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	Barite in hydrothermal environments as a recorder of subseafloor processes: a multiple-isotope study from the Loki's Castle vent field
	Eickmann B. ; Thorseth I. H. ; Peters M. ; Strauss H. ; Brocker M. ; Pedersen R. B.
	2014
关键词	microbial sulfate reduction altered oceanic basalts arctic midocean ridge mid-atlantic ridge east pacific rise gulf-of-mexico sulfur isotope oxygen-isotope anaerobic oxidation southwest pacific
英文摘要	Barite chimneys are known to form in hydrothermal systems where barium-enriched fluids generated by leaching of the oceanic basement are discharged and react with seawater sulfate. They also form at cold seeps along continental margins, where marine (or pelagic) barite in the sediments is remobilized because of subseafloor microbial sulfate reduction. We test the possibility of using multiple sulfur isotopes (delta S-34, Delta S-33, Delta S-36) of barite to identify microbial sulfate reduction in a hydrothermal system. In addition to multiple sulfur isotopes, we present oxygen (delta O-18) and strontium (Sr-87/Sr-86) isotopes for one of numerous barite chimneys in a low-temperature (similar to 20 degrees C) venting area of the Loki's Castle black smoker field at the ultraslow-spreading Arctic Mid-Ocean Ridge (AMOR). The chemistry of the venting fluids in the barite field identifies a contribution of at least 10% of high-temperature black smoker fluid, which is corroborated by Sr-87/Sr-86 ratios in the barite chimney that are less radiogenic than in seawater. In contrast, oxygen and multiple sulfur isotopes indicate that the fluid from which the barite precipitated contained residual sulfate that was affected by microbial sulfate reduction. A sulfate reduction zone at this site is further supported by the multiple sulfur isotopic composition of framboidal pyrite in the flow channel of the barite chimney and in the hydrothermal sediments in the barite field, as well as by low SO4 and elevated H2S concentrations in the venting fluids compared with conservative mixing values. We suggest that the mixing of ascending H-2-and CH4-rich high-temperature fluids with percolating seawater fuels microbial sulfate reduction, which is subsequently recorded by barite formed at the seafloor in areas where the flow rate is sufficient. Thus, low-temperature precipitates in hydrothermal systems are promising sites to explore the interactions between the geosphere and biosphere in order to evaluate the microbial impact on these systems.
出处	Geobiology
卷	12
期	4
页	308-321
收录类别	SCI
语种	英语
ISSN号	1472-4677
内容类型	SCI/SSCI论文
源URL	[http://ir.igsnrr.ac.cn/handle/311030/29906]
专题	地理科学与资源研究所_历年回溯文献
推荐引用方式 GB/T 7714	Eickmann B.,Thorseth I. H.,Peters M.,et al. Barite in hydrothermal environments as a recorder of subseafloor processes: a multiple-isotope study from the Loki's Castle vent field. 2014.

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