stripes
This is a large syenite complex covering several hundred square kilometres, with subordinate carbonatite, foskorite, pyroxenite and syenogabbro (Verwoerd, 1993). However, the body is not continuous there being eastern and western units. The former consists of approximately concentric rings of syenite and granite around a central plug of ultramafic rocks and carbonatite, from which they are separated by a broad zone of paragneiss. The western unit is an irregular intrusion of syenite. The syenites are marginally peralkaline their constituent pyroxenes varying from diopside to aegirine-augite; amphiboles are ferro-edenite to ferro-pargasitic hornblende (R.T. Lubala, pers. comm., 1993). The carbonatite has only been encountered in boreholes and is a sovite of magnesian calcite, apatite, phlogopite, magnetite, clinopyroxene, rutile and feldspar with minor disseminated copper and iron sulphides (Verwoerd, 1990).
R.T. Lubala, pers. comm., 1993; VERWOERD, W.J. 1990. The Saltpeterkop ring structure, Cape Province, South Africa. Tectonophysics, 171: 275-85.WALRAVEN, F., FRICK, C. and LUBALA, R.T. 1992. Pb-isotope geochronology of the Schiel complex, northern Transvaal, South Africa. Journal of African Earth Sciences, 15: 103-10.