Parental melt and geodynamics of the layered mafic-ultramafic massifs of the Kan block of Eastern Sayan

Abstract

Based on the results of simulation of equilibrium crystallization by the program COMAGMAT 3.52 the authors have evaluated the probable temperatures and chemical composition of the parent magma of Talazhinsky mafic-ultramafic massif Kan block (north-western part of Eastern Sayan). The paper introduces for the first time the model of geodynamic conditions for crystallizing the layered series of its rocks. The data obtained allow making the conclusion on the fact that intrusive body is the rhythmically layered plagiodunit-troctolite-gabbro-anorthosite massif, which was formed at crystallization differentiation of low-Ti high-alumina olivine-basalt melt; the latter is characterized by high concentrations of Mg at low HFSE, weak enrichment of LREE, positive Eu-anomaly. The initial melt sources were formed owing to tholeiitic basalts of oceanic plateau at their absorption and further melting in a subduction zone. The subsequent evolution of the melt occurred due to the processes of its movement into magma chamber, which was accompanied by contamination of continental crust rocks.

Keywords

• Talazhinsky massif
• layered complex
• mafites
• ultramafites
• modeling
• parental melt