南海东沙群岛东北部海洋IV号地区GC16站重力柱状沉积物中的有机碳、总氮,以及自生碳酸盐岩矿物的无机碳同位素组成分析结果表明,甲烷流体活动区硫酸盐甲烷转换带(SMTZ—sulfate methane transition zone)是重要的生物地球化学界面,该带内沉积物中有机碳、氮与无机碳同位素组成变化明显。GC16站SMTZ上界面以下的沉积物中有机碳、氮同位素组成分别比其上的沉积物负偏1.4‰PDB和0.93‰,反映该带内甲烷缺氧氧化作用(AOM—anaerobic oxidation of methane)与氨氧化作用发育。无机碳同位素组成表明SMTZ界面之下沉积物中的自生碳酸盐岩矿物为以微生物为媒介的甲烷驱动成因,地质历史时期(至柱状沉积物底部沉积时期)曾发生过2次较强烈的CH4流体活动;目前该区甲烷流体活动较弱,甲烷流体影响深度与SMTZ上界面一致,未能到达海底。
Abstract
Sediments from the site GC16 of Haiyang IV, the South China Sea show anomalous values of δ13Corg, δ15N and δ13Cinorg. The sulfate methane transition zone (SMTZ) is a key biochemical interface in CH4 fluid flowing area. The values of δ13Corg and δ15N show obviously depleted in STMZ. Comparing with the date above the STMZ, depleted 1.4‰PDB and 0.93‰ respectively within the zone. The data of δ13Cinorg also identify the authigenic carbonates as microbially-mediated methane-derived precipitates. The 2 times of vigorous methane-rich fluid expulsion had occurred since the bottom sediments deposition of the core. The depth of methane fluid arriving coincident with the up limited of STMZ.
关键词
稳定位素组成 /
SMTZ /
AOM /
氨氧化作用
Key words
stable isotopic composition /
SMTZ /
AOM /
ammonia oxidation
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基金
国家自然科学基金项目资助(40576059,40976039);浙江省测试科技计划项目资助(2008F70047)
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