The effect of diffusion on lithium isotope ratios in Icelandic basalts
文献类型：期刊论文
| 作者 | Marshall, Edward W.4,5; Halldorsson, Saemundur A.5; Tian, Liyan3 ; Jackson, Matthew G.2; Jenner, Frances1; Stefansson, Andri5
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| 刊名 | CHEMICAL GEOLOGY
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| 出版日期 | 2024-09-05 |
| 卷号 | 662页码:15 |
| 关键词 | Lithium isotopes Iceland Mantle geochemistry Stable isotope Basalt |
| ISSN号 | 0009-2541 |
| DOI | 10.1016/j.chemgeo.2024.122206 |
| 英文摘要 | In recent years, diffusion has gained increasing recognition as an important process for explaining the lithium (Li) isotope ratios (delta Li-7) of magmatic systems. However, the role of diffusion in explaining the variability of mantle-derived basalts has not yet been investigated in detail. We have measured delta Li-7 values in a comprehensive suite of fresh, subglacial Icelandic basalt glasses and observe a wide range of values from 2.4 parts per thousand to 7.3 parts per thousand, the largest range in Li isotope compositions identified at any ocean island. We find that delta Li-7 values do not correlate with lithophile element tracers, but do correlate with He-3/He-4. One possibility is that the high diffusivities of both Li and He permit fractionation of Li isotope compositions that couple it to He-3/He-4, and decouple it from other, slower-diffusing lithophile tracers. In this study, we explore this idea and model diffusive processes in crystal mushes and mantle melt channels, both with and without melt transport. Our modelling indicates that large (>3 parts per thousand) fractionation of Li isotope compositions from MORB-like values can be generated by diffusion and that the coupling of Li isotope ratios and He-3/He-4 signatures can occur as a consequence of diffusive interactions within mantle melt channels. This suggests that the Li isotope compositions of melts cannot be used as a straightforward passive tracer of mantle heterogeneity, because they can be fractionated during magmatic processes. In contrast, we find that diffusive fractionation of He-3/He-4 is small (similar to 1 Ra) next to the variability in Icelandic basalts (similar to 8 to similar to 35 Ra). Diffusive fractionation of Li isotope ratios should be most pronounced at OIB localities whose mantle melts have a wide range of [Li], such as Hawaii and Iceland. Although a mantle source can contain Li isotope heterogeneities as a result of crustal recycling, we show that a mantle that is homogenous in Li isotope composition can still generate melts that have variable delta Li-7 values via diffusion processes. The same diffusion models can also be applied to other stable isotope systems such as H, Mg, Ca, and Fe. Indeed our models show that diffusion during magmatic transport within the mantle may be a significant source of "noise" in the delta Li-7, delta D, and possibly delta Mg-26 isotopic systems. |
| WOS关键词 | HIGH-TEMPERATURE ; TRACE-ELEMENT ; PERIDOTITE XENOLITHS ; SUBMARINE BASALTS ; TRINITY OPHIOLITE ; HYDROGEN ISOTOPES ; MELT PERCOLATION ; UPWELLING MANTLE ; ISLAND BASALTS ; NOBLE-GASES |
| 资助项目 | Icelandic Research Fund[195638-051] |
| WOS研究方向 | Geochemistry & Geophysics |
| 语种 | 英语 |
| WOS记录号 | WOS:001253441500001 |
| 出版者 | ELSEVIER |
| 资助机构 | Icelandic Research Fund |
| 源URL | [http://ir.idsse.ac.cn/handle/183446/11533]  |
| 专题 | 深海科学研究部_深海地质与地球化学研究室 |
| 通讯作者 | Marshall, Edward W. |
| 作者单位 | 1.Open Univ, Sch Environm Earth & Ecosyst Sci, Walton Hall, Milton Keynes MK7 6AA, England 2.Univ Calif Santa Barbara, Dept Earth Sci, Santa Barbara, CA 93106 USA 3.Chinese Acad Sci, Inst Deep Sea Sci & Engn, Sanya 572000, Peoples R China 4.Friedrich Alexander Univ Erlangen Nurnberg, Geozent Nordbayern, D-91054 Erlangen, Germany 5.Univ Iceland, Inst Earth Sci, Nord Volcanol Ctr, Sturlugata 7, IS-101 Reykjavik, Iceland |
| 推荐引用方式 GB/T 7714 | Marshall, Edward W.,Halldorsson, Saemundur A.,Tian, Liyan,et al. The effect of diffusion on lithium isotope ratios in Icelandic basalts[J]. CHEMICAL GEOLOGY,2024,662:15. |
| APA | Marshall, Edward W.,Halldorsson, Saemundur A.,Tian, Liyan,Jackson, Matthew G.,Jenner, Frances,&Stefansson, Andri.(2024).The effect of diffusion on lithium isotope ratios in Icelandic basalts.CHEMICAL GEOLOGY,662,15. |
| MLA | Marshall, Edward W.,et al."The effect of diffusion on lithium isotope ratios in Icelandic basalts".CHEMICAL GEOLOGY 662(2024):15. |
入库方式： OAI收割
来源：深海科学与工程研究所
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