35 results on '"Zhilei Sun"'
Search Results
2. Nitrogen-doped titanium dioxide films fabricated via magnetron sputtering for vascular stent biocompatibility improvement
- Author
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Zhilei Sun, Igor A. Khlusov, Kirill E. Evdokimov, Maksim E. Konishchev, Oleg S. Kuzmin, Olga G. Khaziakhmatova, Vladimir V. Malashchenko, Larisa S. Litvinova, Sven Rutkowski, Johannes Frueh, Anna I. Kozelskaya, and Sergei I. Tverdokhlebov
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Oxygen ,Titanium ,Biomaterials ,Colloid and Surface Chemistry ,Nitrogen ,Materials Testing ,Nitrogen Dioxide ,Humans ,Stents ,Argon ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
Nowadays, vascular stents are commonly used to treat cardiovascular diseases. This article focuses on the influence of nitrogen doping of titanium dioxide thin films, utilized for coating metallic stents to improve their biological properties and biocompatibility. The hereby-investigated titanium oxide thin films are fabricated by magnetron sputtering in a reactive gas atmosphere consisting of argon and oxygen in the first case and argon, nitrogen and oxygen in the second case. Control of the nitrogen and oxygen gas flow rates, and hence their mixing ratios, allows adjustment of the nitrogen-doping level within the titanium dioxide thin films. A correlation of the thin film internal structure on the in vitro behavior of human mesenchymal stem cells derived from adipose tissue is hereby demonstrated. Different nitrogen doping levels affect the surface energy, the wettability, the cell adhesion and thus the cellular proliferation on top of the thin films. The surface colonization of cells on titanium dioxide thin films decreases up to a nitrogen-doping level of ∼ 3.75 at.%, which is associated with a decreasing polar component of the surface energy. For non-doped titanium dioxide thin films, a weak chondrogenesis of adult human adipose-derived mesenchymal stem cells with lower chondrogenic differentiation compared to glass is observed. An increasing nitrogen-doping level leads to linear increase in the chondrogenic differentiation rate, which is comparable to the control value of uncoated glass. Other investigated differentiated cell types do not display this behavior.
- Published
- 2022
3. Insights from modern diffuse-flow hydrothermal systems into the origin of post-GOE deep-water Fe-Si precipitates
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Xiaoming Ma, Xiang-Kun Zhu, Zhilei Sun, Hong Cao, Zhihong Li, Simon W. Poulton, Xijie Yin, Qiu Zhen, Andrey Bekker, Gareth Izon, Aiguo Dong, and Brian Kendall
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chemistry.chemical_classification ,Petrography ,Ferrihydrite ,Mineral ,Sulfide ,chemistry ,Geochemistry and Petrology ,Proterozoic ,Precipitation (chemistry) ,Genetic model ,Geochemistry ,Hydrothermal circulation - Abstract
Post-GOE deep-water Fe-Si precipitates associated with volcanogenic massive sulfide deposits are an important feature of the Proterozoic rock record. Although it is clear that these enigmatic deposits formed in oxygen-deficient and hydrothermally influenced deep-water settings, the oxidation mechanism(s) resulting in their precipitation remain(s) unclear. Whilst existing genetic models typically couple direct and/or bacterially-mediated iron oxidation with abiotic silica precipitation, low temperature diffuse hydrothermal fluids offer a potential mechanistic alternative to explain the observed layering. Herein, via combination of petrographic observations with elemental and isotopic data (Fe, Si, and O), we explore the genesis of the primary mineral phases present within recent Fe-Si precipitates obtained from the Southwest Indian Ridge. Formation of ferrihydrite and opal-A in these precipitates provides insight into the genesis of widely invoked precursor minerals to post-GOE deep-water Fe-Si precipitates. Specifically, we find that the mineralogical layers that typify these Fe-Si precipitates may have originated via biologically mediated ferrihydrite precipitation and abiotic precipitation of opal-A from oversaturated fluids during diffuse flow. By analogy, we propose that diffuse hydrothermal fluid flow played an important role in the formation of post-GOE deep-water Fe-Si precipitates.
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- 2022
4. Fe-Pb-Sr isotopic systematics of the hydrothermal chimney from the Minami-Ensei hydrothermal field, middle Okinawa Trough: Constraint on hydrothermal mineralization process in incipient back-arc basin
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Xia Zhang, Zhilei Sun, and Nengyou Wu
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Geochemistry and Petrology ,Economic Geology ,Geology - Published
- 2023
5. The Late Jurassic Zedong ophiolite: A remnant of subduction initiation within the Yarlung Zangbo Suture Zone (southern Tibet) and its tectonic implications
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Chris Yakymchuk, Hong-Fei Liu, Yun Zhong, Zhilei Sun, Hong Cao, Man Gu, Gongjian Tang, Lifeng Zhong, Weiliang Liu, and Bin Xia
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geography ,Dike ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Subduction ,Geochemistry ,Geology ,Massif ,010502 geochemistry & geophysics ,Ophiolite ,01 natural sciences ,Mantle (geology) ,Island arc ,Suture (geology) ,Forearc ,0105 earth and related environmental sciences - Abstract
The Zedong ophiolite is the largest ophiolite massif east of Dazhuqu in the Yarlung Zangbo Suture Zone in the southern Tibetan Plateau. However, its age, geodynamic setting and relationship to the Xigaze ophiolite remain controversial. New zircon U–Pb ages, whole-rock geochemical and Nd–Pb isotopic data from ophiolitic units provide constraints on the geodynamic and tectonic evolution of the Zedong ophiolite. U–Pb zircon geochronology of dolerite lavas and late gabbro–diabase dikes yield weighted mean ages of 153.9 ± 2.5 Ma and 149.2 ± 5.1 Ma, respectively. Strong positive eNd(t) and positive Δ7/4Pb and Δ8/4Pb values indicate derivation from a highly depleted mantle source with an isotopic composition similar to that of the Indian MORB-type mantle. The geochemistry of ophiolitic lavas and early dikes are analogous to typical island arc tholeiites whereas late dikes are similar to boninites. The geochemistry of these rock types suggests multi-stage partial melting of the mantle and gradually enhanced subduction influences to the mantle source through time. Combined with the MORB-like 162.9 ± 2.8 Ma Luobusha ophiolitic lavas, we suggest that the Luobusha lavas, Zedong lavas and early dikes originated in an infant proto-arc setting whereas late dikes in the Zedong ophiolite originated in a forearc setting. Together, they represent a Neo-Tethyan subduction initiation sequence. The Late Jurassic intra-oceanic proto-arc to forearc setting of the Zedong ophiolite contrasts with the continental margin forearc setting for the Xigaze ophiolite, which suggests a laterally complex geodynamic setting for ophiolites along the Yarlung Zangbo Suture Zone.
