热力学计算模拟对月球镁质岩套源区的约束  

Constraints on the Source of the Lunar Mg-Suite by Thermodynamic Simulation

作　　者：鞠东阳 杜蔚 李瑞[1,2] 庞润连 JU Dong-yang;DU Wei;LI Rui;PANG Run-lian(State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China;Chinese Academy of Sciences Center for Excellence in Comparative Planetology,Hefei 230026,China)

机构地区：[1]中国科学院地球化学研究所,矿床地球化学国家重点实验室,贵阳550081 [2]中国科学院大学,北京100049 [3]中国科学院比较行星学卓越创新中心,合肥230026

出　　处：《矿物岩石地球化学通报》2021年第5期1154-1165,共12页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金项目(41773052,41973058)。

摘　　要：镁质岩套是月球上最重要的岩石之一。通常认为该类岩石的母岩浆来自月幔翻转引起的深部物质的减压熔融或者月壳底部的混合杂化。但是,这两类模型分别面对无法重现样品中橄榄石的Cr_(2)O_(3)含量过低等地球化学特征,也无法解释镁质岩套与其他月球样品年龄重合的问题。本文采用热力学计算方法,通过改变源区物质组成、熔融程度、熔融方式及结晶方式等参数,对两种模型进行了一系列的正演研究。结果表明,月球的镁质岩套有多种成因:月幔物质减压熔融形成的熔体通过平衡结晶可以形成镁质岩套,并满足样品中橄榄石Cr_(2)O_(3)含量的制约;减压熔融模型可以解释某些月球样品年龄的重合,但是成分较为单一,而混合杂化模型形成的镁质岩套成分范围较广。Mg-suite is one of the most important lunar samples. It is generally believed that the parent magma of Mg-suite was sourced from the decompression melting of cumulates deep inside the moon caused by the overturning of lunar mantle or the hybridization of the bottom part of lunar crust. However, these two models neither can reproduce geochemical characteristics of relatively low Cr_(2)O_(3) content in olivine of the Mg-suite, nor explain the chronological overlap of Mg-suite with other lunar samples. In this study, we have carried out thermodynamic simulations to test the two hypothetical models by changing parameters including the compositions of source materials, melting degrees, melting and crystallization modes. Our simulating results indicate that the lunar Mg-suite could be multiple origins:(1) the Mg-Suite could be formed by the equilibrium crystallization of the melt derived from the decompression melting of lunar mantle materials, with its olivine containing low Cr_(2)O_(3) content;(2) the decompression melting model can only be used to explain the overlapped ages of some lunar samples, but the lunar Mg-suite shows little variation on composition, while the compositions of Mg-suites calculated by using the hybridization model vary in a relatively wide range.

关 键 词：热力学计算 镁质岩套 减压熔融 混合杂化 月壳年龄 

分 类 号：P691[天文地球—地质学]