Hsu, and 10 co-authors, reported in 2008 that 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.
The authors concluded that SaU 300 is dominated by a fine-grained crystalline matrix surrounding mineral fragments and lithic clasts. Lithic clasts are mainly anorthositic to noritic. Mare basalt and KREEPy rocks are absent. A second impact event generated veins and glassy impact melts whose compositions are close to anorthositic norite. SaU 300 is a feldspathic impact-melt breccia.
Major element concentrations of SaU 300 are very similar to those of mingled lunar meteorites (e.g., Calcalong Creek and Y-983885). However, SaU 300 is largely free of mare basalt and KREEP rocks. It is mainly composed of highlands feldspathic rocks with a small amount of mafic rocks. With 8.16 wt% FeO, SaU 300 is more mafic than other nominally feldspathic highlands meteorites. The bulk REE abundances of SaU 300 are significantly lower than those of Calcalong Creek and Y-983885, but resemble those of feldspathic highlands meteorites and the average lunar highlands crust. SaU 300 is a unique lunar meteorite and represents a lunar surface composition distinct from any other known lunar meteorites.
The lunar meteorite SaU 300 also contains high siderophile abundances with a chondritic Ni/Ir ratio, indicating its source region close to the lunar surface. Bulk Sr concentration is relatively elevated in SaU 300 compared to other lunar meteorites and Apollo and Luna samples. But Ba concentration in SaU 300 falls within the lower field observed for lunar meteorites and Apollo and Luna samples. The elevated Sr concentration indicates that SaU 300 has experienced moderate terrestrial weathering.
On the basis of the low Th concentration (0.46 ppm) and the lack of KREEPy and mare basaltic components, the source region of SaU 300 could have been within the FHT at a significant distance from the PKT, probably on the lunar far side.
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