- Published
- 2020
6. Inorganic sulfur cycles in sediments of the Pearl River Estuary: Processes, mechanisms, and isotopic indicators
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Xijie Yin, Yunpeng Lin, Yunhai Li, Liang Wang, Zhilei Sun, and Guogang Li
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Aquatic Science ,Oceanography - Published
- 2023
7. Polyphase hydrothermal sulfide mineralization in the minami–ensei hydrothermal field, middle okinawa trough: Implications from sulfide mineralogy and in situ geochemical composition of pyrite
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Xia Zhang, Zhilei Sun, Nengyou Wu, Kun Guo, Wei Geng, and Hong Cao
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Geochemistry and Petrology ,Economic Geology ,Geology - Published
- 2022
8. Oceanic carbon cycle in a symbiotic zone between hydrothermal vents and cold seeps in the Okinawa Trough
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Nengyou Wu, Cuiling Xu, Ang Li, Hong Cao, Ye Chen, Xilin Zhang, Wei Geng, Bin Zhai, Qing Li, and Zhilei Sun
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- 2022
9. Hydrothermal metal supplies enhance the benthic methane filter in oceans: An example from the Okinawa Trough
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Cuiling Xu, Zhilei Sun, Nengyou Wu, Liping Liu, Hong Cao, Xijie Yin, Xianrong Zhang, Wei Geng, and Xilin Zhang
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010504 meteorology & atmospheric sciences ,Geochemistry ,Geology ,Authigenic ,010502 geochemistry & geophysics ,01 natural sciences ,Cold seep ,Methane ,Hydrothermal circulation ,Carbon cycle ,chemistry.chemical_compound ,chemistry ,13. Climate action ,Geochemistry and Petrology ,Anaerobic oxidation of methane ,Carbonate ,14. Life underwater ,Sulfate ,0105 earth and related environmental sciences - Abstract
Highlights • Three distinct types of carbonates exist in cold seeps in the Okinawa Trough. • Carbonate forms between lower part of SMTZ and upper part of methanogenic zone. • Hydrothermal has the potential to foster Fe-AOM in cold seep sediment. • Metal-AOM might have an influence on early Earth's methane flux and metal cycle. Abstract Anaerobic oxidation of methane (AOM) is an important process that regulates methane budget in the global carbon cycle. Sulfate is traditionally regarded as the most important electron acceptor for AOM. However, recent studies reveal that reactive metal reduction-driven AOM (metal-AOM) may also present on natural environments. Partitioning the methane-C sink from anaerobic oxidation between sulfate reduction-driven AOM (sulfate-AOM) and metal-AOM is thus becoming a scientific challenge to be addressed. This study aimed to show that metal-AOM has a potential to complement sulfate-AOM, especially when methane seeps met sediments enriched in iron and manganese oxides supplied by hydrothermal plumes. Samples of authigenic carbonate were collected from the cold seeps on the western slope of the Okinawa Trough (OT), a semi-enclosed back-arc basin with cold seeps and hydrothermal activities coexist spatially. Petrologic and mineralogical observations provided faithful evidence of a close genetic relationship between goethite and authigenic carbonates, likely indicating the presence of metal-AOM although some contributions of organoclastic Fe reduction cannot be ruled out. The most possible place of metal-AOM was between the lower part of the sulfate–methane transition zone (SMTZ) and the immediate upper part of the methanogenic zone. The characteristics of δ13Ccarb [−53.7‰ to −3.3‰ Vienna-PeeDee Belemnite (VPDB)] also point to our carbonate samples as the products of AOM. These authigenic carbonates was further identified as three possible types of carbonate of different sources: sulfate-AOM, metal-AOM, and hydrothermal carbonates, depending on the correlations among concentrations of carbonate-associated sulfate (CAS), δ13Ccarb, and δ18Ocarb. Based on these findings, we tentatively suggested that the reduction of reactive metals carried by hydrothermal plumes might drive the methane oxidation in the adjacent cold seep areas, resulting in the precipitation of unique carbonates and enhancement the efficiency of “the benthic methane filter”. This study reported the coupling or interaction between the two extreme submarine environments by metal-AOM for the first time, which might help in understanding and improving the global carbon and metal cycles now and in the past. Previous article in issue
- Published
- 2019
10. Aerobic microbial oxidation of hydrocarbon gases: Implications for oil and gas exploration
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Qingguo Meng, Changling Liu, Zhilei Sun, Gaowei Hu, Yanlong Li, Xingliang He, M. Santosh, Fulong Ning, and Jing Li
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chemistry.chemical_classification ,010504 meteorology & atmospheric sciences ,business.industry ,Stratigraphy ,Fossil fuel ,chemistry.chemical_element ,Sediment ,Geology ,Fractionation ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Methane ,chemistry.chemical_compound ,Geophysics ,Hydrocarbon ,chemistry ,Propane ,Isotopes of carbon ,Environmental chemistry ,Economic Geology ,business ,Carbon ,0105 earth and related environmental sciences - Abstract
The molecular and carbon and hydrogen isotope compositions associated with the aerobic consumption of methane (Cl), ethane (C2) and propane (C3) were determined from incubations of marine sediments collected from the seafloor surface of the gas- and oil-bearing Bohai Bay in eastern China. The fresh sediment samples were incubated aerobically at 28 °C and treated with three types of hydrocarbon gas mixtures as follows: mixture I (C1:C2:C3 = 100:0:0), II (C1:C2:C3 = 99.00:0.70:0.30) and III (C1:C2:C3 = 79.96:10.04:10.00), corresponding to incubations i, ii and iii, respectively. All the hydrocarbons are of thermogenic origin, except C1 (microbial) in incubation ii. The oxidation of C1-C3 was observed in all three treatments, with variations in carbon isotope fractionation factors (eC) of C1 and average values of −10.5 ± 0.1, −5.7 ± 1.6, and −10.9 ± 2.9, respectively. The hydrogen isotope fractionation factors (eH) of C1 in the three incubations also display variation, with average values of −118.4 ± 3.0, −68.3 ± 15.0 and −56.3 ± 8.4, respectively. Experiments with thermogenic C1 display greater carbon fractionation than those with microbial C1. The eC and eH values for C2 and C3 were obtained only in incubation iii. Compared to C1, C2 and C3 exhibit weaker carbon isotope fractionation but stronger hydrogen isotope fractionation. The fractionation factors presented in this study can be applied to estimate the extent of C1-C3 oxidation in natural environments, especially at seafloor and terrestrial seeps where aerobic microbes are commonly present. Our study has important implications in oil and gas exploration, with an alert for exercising caution when using the molecular and isotopic characteristics of hydrocarbon gases to evaluate the gas sources because these are susceptible to aerobic microbial oxidation.
