Geochemical Indicators of the Relation between Impactites and Late Cenozoic Volcanic Rocks of the EPgygytgyn Depression, Chukotka

摘要

High contents of iron group elements in impactites of the El'gygytgyn Depression relative to those in the primary Cretaceous volcanic rocks of the Okhotsk-Chukot volcanogenic belt (OCVB) have been considered one of the major arguments for a meteoritic origin of impact melts and the depression itself. It is believed that concentration of meteoritic Ni leads to significant change of the Ni/Cr ratio in the impact melts relative to primary rocks. This ratio was used for deciphering the composition of inferred meteorite [1-3]. More comprehensive data on the geology and composition of impactites and volcanic rocks of the El'gygytgyn Depression [4, 5] obtained during field work in 1991 and 1993 make it possible to consider the behavior of Ni, Cr, and Co in real geological bodies (stratigraphic units and dikes) of the OCVB, impact rocks from different localities, and volcanic rocks discovered in Late Cenozoic sequences.