Subducted lithosphere controls halogen enrichments in the Iceland mantle plume source
Subducted lithosphere controls halogen enrichments in the Iceland mantle plume source
复制标题
俯冲岩石圈控制冰岛地幔羽流源中的卤素富集
作者：
S. Halldórsson;J. Barnes;A. Stefánsson;D. Hilton;E. Hauri;E. Marshall
地球内部的氯同位素组成对地球深部卤素循环和地幔化学不均匀性的起源有很强的制约作用。然而，所有幔源火山岩样品的Cl同位素研究，迄今起源于海底火山系统，海水来源的Cl的影响是普遍的。在这里，我们提出了氯同位素数据从冰下火山玻璃从冰岛，在那里的洋中脊系统出现在海平面以上，是免费的海水的影响。冰岛的数据显示，δ 37 Cl值变化很大，从-1.8 ‰到+1.4‰，而且没有区域控制。Cl和O同位素比值之间缺乏相关性，并且缺乏海水导致Cl富集的证据，这表明冰岛玄武岩中δ 37 Cl值的变化可以完全归因于地幔的不均匀性。实际上，δ 37 Cl值与不相容的微量元素比率（例如，La/Y）和长寿命放射成因Pb同位素比值。这些数据是一致的，包括最上面的沉积包，俯冲到冰岛地幔柱源，在冰岛玄武岩相对于邻近的洋中脊熔岩显着的卤素富集与改造岩石圈的合并。
The chlorine isotope composition of Earth’s interior can place strong constraints on deep-Earth cycling of halogens and the origin of mantle chemical heterogeneity. However, all mantle-derived volcanic samples studied for Cl isotopes thus far originate from submarine volcanic systems, where the influence of seawater-derived Cl is pervasive. Here, we present Cl isotope data from subglacial volcanic glasses from Iceland, where the mid-ocean ridge system emerges above sea level and is free of seawater influence. The Iceland data display significant variability in δ 37 Cl values, from −1.8‰ to +1.4‰, and are devoid of regional controls. The absence of correlations between Cl and O isotope ratios and the lack of evidence for seawater-derived enrichments in Cl indicate that the variation in δ 37 Cl values in Icelandic basalts can be solely attributed to mantle heterogeneity. Indeed, positive correlations are evident between δ 37 Cl values and incompatible trace element ratios (e.g., La/Y), and long-lived radiogenic Pb isotope ratios. The data are consistent with the incorporation of altered lithosphere, including the uppermost sedimentary package, subducted into the Iceland mantle plume source, resulting in notable halogen enrichments in Icelandic basalts relative to lavas from adjacent mid-ocean ridges.