Ikaite (СаСО₃·6Н₂O) in bottom sediments of the Laptevs' sea and the role of anaerobic methane oxidation in this mineral-forming process

Krylov A. A., Logvina E. A., Matveeva T. V., Prasolov E. M., Sapega V. F., Demidova A. L., Radchenko M. S.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2015. V. 144. N 4. P. 61-75

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Language: Russian

Abstract

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 phases. Isotopic composition of carbon (δ¹³C) and oxygen (δ¹⁸O) 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 δ¹⁸O 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 sample. The result of the balance calculations points that organic matter was the principal source of carbon in ikaite (88—92 %), with supplementary supply from methane (8—12 %).

Key words: ikaite, the Laptevs’ sea, methane, carbon, anaerobic methane oxidation.