Narssarssuaq

North of Narssarssuaq and north and northwest of the North Qoroq centre of the Igaliko complex, sills, dykes and plugs of carbonatite occur, with a number of diatremes, up to 300 m across, having carbonatitic affinities. These rocks are undoubtedly closely associated with those of the Qagssiarssuk area on the opposite side of the fjord to the west. The sills and dykes rarely exceed one metre in thickness. The diatremes are filled with tuffisites of comminuted and carbonated granitic country rock fragments in a variable matrix of alnoitic material; rounded blocks of ultrabasic rock are also present.