Tertiary tholeiitic basalts are widespread across the northern part of East Greenland, but on Hold with Hope at least two flows with alkaline affinities have been identified. One south of Spaths Plateau is the lowest member of the volcanic succession and is an olivine augitite with amphibole and biotite which proves to be chemically nephelinitic (Upton et al., 1984a, p. 159). A second flow, from the base of the Upper Plateau Lava Series near Knasten, is similar (op. cit., p. 162). Within the Myggbukta complex, in the southwestern part of Hold with Hope, subordinate potassic (trachy)basalts containing biotite occur (Upton et al., 1984b) and some rocks are nepheline normative. Quartz syenites, trachytes and rhyolites may originally have been peralkaline.
UPTON, B.G.J., EMELEUS, C.H. and BECKINSALE, R.D. 1984a. Petrology of the northern West Greenland Tertiary flood basalts: evidence from Hold with Hope and Wollaston Forland. Journal of Petrology, 25: 151-84.
UPTON, B.G.J., EMELEUS, C.H., BECKINSALE, R.D. and MACINTYRE, R.M. 1984b. Myggbukta and Kap Broer Ruys: the most northerly of the East Greenland Tertiary igneous centres (?). Mineralogical Magazine, 48: 323-43.