Authigenic carbonate formation revealed by lipid biomarker inventory at hydrocarbon seeps: A case study from the Okinawa Trough

Guan, Huashi; Sun, Zhilei; Mao, Shipeng; Xu, Lanfang; Cao, Hong; Wang, Geng; Xu, Chao; Zhang, Xianrong; Wu, N.

doi:10.1016/j.marpetgeo.2018.12.028

Cited by 13 publications

(7 citation statements)

References 68 publications

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“…Overall, the lipid biomarker inventory characterized by low sn2-hydroxyarchaeol/archaeol ratios <0.3 and an aiC15:0/iC15:0 FA ratio of 0.1-1.2 was similar to carbonates from other seep sites, including the Congo Fan (Feng et al, 2010), the Gulf of Mexico (Birgel et al, 2011;Feng et al, 2014), and the South China Sea (Guan et al, 2016). In contrast, quite different ANME-and SRB-related lipids were found at other seep sites (e.g., with a much higher sn2-hydroxyarchaeol/archaeol ratio ≫ 1; Niemann et al, 2005;Niemann et al, 2006;Guan et al, 2019). This difference in lipid contents is most likely related to different types of microorganisms that become encased in the carbonate precipitates (Niemann and Elvert, 2008).…”

Section: Aom Communitiesmentioning

confidence: 52%

Biomarker and Isotopic Composition of Seep Carbonates Record Environmental Conditions in Two Arctic Methane Seeps

et al. 2021

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Present-day activity of cold seeps in the ocean is evident from direct observations of methane emanating from the seafloor, the presence of chemosynthetic organisms, or the quantification of high gas concentrations in sediment pore waters and the water column. Verifying past cold seep activity and biogeochemical characteristics is more challenging but may be reconstructed from proxy records of authigenic seep carbonates. Here, we investigated the lipid-biomarker inventory, carbonate mineralogy, and stable carbon and oxygen isotope compositions of seep-associated carbonates from two active Arctic methane seeps, located to the northwest (Vestnesa Ridge; ∼1,200 m water depth) and south (Storfjordrenna; ∼380 m water depth) offshore Svalbard. The aragonite-dominated mineralogy of all but one carbonate sample indicate precipitation close to the seafloor in an environment characterized by high rates of sulfate-dependent anaerobic oxidation of methane (AOM). In contrast, Mg-calcite rich nodules sampled in sediments of Storfjordrenna appear to have formed at the sulfate-methane-transition zone deeper within the sediment at lower rates of AOM. AOM activity at the time of carbonate precipitation is indicated by the 13C-depleted isotope signature of the carbonates [−20 to −30‰ Vienna Pee Dee Belemnite (VPDB)], as well as high concentrations of 13C-depleted lipid biomarkers diagnostic for anaerobic methanotrophic archaea (archaeol and sn2-hydroxyarchaeol) and sulfate-reducing bacteria (iso and anteiso-C15:0 fatty acids) in the carbonates. We also found 13C-depleted lipid biomarkers (diploptene and a 4α-methyl sterol) that are diagnostic for bacteria mediating aerobic oxidation of methane (MOx). This suggests that the spatial separation between AOM and MOx zones was relatively narrow at the time of carbonate formation, as is typical for high methane-flux regimes. The seep-associated carbonates also displayed relatively high δ18O values (4.5–5‰ VPDB), indicating the presence of 18O-enriched fluids during precipitation, possibly derived from destabilized methane gas hydrates. Based on the combined isotopic evidence, we suggest that all the seep carbonates resulted from the anaerobic oxidation of methane during intense methane seepage. The seepage likely was associated to gas hydrates destabilization, which led to the methane ebullition from the seafloor into the water column.

