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

The paper describes the results of the crustal and upper mantle studie s in the region using the areal DSS Technique. The territory covered i s about 400,000 km(2). A number of contrasting anomalies have been dis covered and mapped which reflect the complicated deep structure of the crust and upper mantle. Peculiar emphasis has been placed on the corr elation between the topographies of the principal seismic boundaries o f the crust and the sedimentary cover. Low-amplitude platform structur es of the sedimentary cover correlate well with the contrasting topogr aphy anomalies of the top of the lower crust and the Moho. This implie s, on the basis of the paleostructural analysis of the sedimentary cov er, that activation (or formation) of the deep structures occurred in Middle Paleozoic to Mesozoic time. Synchronous kimberlite magmatism ca n serve an indicator of such activation. Linear deep structures and th e corresponding near-surface structures are indicative of the tectonic regime, This may have been caused by compression accompanied by a hor izontal tectonic flaw of lower crustal matter which produced significa nt changes in crustal thickness. The changes are manifested, to some e xtent, in the near-surface structures. Due to the fact that structures deep in the crust and upper mantle formed contemporaneously with kimb erlite magmatism they can be extremely useful in establishing the cont rols on magmatism near the present surface.