德国明斯特大学Klaver, Martijn及其团队成员的最新研究揭示，月球上富钛的玄武岩质熔体受到反应流动过程的调节。这一研究成果于2024年1月15日发表在国际顶尖学术期刊《自然—地球科学》上。

研究进行了岩石学反应实验，实验结果发现，含钛铁矿堆积体的部分熔体与月幔中的橄榄石和斜方晶辉石发生反应，使熔体组成转变为高钛系列。新的高精度Mg同位素数据证实，高钛玄武岩具有可变且同位素轻的Mg同位素组成，与平衡部分熔融不一致。

研究人员采用扩散模型证明，来自钛铁矿堆积体的部分熔体在反应流动中的动力学同位素分馏，可以解释这些异常轻的Mg同位素组成，以及其他元素(如Fe, Ca和Ti)的同位素组成。

虽然这个模型不能完全复制月球的熔体—固体相互作用，但该团队成员认为，在月球表面喷发的富钛岩浆可以通过含钛铁矿堆积体的部分熔融获得，熔体通过月幔中的反应流动对其元素和同位素组成进行了广泛的修改。因此，反应性流动可能是降低熔体密度并使得高钛熔体在月球表面喷发的关键过程。

据介绍，月球上富钛的玄武岩岩浆活动的起源仍然是个谜。月幔中含钛铁矿的堆积体通常被认为是其的起源，但它们的部分熔融物在成分上并不匹配，且密度太大，无法喷发。

附：英文原文

Title: Titanium-rich basaltic melts on the Moon modulated by reactive flow processes

Author: Klaver, Martijn, Klemme, Stephan, Liu, Xiao-Ning, Hin, Remco C., Coath, Christopher D., Anand, Mahesh, Lissenberg, C. Johan, Berndt, Jasper, Elliott, Tim

Issue&Volume: 2024-01-15

Abstract: The origin of titanium-rich basaltic magmatism on the Moon remains enigmatic. Ilmenite-bearing cumulates in the lunar mantle are often credited as the source, but their partial melts are not a compositional match and are too dense to enable eruption. Here we use petrological reaction experiments to show that partial melts of ilmenite-bearing cumulates react with olivine and orthopyroxene in the lunar mantle, shifting the melt composition to that of the high-Ti suite. New high-precision Mg isotope data confirm that high-Ti basalts have variable and isotopically light Mg isotope compositions that are inconsistent with equilibrium partial melting. We employ a diffusion model to demonstrate that kinetic isotope fractionation during reactive flow of partial melts derived from ilmenite-bearing cumulates can explain these anomalously light Mg isotope compositions, as well as the isotope composition of other elements such as Fe, Ca and Ti. Although this model does not fully replicate lunar melt–solid interaction, we suggest that titanium-rich magmas erupted on the surface of the Moon can be derived through partial melting of ilmenite-bearing cumulates, but melts undergo extensive modification of their elemental and isotopic composition through reactive flow in the lunar mantle. Reactive flow may therefore be the critical process that decreases melt density and allows high-Ti melts to erupt on the lunar surface.

DOI: 10.1038/s41561-023-01362-5

Source: https://www.nature.com/articles/s41561-023-01362-5