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| 1 | Petrographic and geochemical characterization of seep carbonate from Alaminos Canyon,Gulf of Mexico显示文摘Seep carbonates were collected from the Alaminos Canyon lease area, Gulf of Mexico. The carbonates are present as slabs and blocks. Bivalve shell and foraminifer are the dominant bioclasts in carbonate. Pores are common and usually filled with acicular aragonite crystals. XRD investigation shows that aragonite is the dominate mineral (98%). Peloids, clotted microfabirc and botryoidal aragonite are de-veloped in carbonate and suggest a genesis linked with bacterial degradation of the hydrocarbons. The δ13C value of bioclasts in carbonate is from-4.9‰ to-0.6‰, indicating that the carbon source is mainly from sea water as well as the small portion incorporation of the seep hydrocarbon. The microcrystalline and sparite aragonite shows the δ13C value from-31.3‰ to-23.4‰, suggesting that their carbon is derived mainly from microbial degradation of crude oil. 14C analyses give the radiocarbon age of about 10 ka. Rare earth elements (REE) analyses of the 5% HNO3-treated solution of the carbonates show that the total REE content of the carbonates is low, that is from 0.752 to 12.725 μg·g-1. The shale-normalized REE patterns show significantly negative Ce anomalies. This suggests that cold seep carbonate is most likely formed in a relatively aerobic environment. | FENG Dong CHEN DuoFu QI Liang Harry H. ROBERTS | 2008 | Chinese Science Bulletin2008，53，11： | 11 |
| 2 | Controlling factors for gas hydrate occurrence in Shenhu area on the northern slope of the South China Sea显示文摘Temperature and pressure on seafloor of the northern slope in the South China Sea are suitable for gas hydrate formation, but bottom simulation reflector (BSR), an indication of gas hydrate occurrence, only occurred in limited areas of the slope. Drillings in the BSR-distributed area (the District S) on the northern slope of the South China Sea suggested that gas hydrate only occurred at Sites SH2, SH3, and SH7 with high saturation (up to 20%-40%), and there is no hydrate at Sites SH1 and SH5 although the distance between SH1 to SH3 is only 500m. In this paper, we investigated seafloor gradient, fault development, temperature, and pressure in the District S on the northern slope of the South China Sea to understand the possible factors con- trolling BSR distribution and gas hydrate occurrence. The District S is a structurally fractured continental slope zone and its seafloor gradient varied greatly. The BSR-occurred areas have an average gradient of 19.89×10 2 whereas the BSR-free zone has the average gradient of 10.57×10 2 . The calculated relative structural intensities from fault densities and displacements show that the BSR-distributed areas tend to occur in the areas with a moderately high structural intensity, where faults frequently developed close to the seafloor that are possibly favored for lateral migration of gases. On the basis of temperatures and pressures at drilling sites, hydrate-occurred Sites SH2, SH3, and SH7 are located within the thermodynamically stable area for methane hydrate, and hydrate-absent Sites SH1 and SH5 are out of the thermodynamically stable area for methane hydrate formation, suggesting that both BSR and the thermodynamic stability are necessary for hydrate occurrence in the subsurface. | WANG HongBin YANG ShengXiong WU NengYou ZHANG GuangXue LIANG JinQiang CHEN DuoFu | 2013 | Science China Earth Sciences2013，56，4： | 10 |