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- 2019
11. Authigenic carbonate formation revealed by lipid biomarker inventory at hydrocarbon seeps: A case study from the Okinawa Trough
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Wei Geng, Xianrong Zhang, Cuiling Xu, Zhilei Sun, Lanfang Xu, Nengyou Wu, Hong Cao, Hongxiang Guan, and Shengyi Mao
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Calcite ,010504 meteorology & atmospheric sciences ,Stratigraphy ,Aragonite ,Carbonate minerals ,Geochemistry ,Geology ,Authigenic ,engineering.material ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Methane ,Siderite ,chemistry.chemical_compound ,Geophysics ,chemistry ,Anaerobic oxidation of methane ,engineering ,Carbonate ,Economic Geology ,0105 earth and related environmental sciences - Abstract
Authigenic carbonates were recovered from the northern Okinawa Trough at 540–700 m water depth. Development of microbial communities and seepage dynamics driving the precipitation of authigenic carbonates remains poorly constrained, even though the source of methane-rich fluids, formation of Fe-rich carbonates, and the potential driving forces were previously reported. Here, petrologic observations, stable carbon and oxygen isotopic compositions, mineralogy, and lipid inventories of authigenic carbonates from the northern Okinawa Trough were analyzed. The carbonate minerals were comprised predominantly of aragonite, high-magnesium calcite, and siderite. The presence of molecular fossils diagnostic for anaerobic methane oxidizing archaea (ANME) and sulfate-reducing bacteria (SRB) with pronounced 13C depletions (as low as −134‰), together with highly negative δ13Ccarb values (as low as −55.8‰), suggest that the carbonates precipitated from anaerobic oxidation of methane (AOM) with microbial methane as the predominant carbon source. The difference between measured and calculated δ18Ocarb values (based on 0‰ of sea water δ18O vs V-SMOW) was higher than +3‰ in one of the carbonates (GGD16), reflecting an origin from gas hydrate dissociation. Most of the carbonates revealed δ18O offsets between measured and calculated values within +3‰, or a lower measured δ18O than calculated value, suggesting a mixture of methane-derived carbonates (low δ13C/high δ18O) and detrital origin carbonates (high δ13C/low δ18O). Biomarker patterns varied significantly among samples. A suite of 13C-depleted biomarkers indicated the predominance of an ANME-1 assemblage for all samples, suggesting carbonates formed at low to medium methane flux. The predominance of ANME-1, abundant detrital minerals, and allochthonous biomarkers, as well as low carbonate contents indicate that most samples formed at greater depth within the sediment column. Only one carbonate sample in this study is interpreted to have precipitated at relatively shallower depth, as indicated by the occurrence of crocetane, dominance of aragonite, and higher overall carbonate content.
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- 2019
12. Compositional characteristics and sources of DIC and DOC in seawater of the Okinawa Trough, East China Sea
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Xiwu Luan, Xianrong Zhang, Xilin Zhang, Cuiling Xu, Wei Geng, Libo Wang, Dejiang Fan, and Zhilei Sun
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0106 biological sciences ,010504 meteorology & atmospheric sciences ,Stable isotope ratio ,010604 marine biology & hydrobiology ,Trough (geology) ,chemistry.chemical_element ,Geology ,Aquatic Science ,Oceanography ,01 natural sciences ,Cold seep ,Water column ,chemistry ,Environmental chemistry ,Dissolved organic carbon ,Environmental science ,Seawater ,Carbon ,0105 earth and related environmental sciences ,Hydrothermal vent - Abstract
Seafloor hydrothermal systems and cold seeps contribute considerable amounts of dissolved carbon to ocean water. To investigate the compositional characteristics and potential sources of the dissolved carbon in the Okinawa Trough (OT), East China Sea (ECS), we measured the concentrations and distributions of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and their 13C stable isotopes in a full-depth water column in this area. Our results indicate that in the upper layer (water depth
- Published
- 2019
13. Comparison of structure and diversity of benthic communities in the Okinawa Trough and Mariana Trench by environmental DNA metabarcoding
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Jun Liu, Lvpei Du, Zhilei Sun, and Haibin Zhang
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Aquatic Science ,Oceanography - Published
- 2022
14. Precipitation and subsequent preservation of hydrothermal Fe-Mn oxides in distal plume sediments on Juan de Fuca Ridge
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Xianrong Zhang, Wei Geng, Hong Cao, Zhilei Sun, Xijie Yin, Liping Liu, and Aiguo Dong
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Mineralization (geology) ,010504 meteorology & atmospheric sciences ,Geochemistry ,Sediment ,Aquatic Science ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Hydrothermal circulation ,Diagenesis ,Plume ,Paleoceanography ,Seawater ,Selective leaching ,Ecology, Evolution, Behavior and Systematics ,Geology ,0105 earth and related environmental sciences - Abstract
The dispersing process of hydrothermal plumes could be documented in the hydrothermal sediments beneath the plume trajectory. Here we report the results of mineralogical and geochemical analyses of eight surficial distal plume sediment samples recovered from the flank of Endeavour Segment, Juan de Fuca Ridge (JdFR). The geochemical analysis based on selective leaching showed that hydrothermal fluids contribute a proportion of Fe-Mn oxides (4.51–7.17 wt% of bulk sediments) to the plume sediments along with obviously enriched hydrothermally-sourced Al, Ca and some trace elements. The contents of reactive Fe in the sediments had no distinct relationship with the distance to the vents. We propose that the early mineralization of abundant organic matters in the distal plume sediments causes reactive Fe oxyhydroxide to undergo dissimilatory iron reduction (DIR) and thus overprints or even eradicates the original hydrothermal signal. Furthermore, the contents of some elements (P, V, U and Cr), which are traditionally believed to be closely associated with reactive Fe, had no correlation with the Fe content here. However, it was found that, within a distance of 2–15 km, the two-endmember mixing between seawater and hydrothermal fluid could be fingerprinted by the Sr-Nd isotopic ratio associated with the reactive Fe-Mn oxyhydroxides. In addition, reactive Mn content also provides a faithful record of the hydrothermal process. We also show that the decoupling behaviors between active Fe and Mn during precipitation and subsequent early diagenesis in the distal plume sediments provide valuable implications for future studies about the fates and oceanic budgets of various associated scavenging-prone elements.
