Iluilarssuk

In an area southwest of Frederikshab a swarm of northwest-trending, Mesozoic dolerite dykes is paralleled by fewer and generally thinner lamprophyric carbonatite dykes which range from a few mm to about 1 m in thickness. The rocks consist of a matrix of calcite, and less commonly dolomite or ankerite, and magnetite with megacrysts of phlogopite, salite, hornblende and olivine. Analyses indicate SiO2 values of 14-30%, CO2 16-19%, and generally K2O > Na2O (Walton and Arnold, 1970, Table 1). Most are ne normative with normative ac and lc in some. Nodules up to 6 cm in diameter are found, including olivine crystals thought to be of upper mantle origin, various types of granulites, and some with sodic amphibole, aegirine-augite and biotite which textural evidence would suggest are of metasomatic origin.