Trace Element Chemistry of Lunar Highland Meteorites from Oman

Introduction: During the last few years, numerous lunar meteorites have been discovered in the Dhofar region of Oman. All of them are lunar highland brec-cias, except for Dhofar 287A, which is a mare basalt. In this paper, we present the first trace-element chemistry of these new lunar highland meteorites: Dhofar 280, 301-310. Mineralogy and petrology of these meteorites have been reported in [1,2,3]. and 310 were collected near to Dh 081 and Dh 280 in another area. Dh 280 is the largest meteorite in this group, hence, the designation as Dh 280 for this meteorite group. Representative 10-20 mg chips of each meteorite were analyzed for trace elements by INAA. Characteristic trace-element relationships are shown on Figs 1-5, as compared to those of other lunar meteorites and lunar rocks. Lithologic Compositions: Similar to other lunar meteorites, the Dhofar finds are depleted in incompatible elements and show a strong positive correlation on an Sm-Sc plot (Fig. 1). The trend is aligned in the general direction of the Luna 20 highland soil and lies within the noritic anorthosite field [4]. Obviously, lunar meteorites do not contain the MIMB (mafic-impact-melt breccia) component [4], which is of major significance in Apollo 16 soils. They do not show any evidence for contamination by KREEP and mare basalt material. However, the Dh 025 and the Dh 280 families are very different within the range of lunar meteorite compositions. Whereas the Dh 025 meteorites are highest in Sm and Sc, the Dh 280 group is lowest in these elements. Because Sc is present mainly in pyrox-ene, the Sc-and Sm-depleted finds should be enriched in anorthositic and/or troctolitic lithologies, and they are. On the MG# versus Sc plot (Fig. 2), the Dh 025 group appears to indicate the highest pyroxene (Sc) enrichment among lunar meteorites, whereas the low-Sc Dh 280 group shows a large scatter. Individual meteorites Dh 280 and 081 are lowest in MG# and highest in feldspar [2], e.g., highest in the FAN com-form a very compact group of rocks lowest in Sc and highest in MG#. This group is enriched in troctolitic lithologies [3]. Breccias Dh 302 and 305 are intermediate in composition.