- Published
- 2018
15. Rising bottom-water temperatures induced methane release during the middle Holocene in the Okinawa Trough, East China Sea
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Hongxiang Guan, Lei Liu, Yu Hu, Sanzhong Li, Niu Li, Zhilei Sun, Nengyou Wu, and Ian Somerville
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Geochemistry and Petrology ,Geology - Published
- 2022
16. Rare earth elements and Sr, S isotope compositions of hydrothermal deposits from the Okinawa Trough: Insight into mineralization condition and metal sources
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Jie Xu, Zhilei Sun, Zenghui Yu, Xia Zhang, Kun Guo, and Shikui Zhai
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chemistry.chemical_classification ,geography ,geography.geographical_feature_category ,Sulfide ,Geochemistry ,Sediment ,chemistry.chemical_element ,Geology ,Oceanography ,Mineralization (biology) ,Sulfur ,Hydrothermal circulation ,Volcanic rock ,δ34S ,chemistry ,Geochemistry and Petrology ,Seawater - Abstract
As an incipient back-are basin, the mineralization characteristic in the Okinawa Trough (OT) is quite unique. Many studies have been conducted in OT hydrothermal deposits, however the mineralization condition and metal source differences between the middle (MOT) and southern Okinawa Trough (SOT) are still unclear. The rare earth elements (REEs) and Sr, S isotope compositions of the OT hydrothermal deposits were determined in this paper in order to solve these problems. The Eu anomalies of the hydrothermal sulfide samples show large variation, with δEu values range from 0.62 to 21.38, which reflects the differences in the redox condition of their parental hydrothermal fluids. The 87Sr/86Sr ratios of the hydrothermal deposit samples are abnormally high, indicating the fluid/sediment interaction during the fluid circulation. The δ34S values of sulfide samples from the MOT fall between those of basement volcanic rocks and seawater, which can be attributed to the mixing of volcanic and seawater-derived sulfur. While samples from the SOT have abnormally low δ34S values, remobilization of biogenic sulfur in sediments is the major cause of the sulfur isotope anomaly. Both of S and Pb isotopes indicate that the proportions of sediment component in the SOT hydrothermal deposits are higher than those of the MOT. Whereas the Sr isotope compositions of the hydrothermal deposit samples show no systematic difference between the MOT and SOT. We propose that the decoupling of Sr and S, Pb isotopes may be caused by the fluid mobility differences between these three elements during the fluid/sediment interaction.
- Published
- 2022
17. Hydrothermal processes in the Edmond deposits, slow- to intermediate-spreading Central Indian Ridge
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Hong Cao, Shikui Zhai, Zhilei Sun, Zhang Xilin, Wei Huang, Xuejun Jiang, Yong-jun He, Wang Libo, and Zhimin Cao
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Anhydrite ,010504 meteorology & atmospheric sciences ,Chalcopyrite ,Volcanogenic massive sulfide ore deposit ,Geochemistry ,Mineralogy ,Aquatic Science ,engineering.material ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Hydrothermal circulation ,chemistry.chemical_compound ,Sphalerite ,chemistry ,visual_art ,Anglesite ,engineering ,visual_art.visual_art_medium ,Marcasite ,Pyrite ,Ecology, Evolution, Behavior and Systematics ,Geology ,0105 earth and related environmental sciences - Abstract
The Edmond hydrothermal field, located on the Central Indian Ridge (CIR), has a distinct mineralization history owing to its unique magmatic, tectonic, and alteration processes. Here, we report the detailed mineralogical and geochemical characteristics of hydrothermal metal sulfides recovered from this area. Based on the mineralogical investigations, the Edmond hydrothermal deposits comprise of high-temperature Fe-rich massive sulfides, medium-temperature Zn-rich sulfide chimney and low-temperature Ca-rich sulfate mineral assemblages. According to these compositions, three distinctive mineralization stages have been identified: (1) low-temperature consisting largely of anhydrite and pyrite/marcasite; (2) medium-high temperature distinguished by the mineral assemblage of pyrite, sphalerite and chalcopyrite; and (3) low-temperature stage characterized by the mineral assemblage of colloidal pyrite/marcasite, barite, quartz, anglesite. Several lines of evidence suggest that the sulfides were influenced by pervasive low-temperature diffuse flows in this area. The hydrothermal deposits are relatively enriched in Fe (5.99–18.93 wt%), Zn (2.10–10.00 wt%) and Ca (0.02–19.15 wt%), but display low Cu (0.28–0.81 wt%). The mineralogical varieties and low metal content of sulfides in the Edmond hydrothermal field both indicate that extensive water circulation is prevalent below the Edmond hydrothermal field. With regard to trace elements, the contents of Pb, Ba, Sr, As, Au, Ag, and Cd are significantly higher than those in other sediment-starved mid-ocean ridges, which is indicative of contribution from felsic rock sources. Furthermore, the multiphase hydrothermal activity and the pervasive water circulation underneath are speculated to play important roles in element remobilization and enrichment. Our findings deepen our understanding about the complex mineralization process in slow- to intermediate-spreading ridges globally.
- Published
- 2018
18. Sedimentary laminae in muddy inner continental shelf sediments of the East China Sea: Formation and implications for geochronology
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Ming Liu, Zhilei Sun, Jingping Xu, Zuosheng Yang, Yuan Tian, Zhang Xilin, Bin Chen, Weiliang Liu, and Dejiang Fan
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geography ,Varve ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Continental shelf ,Sediment ,010502 geochemistry & geophysics ,Monsoon ,01 natural sciences ,Deposition (geology) ,Oceanography ,East Asian Monsoon ,Sedimentary rock ,Radiometric dating ,Geology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
The sedimentary rhythm is well developed in the environment which is controlled by strong seasonal climate changing condition. This rhythm is important for sediment core dating purpose. In this study, we examine muddy sediments on the inner continental shelf of the East China Sea that are influenced under seasonal change of the East Asian monsoon. We use Ensemble Empirical Mode Decomposition (EEMD) method to process sediment grain size and X-radiograph negatives grayscale value data in three sediment cores from this area and use the results to analyze the patterns of sedimentary variability and the causes of cyclic variability of the sedimentary process. The variability in the grain size and grayscale values of the core sediments has three components: the high-frequency variability, low-frequency variability and a secular trend. Among these components, the high-frequency component reflects variability on annual time scale can be well recognized, we suggest that the annual variability is derived from seasonal variation in the sediment flux from the Yangtze River to the sea, as well as the East Asian monsoon's impact on the sedimentary dynamics of the East China Sea's inner continental shelf. However, the other variability is hard to identify which cycles there are. This variability may reflect decadal winter monsoon oscillation and human activity of dam construction in the Yangtze River. Each annual variability presents a varve in the sediment sequence, which can be used to determine the sediment deposition rate and accurately date the core sediment. We found that the average deposition rates of the three cores from north to south on the inner shelf were 3.1 cm/yr, 1.0 cm/yr, 0.9 cm/yr, indicating that the Yangtze-derived sediment decreased with the increasing distance from the Yangtze estuary to the shelf. The deposition rate of each core varies over time, and the maximum deposition rate can be 3–5 times greater than the minimum rate. The sediment ages obtained from varve chronology and radiometric dating are fairly consistent on a centennial scale, differing only by 2–5 years. Thus, varve counting is a useful supplementary approach to radiometric age dating for constructing chronologies for core sediment in shelf seas influenced by monsoons.
