Global oceanic basalt sources and processes viewed through combined Fe and Mg stable isotopes

doi:10.1016/j.epsl.2024.118749

	Global oceanic basalt sources and processes viewed through combined Fe and Mg stable isotopes
	Soderman, Caroline R.1; Matthews, Simon 2; Shorttle, Oliver 1; Jackson, Matthew G.3; Day, James M. D.4; Kamenetsky, Vadim 5; Williams, Helen M.1
	2024-07-15
发表期刊	EARTH AND PLANETARY SCIENCE LETTERS
ISSN	0012-821X
卷号	638 页码:13
通讯作者	Soderman, Caroline R.([email protected])
摘要	Oceanic basalts show variation in their iron and magnesium isotope compositions. One hypothesis for the origin of this is source variation: radiogenic isotope and trace element abundance studies have long argued that the Earth's upper mantle is geochemically heterogeneous and that subducted crust is a major contributor to this diversity. In contrast, a recent hypothesis posits that stable isotopes record disequilibrium during melt transport and so provide novel insight into the melting process. In this study we investigate the first of these hypotheses, that source heterogeneity explains global Fe-Mg isotope systematics. We compile a global dataset of oceanic basalt Fe and Mg isotopes and complement this with new Fe-Mg isotope data from locations possessing some of the most extreme radiogenic isotope ratios for their setting: ocean island basalts from the Cook-Austral and Society islands and a Mid-Atlantic Ridge basalt. Despite both Fe and Mg isotope systems having the ability to trace recycled crustal material in the mantle, their global systematics are very different in this dataset. The global compilation of primitive oceanic basalts records heavier Fe (higher delta Fe-57) isotope compositions than bulk silicate earth (BSE), but a mixture of heavier and lighter Mg isotope compositions than BSE. By employing a coupled Fe-Mg equilibrium isotope fractionation model during mantle melting we show that much of this isotopic variability can be generated by the mixed melts produced by melting of peridotite mantle containing moderate amounts of recycled crust as a discrete lithology. The Fe isotope composition of the melts is controlled by the bulk isotope composition of the recycled crust (expected to be considerably heavier than BSE, but variable). In contrast, the Mg isotope composition is controlled by source mineralogy. Olivine-poor lithologies such as recycled crust are able to generate large Mg isotope fractionations during melting, both positive and negative (+/- 0.1 parts per thousand) relative to the mantle source, depending on the presence of spinel, clinopyroxene or garnet. These melt Mg isotope fractionations are consistent with the Mg isotope compositions of mid-ocean ridge basalts generated by variable depths of mantle melting. Our equilibrium model provides a baseline to test hypotheses of Fe-Mg isotope variability in basalts: our results show that contributions from recycled crust-derived melts, generated in spinel-, pyroxene-, and garnet-bearing mineral assemblages in the mantle, would be able to produce much of the Fe-Mg isotope variability seen in the global compilation of primitive oceanic basalts, without requiring isotopically extreme mantle components (e.g., carbonate with a light Mg isotope signature) or disequilibrium fractionation. However some basalt variability in ocean island settings may indeed fall outside the paradigm of pyroxenite heterogeneity - whilst we consider carbonates unlikely to be important, disequilibrium processes may in these cases play a role.
关键词	Fe stable isotopes Mg stable isotopes mantle heterogeneity volcanic hotspots OIB
DOI	10.1016/j.epsl.2024.118749
收录类别	SCI
语种	英语
资助项目	Natural Environment Research Council studentship[NE/L002507/1]; UK Research and Innovation Future Leaders Fellowship[MR/V02292X/1]; Natural Environment Research Council[NE/V011383/1]; Natural Environment Research Council[NE/T012455/1]; NSF[OCE-1929095]
WOS研究方向	Geochemistry & Geophysics
WOS类目	Geochemistry & Geophysics
WOS记录号	WOS:001242427200001
出版者	ELSEVIER
WOS关键词	ISLAND BASALTS ; SOURCE REGIONS ; MANTLE SOURCE ; SYSTEMATICS ; FRACTIONATION ; MAGNESIUM ; HAWAIIAN ; LAVAS ; GEOCHEMISTRY ; GARNET
引用统计	被引频次：2[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/186039
专题	深海极端环境与生命过程研究中心
通讯作者	Soderman, Caroline R.
作者单位	1.Univ Cambridge, Dept Earth Sci, Cambridge CB2 3EQ, England 2.Univ Iceland, Inst Earth Sci, Reykjavik, Iceland 3.Univ Calif Santa Barbara, Dept Earth Sci, Santa Barbara, CA 93106 USA 4.Univ Calif San Diego, Scripps Inst Oceanog, San Diego, CA 92093 USA 5.Chinese Acad Sci, Ctr Deep Sea Res, Inst Oceanol, Qingdao 266071, Peoples R China
推荐引用方式 GB/T 7714	Soderman, Caroline R.,Matthews, Simon,Shorttle, Oliver,et al. Global oceanic basalt sources and processes viewed through combined Fe and Mg stable isotopes[J]. EARTH AND PLANETARY SCIENCE LETTERS,2024,638:13.
APA	Soderman, Caroline R..,Matthews, Simon.,Shorttle, Oliver.,Jackson, Matthew G..,Day, James M. D..,...&Williams, Helen M..(2024).Global oceanic basalt sources and processes viewed through combined Fe and Mg stable isotopes.EARTH AND PLANETARY SCIENCE LETTERS,638,13.
MLA	Soderman, Caroline R.,et al."Global oceanic basalt sources and processes viewed through combined Fe and Mg stable isotopes".EARTH AND PLANETARY SCIENCE LETTERS 638(2024):13.