Halogen content of some African primary carbonatites

Colorimetric analyses have been made for F, Cl and I in a suite of African carbonatites specially selected for their freshness. F and Cl vary widely both in absolute and relative amounts between intrusions, but F/Cl ratios are usually consistent in samples from the same intrusion. Although samples from both the 2 b.y. Phalaborwa complex and the modern Oldoinyo Lengai lavas have low F/Cl values, there is considerable variation during geological time. Iodine (up to 1.8 ppm) has been found in the carbonatites of Phalaborwa, Sukulu and Oldoinyo Lengai; the only common factor seems to be the high sulphur content of the carbonatites at these localities.