- Published
- 2018
19. U concentration and 234 U/ 238 U of seawater from the Okinawa Trough and Indian Ocean using MC-ICPMS with SEM protocols
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Xuefeng Wang, Zhibang Ma, Jule Xiao, Zhilei Sun, Hai Cheng, Ye-Jian Wang, and Lisheng Wang
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geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Environmental change ,biology ,Coral ,Trough (geology) ,Pelagic zone ,General Chemistry ,Structural basin ,010502 geochemistry & geophysics ,Oceanography ,biology.organism_classification ,01 natural sciences ,Environmental Chemistry ,Acropora ,Seawater ,Oceanic basin ,Geology ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
The Okinawa Trough, a back-arc basin formed by extension within the continental lithosphere, is one of the most significant ocean basins between the East China Sea and the Pacific Ocean. In an attempt to constrain the U content and the 234 U/ 238 U of seawater, five depths vertical seawater profiles from the Okinawa Trough, two from the Indian Ocean and one from the South China Sea were investigated by MC-ICPMS. The method allows us to contribute most reliable uranium isotopic measurement in seawater and greatly reduces sample size. Results showed that the U contents of seawater profiles for Okinawa Trough were from 3.153 to 3.235 ppb, with an average value of 3.186 ± 0.040 (2σ, n = 37), Indian Ocean were from 3.255 to 3.283 ppb with a mean value of 3.272 ± 0.018 (2σ, n = 19), and South China Sea were from 3.253 to 3.271 averaging 3.263 ± 0.018 (2σ, n = 3) ppb. Similarly, we obtained δ 234 U values of 146.1 ± 1.2, 145.1 ± 1.4, and 145.8 ± 0.5‰ for Okinawa Trough, Indian Ocean and South China Sea, with a mean of 145.7 ± 1.0‰, in good agreement with previous reports within the error limits. With two-ml samples in the Okinawa Trough, it gives a mean δ 234 U of 145.8 ± 1.0‰ which is identical to that observed for 7-ml seawater within the 95% confidence level. These results suggest that the distribution of δ 234 U is homogeneous in the Okinawa Trough and followed U conservative behavior. We also obtained average δ 234 U values of 146.9 ± 2.1‰ (2σ, n = 6) for Acropora coral from the Xisha Islands in the South China Sea. All results show no marked differences with the open ocean and provide significant geochemical information for the study of environmental change in the East China Sea.
- Published
- 2017
20. Sulfate reduction and its important role in organic carbon mineralization in sediments of the Pearl River Estuary
- Author
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Xijie Yin, Guogang Li, Yunpeng Lin, Liang Wang, Yunhai Li, and Zhilei Sun
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Total organic carbon ,chemistry.chemical_classification ,Biogeochemical cycle ,Sediment ,Mineralization (soil science) ,Aquatic Science ,Oceanography ,Diagenesis ,chemistry.chemical_compound ,chemistry ,Environmental chemistry ,Anaerobic oxidation of methane ,Environmental science ,Organic matter ,Sulfate - Abstract
The sulfate reduction process plays an important role in the early diagenesis of organic matter in the estuarine and coastal sediments. In this study, the sulfate reduction rates (SRR) were determined by the 35SO42− radioactive tracer method, and the SO42−, CH4, Cl− of sediment porewater and total organic carbon (TOC), temperature, and redox potential (Eh) of sediment were determined simultaneously at three stations (QA, HQ, and GS) in different sedimentary environments of the Pearl River Estuary to study the sulfate reduction process and its important role in organic matter mineralization. The results show that SRR was mainly controlled by the content and availability of organic matter in sediments of the Pearl River Estuary. The consumption of sulfate mainly included the organic matter mineralization on the upper sediments and the anaerobic oxidation of methane (AOM) driven by sulfate in the sulfate-methane transition zone (SMT), which formed two peaks in the SRR profile, respectively (stations HQ and GS). Affected by physical disturbance, there was only one SRR peak formed above the SMT at station QA. The results of flux calculations for AOM and sulfate reduction show that the contributions of AOM to total sulfate reduction were 7.04 %, 5.46 %, and 42.0 % at stations QA, HQ, and GS, respectively, which were also controlled by the content and availability of organic matter in sediments. The depths of SMT in sediments of stations QA, HQ, and GS were 25, 30, and 213 cm, respectively, which were controlled by the input of organic matter and sulfate concentration in sediments. The calculation results show that total fluxes of sulfate reduction were 22.7, 35.3, and 3.9 mmol m−2 d-l at stations QA, HQ, and GS, respectively, and the rates of organic carbon mineralization by sulfate reduction were 45.4, 70.6, and 7.8 mmol m−2 d-l. In the estuarine mouth (station GS) with relatively weak hydrodynamic force and deep water, the burying efficiency of organic matter in sediment was higher than that in the brackish coast (station HQ); whereas the burial efficiency of organic matter in sediment cannot be comprehensively estimate in the upper estuary (station QA) due to the existence of the fluid mud layer. These findings contribute to a comprehensive understanding of the biogeochemical cycling process of sulfate and methane in sediments of the Pearl River Estuary.
- Published
- 2021
21. A new method for the U–Th dating of a carbonate chimney deposited during the last glaciation in the northern Okinawa Trough, East China Sea
- Author
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Yanhong Liu, Lisheng Wang, Xuefeng Wang, Hong Cao, Jule Xiao, Hong-Chun Li, Zhibang Ma, and Zhilei Sun
- Subjects
Stratigraphy ,Geochemistry ,Geology ,Last Glacial Maximum ,Authigenic ,Seafloor spreading ,Cold seep ,chemistry.chemical_compound ,chemistry ,Continental margin ,Earth and Planetary Sciences (miscellaneous) ,Carbonate ,Chimney ,Glacial period - Abstract
Authigenic carbonates from cold seep systems, such as chimney and crust carbonate deposits, are important archives of biogeochemical processes associated with the migration and seepage of methane-rich fluids and seepages on the seafloor. Here we use a new U–Th dating method to precisely determine the ages of the authigenic carbonates of a chimney in the Okinawa Trough (OT), East China Sea. The method uses a series of heavy liquids (HL, a mixture of tribromomethane and alcohol with a density of 2.71–2.80 g/cm3) to separate subsamples of carbonate contaminated by detrital material. The contents of relevant elements (Al, Rb, Zr, Nb, and rare earth elements) of the subsamples reveal that the separation of the mineral phase was successful. Five samples from along the radius of a well-structured chimney (PES-1) from station D2-5 in the OT were analyzed and yielded U–Th ages of 28.8 ± 0.4 ka, 26.1 ± 0.5 ka, 24.4 ± 0.7 ka, 22.5 ± 0.6 ka and 20.1 ± 0.6 ka, from the exterior to the interior of the chimney section, and AMS 14C dating of the same samples produced the similar results. The agreement between the 230Th/U and AMS 14C ages suggests that the application of heavy liquid methods in U–Th dating can be very successful, and it reduces the influence of detrital contamination. Therefore, the approach has a great potential space for studying the evolutionary history of authigenic carbonates in cold seep systems. Moreover, the new 230Th/U ages show that the carbonate chimney was formed during the Last Glacial Maximum (LGM), which corresponding to the large sea-level fall in the East China Sea. Together with information on biogeochemical processes, the results will provide valuable geochronological information for the future study of active fluid venting on continental margins.
