近日，美国洛杉矶大学Peng Ni团队研究了地球下地幔板块地幔熔融的开始：来自超深钻石中铁方镁石的证据。相关论文于2025年10月17日发表在《科学进展》杂志上。
铁方镁石（[Mgx,Fe1-x]O）作为亚岩石圈金刚石中最常见的包裹体，其结晶历史与成因深度至今尚未明晰。
研究组从具有地幔碳同位素特征的朱伊纳与康康金刚石中分离出的十九颗不同镁铁比值的微米级铁方镁石颗粒，可用于镁铁同位素分析。根据金刚石生长特征，可将其中的铁方镁石包裹体划分为两类：一类为预先存在的高镁铁比值包裹体，其镁铁同位素组成与地幔源区一致（δ26Mg = −0.23 ± 0.22‰；δ56Fe = 0.00 ± 0.14‰）；另一类为同期形成的低镁铁比值包裹体，呈现非地幔特征的重铁同位素（δ56Fe可达+0.3‰）与轻镁同位素组成（δ26Mg低至−1.4‰）。
研究组认为这些同期铁方镁石包裹体是由俯冲至下地幔深度的水合碳酸化橄榄岩质板片组分发生熔融所形成。这些熔体与周围还原性干性板片方辉橄榄岩持续反应，能够解释该研究中铁方镁石系列较大的镁铁比值和镍含量变化范围——该现象亦是全球铁方镁石数据中长期未获解释的重要特征。
附：英文原文
Title: Onset of slab mantle melting in Earth’s lower mantle: Evidence from ferropericlase in superdeep diamonds
Author: Peng Ni, Steven B. Shirey, Michael J. Walter, Janina Czas, Davide Novella, Fabrizio Nestola, Nico Kueter, Evan M. Smith, Thomas Stachel, D. Graham Pearson, Andrew Steele, Laura L. Gardner, Steven D. Jacobsen, Ben Harte, Jeffrey W. Harris, Anat Shahar
Issue&Volume: 2025-10-17
Abstract: Ferropericlase ([Mgx,Fe1-x]O), the most common inclusion in sublithospheric diamonds, has a poorly understood crystallization history and depth of origin. Nineteen microscopic ferropericlase grains with different Mg#s were released from Juína and Kankan diamonds with mantle-like carbon, for Mg and Fe isotopic analysis. Two groups of ferropericlase inclusions can be distinguished with respect to diamond growth: high-Mg# inclusions with mantle-like Mg and Fe (δ26Mg = 0.23 ± 0.22‰; δ56Fe = 0.00 ± 0.14‰) inferred to be preexisting and lower Mg# inclusions with non–mantle-like heavy Fe (δ56Fe up to +0.3‰) and light Mg (δ26Mg down to 1.4‰) inferred to be coeval. We propose that coeval ferropericlase inclusions formed by melting of hydrated and carbonated peridotitic slab components subducted to lower mantle depths. Continuous reaction of these melts with surrounding reduced, dry slab harzburgite can produce the large range in Mg# and Ni contents of our ferropericlase suite—a heretofore unexplained feature of global ferropericlase data.
DOI: adt9106
Source: https://www.science.org/doi/10.1126/sciadv.adt9106