Alkaline basic lavas cap a number of nunataks extending westwards from Arnold Eschers Land to Hobbs Land, with one small area further south in J. L. Mowinkels Land, and another to the northeast at Wilkins Nunatakker. The lavas are flat-lying and overlie Caledonian, and possibly older, schists and gneisses. Some dykes have been reported from Hobbs Land and a possible volcanic neck identified (Brooks et al., 1979, Fig. 3). The rocks characteristically contain phenocrysts of olivine and clinopyroxene, and in some xenocrysts of kaersutite replaced by clinopyroxene, rhonite and a yellow sheet silicate, in a variable groundmass including glass, clinopyroxene, magnetite, and in some samples mica, perovskite, nepheline, analcime, ilmenite and plagioclase. They vary essentially from nephelinitic through basanitic types to nepheline hawaiites. Analyses of a range of minerals and of glass, which has a phonolitic composition, together with rock analyses, including trace elements, are given by Brooks et al. (1979).
BROOKS, C.K., PEDERSEN, A.K. and REX, D.C. 1979. The petrology and age of alkaline mafic lavas from the Nunatak Zone of central East Greenland. Bulletin, Gronlands Geologiske Undersogelse, 133: 1-28.