- Published
- 2021
22. Geochemistry of iron and sulfur in the Holocene marine sediments under contrasting depositional settings, with caveats for applications of paleoredox proxies
- Author
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Kui Ma, Xianrong Zhang, Chang-Hong Sun, Zhilei Sun, Mao-Xu Zhu, Wen-Xuan Sun, and De-Yan Wang
- Subjects
0106 biological sciences ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,010604 marine biology & hydrobiology ,Geochemistry ,Sediment ,Estuary ,Aquatic Science ,engineering.material ,Oceanography ,01 natural sciences ,Diagenesis ,Sedimentary depositional environment ,Continental margin ,Benthic zone ,engineering ,Environmental science ,Pyrite ,Sediment transport ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
Cycling and fates of iron (Fe) and sulfur (S) in marine sediments are influenced by depositional settings to differential extents. The information is crucial for addressing the responses of their benthic diagenesis to changing climates and environments and also for reconstructing paleo-depositional conditions, but has not been well constrained. Detailed chemical speciation was utilized to characterize geochemistry of Fe and S, and then to reveal the impacts of depositional settings on their diagenesis at three locations, representing contrasting depositional environments: (i) highly dynamic Yangtze River estuary (YRE), (ii) the depocenter of South Yellow Sea (SYS), which is only remotely impacted by large river, and (iii) the middle Okinawa trough (OT), a back-arc deep basin along the outer edge of the East China Sea (ECS) slope. Results show that the YRE sediments favor accumulation of total highly reactive Fe (FeHR), while the SYS sediments are poor in FeHR due to low FeHR in their source material and/or preferential trapping of FeHR during sediment transport through the semi-enclosed Bohai Sea. Ferruginous sediment regimes in the highly dynamic YRE system facilitate Fe(III) reduction and burial of unsulfidized Fe(II), while the SYS and OT sediments favor sulfate reduction and pyritization of Fe(II). Pyrite is always the main sink of reduced S that escapes reoxidation in the entire continental margin, regardless of depositional environments. Abundant reactive Fe(III) but low total reduced inorganic sulfide (TRIS) contents in the three sites suggest that TRIS burial is largely controlled by the availability of degradable OC and/or dynamic regimes of sediments. The applicability of two widely used Fe- and S-based proxies to distinguish bottom-water conditions, that is, OC/TRIS ratio and FeHR to total Fe (FeHR/FeT) ratio, were examined in the three contrasting environments, and caveats were given for future applications of the two proxies.
- Published
- 2021
23. Source origin and ore-controlling factors of hydrothermal sulfides from the Tianzuo hydrothermal field, Southwest Indian Ridge
- Author
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Wei Geng, Zike Jiang, Aiguo Dong, Zhang Xilin, Xin Li, Zhilei Sun, Hong Cao, Dawei Yan, and Weiliang Liu
- Subjects
Basalt ,chemistry.chemical_classification ,Mineralization (geology) ,Stockwork ,Sulfide ,020209 energy ,Volcanogenic massive sulfide ore deposit ,Geochemistry ,Geology ,02 engineering and technology ,010502 geochemistry & geophysics ,01 natural sciences ,Hydrothermal circulation ,chemistry ,Geochemistry and Petrology ,Ultramafic rock ,0202 electrical engineering, electronic engineering, information engineering ,Economic Geology ,0105 earth and related environmental sciences ,Hydrothermal vent - Abstract
A newly confirmed hydrothermal sulfide ore hosted by ultramafic rocks was identified in the Tianzuo field on the Southwest Indian Ridge. In this study, detailed mineralogy, geochemistry, and stable isotope analyses were carried out to assess the source origin and mineralization of the Tianzuo field sulfide deposits. The mineralogical examination indicates that the massive sulfides recovered from the seafloor in this area exhibit multi-stage deposition features with four distinct mineralization stages. In terms of geochemistry, the deposit is characterized by high Fe (31.57–44.59 wt%), Co (up to 2400 ppm), and Ba contents (up to 47.89 ppm), and relatively low Cu + Zn (0.17–7.25 wt%) and Ni contents (3.74–30.6 ppm). These results somewhat different from the features of massive sulfides of the ultramafic-hosted ridge in the Atlantic Ocean. The elevated Ba and Co contents presumably reflect a contribution of deep gabbroic intrusions that, together with serpentinization, drove the high-temperature (~335 °C) hydrothermal vent activity in the Tianzuo field. The Co distribution is influenced by high-temperature and high-gradient conditions apart from the basement rock. In contrast, the depletion of Ni suggests that most of the Ni-rich sulfides are concentrated in the deep stockwork mineralization, whereas the low Cu + Zn content indicates a partial influence of the depleted mantle. With regard to isotopic composition, the sulfide in the Tianzuo field shows relatively heavy in situ S isotopic values, which implies that the widely developed transform faults and episodic hydrothermal events allowed cold seawater to repeatedly rinse the entire plumbing system. In comparison, the bulk Pb isotopic composition indicates that Pb in these sulfide deposits is mainly derived from the leaching of basalts and peridotites by seawater. By integrating all of the evidence, we demonstrate that, apart from the basement rock composition, the pervasive transform faults and multistage hydrothermal activity are important factors that affect the composition of the Tianzuo field sulfide.
- Published
- 2021
24. Formation of carbonate pipes in the northern Okinawa Trough linked to strong sulfate exhaustion and iron supply
- Author
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Zhilei Sun, Shun Chen, Jiwei Li, Lijuan Zhang, Jianchao Zhang, Hengchao Xu, Xiaotong Peng, Mengran Du, Kaiwen Ta, and Zixiao Guo
- Subjects
Biogeochemical cycle ,010504 meteorology & atmospheric sciences ,Geochemistry ,Authigenic ,engineering.material ,010502 geochemistry & geophysics ,01 natural sciences ,Cold seep ,Methane ,chemistry.chemical_compound ,chemistry ,Geochemistry and Petrology ,Anaerobic oxidation of methane ,engineering ,Carbonate ,Pyrite ,Sulfate ,Geology ,0105 earth and related environmental sciences - Abstract
The microbial anaerobic oxidation of methane (AOM), a key biogeochemical process that consumes substantial amounts of methane produced in seafloor sediments, can lead to the formation of carbonate deposits at or beneath the sea floor. Although Fe oxide-driven AOM has been identified in cold seep sediments, the exact mode by which it may influence the formation of carbonate deposits remains poorly understood. Here, we characterize the morphology, petrology and geochemistry of a methane-derived Fe-rich carbonate pipe in the northern Okinawa Trough (OT). We detect abundant authigenic pyrites, as well as widespread trace Fe, within microbial mat-like carbonate veins in the pipe. The in situ δ 34 S values of these pyrites range from −3.9 to 31.6‰ (VCDT), suggesting a strong consumption of seawater sulfate by sulfate-driven AOM at the bottom of sulfate reduction zone. The positive δ 56 Fe values of pyrite and notable enrichment of Fe in the OT pipe concurrently indicate that the pyrites are primarily derived from Fe oxides in deep sediments. We propose that the Fe-rich carbonate pipe formed at the bottom of sulfate reduction zone, below which Fe-driven AOM, rather than Fe-oxide reduction coupled to organic matter degradation, might be responsible for the abundantly available Fe 2+ in the fluids from which pyrites precipitated. The Fe-rich carbonate pipe described in this study probably represents the first fossil example of carbonate deposits linked to Fe-driven AOM. Because Fe-rich carbonate deposits have also been found at other cold seeps worldwide, we infer that similar processes may play an essential role in biogeochemical cycling of sub-seafloor methane and Fe at continental margins.
