scholarly journals Numerical Simulation on Authigenic Barite Formation in Marine Sediments

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 98 ◽  
Author(s):  
Tianfu Xu ◽  
Songhua Shang ◽  
Hailong Tian ◽  
Keqi Bei ◽  
Yuqing Cao
Keyword(s):  
Numerical Simulation ◽  
Methane Flux ◽  
Simulation Method ◽  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Forming Process ◽  
Authigenic Minerals ◽  
Methane Leakage ◽  
Leakage Flux ◽  
Oxidation Of Methane

Submarine cold seep and its associated authigenic minerals in sediment are meaningful to indicate the existence of underlying natural gas hydrate. The anaerobic oxidation of methane (AOM) is coupled with sulfate reduction (SR) and influences the dissolution and precipitation of barite. However, the forming mechanism of barite is not yet clearly understood. In order to investigate the forming process of authigenic barite and its relationship with methane leakage flux, based on the measured data of the Qiongdongnan Basin in the Northern slope of the South China Sea, we constructed a 1D model of a sedimentary column to reproduce the formation of barite using the numerical simulation method. The results show that the original equilibrium of barite was broken by the cold seep fluids and Ba2+ was carried upward to the sulfate-rich zone leading to the formation of barite front. When there is no flux of methane from the bottom of sediment, the barite front disappears. The relationship between methane leakage flux and authigenic minerals was also discussed. It can be concluded that high methane flux corresponds to a shallow barite front in the sediment, furthermore, the barite content first increases and then decreases as the methane flux increases. At the same time, an inverse relationship between the ratio of authigenic barite to calcite and methane flux was obtained.

scholarly journals Phosphorus Species in Deep-Sea Carbonate Deposits: Implications for Phosphorus Cycling in Cold Seep Environments

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 645
Author(s):  
Junlie Zhou ◽  
Mengran Du ◽  
Jiwei Li ◽  
Hengchao Xu ◽  
Kaiwen Ta ◽  
...  
Keyword(s):  
Deep Sea ◽  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Cold Seeps ◽  
Organic P ◽  
Anaerobic Oxidation ◽  
Phosphorus Species ◽  
China Sea ◽  
Oxidation Of Methane ◽  
Deep Sediments

Phosphorus (P) is an important nutrient for biological communities in cold seeps. However, our knowledge on the source, species, and cycling of P in cold seep environments is limited. In this study, the concentration, species, and micro to nanometer scale distribution of P in seep carbonates were examined at three deep-sea cold seeps in the South China Sea and East China Sea. The Ca-P accounts for the largest proportion of P—followed by detrital-P, Fe-P, organic-P, and exchangeable-P. The distribution patterns of Ca-P, detrital-P, and organic-P in the seep carbonates differ from one another, as shown by elemental mapping with NanoSIMS and scanning electron microscopy. The covariation of P with Ca and C reveals that Ca-P co-precipitates with Ca-carbonate, which is linked to the process of sulfate-driven anaerobic oxidation of methane. Organic-P is also observed within biofilm-like organic carbon aggregates, revealing the microbial enrichment of P by fluids in the process of anaerobic oxidation of methane. P with a granulated morphology was identified as detrital-P derived from deep sediments. Most importantly, it is evident that Ca-P is positively correlated to the Fe content in all the seep carbonates. This indicates the likelihood that the dissolved P in cold-seep fluids is released primarily from Fe oxides through Fe-driven anaerobic oxidation of methane in deep sediments. These processes associated with different species of P may have significant implications for P geochemical cycling and anaerobic oxidation of methane impelled by Fe and sulfate reduction in cold seep environments.

scholarly journals Anaerobic oxidation of methane in hypersaline cold seep sediments

2012 ◽  
Vol 83 (1) ◽  
pp. 214-231 ◽  
Author(s):  
Loïs Maignien ◽  
R. John Parkes ◽  
Barry Cragg ◽  
Helge Niemann ◽  
Katrin Knittel ◽  
...  
Keyword(s):  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Anaerobic Oxidation ◽  
Oxidation Of Methane

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

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 948
Author(s):  
Alexey Ruban ◽  
Maxim Rudmin ◽  
Oleg Dudarev ◽  
Alexey Mazurov
Keyword(s):  
Seawater Temperature ◽  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Laptev Sea ◽  
Cold Seeps ◽  
Authigenic Carbonates ◽  
Oxidation Of Methane ◽  
Major Oxide ◽  
Mg Content ◽  
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 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.

