^a,bH. Li, ^bZ. Wang, ^cZ. Chen, ^bW. Tian, ^dW-R. Wang, ^bG. Zhang ^bL. Zhang
Geochimica et Cosmochimica acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.09.002]
^aCenter for High Pressure Science and Technology Advanced Research (HPSTAR), Beijing 100193, China

^bMOE Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China
^cLaboratory of Metallogeny and Mineral Assessment of MNR, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
^dKey Laboratory of Paleomagnetism and Tectonic Reconstruction of MNR, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
Copyright Elsevier

Apatite is ubiquitous in lunar samples and has been used widely for estimating volatile abundances in the lunar interior. However, apatite compositional and isotopic variations within and between samples have resulted in varying and ambiguous results. Understanding apatite petrogenesis will help with both identifying the appropriate composition for volatile estimation and interpreting isotopic variations. Here we report a comprehensive petrogenetic investigation of apatite in Chang’E-5 (CE5) basaltic sample CE5C0800YJYX013GP. Apatite displays both intra-grain and inter-grain compositional variations with F and Cl contents falling in the ranges of 0.97–2.47 wt% and 0.24–1.09 wt%, respectively. These apatite compositions show relatively low F and high Cl characteristics in comparison to apatites of Apollo high-Ti and low-Ti mare basalts, but are similar to those reported for lunar meteorites LAP 04841 and MIL 05035. We discern three zoning profiles: fractional crystallization (FC)-dominated, degassing-induced and a third indicated by REE-enriched cores, which are interpreted as representing different generations of apatite. FC-dominated zoning is characterized with decreasing F and increasing Cl and S contents from core to rim; while the opposite is true for the degassing-induced zoning. Regardless of the zoning patterns, apatite Cl and S contents display positive correlations, with S contents up to ∼ 3000 ppm, much higher than previous reports for Apollo samples (up to ∼ 600 ppm). We demonstrate that the fractional crystallization model proposed by Boyce et al. (2014) in combination with H₂O degassing and high S contents in melt (likely at sulfide saturation) can explain these high Cl and S contents observed in CE5 apatite.

Based on the core composition of the FC-dominated zoning profile, which has the lowest incompatible element concentrations, bulk F, Cl and H₂O contents in the parental melt are estimated to be ∼ 72 ± 21, ∼43 ± 14 and ∼ 1576 ± 518 ppm, respectively. These estimates have lower F/Cl ratios than those measured in olivine-hosted melt inclusions from Apollo mare basalts. By adopting the petrogenetic model for CE5 basalt proposed by Su et al. (2022), i.e., 10 % partial melting of a hybrid mantle source, followed by ∼ 30–70 % fractional crystallization (∼50 % for our sample), we estimate the F, Cl, H₂O and S contents in the mantle source are in the ranges of ∼ 2.5–4.6, ∼0.7–1.4, ∼53–105 and ∼ 38–125 ppm, respectively, similar to estimates for both depleted Earth mantle and primitive lunar mantle. However, by adopting the model of Tian et al. (2021), 2–3 % partial melting of a mantle source composed of 86 PCS+2% TIRL (PCS, percent crystallized solid; TIRL, trapped instantaneous residual liquid), followed by 43–88 % fractional crystallization, these estimates will be 5–10 times lower. To be certain whether the relatively low F and high Cl characteristics of CE5 apatite imply an enriched mantle source requires further evaluation of the petrogenetic models for CE5 basalt.

^1,2A. Kereszturi et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14255]
¹Konkoly Thege Astronomical Institute, HUN-REN Research Centre for Astronomy and Earth Sciences, Budapest, Hungary
²CSFK, MTA Centre of Excellence, Budapest, Hungary

A medium-grade, poorly weathered CO3-type meteorite was subjected to artificial space weathering by 1 keV protons in three subsequent steps, with gradually increasing doses from 10¹¹ to 10¹⁷ protons per cm². The resulting mineral modifications were identified by Raman spectroscopy, with specific emphasis on main minerals such as olivine (bands: 817, 845 cm⁻¹), pyroxene (1007 cm⁻¹), and partly amorphous feldspar (509 cm⁻¹), considering variation in band shift and bandwidth (full width at half maximum, FWHM). After the first and second irradiations, variable band position changes were observed, probably from metastable alterations by Mg loss of the minerals, while the third stronger irradiation showed band shift dominated by amorphization. The olivine and pyroxene show weak increase in FWHM after the first irradiation, while more changes happened after the second and third irradiations. The flux after the third irradiation was higher than in other works, caused stronger damage in crystal lattice, partly resembling to dimerization as described by shock metamorphism. The glassy feldspar was characterized by high FWHM values already at the beginning, indicating weak crystallinity already that become even less crystallized, thus their bands disappeared after the third irradiation. Bands of hydrous minerals (goethite clay, chlorite) were not visible after the third irradiation, confirming some earlier results in the literature. Based on our results, moderately fresh surfaces could show stochastic but small spectral differences compared to the fresh most meteorites by metastable mineral alterations. The interpretation of Raman spectra of heavily space-weathered surfaces could further benefit from the joint evaluation of alteration induced by both shock impact alteration and space weathering.