Significant boron isotopic fractionation in the magmatic evolution of Himalayan leucogranite recorded in multiple generations of tourmaline
文献类型：期刊论文
| 作者 | Cheng, Lining1,3; Zhang, Chao2,3; Liu, Xiaochi4,5 ; Yang, Xiaosong1; Zhou, Yongsheng1; Horn, Ingo3; Weyer, Stefan3; Holtz, Francois3
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| 刊名 | CHEMICAL GEOLOGY
 |
| 出版日期 | 2021-06-20 |
| 卷号 | 571页码:13 |
| ISSN号 | 0009-2541 |
| 关键词 | Tourmaline Boron isotopic fractionation Degassing Himalayan leucogranites Boron recycling |
| DOI | 10.1016/j.chemgeo.2021.120194 |
| 英文摘要 | The late-stage evolution of leucogranite magmas and related magmatic-hydrothermal processes which could lead to rare-metal mineralization are still poorly studied in the Himalayas. Since tourmaline is among the minerals that are present in evolved granites of the Himalayas, the geochemistry of this mineral, and in particular the boron isotopic composition, is a powerful tool to trace evolution processes and sources of these magmas. This study focuses on the analysis of tourmalines in the Gurla Mandhata tourmaline leucogranites (GMTL) from the northwest of the Himalayan orogen. Two generations of tourmaline show clear differences in texture, major element, and B isotopic compositions. Early-stage tourmalines have high-Mg# [Mg/(Mg + Fe) 0.39?0.45] and occur as inclusions in late-stage tourmalines [Mg# 0.34] and other minerals. The ?11B values are in the range of -7 - -8%o for the early-stage tourmaline and in the range of -12 - -15%o for the late-stage tourmaline. The occurrence of tourmalines with contrasting B isotopic compositions from the same leucogranite body (even in a same specimen) can be explained either by mixing of magmas from different sources with different B isotopic compositions or by remarkable B isotopic fractionation during magma differentiation. As indicated by mineral textures and compositions, the mixing of different magma batches can be ruled out as a major cause in the case of GMTL. Alternatively, the bimodal distribution of tourmaline ?11B most likely suggests the occurrence of multiplestage B isotopic fractionation during the magma evolution. Our modeling based on Rayleigh fractionation shows that this fractionation may have been induced mainly by extraction of fluid at a late magmatic stage, but crystallization of tourmaline may have also played a minor role. Interestingly, a compilation of ?11B values ( 260 data points) in magmatic tourmaline from eight Himalayan leucogranite bodies systematically shows a similar bimodal distribution (i.e., with peaks at -7%o and - 13%o), implying that this significant B isotopic fractionation may be a common scenario during magma evolution of the Himalayan leucogranites. However, multiple magma sources with contrasting B isotopic compositions cannot be fully ruled out for explaining the bimodal distribution of B isotopic composition. Combining our results with Sr?Nd isotopic and other geochemical characteristics of the Himalayan leucogranites, we propose that the granitic magmas with high ?11B originated either from fluid-present melting involving boron-rich fluids, or more probably from dehydration melting of the Greater Himalayan Sequence that had been metasomatized by boron-rich fluids. The geological context implies that these fluids were probably derived from dehydration of mica-rich rocks from the Lesser Himalayan Sequence underlying the Greater Himalayan Sequence. |
| WOS关键词 | CONTINENTAL-CRUST ; RICH FLUIDS ; GRANITE ; MINERALS ; ROCKS ; WATER ; MELT ; CRYSTALLIZATION ; CONSTRAINTS ; PEGMATITES |
| 资助项目 | National Natural Science Foundation of China[41772223] ; Basic Research Fund of the Institute of Geology, China Earthquake Administration[IGCEA2018] ; Basic Research Fund of the Institute of Geology, China Earthquake Administration[IGCEA1914] |
| WOS研究方向 | Geochemistry & Geophysics |
| 语种 | 英语 |
| 出版者 | ELSEVIER |
| WOS记录号 | WOS:000641459400003 |
| 资助机构 | National Natural Science Foundation of China ; National Natural Science Foundation of China ; Basic Research Fund of the Institute of Geology, China Earthquake Administration ; Basic Research Fund of the Institute of Geology, China Earthquake Administration ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Basic Research Fund of the Institute of Geology, China Earthquake Administration ; Basic Research Fund of the Institute of Geology, China Earthquake Administration ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Basic Research Fund of the Institute of Geology, China Earthquake Administration ; Basic Research Fund of the Institute of Geology, China Earthquake Administration ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Basic Research Fund of the Institute of Geology, China Earthquake Administration ; Basic Research Fund of the Institute of Geology, China Earthquake Administration |
| 源URL | [http://ir.iggcas.ac.cn/handle/132A11/101155]  |
| 专题 | 地质与地球物理研究所_岩石圈演化国家重点实验室 |
| 通讯作者 | Cheng, Lining |
| 作者单位 | 1.China Earthquake Adm, Inst Geol, State Key Lab Earthquake Dynam, Beijing 100029, Peoples R China 2.Northwest Univ, Dept Geol, State Key Lab Continental Dynam, Xian 710069, Peoples R China 3.Leibniz Univ Hannover, Inst Mineral, D-30167 Hannover, Germany 4.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China 5.Chinese Acad Sci, Inst Earth Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China |
| 推荐引用方式 GB/T 7714 | Cheng, Lining,Zhang, Chao,Liu, Xiaochi,et al. Significant boron isotopic fractionation in the magmatic evolution of Himalayan leucogranite recorded in multiple generations of tourmaline[J]. CHEMICAL GEOLOGY,2021,571:13. |
| APA | Cheng, Lining.,Zhang, Chao.,Liu, Xiaochi.,Yang, Xiaosong.,Zhou, Yongsheng.,...&Holtz, Francois.(2021).Significant boron isotopic fractionation in the magmatic evolution of Himalayan leucogranite recorded in multiple generations of tourmaline.CHEMICAL GEOLOGY,571,13. |
| MLA | Cheng, Lining,et al."Significant boron isotopic fractionation in the magmatic evolution of Himalayan leucogranite recorded in multiple generations of tourmaline".CHEMICAL GEOLOGY 571(2021):13. |
入库方式： OAI收割
来源：地质与地球物理研究所
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