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

Demidova, S.I.; Nazarov, M.A.; Anand, Mahesh and Taylor, L.A. (2003). Lunar regolith breccia Dhofar 287B: A record of lunar volcanism. Meteoritics and Planetary Science, 38(4) pp. 501–514.

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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.

Item Type: Journal Article
ISSN: 1086-9379
Keywords: Dhofar 287B; lunar meteorite; regolith
Academic Unit/Department: Science > Environment, Earth and Ecosystems
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 2181
Depositing User: Mahesh Anand
Date Deposited: 07 Jun 2006
Last Modified: 02 Dec 2010 19:46
URI: http://oro.open.ac.uk/id/eprint/2181
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