与岩石圈剪切、伸展期有关的深熔作用有关,澜沧江洋的闭合时间可能为273Ma左右。
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| 关 键 词： | 吉塘复式花岗岩 岩石地球化学特征 LA-ICP-MS锆石U-Pb年龄 岩石成因 |
| 收稿时间： | 2018/12/19 0:00:00 |
| 修稿时间： | 2019/3/22 0:00:00 |
The genesis of Jitang duplex granites in east Tibet: Evidence from the zircon UPb age and rock geochemistry |
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| FAN Bingliang,ZHANG Xinli,YU Tao,BAI Tao and FENG Dexin.The genesis of Jitang duplex granites in east Tibet: Evidence from the zircon UPb age and rock geochemistry[J].Geologcal Bulletin OF China,2019,38(8):1274-1286. |
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| Authors: | FAN Bingliang ZHANG Xinli YU Tao BAI Tao and FENG Dexin |
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| Institution: | Geothermal Geological Survey Party, Tibet Bureau of Geology and Mineral Exploration and Development, Lhasa 850000, Tibet, China,Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources Laboratory, Qinghai, Xining 810012, Qinghai, China;Qinghai Geological Survey Institute, Xining 810012, Qinghai, China,College of Science, Tibet University, Lhasa 850000, Tibet, China,Department of Geology College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, Sichuan, China and Geothermal Geological Survey Party, Tibet Bureau of Geology and Mineral Exploration and Development, Lhasa 850000, Tibet, China |
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| Abstract: | Jitang duplex granites are located in the northern section of the Lancang River magma belt, and serve as an important window for studying the evolution process of Lancang River juncture zone. In this paper, the LA-ICP-MS zircon U-Pb chronology and rock geochemistry of biotite monzonitic granite and granitic diorite in Jitang duplex granites of Kakagong area along northern Lancang River were studied. The results show that the selected zircon samples exhibit obvious growth ring zone, the Th/U ratio is generally higher than 0.4, and the typical magma zircon has average weighted 206Pb/238U age of 222.8±1.5Ma (MSWD=1.60, n=16), 213.6±1.1Ma (MSWD=0.98, n=20) and 221.1±1.5Ma (MSWD=1.30, n=15), suggesting Late Triassic. The geochemical characteristics of rocks show that the Jitang biotite monzonitic granite and granitic diorite have relatively consistent content of main and trace elements, and their changing characteristics are also consistent. It is shown that these two kinds of rocks might have been derived from the same magma, and the Jitang duplex granites belong to the aluminum S-type granite, which has the same petrogeochemical properties as Lincang granite and Newcastle granite, and has a unified tectonic magmatic activity mode along the Lancang River granite belt. The formation of Jitang duplex granites was related to the thickening and warming of the crust and the deep melting effect related to the shearing and stretching period of lithosphere, with the closure time of Lancang Jiang Ocean was probably at about 273Ma. |
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| Keywords: | Jitang duplex granites rock geochemical characteristics LA-ICP-MS zircon U-Pb age rock genesis |
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