阿波罗月壤样品(E21)岩石学研究及溯源

中国科学院地质与地球物理研究所博物馆珍藏了一份阿波罗月壤样品（编号E21），但具体来自哪一次任务返回样品并不清楚。为了对该样品进行溯源，本文开展了初步的岩石学研究。结果显示，该样品由玄武岩岩屑、角砾岩屑和玻璃珠组成，其中玄武岩岩屑的矿物组成、结构和成分与月海玄武岩高度相似，且钛铁矿含量（平均~14.8vol%）、全岩（平均~10.5% TiO₂）以及富Mg橄榄石的Ti含量（平均Ti~1000×10^-6）均显示为典型的高Ti玄武岩特征。结合较低的高地物质比例，以及部分玄武岩K₂O含量偏高的特点，可以推断E21号月壤来自阿波罗11任务返回样品。
此次研究还发现两颗来自高地镁质岩套岩屑，全岩和矿物化学成分指示其为苏长岩。玄武岩岩屑的橄榄石微量元素特征表明，高Ti玄武岩的母岩浆具有较低的Ni、Cr和P含量，这一特征可能反映其源区物质相对亏损这些元素，或在形成过程中有低Ni、Cr组分混入。E21月壤对探究月球早期演化历史以及嫦娥五号月壤研究均有重要意义。

Tracing the source of Apollo lunar soil (E21): Petrological evidence

Institute of Geology and Geophysics, Chinese Academy of Sciences preserves an Apollo lunar soil sample (E21). However, it is still unclear which mission returned the sample. In this paper, we conduct a preliminary petrological study on this soil to trace its source. This sample consists of basalt clasts, breccia clasts, and glass spheres. The basalt clasts have mineral constitutions, microtextures, and compositions similar to mare basalt. It is further confirmed that the studied clasts belong to high-Ti mare basalt, according to the high modal abundance of ilmenite (average~14.8vol%), bulk TiO2 content (average~10.
5%), and Ti concentrations (average~1000×10-6) in the early crystallized olivine (Fo72). The scarce highlands materials and high K2O contents in some basalt clasts indicate that the E21 sample was most likely sourced from Apollo 11 soils. Two lithic clasts dominated by orthopyroxene and plagioclase are identified as highlands norite, based on bulk rock and low-Ca pyroxene composition. Trace element composition of olivine indicates that the parental magma of high-Ti basalt has low concentrations of Ni, Cr, and P. This feature may result from the depletion of such elements in its mantle source or the assimilation of shallow, low Ni and Cr components. The Apollo 11 soil E21 would have implications for our understanding of the early evolutionary history of the Moon and provides a good comparable sample for the Chang'e-5 lunar soils.