Alkaline Rocks and Carbonatites of the World

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Occurrence number: 
Longitude: 15.72, Latitude: -27.93

This is a small plug situated in the Diamond Area north of the mouth of the Orange River, which is normally inaccessible. The plug is about 100x50 m in plan, 30 m high and forms an eastward-facing escarpment. It has an irregular outline sending numerous apophyses into the country rocks. Large blocks of schist and numerous other fragments of country rocks cram the plug, between which are irregular bodies of siliceous carbonatite and veinlets of drusy quartz. The carbonatite is a beforsite with rhombohedra of dolomite with rims and interstitial material of parankerite. Accessories include quartz, microcline perthite, pyrite, zircon. rutile, greenish amphibole and biotite. Phonolite plugs are reported from this area by Mathias (1974) who indicates that they occur as far south as 28°13'.

A phonolite plug 'Swartkop' north of Chamais has been dated by K-Ar on a whole rock at 37 Ma (Mathias, 1974).
MATHIAS, M. 1974. Alkaline rocks of southern Africa. In H. Sorensen (ed) The alkaline rocks. 189-202. John Wiley, London.VERWOERD, W.J. 1967. The carbonatites of South Africa and South West Africa. Handbook, Geological Survey of South Africa, 6: 1-452.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith