Lunar meteorite Queen Alexandra Range 94281: Glass compositions and other evidence for launch pairing with Yamato 793274

Lunar meteorite Queen Alexandra Range 94281 is remarkably similar to Yamato 793274. Pairing in the conventional Earth-entry sense is difficult to reco ncile with the 2500 lan separation between the find locations for these two samples. Nonetheless, both of these regolith breccias are dominated by ver y-low-Ti (VLT) mare basalt, the pyroxenes of which feature exsolution lamel lae on a remarkably coarse scale (typical lamella width = 0.5-1 mu m) by ma re standards. The pyroxenes also show similar compositional variations (e.g ., Fe# vs. Ti# trends, which confirm parentage from VLT mare basalt). Plots using Al2O3 or FeO as a tracer of the highland component indicate indistin guishable internal mare-highland geochemical mixing trends. The same two di stinctive glass types dominate the mare glass populations of both breccias. Glass type YQ1 features 0.37-0.63 wt% TiO2, 10-17 wt% MgO, and 9-11 wt% Al 2O3 Glass type YQ2 features higher TiO2 (0.99-1.22 wt%), which is inversely correlated with MgO (12.6-13.8 wt%), and nearly constant (8.8 wt%) Al2O3 A ll of these similarities suggest that Y-793274 and QUE 94281 are a launch p air, which we designate YQ. Most of these similarities also extend to anoth er mare-breccia meteorite, Elephant Moraine 87521. However, the EET 87521 m are basalt is unusually V-poor (similar to 88 mu g/g), whereas the YQ mare component contains similar to 166 mu g/g. Queen Alexandra Range 94281 featu res a variety of textural domains. Discrete patches of dark matrix material appear to represent clods of mature regolith that have been mixed with a c oarser, relatively immature material. Interior to a frothy fusion crust are areas of massive glass that probably formed as a splash coating on QUE 942 81 when it was still on the Moon. The coarse YQ and EET 87521 pyroxene exso lution features imply relatively slow cooling in either a very shallow sill or an unusually thick (ponded) lava and/or later annealing within a crypto mare. Mare pyroclastic glasses, including the two YQ varieties, are systematicall y MgO-rich compared to crystalline mare basalts. This disparity may be a co nsequence of limited survival of graphite--the main fuel for explosive volc anism--during formation of the mare source regions as magma ocean cumulates . Graphite (2.2 g/cm(3)) survived preferentially in regions that avoided ex tensive early melting and thus remained MgO-rich. An apparent bimodality in the TiO2 contents of mare volcanics, especially the pyroclastic glasses, a lso seems a plausible consequence of petrogenesis by remelting of magma oce an cumulates. Cumulates deposited after the magma ocean evolved to ilmenite saturation had vastly higher TiO2 contents than cumulates deposited shortl y before. The YQ regolith's subequal proportions of mare and highland matte r are consistent with derivation from a terrain close to a mare-highland bo undary. However, a similar mixture might also develop through vertical mixi ng in a cryptomare or a region of thin mare coverage. Thus, unfortunately, the YQ bulk composition is not a very useful clue to the identity of the so urce crater.