Age of the Batoka basalts, northern Zimbabwe, and the duration of Karoo Large Igneous Province magmatism

Analysis of the Batoka Basalts exposed in the Zambezi Gorge some 40 km east of Victoria Falls characterizes them as high Fe, moderately high Ti, and l ow K, P, and Zr tholeiites. The Ar-40-Ar-39 age determinations are tightly clustered at 180-179 Ma. All of the lavas that were sampled have normal pal eomagnetic polarity, and the corresponding pole position is 63.9 degreesN, 260.6 degreesE, A(95) = 14.9 degrees. In South Africa, Lesotho, and Namibia the vase majority of Karoo basalts were extruded at 183 +/- 1 Ma with some as young as 179 Ma [Duncan et al., 1997]. Paleomagnetic and geochemical co rrelation of the similar to 179 Ma rocks between Zimbabwe and Lebombo suppo rts the conclusion that the age difference is real and hence confirms the e stimate of similar to5 Myr for the duration of emplacement of the Karoo Lar ge Igneous Province.