| Genesis and tectonic setting of Late Jurassic-Early Cretaceous granites in Nachatang area,Central Lhasa Terrane: Constraints from geochemistry,chronology and Hf isotopesSCIEI北大核心CSCD |
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| 引用本文： | 冷秋锋,李文昌,戴成龙,张向飞,吴松洋,曹华文.Genesis and tectonic setting of Late Jurassic-Early Cretaceous granites in Nachatang area,Central Lhasa Terrane: Constraints from geochemistry,chronology and Hf isotopesSCIEI北大核心CSCD[J].岩石学报,2022,38(1):209-229. |
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| 作者姓名： | 冷秋锋 李文昌 戴成龙 张向飞 吴松洋 曹华文 |
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| 作者单位： | 中国地质调查局成都地质调查中心, 成都 610081;成都理工大学地球科学学院, 成都 610059 |
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| 基金项目： | 本文受国家自然科学基金重点项目（92055314）、中国地质调查局项目（DD20190444）、四川省“天府万人计划”杰出科学家项目（川万人第023号）和云南省科学技术奖-杰出贡献奖项目（2017001）联合资助 |
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| 摘 要： | 西藏中拉萨地块东段大规模侏罗纪-白垩纪花岗岩类的成因类型及构造背景尚未得到有效约束,该时期岩浆作用的时空分布、岩石成因以及深部动力学机制等问题亟需新的深入研究。本文对中拉萨地块东段南缘那茶淌地区的花岗岩类进行了系统的岩相学、元素地球化学、年代学和锆石Hf同位素研究。LA-MC-ICPMS锆石U-Pb定年结果显示,那茶淌地区黑云母二长花岗岩成岩年龄为147±1.4Ma,花岗闪长岩年龄为140.6±1.3Ma,系晚侏罗世-早白垩世中酸性岩浆活动的产物。在元素地球化学组成上,黑云母二长花岗岩和花岗闪长岩的主量元素组成具有富SiO2(分别为71.02%～71.81%和65.17%～66.73%)、Al2O3(分别为13.45%～13.57%和14.43%～15.20%)、碱金属(Na2O+K2O)(分别为6.79%～7.48%和6.55%～7.37%),贫TiO2(分别为0.15%～0.21%和0.10%～0.13%)等特征,显示I型准铝-弱过铝质(A/CNK=0...
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| 关 键 词： | 地球化学 锆石U-Pb定年 Hf同位素 那茶淌地区 中拉萨地块 |
| 收稿时间： | 2021/8/2 0:00:00 |
| 修稿时间： | 2021/11/20 0:00:00 |
Genesis and tectonic setting of Late Jurassic-Early Cretaceous granites in Nachatang area, Central Lhasa Terrane: Constraints from geochemistry, chronology and Hf isotopes |
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| LENG QiuFeng,LI WenChang,DAI ChengLong,ZHANG XiangFei,WU SongYang,CAO HuaWen.Genesis and tectonic setting of Late Jurassic-Early Cretaceous granites in Nachatang area, Central Lhasa Terrane: Constraints from geochemistry, chronology and Hf isotopes[J].Acta Petrologica Sinica,2022,38(1):209-229. |
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| Authors: | LENG QiuFeng LI WenChang DAI ChengLong ZHANG XiangFei WU SongYang CAO HuaWen |
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| Institution: | Chengdu Center, China Geological Survey, Chengdu 610081, China;College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China |
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| Abstract: | The genetic types and tectonic settings of the large-scale Jurassic-Cretaceous granites in the eastern part of the Central Lhasa Terrane in Tibet have not been well constrained, and the temporal and spatial distribution of their magmatism, petrogenesis and deep dynamic mechanism in this period are in urgent need of further research. In this paper, the lithography, chronology, geochemistry and zircon Hf isotope of the biotite monzogranite and granodiorite from the Nachatang area in the southern margin of the eastern segment of the Central Lhasa Terrane are systematically studied. LA-MC-ICPMS zircon U-Pb dating results show that the biotite monzogranite and granodiorite are 147 +/- 1. 4Ma and 140. 6 +/- 1. 3Ma, respectively, showing they are the products of magmatism in Late Jurassic-Early Cretaceous. In terms of geochemical compositions , the biotite monzogranite and granodiorite have low TiO2 (0.15% similar to 0. 21% and 0.10% similar to 0. 13%) , high SiO2 (71.02% similar to 71.81% and 65.17% similar to 66.73%) , Al2O3 (13. 45% similar to 13. 57% and 14.43% similar to 15. 20% ) and alkali (Na2O + K2O) (6. 79% similar to 7. 48% and 6. 55% similar to 7.37% ) contents, showing the characteristics of I-type peraluminum to weak peraluminum calc-alkaline series (A/CNK = 0. 98 similar to 1. 14 ) . Trace element compositions of the measured samples are characterized by enrichment of large ion lithophile elements such as K, Rb , Ba and Th, and depletion of high field strength elements such as Ta, Nb , P and Ti. The total amount of REE in the granodiorite (Sigma REE =263. 9 x 10(-6) similar to 313. 8 x 10(-6)) is higher than that in the biotite monzonite (Sigma REE = 116. 3 x 10(-6) similar to 168. 8 x 10(-6)) , which shows the enrichment of LREE and relative depletion of HREE, with weak negative Eu anomaly. The zircon Hf isotopes are characterized by negative epsilon(Hf) (t) values and ancient crustal model ages. The epsilon(Hf) (t) values of the biotite monzogranite range from - 21. 64 to - 7. 66 , and the crustal model ages (t(DM)(C) ) range from 1. 68Ga to 2. 56Ga. epsilon(Hf)(t) values of the granodiorite vary from - 11. 95 to - 8. 15, and the crustal model ages (t(DM)(C)) from 1. 71Ga to 1. 95Ga. Finally, we conclude that the tectonic setting of Late Jurassic to Early Cretaceous granites in the Nachatang area is related to the southward subduction of the Bangong-Nujiang Ocean seafloor, and the magma is derived from the remelting of ancient lower crust material induced by subduction. |
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| Keywords: | Geochemistry Zircon U-Pb dating Hf isotope Nachatang area Central Lhasa Terrane |
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