Study on the Large Module Spur Gear Cold Forming Process by Means of Numerical Simulation

2011 ◽  
Vol 189-193 ◽  
pp. 2642-2646 ◽  
Author(s):  
Qian Li ◽  
Yi Bian ◽  
Zhi Ping Zhong ◽  
Gui Hua Liu ◽  
Ying Chen
Keyword(s):  
Numerical Simulation ◽  
Simulation Method ◽  
Spur Gear ◽  
Cold Forging ◽  
Forming Process ◽  
Cold Forming ◽  
Forging Process ◽  
Flow Method ◽  
Precision Forging ◽  
Cold Precision Forging

The cold forging process of large module spur gear with four modules and 59mm breadth is performed by means of numerical simulation method. Two processes to forming such spur gears were compared by the simulation method, one is with the closed-die performing and extrusion in the finish-forging, the other is with divided-flow method in the finish-forging. Especially, the divided-flow method is analyzed in detail. The necessary reference and basis to realize practical cold precision forging process of spur gear with large modulus is provided eventually.

scholarly journals Miniaturized biosignature analysis reveals implications for the formation of cold seep carbonates at Hydrate Ridge (off Oregon, USA)

2007 ◽  
Vol 4 (6) ◽  
pp. 4443-4458 ◽  
Author(s):  
T. Leefmann ◽  
J. Bauermeister ◽  
A. Kronz ◽  
V. Liebetrau ◽  
J. Reitner ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Cold Seep ◽  
Chemical Compositions ◽  
Anaerobic Oxidation Of Methane ◽  
Oxidation Of Methane ◽  
Hydrate Ridge ◽  
The Individual ◽  
A Minor ◽  
Relationship Of ◽  
The Relationship

Abstract. Methane-related carbonates from Hydrate Ridge typically show several macroscopically distinguishable phases, namely whitish aragonite, lucent aragonite, and gray micrite. The relationship of these phases to particular microorganisms or biogeochemical processes is as yet unclear. We used a miniaturized biomarker technique on mg samples, combined with factor analysis and subsequent electron microprobe analysis, to study lipid biomarkers and chemical compositions of the individual phases. This allows us to identify particular mechanisms involved in the formation of the different carbonate precipitates. Our combined analysis of biomarkers and petrographic traits shows that most of the lipids related to the anaerobic oxidation of methane (>90% by weight) are concentrated within only a minor compartment (~20% by volume) of the Hydrate Ridge carbonates (whitish aragonite). The patterns indicate that the whitish aragonite represents fossilized biofilms of methanotrophic consortia, whereas the precipitation of the lucent aragonite does not seem to be directly controlled by microorganisms. The gray micrite shows a partly Mg-calcitic mineralogy, higher pyrite contents, and a much higher proportion of allochthonous biomarkers. The formation of these precipitates is interpreted to reflect periodic methane-rich fluid pulses that disrupted the sediments and promoted the growth of the respective methanotrophic consortia along fluid pathways.

scholarly journals Efficiency and adaptability of the benthic methane filter at Quepos Slide cold seeps, offshore of Costa Rica

2015 ◽  
Vol 12 (22) ◽  
pp. 6687-6706 ◽  
Author(s):  
P. Steeb ◽  
S. Krause ◽  
P. Linke ◽  
C. Hensen ◽  
A. W. Dale ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Costa Rica ◽  
Sediment Cores ◽  
Methane Flux ◽  
Sediment Surface ◽  
Anaerobic Oxidation Of Methane ◽  
Cold Seeps ◽  
Osa Peninsula ◽  
Oxidation Of Methane

