Study On Petromineralogical Characteristics And Pairing Discrimination Of Lunar Meteorites NWA 15062 And NWA 15063

The formation and evolution of the Moon is one of the key scientific problems in the fields of solid earth and planetary science.Lunar feldspathic crust that firstly crystallized from the Lunar Magma Ocean can help us to understand the geological evolution history of the Moon and other terrestrial planets.However,the lack of lunar highland returned samples and the low precision of remote sensing data greatly restrict the understanding of the composition and geological processes of lunar highlands.Lunar meteorites randomly ejected from the Moon are the supplementary materials for the returned samples and remote sensing data.Lunar highland breccia is the polymict rock that was consolidated from the highland lithologies and mineral fragments.Such meteorites could preserve the composition and geological records of the lunar crust.This paper analyzes the rock textures,mineral composition,geochemical composition,and shock metamorphism features of two newly discovered lunar anorthositic troctolitic brecciated meteorites that have not been deeply studied before,NWA 15062 and NWA 15063,and combines existing sample analysis data（including Apollo/Luna return samples and lunar meteorites）using in-situ analysis techniques such as optical microscopy,scanning electron microscopy,electron probe microanalysis,and laser Raman spectroscopy.The research content and new knowledge obtained in this paper are as follows:1.Based on the major element compositions of NWA 15062 and NWA 15063,the Mg#of mafic minerals and the An#of plagioclase,and the Fe²⁺/Mn（mol）ratios of olivine and pyroxene,both meteorites are suggested to originate from the highlands of the Moon and are classified as Lunar anorthositic troctolitic breccia.2.NWA 15062 and NWA 15063 exhibit clear shock metamorphic features,with numerous shock veins observed in both samples.The plagioclase in NWA 15062 is almost completely transformed into maskelynite,while some plagioclase is still preserved in NWA 15063.The development of abundant fractures in mafic minerals,which radiate outward,suggests that these fractures formed after the formation of the maskelynite.The two meteorites experienced extensive recrystallization after the shock metamorphism,followed by rapid cooling.However,the cooling rate of NWA15063 was too fast for the recrystallization to reach a state of equilibrium.The shock pressure of both meteorites was not lower than 30 GPa,and the peak temperature of thermal metamorphism was around 1100℃.The shock metamorphic grade is estimated to be S5,and the degree of weathering is W1.3.Combining the petrological and chemical analyses of the two meteorite samples,the heat source for thermal metamorphism was likely the impact melt layer generated by the impact in the lunar crater.The locations where thermal metamorphism occurred were the accumulated areas below the impact melt layer and the upper edges of the melt layer,which are close to the lunar surface and have a high rate of heat dissipation,resulting in a short duration of thermal metamorphism4.Based on the petrological characteristics,mineral abundances and chemical compositions,major element compositions,shock metamorphic degree,and weathering degree of the two meteorites,it is suggested that NWA 15062 and NWA15063 may be paired meteorites...