Alkaline Rocks and Carbonatites of the World

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Pompue

stripes

Occurrence number: 
114-00-026
Country: 
Mozambique
Location: 
Longitude: 34.28, Latitude: -17.42

South of the Pompue River and north of the Sangadze River a number of small hills, including Junje, Jajenji, Chinje, Yamchech and Kuti are described by Teale and Smith (1923) as consisting of phonolite and nephelinite. The phonolites differ from hill to hill but may contain phenocrysts and microphenocrysts including alkali feldspar, nepheline, aegirine or aegirine-augite and katophorite in a groundmass in which alkali feldspar or nepheline may be abundant, zeolite often occurs and there may be patches of aenigmatite or a blue sodic amphibole; vesicles may be filled with analcime or possible sodalite. A nephelinite from Kuti Hill consists of very fine-grained nepheline and augite, a little magnetite and an indistinguishable base. A rock from Yamchech Hill is referred to as nephelinite by Teale and Smith (1923) although it contains a groundmass of about equal parts of nepheline plates and twinned alkali feldspar with crowds of tiny augite and magnetite crystals and flakes of biotite; there are augite phenocrysts.

References: 
TEALE, E.O. and SMITH, W.C. 1923. Nepheline-bearing lavas and intrusive rocks from south of the Zambezi River, with a note on an outcrop of Karroo lavas in the Buzi Valley, Portuguese East Africa. Geological Magazine, 60: 226-37.
Location: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith