New acquired and reprocessed three-dimensional(3D)seismic data were used to delineate the distribution and characterization of bottom simulating reflections(BSRs)in the Chaoshan Sag,in the eastern part of Dongsha Isla...New acquired and reprocessed three-dimensional(3D)seismic data were used to delineate the distribution and characterization of bottom simulating reflections(BSRs)in the Chaoshan Sag,in the eastern part of Dongsha Island,South China Sea.Three submarine canyons with different scales were interpreted from the 3D seismic data,displaying three stages of canyon development and are related with the variation of BSR.Abundant faults were identified from the coherence and ant-tracing attributions extracted from 3D seismic data,which provide the evidence for fluid migration from deeper sediments to the gas hydrate stability zone(GHSZ).The uplift of Dongsha Island created a large number of faults and leads to the increased seafloor erosion.The erosion caused the cooling of the seafloor sediments and deepening of the base of the gas hydrate stability zone,which is attributed to the presence of paleo-BSR and BSR downward shift in the study area.Hence,methane gas may be released during the BSR resetting and gas hydrate dissociation related with seafloor erosion.展开更多
The distributions of lipids in surface and subsurface sediments from the northern South China Sea were determined. The n-alkanes were in bimodal distribution that is characterized by a centre at n-C16 –n-C20 with max...The distributions of lipids in surface and subsurface sediments from the northern South China Sea were determined. The n-alkanes were in bimodal distribution that is characterized by a centre at n-C16 –n-C20 with maximum at C18（or C19） and n-C27 –n-C31 as well as at C29（or C31）. The short-chain alkanes suffered from significant losses due to their slow deposition in the water column, and their presence with a slight even carbon predominance in shallow seafloor sediments was ascribed mainly to the direct input from the benthos. The long-chain alkanes with odd predominance indicate transportion of terrigenous organic matter. Immature hopanoid biomarkers reflect the intense microbial activity for bacteria–derived organic matter and the gradual increase of maturity with burial depth. Abundant n-fatty acid methyl esters（n-FAMEs） that are in distributions coincident with fatty acids were detected in all samples. We proposed that the observed FAMEs originated from the methyl esterification of fatty acids; methanol production by methanotrophs and methanogenic archaea related to the anaerobic oxidation of methane, and sulfate reduction provided an O–methyl donor for methylation of fatty acids. The CH4 released from hydrate dissociation at oxygen isotope stage II of Cores ZD3 and ZS5, which had been confirmed by the occurrence of negative δ13C excursion and spherical pyrite aggregates, could have accelerated the above process and thus maximized the relative content of FAMEs at ZD3-2（400–420 cm depth） and ZS5-2（241–291 cm depth）.展开更多
This paper presents a meso-level simulation of gas hydrate dissociation in low-permeability marine sediments. Interstitial pores are defined to describe fluid flow and particle movement. The proposed model couples mul...This paper presents a meso-level simulation of gas hydrate dissociation in low-permeability marine sediments. Interstitial pores are defined to describe fluid flow and particle movement. The proposed model couples multiphase fluid flow with particle movement to simulate the thermodynamics of gas hydrate dissociation triggered by sharp temperature rises. Hydrates respond quickly to temperature rise in low-permeability sediments. Dissociation causes pore pressure to rise rapidly to equilibrium then steadily increase above equilibrium pressure. Lower permeability sediment builds up greater excess pore pressure as the dissipation of pore pressure is constrained.展开更多
Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used...Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used and the avalanche of electrons is taken into account in this simulation. The average energy distribution of electrons and the space distribution of effective species such as CH3, CH+3, CH+ and H at various gas pressures are given in this paper, and optimum experimental conditions are inferred from these results.展开更多
基金the National Key R&D Program of China(No.2017YFC0307301-1)the National Natural Science Foundation of China(No.41676041)+1 种基金the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0104)the National High Technology Research and Development Program of China(863 Program)(No.2013AA092601)。
文摘New acquired and reprocessed three-dimensional(3D)seismic data were used to delineate the distribution and characterization of bottom simulating reflections(BSRs)in the Chaoshan Sag,in the eastern part of Dongsha Island,South China Sea.Three submarine canyons with different scales were interpreted from the 3D seismic data,displaying three stages of canyon development and are related with the variation of BSR.Abundant faults were identified from the coherence and ant-tracing attributions extracted from 3D seismic data,which provide the evidence for fluid migration from deeper sediments to the gas hydrate stability zone(GHSZ).The uplift of Dongsha Island created a large number of faults and leads to the increased seafloor erosion.The erosion caused the cooling of the seafloor sediments and deepening of the base of the gas hydrate stability zone,which is attributed to the presence of paleo-BSR and BSR downward shift in the study area.Hence,methane gas may be released during the BSR resetting and gas hydrate dissociation related with seafloor erosion.
基金supported by the National Major Fundamental Research and Development Project of China (No. 2009CB219501)the National Natural Science Foundation of China (No. 40976035 and No. 41276046)
文摘The distributions of lipids in surface and subsurface sediments from the northern South China Sea were determined. The n-alkanes were in bimodal distribution that is characterized by a centre at n-C16 –n-C20 with maximum at C18（or C19） and n-C27 –n-C31 as well as at C29（or C31）. The short-chain alkanes suffered from significant losses due to their slow deposition in the water column, and their presence with a slight even carbon predominance in shallow seafloor sediments was ascribed mainly to the direct input from the benthos. The long-chain alkanes with odd predominance indicate transportion of terrigenous organic matter. Immature hopanoid biomarkers reflect the intense microbial activity for bacteria–derived organic matter and the gradual increase of maturity with burial depth. Abundant n-fatty acid methyl esters（n-FAMEs） that are in distributions coincident with fatty acids were detected in all samples. We proposed that the observed FAMEs originated from the methyl esterification of fatty acids; methanol production by methanotrophs and methanogenic archaea related to the anaerobic oxidation of methane, and sulfate reduction provided an O–methyl donor for methylation of fatty acids. The CH4 released from hydrate dissociation at oxygen isotope stage II of Cores ZD3 and ZS5, which had been confirmed by the occurrence of negative δ13C excursion and spherical pyrite aggregates, could have accelerated the above process and thus maximized the relative content of FAMEs at ZD3-2（400–420 cm depth） and ZS5-2（241–291 cm depth）.
基金supported by the National Basic Research Program of China(2013CB035902)the National Natural Science Foundation of China(51038007)the State Key Laboratory of Hydroscience and Engineering Project(2013-KY-04 and 2014-KY-03)
文摘This paper presents a meso-level simulation of gas hydrate dissociation in low-permeability marine sediments. Interstitial pores are defined to describe fluid flow and particle movement. The proposed model couples multiphase fluid flow with particle movement to simulate the thermodynamics of gas hydrate dissociation triggered by sharp temperature rises. Hydrates respond quickly to temperature rise in low-permeability sediments. Dissociation causes pore pressure to rise rapidly to equilibrium then steadily increase above equilibrium pressure. Lower permeability sediment builds up greater excess pore pressure as the dissipation of pore pressure is constrained.
基金This work was supported by Doctor Foundation of Hebei Education Committee Hebei Natural Science Foundation(599091 ) of China
文摘Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used and the avalanche of electrons is taken into account in this simulation. The average energy distribution of electrons and the space distribution of effective species such as CH3, CH+3, CH+ and H at various gas pressures are given in this paper, and optimum experimental conditions are inferred from these results.