- Published
- 2017
25. Numerical simulation of the heat extraction in EGS with thermal-hydraulic-mechanical coupling method based on discrete fractures model
- Author
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Wang Haoxuan, Cai Mingyu, Huang Yong, Jun Yao, Xu Zhang, Shuhuan Lv, Zhilei Sun, Zhixue Sun, Xu Yi, and Xiaoxue Huang
- Subjects
Petroleum engineering ,Computer simulation ,020209 energy ,Mechanical Engineering ,02 engineering and technology ,Building and Construction ,Enhanced geothermal system ,Pollution ,Industrial and Manufacturing Engineering ,Thermal hydraulics ,General Energy ,Hydraulic fracturing ,Heat transfer ,0202 electrical engineering, electronic engineering, information engineering ,Fracture (geology) ,Fluid dynamics ,Geotechnical engineering ,Electrical and Electronic Engineering ,Rock mass classification ,Geology ,Civil and Structural Engineering - Abstract
The Enhanced Geothermal System (EGS) creates an artificial geothermal reservoir by hydraulic fracturing which allows heat transmission through the fractures by the circulating fluids as they extract heat from Hot Dry Rock (HDR). The technique involves complex thermal–hydraulic–mechanical (THM) coupling process. A numerical approach is presented in this paper to simulate and analyze the heat extraction process in EGS. The reservoir is regarded as fractured porous media consisting of rock matrix blocks and discrete fracture networks. Based on thermal non-equilibrium theory, the mathematical model of THM coupling process in fractured rock mass is used. The proposed model is validated by comparing it with several analytical solutions. An EGS case from Cooper Basin, Australia is simulated with 2D stochastically generated fracture model to study the characteristics of fluid flow, heat transfer and mechanical response in geothermal reservoir. The main parameters controlling the outlet temperature of EGS are also studied by sensitivity analysis. The results shows the significance of taking into account the THM coupling effects when investigating the efficiency and performance of EGS.
- Published
- 2017
26. Characterizing geochemistry of organic carbon, sulfur, and iron in sediments of the middle Okinawa Trough since the last glacial maximum
- Author
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Mao-Xu Zhu, Bin Zhai, Xianrong Zhang, Cuiling Xu, Tie Li, Wei Geng, Kui-Ying Ding, Hong Cao, Kui Ma, Xilin Zhang, and Zhilei Sun
- Subjects
Total organic carbon ,Geochemistry ,Last Glacial Maximum ,Aquatic Science ,engineering.material ,Oceanography ,Anoxic waters ,Diagenesis ,Sedimentary depositional environment ,engineering ,Sedimentary rock ,Glacial period ,Pyrite ,Geology - Abstract
The diagenetic interplays of organic carbon (OC), sulfur (S), and iron (Fe) in marine sediments and their responses to changes in depositional and climatic conditions are poorly characterized. In this study, chemical speciation and isotopes were combined to characterize diagenesis of OC, S and Fe in sediments of the middle Okinawa Trough (OT), a back-arc deep basin along the edge of the East China Sea outer shelf, since the Last Glacial Maximum (LGM). Two key geochemical proxies, i.e., OC/pyrite-S ratios and the degrees of pyritization, indicate anoxic bottom-water conditions during the last Glacial/Deglacial, which promoted burial of OC and pyrite. However, a shift to oxic conditions during the Deglacial-Holocene transition facilitated aerobic respiration, resulting in lower burial of OC and pyrite. In contrast to previous studies, the environmental changes induced by large sea-level rises since the LGM have not triggered significant variations in pyrite-S isotopic compositions, probably due to persistently low sedimentation rates. Variable extents of Fe enrichment are identified in the sediments since the LGM, with lower enrichment during the Holocene probably due to increased distance of Fe shuttling and concomitant Fe ageing. Anoxic bottom water during the Glacial/Deglacial did not induce an expected intensification of OC sulfurization, probably because sedimentary Fe enrichment favored pyrite formation but competitively dampened OC sulfurization. Lines of geochemical evidence hint at a discontinuous deposition at ~200 cm depth probably caused by mass wasting.
- Published
- 2021
27. Assessing methane cycling in the seep sediments of the mid-Okinawa Trough: Insights from pore-water geochemistry and numerical modeling
- Author
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Bin Zhai, Nengyou Wu, Xianrong Zhang, Xilin Zhang, Cuiling Xu, Zhilei Sun, Libo Wang, Wei Geng, and Hong Cao
- Subjects
020209 energy ,Clathrate hydrate ,Geochemistry ,chemistry.chemical_element ,Carbon sink ,Geology ,02 engineering and technology ,010502 geochemistry & geophysics ,01 natural sciences ,Methane ,Cold seep ,Carbon cycle ,chemistry.chemical_compound ,Water column ,chemistry ,Geochemistry and Petrology ,Anaerobic oxidation of methane ,0202 electrical engineering, electronic engineering, information engineering ,Economic Geology ,Carbon ,0105 earth and related environmental sciences - Abstract
The methane-enriched fluids in cold seeps are likely to crystallize as gas hydrates and serve as crucial sources of carbon to seawater. In this research, we analyzed the pore-water composition in terms of CH4, dissolved inorganic carbon (DIC), Cl−, Br−, SO42−, Na+, Mg2+, Ca2+, Sr2+, and NH4+, and the δ13CDIC, δ13CCH4, and δDCH4 values of two gravity cores and six remotely operated vehicle (ROV) video-guided push cores retrieved from fault scarps and dome-like structures (DSs) on the western slope of the mid-Okinawa Trough. In addition, a reaction–transport model was applied to quantify the methane fluxes and related biogeochemical processes. Active seepage of biogenic (δ13CCH4 ~ –70‰ V-PDB) and thermogenic (δ13CCH4 = −40‰ to −56‰ V-PDB) methane was identified on fault scarps and dome structures, respectively. Methane seepage was controlled by the transport and dissolution of the ascending gas rather than by clay dehydration or gas hydrate dissociation-induced fluid advection. The high methane concentrations and shallow sulfate–methane transition zones (SMTZs; between 0.1 and 0.4 mbsf) at sites R3-C2, R4-C4, and R6-C1 suggest strong methane seepage at three of the four studied DS (the highest gas dissolution rates are 6450, 1475, and 515 mmol m−2 yr−1). Site GC08, located along a fault scarp, exhibits a moderate methane seepage; the SMTZ is located at ~2.5 mbsf, and the rate of anaerobic oxidation of methane (AOM) is 130 mmol m−2 yr−1. The methane migrating from depth is mainly consumed by AOM. However, ~12%–66% of the methane released from the two most intensive seep sites escapes to the water column. The precipitation of high–Mg calcite (at all sites) and aragonite (only at site R3-C2) has fixed 27%–50% (average = 39%) of the DIC. Therefore, the carbon outputs to the water column have been reduced. In the study area, the area-weighted seafloor CH4 and DIC fluxes are ~30 and 20 mmol m−2 yr−1, respectively. Together, they correspond to ~7%–14% of the organic carbon burial rate, indicating that sediments could not be simply regarded as a stable carbon sink because they provide methane and a certain amount of DIC to the water column. Our findings contribute to the results of the ongoing efforts in understanding carbon cycling in submarine cold seep systems.
