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.