| 3 | First discovery and characterizations of late Cretaceous seep carbonates from Xigaze in Tibet,China显示文摘Hydrocarbon seeps,widely occurring in continental margins,have become increasingly focused owing to their close relationships with gas hydrates,strong greenhouse gas methane,and biological resources in extreme environments.Ancient hydrocarbon seeps have already been recognized from Devonian to Quaternary strata worldwide based on seep carbonates or seep-related fossil chemosynthetic assemblages.However,seep-related deposits are rarely found from ancient strata in the China's Mainland.Here,we report the first discovery of an ancient seep deposit,specifically late Cretaceous seep carbonates from Xigaze in Tibet,China.Xigaze seep carbonates,occurring as nodules,are enclosed in upper Cretaceous turbidite strata in Xigaze forearc basin.These carbonates are composed of authigenic carbonate(56.2% on average),clastic quartz and feldspar(27.3% on average),and clay minerals(chlorite,illite and smectite,16.5% on average).Clotted micrites,peloids and framboid pyrites are frequently observed,all of which are common in modern seep carbonates.The carbonates have negative δ13 C values varying from 27.7‰ to 4.0‰(V-PDB),suggesting that thermogenic methane is the primary carbon source.Ce/Ce* values revised by eliminating La effects show no real Ce anomaly,indicating the carbonates were primarily precipitated in a weak reducing environment.Overall,these features provide unequivocal evidences that the seafloor of Xigaze forearc basin developed hydrocarbon seeps in late Cretaceous. | TONG HongPeng CHEN DuoFu | 2012 | Chinese Science Bulletin2012，57，33： | 6 |
| 4 | Influence of water flow on gas hydrate accumulation at cold vents显示文摘感冒发泄是充满甲烷的液体渗出物发生的一个区域。这渗出物可以改变煤气的水合物的本地温度,咸度,和随后的累积。用一个运动煤气的水合物形成模型并且在在水合物理兹的南部的顶点的温度,咸度和液体流动的 situ 测量,我们在三个不同液体地点模仿煤气的水合物累积:蚌,细菌的地席,和气体解除地点。在蚌地点(毛孔水流动 < 20 kg m2 yr1 ) ,毛孔水移流几乎没在温度和咸度上有小影响。然而,咸度和温度被增加(山峰咸度 > 0.8 摩尔 kg1 ) 由引起水合物稳定性地区的底在 seafloor (mbsf ) 下面从 115 ~ 70 米逐渐地移动的煤气的水合物的形成。在蚌地点的煤气的水合物浸透相对高。在细菌的地席地点的水流动从 100 ~ 2500 kg m2 yr1 。水流动在咸度比海水的导致咸度结束到或稍微高压制增加(< 0.65 摩尔 kg1 ) 。热移流走水路,流动显著地增加温度,转移水合物稳定性地区的底到上面 50 或甚至 3 mbsf。煤气的水合物浸透在细菌的地席地点是相对低的。在煤气的分泌物地点,毛孔水流动能到达 1010 kg m2 yr1,并且温度能在 9 min 到达来源区域的。在煤气的分泌物地点没有煤气的水合物形成。我们的模拟分析因此表明更低的毛孔水流动将导致更低的咸度,更高的温度,和水合物稳定性地区的一个更浅的底。这接着导致更低的煤气的水合物形成率,更低的水合物浸透,并且最后不太煤气的水合物资源。 | CAO YunCheng SU Zheng CHEN DuoFu | 2013 | Science China Earth Sciences2013，56，4： | 3 |
| 5 | Composition and origin of lipid biomarkers in the surface sediments from the southern Challenger Deep, Mariana Trench显示文摘The surface sediments collected from the southern Mariana Trench at water depths between ca.4900 m and 7068 m were studied using lipid biomarker analyses to reveal the origin and distribution of organic matters. For all samples, an unresolved complex mixture(UCM) was present in the hydrocarbon fractions, wherein resistant component tricyclic terpanes were detected but C_(27)-C _(29) regular steranes and hopanes indicative of a higher molecular weight range of petroleum were almost absent.This biomarker distribution patterns suggested that the UCM and tricyclic terpanes may be introduced by contamination of diesel fuels or shipping activities and oil seepage elsewhere. The well-developed faults and strike-slip faults in the Mariana subduction zone may serve as passages for the petroleum hydrocarbons. In addition, the relative high contents of even n-alkanes and low Carbon Preference Indices indicated that the n-alkanes were mainly derived from bacteria or algae. For GDGTs, the predominance of GDGT-0 and crenarchaeol, together with low GDGT-0/Crenarchaeol ratios(ranging from0.86 to 1.64), suggests that the GDGTs in samples from the southern Mariana Trench were mainly derived from planktic Thaumarchaeota. However, the high GDGT-0/crenarchaeol ratio(10.5) in sample BC07 suggests that the GDGTs probably were introduced by methanogens in a more anoxic environment. Furthermore, the n-alkanes C_(19)-C_(22) and the n-fatty acids C_(20:0)-C_(22:0) were depleted in^(13)C by 3‰ compared to n-alkanes C_(16)-C_(18) and the n-fatty acids C_(14:0)-C_(18:0), respectively, which was interpreted to result from the preferential reaction of fatty acid fragments with carbon 'lighter' terminal carboxyl groups during carbon chain elongation from the precursors to products. The abundance of total alkanes, carboxylic acids, alcohols and total lipids were generally increased along the down-going seaward plate, suggesting the lateral organic matter inputs play an important role in organic matter accumulation in hadal trenches. The extremely high contents of biomarkers in sample BC11 were most likely related to trench topography and current dynamics, since the lower steepness caused by graben texture and proximity to the trench axis may result in higher sedimentation rate. This paper, for the first time, showed the biomarker patterns in surface sediments of the Mariana Trench and shed light on biogeochemistry of the hardly reached trench environment. | Hongxiang Guan Linying Chen Min Luo Lihua Liu Shengyi Mao Huangmin Ge Mei Zhang Jiasong Fang Duofu Chen | 2019 | Geoscience Frontiers2019，10，1： | 2 |
