LATE VENDIAN POTASSIC VOLCANIC ROCKS OF THE OLENEK HIGHLANDS ON THE NORTHEAST OF THE SIBERIAN CRATON

Abstract

The authors investigated a rock complex in the northern part of the Olenek Highlands on the Siberian craton, where it lies in the Khorbusuonka, Erkeket, and Kersyuke river basins. These potassic volcanics are found over an area of about 1500 to 2000 km2, in clusters of 3 to 8 diatremes, such diatremes being separated from each other by distances ranging from a few dozen to 500 m. The rock bodies in these pipes are nominally divided into two groups. One of these is comprised of volcanic rocks erupted in a single event, and consist of yellowish gray tuff agglomerate containing as much as 50 percent of fragments of the enclosing dolomite. The second group of bodies is varicolored and is made up of volcano- and lithoclasts, in variable ratios. Given the specific spectrum of minerals of the heavy fraction, which is characteristic (in terms of most of its components) of the ultramafic paragenesis, the authors conclude that the parent magma of the potassic volcanic melted out at greater depths than that which produced the alkalic basalts. In terms of their petrology these potassic volcanics probably constitute the previously unknown link between kimberlite and alkalic basalt.