The Formation of Authigenic Carbonates at a Methane Seep Site in the Northern Part of the Laptev Sea

Authigenic carbonates from cold seeps are unique archives for studying environmental conditions, including biogeochemical processes associated with methane-rich fluid migration through the sediment column. The aim of this research was to study major oxide, mineralogical, and stable isotopic composit...

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Bibliographic Details
Published in:Minerals
Main Authors: Alexey Ruban, Maxim Rudmin, Oleg Dudarev, Alexey Mazurov
Format: Article in Journal/Newspaper
Language:English
Published: MDPI AG 2020
Subjects:
authigenic carbonate
cold seep
anaerobic methane oxidation
oxygen and carbon isotopes
fluid source
Laptev Sea
Mineralogy
QE351-399.2
laptev
Online Access:https://doi.org/10.3390/min10110948
https://doaj.org/article/30bee2b32e22453cafdf6b91b1b52683
Description
Summary:Authigenic carbonates from cold seeps are unique archives for studying environmental conditions, including biogeochemical processes associated with methane-rich fluid migration through the sediment column. The aim of this research was to study major oxide, mineralogical, and stable isotopic compositions of cold-seep authigenic carbonates collected in the northern part of the Laptev Sea. These carbonates are represented by Mg-calcite with an Mg content of 2% to 8%. The δ 13 C values range from −27.5‰ to −28.2‰ Vienna Peedee belemnite (VPDB) and indicate that carbonates formed due to anaerobic oxidation of methane, most likely thermogenic in origin. The authigenic pyrite in Mg-calcite is evidence of sulfate reduction during carbonate precipitation. The δ 18 O values of carbonates vary from 3.5‰ to 3.8‰ VPDB. The calculated δ 18 O fluid values show that pore water temperature for precipitated Mg-calcite was comparable to bottom seawater temperature. The presence of authigenic carbonate in the upper horizons of sediments suggests that the sulfate–methane transition zone is shallowly below the sediment–water interface.

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