Geochemistry and petrology of lunar meteorite Queen Alexandra Range 94281, a mixed mare and highland regolith breccia, with special emphasis on very‐low‐titanium mafic components

Abstract

Abstract-Queen Alexandra Range (QUE) 94281, a lunar meteorite recently discovered in Antarctica, is a glassy-matrix, clast-rich regolith breccia containing a mixture of mafic, volcanic-glass and gabbroic constituents and a diverse set of highland constituents. In thin section, the clast assemblage is dominated by coarse mineral debris from a shallow intrusive or hypabyssal setting, or from deep within a thick mare flow. Abundant coarse-grained pyroxene clasts have fine-scale exsolution lamellae and compositions similar to pyroxenes of known lunar very-low-Ti (VLT) basalts and other lunar meteorites of basaltic composition. Pyroxene compositions follow Fe-enrichment extending to hedenbergite, which is associated with fayalite and cristobalite, indicating slow cooling. We refer to the protolith of the crystalline VLT component as VLT gabbro. Fragments of pyroclastic glasses that have high Fe and low Ti concentrations, similar to the pyroclastic green glasses known from Apollo samples, are common. Lithic clasts include abundant subrounded, glassy to cryptocrystalline, aluminous (-17-30 wt% Al2O3) KREEP-poor melt breccias of highland origin and a variety of other feldspathic impactites. On the basis of composition of our subsamples, QUE 94281 consists of -54 wt% mafic or "mare" components and 46 wt?h feldspathic or "highland" components.The bulk composition of QUE 94281 is similar to that of Yamato (Y) 793274, but QUE 94281 has slightly greater concentrations of some siderophile elements and slightly lower concentrations of those elements contributed mainly by mafic constituents. Differences in siderophile element concentrations are consistent with longer surface exposure of QUE 94281. Minor differences in trace element variations of subsamples of the two meteorites suggest subtle differences in the composition of their highland constituents. Nonetheless, the overall similarity of compositions supports the possibility that they were ejected from the same source region on the Moon.The crystalline VLT component of QUE 94281 differs from those known from Apollo 17 and Luna 24 VLT lithologies and from that of basaltic breccia Elephant Moraine (EET) 8752 1. The VLT-gabbro component and the ferroan VLT 'volcanic glasses in QUE 94281 have compositions that may be petrogenetically related by derivation from a common picritic parent composition, represented by an ultramafic glass found in QUE 9428 1.

Labile trace elements in basaltic achondrites: Can they distinguish between meteorites from the Moon, Mars, and V‐type asteroids?

“…Results for QUE 93069 include: Au, Sb, Se, Ag, Zn, Rb, Cs and U (Koeberl et al 1996); and Au and U (Korotev et al 1996). For QUE 94281 data exist for Ga and U (Dreibus et al 1996); Au, Ga, and U (Arai and Warren 1999); Au and U (Korotev et al 2003b); and Au, Cs, and U (Jolliff et al 1998). Results for Y-981031 include Au, Cs, and U (Korotev et al 2003b).…”

Petrography, mineralogy, and trace element geochemistry of lunar meteorite Dhofar 1180

“…Mafic minerals in both C-6 and C-10 have relatively high Mg#, probably representing Mg-rich basalts. The mineral assemblage of fayalite, ferroaugite, and silica has been observed in other lunar breccias (e.g., QUE 94281, Jolliff et al 1998;EET 96008, Anand et al 2003; breccia portion of NWA 773, Fagan et al 2003;Miller Range [MIL] 05035, Liu et al 2009). This mineral assemblage indicates an extreme differentiation and Fe-enrichment with very low Mg# values (0.12 for fayalite and 0.25-0.26 for ferroaugite).…”

“…Mafic minerals in Calcalong Creek are also Mgricher than those of Dhofar 1180 (Hill and Boynton 2003). There are several other mingled lunar breccias, such as EET 96008 (Anand et al 2003), Y-793274 (Koeberl et al 1991;Arai and Warren 1999), and QUE 94281 (Jolliff et al 1998). Compared to these lunar breccias, Dhofar 1180 contains higher Al 2 O 3 content and lower FeO content, implying a lower mafic component.…”

“…The bulk compositions of Calcalong Creek (Hill and Boynton 2003), Sayh al Uhaymir (SaU) 300 (Hsu et al 2008), as well as data for Yamato 793274 (Koeberl et al 1991), Elephant Moraine (EET) 96008 (Anand et al 2003), Queen Alexandra Range (QUE) 94281 (Jolliff et al 1998), are also listed for comparison. In our Dhofar 1180 sample, only 4.91 wt% Fe (=6.31 wt% FeO) was detected, lower than that (9.3 wt% FeO) reported by Bunch et al (2006), which is probably due to sampling bias.…”

“…CI-normalized (Anders and Grevesse 1989) REE abundances of Dhofar 1180 and some lunar meteorites. Data are from Koeberl et al (1991);Jolliff et al (1998);Anand et al 2003;Hill and Boynton (2003), Karouji et al (2006), andHsu et al (2008). Although impacts could cause melting of target materials, most impact glasses are considered as products of small impacts.…”