RARE-EARTH ELEMENTS IN BASALTS OF THE PUTORAN PLATEAU

Abstract

Plateau basalts of the Siberian craton, of which the basalts of the Putoran Plateau in the northern part of the Tunguska syneclise constitute a sizable part, are a representative province of cratonic tholeiite magmatism. Incongruent and, in particular, rare-earth elements (REE) are specially important for studying the problem of plateau-basalt development. Having low coefficients of partition between rock-forming minerals, these elements are not markedly redistributed upon moderate fractional crystallization of melts and, therefore, contain information on the subcrustal conditions of such a process. The authors studied REE in representative aphyric and porphritic samples, collected from a broad area of volcanic rocks and typifying the complete range of basalt differentiation. The analysis was done by the neutron-activation method; the values obtained were normalized relative to chondrites. Study results are discussed.