stripes
Three small plugs of olivine melilitite are known in the Heidelberg area. The Spiegelsrivier plug lies 12 km northeast of Heidelberg and is 200x275 m. The rock contains phenocrysts of olivine (Fo83-91) and microphenocrysts of melilite, titanomagnetite and perovskite in a groundmass of clinopyroxene, nepheline, titanomagnetite, rare biotite and glass. Gerrard (1958) identified leucite (see Dingle and Gentle, 1972, Table 1). The Kruisrivier occurrence lies about 7 km west of Spiegelsrivier and is deeply weathered. This rock and that of a dyke 50 m north of the main body contains what appear to be pseudomorphs after melilite (Verwoerd et al., 1990). At Doringkraal, 6 km west of Kruisrivier, there are several dykes and a pipe-like body the rock of the last being characterised by calcite-filled vesicles, olivine phenocrysts and melilite laths. Analyses are available in Rogers and du Toit (1904), Duncan et al. (1978) and Verwoerd et al., 1990.
DINGLE, R.V. and GENTLE, R.I. 1972. Early Tertiary volcanic rocks on the Agulhas Bank, South African continental shelf. Geological Magazine, 109: 127-36.DUNCAN, R.A., HARGRAVES, R.B. and BREY, G.P. 1978. Age, palaeomagnetism and chemistry of melilite basalts in the southern Cape, South Africa. Geological Magazine, 115: 317-27.GERRARD, I. 1958. The olivine melilitites from the western Cape. M.Sc. thesis, University of Cape Town.ROGERS, A.W. and DU TOIT, A.L. 1904. The Sutherland volcanic pipes and their relationship to other vents in South Africa. Transactions of the South African Philosophical Society, 15: 61-83.TALJAARD, M.S. 1937. South African melilite basalts and their relations. Transactions and Proceedings of the Geological Society of South Africa, 39: 281-316.VERWOERD, W.J., VILJOEN, J.H.A. and VILJOEN, K.S. 1990. Olivine melilitites and associated intrusives of the southwestern Cape province. Guidebook Geocongress ’90, Geological Society of South Africa, PR3: 1-60.