Aryasova O. Geodynamical processes in lithosphere and kimberlite magmatism

The thesis focuses on geodynamical processes both in the continental and in the suboceanic lithosphere with the data on spatial/temporal distributions of kimberlitic magmatism as well as on the composition of kimberlites and their xenoliths being widely used. The characteristic features of an interaction of regular mantle convection with the continental and oceanic lithosphere are studied, and a new approach to the thermal modeling of quasi-stationary lithosphere, which allows to develop quantitative models, is suggested. The modeling results agree well with the thermobarometry of the kimberlite xenoliths/xenocrysts and also with the heat flow measurements and the seismological observations in the old oceanic crust regions. It is shown that the correlations between magma composition and lithosphere thickness observed in the regions of continental flood basalts and along the continental extension of hotspots tracks are best explained in terms of a spreading of anomalously hot mantle uplifts (mantle plumes) along the relief of the lithosphere bottom. The variations with depth of the inter-element ratios in the group of rare earth elements are detected, and the physical causes of the effect are discussed. For the problem of matrix compaction and melt segregation a new mush continuity equation is found. The equation closes the system of governing equations and allows to treat the segregation of low-viscosity melts (kimberlites, carbonatites) consistently.