Vote on the alkali-lavas of Mount Nimrud, Armenia

Abstract

The object of this note is not to give elaborate descriptions of rocksections, but to call attention to tile fact that the old volcano of Nimrud, situated on the west side of lake Van in Armenia, was the centre of eruption of alkali-lavas presenting striking similarities to some of the alkali-rocks of the tlift Valley in East Africa. To Dr. Felix Oswald, in his book on the geology of Armenia, we owe a detailed description of this ancient volcano, of which the vast crater, now half occupied by a deep lake, is more than five miles across. An interesting series of the lavas from the volcano was collected by Dr. Oswald and was presented by him to the British Museum. On looking over thin slices of these rocks under the microscope, I was at once struck by the surprising resemblance of some of them, with their phenocrysts of anorthoclase and scattered tufts of aegirine and the soda-amphiboles, riebeckite and cossyrite, to rocks in Prof. J. W. Gregory's collection from the Rift Valley which I had described.