| 6 | Types of gashydrates in marine environments and their thermodynamiccharacteristics 显示文摘 | CHEN DUOFU SU ZHENQ CATHLES L M | 2006 | Terrestrial Atmospheric and OceanicSciences2006，17，4： | 1 |
| 7 | Quantification of Methane Fluxes from Hydrocarbon Seeps to the Ocean and Atmosphere:Development of an in situ and Online Gas Flux Measuring System显示文摘Natural hydrocarbon seeps in the marine environment are important contributors to greenhouse gases in the atmosphere. Such gases include methane, which plays a significant role in global carbon cycling and climate change. To accurately quantify the methane flux from hydrocarbon seeps on the seafloor, a specialized in situ and online gas flux measuring(GFM) device was designed to obtain high-resolution time course gas fluxes using the process of equal volume exchange. The device consists of a 1.0-m diameter, 0.9-m tall, inverted conical tent and a GFM instrument that contains a solenoid valve, level transducer, and gas collection chamber. Rising gas bubbles from seeps were measured by laboratory-calibrated GFM instruments attached to the top of the tent. According to the experimental data, the optimal anti-shake time interval was 5 s. The measurement range of the device was 0–15 L min^(-1), and the relative error was ± 1.0%. The device was initially deployed at an active seep site in the Lingtou Promontory seep field in South China Sea. The amount of gas released from a single gas vent was 30.5 m^3 during the measurement period, and the gas flow rate ranged from 22 to 72 Lh^(-1), depending on tidal period, and was strongly negatively correlated with water depth. The measurement results strongly suggest that oceanic tides and swells had a significant forcing effect on gas flux. Low flow rates were associated with high tides and vice versa. The changes in gas volume escaping from the seafloor seeps could be attributed to the hydrostatic pressure induced by water depth. Our findings suggest that in the marine environment, especially in the shallow shelf area, sea level variation may play an important role in controlling methane release into the ocean. Such releases probably also affect atmospheric methane levels. | DI Pengfei CHEN Qinghua CHEN Duofu | 2017 | Journal of Ocean University of China2017，16，3： | 1 |
| 8 | Bio- genic fabrics in seep carbonates from an active gas vent site in Green Canyon Block 238 ,Gulf of Mexico显示文摘 | CHEN Duofu LIU Qian ZHANG Zhengwei | 2007 | Marine and Petroleum Geology2007，24，5： | 1 |
| 9 | Seep carbonates and preserved methane oxidizing archaea and sulfate reducing bacteria fossils suggest recent gas venting on the seafloor in the Northeastern South China Sea 显示文摘 | Chen Duofu Huang Yongyang Yuan Xunlai | 2005 | Marine and Petroleum Geology2005，22，： | 1 |
| 10 | The distribution and variation in the gas composition of macro-seeps on the near-shore Lingtou Promontory in the South China Sea显示文摘Natural hydrocarbon seeps in a marine environment are one of the important contributors to greenhouse gases in the atmosphere,including methane,which is significant to the global carbon cycling and climate change.Four hydrocarbon seep areas,the Lingtou Promontory,the Yinggehai Rivulet mouth,the Yazhou Bay and the Nanshan Promontory,occurring in the Yinggehai Basin delineate a near-shore gas bubble zone.The gas composition and geochemistry of venting bubbles and the spatial distribution of hydrocarbon seeps are surveyed on the near-shore Lingtou Promontory.The gas composition of the venting bubbles is mainly composed of CO_2,CH_4,N_2 and O_2,with minor amounts of non-methane hydrocarbons.The difference in the