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Petrographic and geochemical data are presented for some ouachitites from the Schirmacher Oasis. The studied dike intruded into the metamorphic basement of the East Antarctic craton. The ouachitite samples contain substantial amounts of zoned phlogopite and diopsidic to salitic pyroxene as phenocrysts. K-rich nepheline is the predominant phase of the matrix. The rocks are characterized by low SiO2 concentrations (up to 36.5 wt.%), low mg# and high abundances of Al2O3, alkalis and volatiles. Trace element compositions of the Schirmacher ouachitites differ from those of ultramafic lamprophyres from other regions in that they contain significantly lower Cr and Ni concentrations and relatively low enrichments in LILE and LREE. The studied rocks have low Nd-143/Nd-144 and enhanced Sr-87/Sr-86 ratios. Pb isotope compositions of the ouachitites closely resemble those of MORE. The delta(18)O values range between 4. 1 and 4.7 parts per thousand which may be due to interactions with meteoric water. Because the Schirmacher ouachitites are only represented by a few samples it is impossible to discuss the petrogenesis of this magma. However, according to trace element and isotopic characteristics, it can be ruled out that Schirmacher ouachitites and associated minettes (documented in Hoch, 1997; Hoch and Tobschall, 1998) were derived from the same mantle reservoir.