Ikait (CaCO3·6H2O) v donnykh otlozheniyakh morya Laptevykh i rol’ anaerobnogo okisleniya metana v protsesse ego formirovaniya (Ikaite (CaCO3.6H2O) in bottom sediments of the Laptevs' Sea and the role of anaerobic methane oxidation in this mineral-forming process)

Studied samples of ikaite have been collected in the southern part of the Laptevs’ sea in 2008. XRD analysis data have shown that by destruction ikaite is transformed into calcite and waterite pha- ses. Isotopic composition of carbon (d13C) and oxygen (d18O) in the sample composed of the ikaite, calcite and vaterite mixture was –31.0 and –0.39 ‰, respectively, and after the complete destruction of ikaite it has become –29.0 and 0.67 ‰ VPDB, respectively. Calculated theoretical values of d18O in porous water, from which ikaite has formed in equilibrium conditions, vary from 4.0 to –2.8 ‰ VSMOW. It evidences the weak influence of the Lena river water upon formation of the studied sam- ple. The result of the balance calculations points that organic matter was the principal source of car- bon in ikaite (88—92 %), with supplementary supply from methane (8—12 %).