Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Mbalizi

stripes

Occurrence number: 
163-00-039
Country: 
Tanzania
Location: 
Longitude: 33.37, Latitude: -8.92
Carbonatite: 
Yes

Outcrops of carbonatite along the main road west of Mbeya and in the bed of a tributary of the Nzowwe River about 2 km north of Mbalizi led Pentel'kov and Voronovskiy (1977) to suggest that they represented parts of a carbonatite stock several hundred metres in diameter. The adjacent Precambrian gneisses were fenitized to quartz- and aegirine-bearing rocks with perovskite and zircon, and close to the carbonatite zones rich in phlogopite and apatite are present (van Straaten, 1989). There are also carbonatite breccias and feldspathic rocks with trachytic textures. The central area of the stock consists mainly of calcite carbonatite including (1) coarse-grained apatite sovite, (2) coarse-grained, variably massive or banded carbonatite with concentrations of pyrochlore, with crystals from 5-10 mm diameter, apatite, phlogopite, tetraferriphlogopite, and martitized magnetite and (3) fine-grained apatite-calcite carbonatite with dolomite, amphibole, pyrochlore, magnetite, pyrrhotite, pyrite, chalcopyrite and fluorite. van Straaten (1989) reports that detailed mapping has shown that the main exposed carbonatite is a phosphatic sovite which cuts a central pyroxenite and reports analyses of sovite, pyroxenite and apatite-phlogopite fenite.

Age: 
K-Ar determinations on two samples of phlogopite from carbonatite gave 122±8 and 118±9 Ma (Pentel'kov and Voronovskiy, 1977).
References: 

MTUY, F.T., MCHIHIYO, E.P., MASAO, P. and VAN STRAATEN, P. 1987. Phosphate mineralization associated with the Panda, Mbalizi and Songwe Scarp carbonatites, Mbeya region, Tanzania. Abstract, 14th Colloquium on African Geology, Berlin.PENTEL'KOV, V.G. and VORONOVSKIY, S.N. 1977. Radiometric age of the Mbalizi carbonatite, Tanzania, and correlation with other carbonatites of the Rukwa-Malawi rift zone. Doklady of the Academy of Sciences, USSR, Earth Science Sections, 235: 92-4.VAN STRAATEN, P. 1989. Nature and structural relationships of carbonatites from southwest and west Tanzania. In K. Bell (ed.) Carbonatites: genesis and evolution. 177-99. Unwin Hyman, London.

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith