Abstract

Application of von Eckermann's concept that calcitic dikes occupy a higher level than melilitic and dolomitic dikes in the course of a carbonatite diatreme rising and undergoing changes in the crust indicates that the occurrence of melilite in dikes in the peripheral area of the Rangwa complex of western Kenya is evidence of a deeper facies than that represented in the vent. This could be explained by caldron subsidence, and such an explanation seems to be more satisfactory for all the features of the Rangwa type of ring complex. The Ruri complexes farther east have been reconsidered on this basis; updoming and subsidence may have occurred here also. Further field investigation is warranted.

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