STRUCTURE AND EVOLUTION OF THE CRUST AND UPPERMOST MANTLE BENEATH THE KIMBERLITE PROVINCE OF YAKUTIA BASED ON SEISMIC EVIDENCE

Abstract

The paper describes the results of the crustal and upper mantle studies in the region using the areal DSS technique. The territory covered is about 400 thousand sq. km. A number of contrasting anomalies have been discovered and mapped which reflect the complicated deep structure of the crust and upper mantle. Peculiar emphasis has been placed on the correlation between the topographies of the principal seismic boundaries of the crust and the sedimentary cover. Low-amplitude platform structures of the sedimentary cover correlate well with the contrasting topography anomalies of the top of the lower crust and the Moho. This implies, on the basis of the paleo-structural analysis of the sedimentary cover that activation (or formation) of the deep structures occurred in Middle Paleozoic to Mesozoic time. Synchronous kimberlite magmatism can serve an indicator of such activity. Linear deep structures and the corresponding near-surface structures are indicative of the tectonic regime. This may have been caused by compression accompanied by a horizontal tectonic flow of lower crustal matter which produced significant changes in crustal thickness. The changes are manifested, to some extent, in the near-surface structures. Due to the fact that structures deep in the crust and upper mantle formed contemporaneously with kimberlite magmatism they can be extremely useful in establishing the controls on magmatism near the present surface.