^1,2Le Zhang,^1,2Ya-Nan Yang,^1,2Jintuan Wang,^1,2Ze-Xian Cui,^1,2Cheng-Yuan Wang,^1,2Peng-Li He,^1,2Yan-Qiang Zhang,^1,2Mang Lin,^1,2 Yi-Gang Xu
American Mineralogist 110, 1462-1471 Link to Article [https://doi.org/10.2138/am-2024-9577]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
²CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, China
Copyright: The Mineralogical Society of America

Silicate liquid immiscibility was a common mechanism during the late-stage evolution of lunar basaltic magmas, which produced coexisting and immiscible Si- and Fe-rich melts. However, the relationship between silicate liquid immiscibility and lunar granitic rocks is debated. In this study, we investigated Si-rich melt inclusions hosted in fayalite fragments from lunar soil returned by the Chang’e 5 mission. These melt inclusions have high SiO2 (76.4 wt%), Al2O3 (11.1 wt%), and K2O (5.8 wt%), and low FeO (2.8 wt%), TiO2 (0.42 wt%), and MgO (0.02 wt%) contents. The texture and chemical composition indicate that these Si-rich melt inclusions formed through late-stage silicate liquid immiscibility of the Chang’e 5 mare basaltic magma. Mass balance considerations show that the unfractionated rare earth element patterns and Eu anomalies of these melt inclusions are similar to those of lunar granitic rocks. Dynamic calculations indicate that the accumulation of Si-rich melt was hindered by the high cooling rate of the Chang’e 5 basaltic magma after eruption. However, in deep-crustal magma chambers, basaltic magma would have cooled slowly, and the Si-rich melt generated by late-stage silicate liquid immiscibility would possibly have had enough time to migrate upward and accumulate to form a granitic melt body of significant size. The results of this study support the possibility that lunar granitic rocks are products of silicate liquid immiscibility.

¹D. Rezes,²I. Gyollai,³S. Biri,⁴K. Fintor,³Z. Juhász,³R. Rácz,³B. Sulik,^2,5M. Szabó,^1,5Á. Kereszturi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70038]
¹Konkoly Thege Miklos Astronomical Institute, Research Centre for Astronomy and Earth Sciences, HUN-REN, Budapest, Hungary
²Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, HUN-REN, Budapest, Hungary
³Institute for Nuclear Research Debrecen, HUN-REN, Debrecen, Hungary
⁴Department of Geology, University of Szeged, Szeged, Hungary
⁵MTA Centre of Excellence Budapest, Research Centre for Astronomy and Earth Sciences, Budapest, Hungary
Published by arrangement with John Wiley & Sons

This paper presents the results of proton irradiation actions of three meteorites which were studied by LV-SEM, Raman spectroscopy, and FTIR spectroscopy methods, both before and after the artificial irradiations. The three samples are the Dhofar (Dho) 007 eucrite, the Northwest Africa (NWA) 4560 LL3.2, and the NWA 5838 H6 chondrite meteorites, which were irradiated by 1 keV average solar wind protons using the ECR ion source at ATOMKI with 1017 and 1019 ions cm−2 fluence values. According to FTIR spectra, the first irradiation induced metastable alteration, and after the second irradiation, crystals organized into more stable phases. In the Dho 007 sample, the pyroxene shows a positive peak shift and FWHM change after the first irradiation, with decreased intensity of spectra. After the second irradiation, the peak position and FWHM decreased but showed an increase in comparison with the state before the irradiation in the FTIR spectra. The minor band near 620 cm−1 disappeared after the irradiations in the FTIR spectra; however, the Raman spectra do not show the disappearance of minor bands. The olivine (in NWA 4560 and NWA 5838) and pyroxene (in Dho 007) showed negative peak shifts indicating escape of Mg2+ ions from the crystal lattice, together with positive peak shifts and increase of FWHM indicating amorphization of the crystal structure. Considering band shapes and intensities, both FTIR and Raman spectra showed decreasing intensity after the first irradiation, with possible metastable alteration. However, the spectra after the second irradiation show a moderate increase in FWHM change, which indicates a change in the crystal lattice. In the FTIR spectra, the minor band at 620 cm−1 disappeared in the case of pyroxene.