Lunar Meteorites in FeO and Th Composition Space

The chart above is one of several that can be used to classify lunar meteorites by composition. This particular chart is useful because both FeO (total iron expressed as percent FeO) and Th (thorium expressed in µg/g or ppm [parts-per-million]) have been measured on the surface of the Moon by orbital spacecraft (Clementine and Lunar Prospector). In the large chart, Th is shown on a logarithmic scale because the range in concentrations is so great. The same data are shown in the inset on upper right, which excludes only the highest-Th point (30 µg/g), that for the impact-melt breccia lithology of SaU 169. For most meteorites, one point representing the mean composition is plotted. For a few meteorites with multiple lithologies (e.g., SaU 169 [$], Kalahari 008/009 [ß], NWA 773 and pairs [x]) 2 or 3 points are plotted, each representing a different lithology. Keep in mind that meteorites that plot together on this chart (e.g., the tight cluster of the inset in the upper left) may plot apart in charts using other element pairs. All of the data represented here is from my laboratory.