DOI: 10.1016/j.epsl.2019.115973
论文题名: A multi-proxy investigation of mantle oxygen fugacity along the Reykjanes Ridge
作者: Novella D. ; Maclennan J. ; Shorttle O. ; Prytulak J. ; Murton B.J.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 531 语种: 英语
英文关键词: Fe3+/Fetot
; isotopes
; mantle
; MORB
; oxygen fugacity
; vanadium
Scopus关键词: Basalt
; Isotopes
; Magnesia
; Metal melting
; Oxygen
; Trace elements
; Vanadium
; Basalt petrogenesis
; Incompatible element
; Isotopic fractionations
; mantle
; MORB
; Oxygen fugacity
; Potential temperature
; Redox-sensitive trace elements
; Vanadium compounds
; fugacity
; igneous geochemistry
; iron
; isotopic analysis
; isotopic composition
; isotopic fractionation
; lava
; mantle
; mid-ocean ridge basalt
; oxygen
; trace element
; vanadium
; Atlantic Ocean
; Reykjanes Ridge
英文摘要: Mantle oxygen fugacity (fO2) governs the physico-chemical evolution of the Earth, however current estimates from commonly used basalt redox proxies are often in disagreement. In this study we compare three different potential basalt fO2 proxies: Fe3+/Fetot, V/Sc and V isotopes, determined on the same submarine lavas from a 700 km section of the Reykjanes Ridge, near Iceland. These samples provide a valuable test of the sensitivities of fO2 proxies to basalt petrogenesis, as they formed at different melting conditions and from a mantle that towards Iceland exhibits increasing long-term enrichment of incompatible elements. New trace element data were determined for 63 basalts with known Fe3+/Fetot. A subset of 19 lavas, covering the geographical spread of the ridge transect, was selected for vanadium isotope analyses. Vanadium is a multi-valence element whose isotopic fractionation is theoretically susceptible to redox conditions. Yet, the δ51VAA composition of basaltic glasses along the Reykjanes Ridge covers only a narrow range (δ51VAA = −1.09 to −0.86‰; 1SD = 0.02–0.09) and does not co-vary with fractionation-corrected Fe3+/Fetot (0.134–0.151; 1SD = 0.005) or V/Sc (6.6–8.5; 1SD = 0.1-1.3) ratios. However, on a global scale, basaltic δ51VAA may be controlled by the extent of melting. The V/Sc compositions of primitive (MgO > 7.5 wt%) basalts show no systematic change along the entire length of the Reykjanes Ridge. Typical peridotite melting models in which source Fe3+/Fetot is constant at 5% and that account for the increased mantle potential temperature nearer the plume center and the fO2 dependent partitioning of V, can reproduce the V/Sc data. However, while these melting models predict that basalt Fe3+/Fetot ratios should decrease with increasing mantle potential temperature towards Iceland, fractionation-corrected Fe3+/Fetot of Reykjanes Ridge lavas remain nearly constant over the ridge length. This discrepancy is explained by source heterogeneity, where an oxidized mantle pyroxenite component contributes to melting with increasing proximity to Iceland. Comparison of observed and modeled Fe3+/Fetot indicate that source variation in fO2 is present under the Reykjanes Ridge, with higher Fe3+/Fetot closer to Iceland. This source variability in fO2 cannot be resolved by V isotopes and redox-sensitive trace element ratios, which instead appear to record magmatic processes. © 2019 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/159972
Appears in Collections: 气候变化与战略
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作者单位: Department of Earth Sciences, University of Cambridge, United Kingdom; Institute of Astronomy, University of Cambridge, United Kingdom; Department of Earth Sciences, Durham University, United Kingdom; Department of Earth Science and Engineering, Imperial College, London, United Kingdom; National Oceanography Centre, Southampton, United Kingdom
Recommended Citation:
Novella D.,Maclennan J.,Shorttle O.,et al. A multi-proxy investigation of mantle oxygen fugacity along the Reykjanes Ridge[J]. Earth and Planetary Science Letters,2020-01-01,531