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Section: Aom Communitiesmentioning

confidence: 52%

Biomarker and Isotopic Composition of Seep Carbonates Record Environmental Conditions in Two Arctic Methane Seeps

et al. 2021

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“…(d) Gas plumes indicating the escape of free gases from marine sediments (from [14]). thermogenic origin is not observed in the NOT, in which the isotopic analysis of authigenic carbonates supports the predominance of the microbial methane in the past seeping activity [24]. We think the data published till now would not suffice to fully understand this origin in the OT.…”

Section: Geochemical Constraintsmentioning

confidence: 82%

“…Fe-rich minerals exist in the form of goethite and hematite in the NOT and ankerite in the MOT [18,22,26,27]. The minerals and the biomarker patterns indicate that the MDAC formed at depth in an environment of low-to-medium flux of methane [24]. Some reasonable explanations concerning the origin of methanerich fluids were provided based on δ 13 C and δ 18 O values of the seep carbonates (Figure 9).…”

Section: Methane-derived Authigenicmentioning

confidence: 96%

“…The pore water and the authigenic minerals serve as the main geological record of the seeps and have been sampled by grabbing of remotely operated vehicles (ROVs), dredging and gravity-piston coring, and seafloor drilling. Geochemical investigation of these samples reveals the involved biogeochemical processes, the origin of the methane, the interaction between the pore fluids and the seep-impacted sediments, and the evolution of the seeps [17][18][19][20][21][22][23][24][25][26][27][28]. The seeps studied most in the OT are in its northern section (30.5 °N-30.8 °N) and were detected by R/V Kexue Yihao from July to August 2013 [18].…”

Section: Introductionmentioning

confidence: 96%

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Review of Methane Seepages in the Okinawa Trough: Progress and Outlook

et al. 2021

Geofluids

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It has been two decades since the cold seeps were firstly found in the Okinawa Trough (OT). The scientific cruises and the geological surveys since then have unveiled the currently active submarine methane seeps and significantly improved the understanding of methane seeps in the back-arc basin of the OT. In this paper, we review the up-to-date progress of the research of methane seepages then put forward the promising, yet challenging, outlook by listing the unsolved questions of the cold seeps in the OT. Multiple approaches and techniques, including seismic and echo-sounder recording, dredging, gravity-piston and ROV coring, seafloor drilling, and isotopic and microarray-based genomic analysis, have been used to reveal the geological processes responsible for the seeping activities and the biogeochemical processes related to them. The geophysical signature associated with gas seeps mainly includes the acoustic turbidity in the subsurface, the anomaly of the backscattering intensity at the seabed, and the gas plumes observed in the water column. Pore water and methane-derived authigenic carbonate archive the intensification of methane seepage and the paleoenvironment changes at different time scales. The methane feeding of the seeps in the OT was generated mostly via the microbially mediated process and has an origin mixed by thermogenic hydrocarbon gas in the middle OT. Sulfate-driven and Fe-driven anaerobic oxidations of methane are suggested to be the key biogeochemical processes, which would shape the material cycling in the seeping environment. The future research on the cold seeps in the OT is worth looking forward to due to its geographic and potential geologic links with the nearby hydrothermal activities. Multidisciplinary studies are expected to concentrate on their link with the undiscovered gas hydrates, the amount of methane transferring into the oceans and its impact on the climatic change, and the evolution of the seeping activities accompanied by the biogeochemical processes.

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“…Methane cold seeps are a widespread phenomenon that occurs on the shelves and continental slopes of inland and marginal seas around the world [1][2][3][4][5][6][7], including the arctic seas [8][9][10]. They represent areas of the seafloor where methane-rich fluids in chemical non-equilibrium with seawater are transported through the sub-seafloor environment and are released at the bottom-sediment-seawater interface [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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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 δ13C 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 δ18O values of carbonates vary from 3.5‰ to 3.8‰ VPDB. The calculated δ18Ofluid 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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Authigenic carbonate formation revealed by lipid biomarker inventory at hydrocarbon seeps: A case study from the Okinawa Trough

Cited by 13 publications

References 68 publications

Biomarker and Isotopic Composition of Seep Carbonates Record Environmental Conditions in Two Arctic Methane Seeps

Biomarker and Isotopic Composition of Seep Carbonates Record Environmental Conditions in Two Arctic Methane Seeps

Review of Methane Seepages in the Okinawa Trough: Progress and Outlook

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

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