COMPOSITIONAL VARIATION IN PYROCHLORE FROM THE BINGO CARBONATITE, ZAIRE

The composition of pyrochlore from the calcite carbonatite and its ass ociated laterite at Binge, Zaire was determined and compared with pyro chlore from the nearby and geologically-similar carbonatite at Lueshe. Large compositional variations exist in the Binge pyrochlore which re late both to primary magmatic zonation and, more commonly, a secondary alteration process. Altered pyrochlore is rich in Ba and Si. At Luesh e an identical primary magmatic trend is observed, but secondary alter ation is subordinate. Pyrochlore from the Binge laterite is bariopyroc hlore, whereas at Lueshe the predominant variety is kalipyrochlore. (C ) 1997 Elsevier Science Limited.