| 2181 |
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. |