Abstract. Large amounts of methane are delivered by fluids through the erosive forearc of the convergent margin offshore of Costa Rica and lead to the formation of cold seeps at the sediment surface. Besides mud extrusion, numerous cold seeps are created by landslides induced by seamount subduction or fluid migration along major faults. Most of the dissolved methane migrating through the sediments of cold seeps is oxidized within the benthic microbial methane filter by anaerobic oxidation of methane (AOM). Measurements of AOM and sulfate reduction as well as numerical modeling of porewater profiles revealed a highly active and efficient benthic methane filter at the Quepos Slide site, a landslide on the continental slope between the Nicoya and Osa Peninsula. Integrated areal rates of AOM ranged from 12.9 ± 6.0 to 45.2 ± 11.5 mmol m−2 d−1, with only 1 to 2.5 % of the upward methane flux being released into the water column. Additionally, two parallel sediment cores from Quepos Slide were used for in vitro experiments in a recently developed sediment-flow-through (SLOT) system to simulate an increased fluid and methane flux from the bottom of the sediment core. The benthic methane filter revealed a high adaptability whereby the methane oxidation efficiency responded to the increased fluid flow within ca. 170 d. To our knowledge, this study provides the first estimation of the natural biogeochemical response of seep sediments to changes in fluid flow.

Numerical Simulation Techniques for Hollow Vacuum Forming of Double-Layered Plastic Sheets

2010 ◽  
Vol 154-155 ◽  
pp. 68-73
Author(s):  
Bin Gao ◽  
Bai Zhong Wu
Keyword(s):  
Numerical Simulation ◽  
Theoretical Calculation ◽  
Temperature Variation ◽  
New Products ◽  
Simulation Method ◽  
Simulation Software ◽  
New Materials ◽  
Forming Process ◽  
Simulation Techniques ◽  
Vacuum Forming

Products made from double-layered hollow vacuum forming are widely used for their various advantages. The hollow vacuum forming process has been studied in this paper. Numerical simulation method for the hollow vacuum forming process of double-layered plastic sheets has been introduced by the simulation software Polyflow, which is suitable for viscoelasticity fluid bodies. This method can vividly and intuitively estimate the thickness, temperature variation and distribution in the double-layered vacuum forming processes. Based on this method, reliably theoretical calculation data can be provided to design the reasonable vacuum forming process for double-layered vacuum forming of new materials or new products. The proposed method has been verified to be applicable and effective by prototype fabrications.

scholarly journals An experimental study on short-term changes in the anaerobic oxidation of methane in response to varying methane and sulfate fluxes

2009 ◽  
Vol 6 (5) ◽  
pp. 867-876 ◽  
Author(s):  
G. Wegener ◽  
A. Boetius
Keyword(s):  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Cold Seeps ◽  
Anaerobic Oxidation ◽  
Short Term ◽  
Sulfate Reducing ◽  
Oxidation Of Methane ◽  
Column System ◽  
Methane Fluxes ◽  
Anaerobic Methanotrophs

Abstract. A major role in regulation of global methane fluxes has been attributed to the process of anaerobic oxidation of methane (AOM), which is performed by consortia of methanotrophic archaea and sulfate reducing bacteria. An important question remains how these energy limited, slow growing microorganisms with generation times of 3–7 months respond to rapid natural variations in methane fluxes at cold seeps. We used an experimental flow-through column system filled with cold seep sediments naturally enriched in methanotrophic communities, to test their responses to short-term variations in methane and sulfate fluxes. At stable methane and sulfate concentrations of ~2 mM and 28 mM, respectively, we measured constant rates of AOM and sulfate reduction (SR) for up to 160 days of incubation. When percolated with methane-free medium, the anaerobic methanotrophs ceased to produce sulfide. After a starvation phase of 40 days, the addition of methane restored former AOM and SR rates immediately. At methane concentrations between 0–2.3 mM we measured a linear correlation between methane availability, AOM and SR. At constant fluid flow velocities of 30 m yr−1, ca. 50% of the methane was consumed by the anaerobic methanotrophic (ANME) population at all concentrations tested. Reducing the sulfate concentration from 28 to 1 mM, a decrease in AOM and SR by 50% was observed, and 45% of the methane was consumed. Hence, the marine anaerobic methanotrophs (ANME) are capable of oxidizing substantial amounts of methane over a wide and variable range of fluxes of the reaction educts.

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