Petrology of ALHA 81005, the first lunar meteorite
The meteorite thought to be best described as a lunar highland regolith breccia from a non-KREEPy region. The controversy that remains as to the most likely source region is discussed. It is noted that several large lunar nearside craters have been proposed (Ostertag and Ryder, 1983). After finding a very-low-titanium (VLT) mare basalt clast in a thin section of ALHA 81005, Treiman and Drake (1983) have suggested that this constrains the source to being near a region with VLT basalt. It is pointed out, however, that the unexplored far side of the moon cannot be ruled out. Most of the lithic clasts that are abundant in the meteorite are members of the anorthosite-norite-troctolite highland suite. It is noted that plagioclase compositions in lithic clasts and single grains are calcic (An94-98).