Abstract
We report here the petrography, mineralogy, and geochemistry of lunar meteorite Sayh al
Uhaymir 300 (SaU 300). SaU 300 is dominated by a fine-grained crystalline matrix surrounding
mineral fragments (plagioclase, pyroxene, olivine, and ilmenite) and lithic clasts (mainly feldspathic
to noritic). Mare basalt and KREEPy rocks are absent. Glass melt veins and impact melts are present,
indicating that the rock has been subjected to a second impact event. FeNi metal and troilite grains
were observed in the matrix. Major element concentrations of SaU 300 (Al2O3 21.6 wt% and FeO
8.16 wt%) are very similar to those of two basalt-bearing feldspathic regolith breccias: Calcalong
Creek and Yamato (Y-) 983885. However, the rare earth element (REE) abundances and pattern of
SaU 300 resemble the patterns of feldspathic highlands meteorites (e.g., Queen Alexandra Range
(QUE) 93069 and Dar al Gani (DaG) 400), and the average lunar highlands crust. It has a relatively
LREE-enriched (7 to 10 × CI) pattern with a positive Eu anomaly (∼11 × CI). Values of Fe/Mn ratios
of olivine, pyroxene, and the bulk sample are essentially consistent with a lunar origin. SaU 300 also
contains high siderophile abundances with a chondritic Ni/Ir ratio. SaU 300 has experienced moderate
terrestrial weathering as its bulk Sr concentration is elevated compared to other lunar meteorites and
Apollo and Luna samples. Mineral chemistry and trace element abundances of SaU 300 fall within the
ranges of lunar feldspathic meteorites and FAN rocks. SaU 300 is a feldspathic impact-melt breccia
predominantly composed of feldspathic highlands rocks with a small amount of mafic component.
With a bulk Mg# of 0.67, it is the most mafic of the feldspathic meteorites and represents a lunar
surface composition distinct from any other known lunar meteorites. On the basis of its low Th
concentration (0.46 ppm) and its lack of KREEPy and mare basaltic components, the source region of
SaU 300 could have been within a highland terrain, a great distance from the Imbrium impact basin,
probably on the far side of the Moon.
