Lunar regolith breccia Dhofar 287B: A record of lunar volcanism

Abstract

Abstract-Dhofar 287 (Dho 287), a recently found lunar meteorite, consists in large part (95%) of low-Ti mare basalt (Dho 287A) and a minor, attached portion (~5%) of regolith breccia (Dho 287B). The present study is directed mainly at the breccia portion of this meteorite. This breccia consists of a variety of lithic clasts and mineral fragments set in a fine-grained matrix and minor impact melt. The majority of clasts and minerals appear to have been mainly derived from the low-Ti basalt suite, similar to that of Dho 287A. Very low-Ti (VLT) basalts are a minor lithology of the breccia. These are significantly lower in Mg# and slightly higher in Ti compared to Luna 24 and Apollo 17 VLT basalts. Picritic glasses constitute another minor component of the breccia and are compositionally similar to Apollo 15 green glasses. Dho 287B also contains abundant fragments of Mg-rich pyroxene and anorthite-rich plagioclase grains that are absent in the lithic clasts. Such fragments appear to have been derived from a coarse-grained, Mg#-rich, Na-poor lithology. A KREEP component is apparent in chemistry, but no highlands lithologies were identified. The Dho 287 basaltic lithologies cannot be explained by near-surface fractionation of a single parental magma. Instead, magma compositions are represented by a picritic glass; a low-Ti, Na-poor glass; and a low-Ti, Na-enriched source (similar to the Dho 287A parental melt). Compositional differences among parent melts could reflect inhomogeneity of the lunar mantle. Alternatively, the low-Ti, Na-poor, and Dho 287A parent melts could be of hybrid compositions, resulting from assimilation of KREEP by picritic magma. Thus, the Dho 287B breccia contains lithologies from multiple magmatic eruptions, which differed in composition, formational conditions, and cooling histories. Based on this study, the Dho 287 is inferred to have been ejected from a region located distal to highlands terrains, possibly from the western limb of the lunar nearside, dominated by mare basalts and KREEP-rich lithologies.

Compositional and lithological diversity among brecciated lunar meteorites of intermediate iron concentration

“…It is ironic that the existence of Kalahari 008/009 and other multi-lithologic lunar meteorites Demidova et al 2003;Gnos et al 2004;Haloda et al 2009) weakens inferences that we make here that a compositional and petrographic difference between two lunar meteorite stones provides evidence that the two stones are not paired. Nevertheless, if the Kalahari 008 and 009 stones made the Moon-Earth trip as part of a single meteoroid, that meteoroid was an unusual lunar rock.…”

Petrogenesis of lunar highlands meteorites: Dhofar 025, Dhofar 081, Dar al Gani 262, and Dar al Gani 400

“…It has been noted previously that desert weathering tends to alter the LREE chemistry of hot-desert meteorites, (Anand et al 2003;Demidova et al 2002;Fagan et al 2001b;Jolliff et al 1998;Koeberl et al 1991b;Lindstrom et al 1991;Snyder et al 1999;Kallemeyn 1989, 1993); b) enlarged view of the highland breccia suite. The filled diamonds are lunar highland meteorites Dho 025, Dho 081, DaG 262, and DaG 400 Warren et al 2001;Zipfel et al 1998).…”

Constraining the source regions of lunar meteorites using orbital geochemical data

“…Average Apollo and Luna landing sites bulk soil and regolith breccia compositions used for the validation exercise of this study AE the analytical 1r standard deviation. Data obtained from Rhodes and Blanchard (1981), Morris et al (1983), Simon et al (1985), McKay et al (1986aMcKay et al ( , 1986b, Jerde et al (1987Jerde et al ( , 1990, and Korotev (1997 (Boynton and Hill 1983;Korotev et al 1983Korotev et al , 2003Korotev et al , 2009Laul et al 1983;Palme et al 1983;Fukukoa et al 1986;Bischoff et al 1987;Eugster et al 1989;Koeberl et al 1989;Yanai and Kojima 1991;Jolliff et al 1993Jolliff et al , 2003Koeberl et al 1993;Lindstrom et al 1991;Warren and Kallemeyn 1993;Daubar et al 2002;Anand et al 2003Anand et al , 2006Demidova et al 2003Demidova et al , 2007Fagan et al 2003;Hill and Boynton 2003;Karouji et al 2004;Righter et al 2005;Zeigler et al 2005Zeigler et al , 2007Day et al 2006;Joy et al 2006Joy et al , 2008aJoy et al , 2008bJoy et al , 2010Nyquist et al 2006;…”

“…The basalt clast has low-Ti content and a higher concentration of LREE elements compared with other low-Ti basalts, see Table 2. The regolith breccia portion contains low-Ti basalts, impact melt breccia fragments, and glass and mineral fragments, but no evidences of anorthositic lithologies Demidova et al 2003). Sm-Nd and U-Pb analysis of the basalt clast give ages of 3.4 Ga (Shih et al 2002;Terada et al 2008).…”