Alkaline Rocks and Carbonatites of the World

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

Gakara (Karonge)


Occurrence number: 
Longitude: 29.45, Latitude: -3.5

Within a 20x20 km area near Gakara metasediments, gneisses and granites are cut by sets of veins and veinlets, which often form dense stockworks that are concentrated in three zones. The veins consist of quartz, baryte, microcline and biotite with a broad range of rare earth and other minerals, including bastnaesite, monazite, cerianite, fluocerite, pyromorphite, Ce and La rhabdophane, galena and other sulphides. There are potassic metasomatic zones adjacent to the veins. The principal REE mineral in the veins is bastnaesite and analyses of this using several techniques are given and discussed by Lehmann et al. (1994), while further REE data of this and other RE minerals are given by Van Wambeke (1977). This location is included here because Van Wambeke, and some earlier writers, have suggested that this occurrence is related to carbonatite, although carbonates do not occur in the veins. Others have suggested an association with granite. The position is unclear at present.

The occurrence has been worked for rare earths (bastnaesite) and Thoreau et al. (1958) give details of the workings illustrated by diagrams and photographs.
La-Ba dating of bastnaesite has yielded an age of 586.8±3.7 Ma (Nakai et al., 1988).

LEHMANN, B., NAKAI, S., HOHNDORF, A., BRINCKMANN, J., DULSKI, P., HEIN, U.F. and MASUDA, A. 1994. REE mineralization at Gakara, Burundi: evidence for anomalous upper mantle in the Western Rift Valley. Geochimica et Cosmochimica Acta, 58: 985-92.NAKAI, S., MASUDA, A. and LEHMANN, B. 1988. La-Ba dating of bastnaesite. American Mineralogist, 73: 1111-3.THOREAU, J., ADERCA, B. and VAN WAMBEKE, L. 1958. Le gisement de terres rares de la Karonge (Urundi). Bulletin des Séances, Académie Royale des Sciences Coloniales, Bruxelles, N.S. 4: 684-718.VAN WAMBEKE, L. 1977. The Karonge rare earth deposits, Republic of Burundi: new mineralogical-geochemical data and origin of the mineralization. Mineralium Deposita, 12: 373-80.

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