TRACE-ELEMENTS IN 59 MOSTLY HIGHLAND MOON ROCKS

We report new chemical analyses for up to 26 trace elements, including seldom-determined highly siderophile elements Ir, Os, Re, Au, Pd, and Ge, for 59 lunar samples. Most of these samples are polymict breccias from Apollo 16. Remarkably few have Group 7 (extremely low Au/Ir) meteoritic components. Several samples have uncommonly high Au/(Ir + Re) ratios, even higher than group IL. Volatile-element enrichments are found in several fragments from ''rusty rock'' 66095. A matrix sample from fragmental breccia 60639 shows Cd and In enrichments, also observed previously in samples of anorthosite and mare basalt from the same breccia. Evidently, for these highly labile elements, chemical exchange has affected clasts that for most other elements are pristine. Interesting pristine samples analyzed include the sodic ferrogabbro component of 67915, which has an extraordinarily high Re concentration, by pristine rock standards; KREEP basalt 15386, which has extremely low Ir, but (in common with most other pristine KREEP rocks) a relatively high Ge concentration; and FAS anorthosite 65315, which has probably the lowest REE levels of any lunar anorthosite.