bubbles' composition is a possible consequence of gas exchange during bubble ascent.The seepage gases from the seafloor are characterized by a high CO_2 content(67.35%) and relatively positive δ^(13)C_(V_PDB) values(-0.49×10^(-3)-0.86×10^(-3)),indicating that the CO_2 is of inorganic origin.The relatively low CH_4 content(23%) and their negative δ^(13)C_(V-PDB) values(-34.43×10^(-3)--37.53×10^(-3)) and high ratios of C_1 content to C_(1-5) one(0.98-0.99)as well point to thermogenic gases.The hydrocarbon seeps on the 3.5 Hz sub-bottom profile display a linear arrangement and are sub-parallel to the No.1 fault,suggesting that the hydrocarbon seeps may be associated with fracture activity or weak zones and that the seepage gases migrate laterally from the central depression of the Yinggehai Basin. | DI Pengfei FENG Dong CHEN Duofu | 2016 | Acta Oceanologica Sinica2016，35，11： | 1 |
| 11 | In-situ and on-line measurement of gas flux at a hydrocarbon seep from the northern South China Sea显示文摘 | Di Pengfei Feng Dong Chen Duofu | 2014 | Continental shelf research2014，81，： | 1 |
| 12 | Natural gas hydrate research of United States and the research countermeasure of China 显示文摘 | CHEN Duofu YAO Bochu XU Wenxin | 2002 | Marine Geology2002，，2： | 1 |
| 13 | Types of gashydrates in marine environments and their thermodynamic-characteristics 显示文摘 | CHEN DUOFU SU ZHEN CATHLES L M | 2006 | Terrestrial Atmospheric and OceanicSciences2006，17，4： | 1 |
| 14 | Possible REE constraints on the depositional and diagenetic environment of Doushantuo Formation phosphorites containing the earliest metazoan fauna 显示文摘 | Duofu Chen Weiquan Dong Liang Qi Guangqian Chen Xianpei Chen | 2003 | Chemical Geology2003，201，： | 1 |
| 15 | Thephysics of gas chimney and pockmark formation, withimplications for assessment of seafloor hazards and gassequestration 显示文摘 | CATHLES L M SU ZHENG CHEN DUOFU | 2010 | Marine and Petroleum Geology2010，27，1： | 1 |
| 16 | Using iron speciation in authigenic carbonates from hydrocarbon seeps to trace variable redox conditions显示文摘 | Yu Hu Dong Feng Linying Chen Guodong Zheng J?rn Peckmann Duofu Chen | 2015 | Marine and Petroleum Geology2015，，： | 1 |
| 17 | Lipid Biomarkers and Their Stable Carbon Isotopes in Ancient Seep Carbonates from SW Taiwan, China显示文摘Four massive brecciated, chimney-like, and slender pipe network carbonate samples(JA-4, JA-5, JX-8 and BG-12) were collected from southwestern Taiwan, which were suggested to have formed as a result of anaerobic oxidization of methane(AOM). Considering that the environmental conditions of the carbonates precipitation and the sources of carbon and organic matter need to be further declared, molecular fossils and compound-specific carbon isotopic investigations of the carbonates were conducted in this study. According to lipid biomarkers of 2,6,10,15,19-pentamethyleicosane(PMI) and squalane diagnostic to methanotrophic archaea, as well as the extremely low δ^(13)C values(as low as -1^(13).4‰) detected in samples JA-4, JA-5 and JX-8, these carbonates were revealed to be a result of AOM. Based on the varied δ^(13)C values of characteristic archaea biomarkers in specific samples, biogenic methane was proposed to be responsible for the formation of samples JA-4 and JA-5, whereas a mixed carbon source of ^(13)C-depleted methane and ^(13)C-enriched residual CO_2 from methanogenesis was suggested for the carbonate of JX-8 due to the co-occurrence of a highly positive δ^(13) C_(carb) value(+8‰) and a moderate ^(13)C depletion of PMI. The low content of AOM-related biomarkers and the absence of indicators for ANME-2 suggested that these carbonates were formed in weak seep settings. By comparison, no typical lipid biomarkers for methanotrophic archaea was detected in carbonate BG-12. The short-chain and long-chain n-alkanes accounted for 30% and 45% of all hydrocarbons, respectively, with a CPI value of 1.2, suggesting that the n-alkanes were derived from both marine organisms and terrestrial inputs. A low thermal maturity could be revealed by the incomplete equilibrium value of the C^(31)αβ 22S/(22S+22R) ratio(0.5), and the carbonate BG-12 was probably deposited in a suboxic condition indicated by a value of Pr/Ph ratio(2.5). | GUAN Hongxiang XU Lanfang WANG Qinxian CHEN Duofu WU Nengyou MAO Shengyi | 2019 | Acta Geologica Sinica(English Edition)2019，93，1： | 0 |
