铁同位素分馏与地幔的氧逸度

Iron isotope fractionation and the oxygen fugacity of the mantle.

作者信息

Williams Helen M, McCammon Catherine A, Peslier Anne H, Halliday Alex N, Teutsch Nadya, Levasseur Sylvain, Burg Jean-Pierre

机构信息

Department of Earth Sciences, ETH-Zurich, Sonneggstrasse 5, CH-8092 Switzerland.

出版信息

Science. 2004 Jun 11;304(5677):1656-9. doi: 10.1126/science.1095679.

DOI:10.1126/science.1095679

PMID:15192225

Abstract

The oxygen fugacity of the mantle exerts a fundamental influence on mantle melting, volatile speciation, and the development of the atmosphere. However, its evolution through time is poorly understood. Changes in mantle oxidation state should be reflected in the Fe3+/Fe2+ of mantle minerals, and hence in stable iron isotope fractionation. Here it is shown that there are substantial (1.7 per mil) systematic variations in the iron isotope compositions (delta57/54Fe) of mantle spinels. Spinel delta57/54Fe values correlate with relative oxygen fugacity, Fe3+/sigmaFe, and chromium number, and provide a proxy of changes in mantle oxidation state, melting, and volatile recycling.

摘要

地幔的氧逸度对地幔熔融、挥发物形态以及大气的演化有着根本性的影响。然而，人们对其随时间的演化了解甚少。地幔氧化态的变化应反映在地幔矿物的Fe3+/Fe2+中，进而反映在稳定铁同位素分馏中。本文表明，地幔尖晶石的铁同位素组成（δ57/54Fe）存在显著的（1.7‰）系统变化。尖晶石δ57/54Fe值与相对氧逸度、Fe3+/∑Fe以及铬数相关，并可作为地幔氧化态、熔融和挥发物再循环变化的一个指标。