QUATERNARY PERPOTASSIC MAGMATISM IN UGANDA (TORO-ANKOLE VOLCANIC PROVINCE) - AGE ASSESSMENT AND SIGNIFICANCE FOR MAGMATIC EVOLUTION ALONG THE EAST-AFRICAN RIFT
A. Boven et al., QUATERNARY PERPOTASSIC MAGMATISM IN UGANDA (TORO-ANKOLE VOLCANIC PROVINCE) - AGE ASSESSMENT AND SIGNIFICANCE FOR MAGMATIC EVOLUTION ALONG THE EAST-AFRICAN RIFT, Journal of African earth sciences, and the Middle East, 26(3), 1998, pp. 463-476
The Toro-Ankole volcanics in the northern sector of the Western Branch
of the East African Rift are generally assumed to be of Quaternary ag
e. New field observations and comparative K-Ar and Ar-Ar analyses on w
hole rock samples and phenocrysts of perpotassic lavas reveal the pres
ence of excess Ar and led to the conclusion that apparently no volcani
cs have been erupted prior to 50 ka. The present geochronological data
, compared with previous ones for the Virunga and South Kivu volcanic
fields, suggest that a Late Quaternary pulse of volcanic activity occu
red in the three areas, with the emission of perpotassic, mildly potas
sic or sodic alkaline magmas. The genetic implications of such a synch
ronous activity with wide compositional variation are briefly discusse
d with respect to basement age and assumed lithosphere characteristics
. (C) 1998 Elsevier Science Limited.