Variations in the depths of sulfate-methane transition zone (SMTZ) in UBGH2-6 drilling site in Ulleung Basin, East sea of Korea
Abstract
The second Ulleung Basin Gas hydrate Drilling Expedition (UBGH2) was conducted in the Ulleung Basin, East Sea of Korea in 2010. Gas hydrates were observed in depth interval from 140 mbsf (meter below seafloor) to 160 mbsf in core sediment taken from UBGH2-6 drilling site, located in the north-western part of the basin (2,164 m water depth). To characterize the geochemical process for UBGH2-6 core sediments, pore fluid samples and headspace gas samples were extracted from core sediments and analyzed SO42- and CH4 concentrations. Based on SO42- and CH4 concentrations, sulfate-methane transition zone (SMTZ), where SO42- is depleted to zero and CH4 starts to increase was defined at a depth of approximately 6.50 mbsf in 2010. And in order to identify the variations in the depths of SMTZ at UBGH2-6 drilling site since 2010 (UBGH2), whole-round piston cores were collected from UBGH2-6 drilling site from 2013 to 2015. We analyzed SO42- and CH4 concentrations and identified the SMTZ for the last 3 years. The depths of SMTZ for the cores obtained from 2013, 2014 and 2015 are approximately 3.50 mbsf, 5.00 mbsf, and 5.00 mbsf respectively. The analysis results indicate that the SMTZ in 2013, 2014, and 2015 are shallower than the SMTZ of 2010.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMOS51B2056K
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 3004 Gas and hydrate systems;
- MARINE GEOLOGY AND GEOPHYSICSDE: 4203 Analytical modeling and laboratory experiments;
- OCEANOGRAPHY: GENERALDE: 4255 Numerical modeling;
- OCEANOGRAPHY: GENERAL