| 18 | 海底水合物区或存在大量以往被忽视的深部来源甲烷显示文摘量化天然气水合物富集区海底硫酸盐还原速率和甲烷氧化速率对了解海洋碳、硫循环至关重要.以南海北部神狐海域为例,基于实测的大面积(达5.2 10^(11)km^(2))、多站位(85个)海底表层沉积物硫酸盐浓度剖面,我们获得的区域硫酸盐还原速率为5.39 10^(11)mmol a^(-1).该值明显高于前人利用沉积速率估算的区域硫酸盐还原速率(3.52 10^(11)mmol a^(-1)).有意思的是,两种不同方法获得的区域硫酸盐还原速率的差值(1.87 10^(11)mmol a^(-1))恰好能限定来自深部地层中的甲烷通量大小.据此,我们认为以往海底表层沉积环境区域、乃至全球的硫酸盐还原速率可能被较大程度低估.研究同时突显了海底水合物和甲烷渗漏区表层硫酸盐消耗的甲烷相当一部分来自深部地层,而非原地有机质产甲烷形成.今后在进行精确评估全球海底硫酸盐还原和甲烷氧化速率以及水合物资源环境效应时须充分考虑海底深部甲烷的贡献. | Yu Hu Xinxin Zhang Dong Feng Jörn Peckmann Junxi Feng Hongbin Wang Shengxiong Yang Duofu Chen | 2022 | Science Bulletin2022，67，2： | 0 |
| 19 | Fatty-acids and their δ^(13)C characteristics of seep carbonates from the northern continental slope of Gulf of Mexico显示文摘Here we reported the fatty-acids and their δ13 C values in seep carbonates collected from Green Canyon lease block 185 (GC 185;Sample GC-F) at upper continental slope (water depth:~540 m),and Alaminos Canyon lease block 645 (GC 645;Sample AC-E) at lower continental slope (water depth:~2200 m) of the Gulf of Mexico.More than thirty kinds of fatty acids were detected in both samples.These fatty acids are maximized at C 16.There is a clear even-over-odd carbon number predominance in carbon number range.The fatty acids are mainly composed of n-fatty acids,iso-/anteiso-fatty acids and terminally branched odd-numbered fatty acids (iso/anteiso).The low δ13 C values (-39.99‰ to -32.36‰) of n-C 12:0,n-C 13:0,i-C 14:0 and n-C 14:0 suggest that they may relate to the chemosynthetic communities at seep sites.The unsaturated fatty acids n-C 18:2 and C 18:1 △9 have the same δ13 C values,they may originate from the Beggiatoa/Thioploca.Unlike other fatty acids,the terminally branched fatty acids (iso/anteiso) show lower δ13 C values (as low as -63.95‰) suggesting a possible relationship to sulfate reducing bacteria,which is common during anaerobic oxidation of methane at seep sites. | GUAN HongXiang FENG Dong WU NengYou CHEN DuoFu ROBERTS H H WU DaiDai | 2010 | Chinese Science Bulletin2010，55，8： | 0 |
| 20 | The crucial role of deep-sourced methane in maintaining the subseafloor sulfate budget显示文摘Methane(CH4)is a powerful greenhouse gas and its largest reservoir on Earth is held in marine sediments.CH4 in marine sediments is mainly stored in gas-hydrate reservoirs and deep sedimentary strata along continental margins,where large amounts of deep-sourced CH4 ascend to different degrees toward the seafloor.However,the amount of deep-sourced CH4 and its role in subseafloor carbon and sulfur cycling remains poorly constrained.We analyzed sulfate(SO_(4)^(2-))profiles of 157 sites along with previous published 85 sites to determine the regional distribution and amount of SO_(4)^(2-) reduction for an area of 1.23×10^(5) km^(2) of the northern South China Sea.Then we compared these obtained results with estimates based on sedimentation rates from the same area.Significantly higher regional SO_(4)^(2-) flux estimates based on SO_(4)^(2-) profiles(4.26×10^(-3)Tmol a^(-1)),compared to lower estimates based on sedimentation rates(1.23×10^(-3)Tmol a^(-1)),reflect abundant ascending deep-sourced CH4.The difference of the regional SO_(4)^(2-) flux estimates(3.03×10^(-3)Tmol a^(-1))represents the amount of SO_(4)^(2-) reduced by CH_(4) through the anaerobic oxidation of CH_(4)(AOM).Deep-sourced CH_(4) contributes 71%to total SO_(4)^(2-) consumption in the study area,largely exceeding SO_(4)^(2-) consumption by organoclastic sulfate reduction.Our findings substantiate that deep-sourced CH4 governs subseafloor carbon and sulfur cycling to a previously underrated extent,fueling extensive chemosynthesis-based ecosystems along continental slope and rise. | Yu Hu Dong Feng Jörn Peckmann Xinxin Zhang Linying Chen Junxi Feng Hongbin Wang Duofu Chen | 2023 | Geoscience Frontiers2023，14，3： | 0 |
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