- Published
- 2021
28. The effect of methane seeps on the bacterial tetraether lipid distributions at the Okinawa Trough
- Author
-
Zhilei Sun, Zhe-Xuan Zhang, Xiaotong Peng, Zhiyan Chen, Jiwei Li, Huan Yang, and Meiyan Fu
- Subjects
Total organic carbon ,Terrigenous sediment ,General Chemistry ,Authigenic ,Oceanography ,Cold seep ,Seafloor spreading ,Methane ,chemistry.chemical_compound ,Water column ,chemistry ,Environmental chemistry ,Paleoclimatology ,Environmental Chemistry ,Environmental science ,Water Science and Technology - Abstract
The branched glycerol dialkyl glycerol tetraethers (brGDGTs) can be produced in situ under methanotrophic/hypoxic conditions in lakes. However, the effect of dynamic methanotrophic activities in the widely-distributed seafloor methane seeps on brGDGTs distributions in global continent margins remains enigmatic. In this study, we firstly report the occurrence of in situ produced brGDGTs in cold seep environments, based on the analysis of tetraether lipid distributions in the authigenic carbonates collected from the northern section of the Okinawa Trough (OT). The abundance ratio of isoGDGTs to brGDGTs (Ri/b) was much lower in the authigenic carbonates (0.94 to 2.25) than in the adjacent normal marine sediments (>10) and suspended particulate matter (>60) in the East China Sea (ECS). Such significant higher bacterial branched GDGTs ratios in the authigenic carbonates indicate its additional sources besides terrestrial and/or water column inputs. Specifically, the brGDGT (Ia), brGDGT (IIa) and brGDGT (IIa’) appear to form in situ in cold seeps, and are influenced by the methane flux significantly as indicated by the fractional abundances of GDGTs along the transect of pipes, network analysis, and correlations between Methane Index (MI) and brGDGTs. Our study highlights that the distributions of seafloor methane seeps could impact the bacterial tetraether lipid distributions in ocean, which would hamper the universal application of brGDGT-based proxies for terrigenous organic carbon tracing and paleoclimate reconstruction in marine environments.
- Published
- 2020
29. Examining bulk and iron-associated organic carbon through depth in margin sea sediments (China) under contrasting depositional settings: Chemical and NEXAFS spectral characterization
- Author
-
Wei-Wei Ma, Shu-Hu Liu, Kui-Ying Ding, Mao-Xu Zhu, Chang-Hong Sun, Zhilei Sun, and Xianrong Zhang
- Subjects
0106 biological sciences ,Total organic carbon ,chemistry.chemical_classification ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,010604 marine biology & hydrobiology ,Sediment ,Estuary ,Aquatic Science ,Oceanography ,01 natural sciences ,XANES ,Sink (geography) ,Sedimentary depositional environment ,chemistry ,Environmental chemistry ,Environmental science ,Sedimentary rock ,Organic matter ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
Marine sediments are the largest sink for organic carbon (OC) on Earth, and iron (Fe) oxides play an important role in stabilization of sedimentary OC. However, the roles of Fe oxides in OC stabilization during prolonged burial, for example, up to tens of thousands of years or more are still poorly constrained. In this study, we used traditional chemical extraction and near-edge X-ray absorption fine structure (NEXAFS) spectroscopic technique to characterize bulk OC and Fe-associated OC (Fe-OC) through depth in gravity cores collected from three sites near the Yangtze River Estuary (YRE), in the South Yellow Sea (SYS), and in the middle Okinawa Trough, which have contrasting depositional environments. Results show that depositional environments have exerted quite different influences on sources and burial of sedimentary OC, and thus on OC degradation during prolonged burial at the three sites. Reactive Fe (FeR) contents at the three sites are greatly influenced by sediment sources, the history of its transport, and its reworking intensity, with FeR contents near the highly dynamic YRE much higher than at the central SYS and the middle Okinawa Trough. The fractions of Fe-OC in total OC (fFe-OC) displayed no clear or consistent trends with depth or by site, probably due to the dual roles of Fe redox cycling in OC protection versus its oxidation. As indicated by the fFe-OC, reactive Fe plays a limited role in OC preservation in margin sea sediments of East China. A combination of NEXAFS spectra and isotopic compositions of bulk OC and Fe-OC indicates that main OC functionalities have not experienced differential alterations and/or no specific OC moieties have been selectively stabilized/released during prolonged burial in the three contrasting depositional environments.
- Published
- 2020
30. Effect of nitrogen-doping and post annealing on wettability and band gap energy of TiO2 thin film
- Author
-
M. E. Konishchev, Ke Li, Viktor N. Kudiiarov, Maxim Syrtanov, K. E. Evdokimov, Sergei I. Tverdokhlebov, Zhilei Sun, and Vladimir F. Pichugin
- Subjects
Phase transition ,Anatase ,Materials science ,Band gap ,Annealing (metallurgy) ,General Physics and Astronomy ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Contact angle ,chemistry.chemical_compound ,chemistry ,Titanium dioxide ,Wetting ,Composite material ,Thin film ,0210 nano-technology - Abstract
Titanium dioxide film is one of the most promising self-cleaning materials. The self-cleaning performance is directly related to the photocatalytic activity and surface wettability, which, in turn, depends on the TiO2 film structure parameters. Nitrogen-doping and post annealing are commonly used for TiO2 film treatment. The present paper addresses the mechanisms of N-doping and annealing induced TiO2 film structure transition, band gap narrowing and wettability transition. It is shown that N-doping combined with annealing leads to anatase → rutile phase transition, formation of hierarchical topography, change of surface chemical composition, and consequently results in reduction of band gap energy and water contact angle. N-doping level and N-linkages are found to significantly affect the structure/properties of annealed TiO2 and N-doped TiO2 films. The proposed mechanisms might help optimize TiO2 film synthesis and post treatment procedures. Moreover, annealed N-doped TiO2 film with highest N-content, simultaneously exhibiting anatase-rutile polycrystalline structure, high roughness, as well as lowest band gap energy and water contact angle, is supposed to present optimal self-cleaning performance.
- Published
- 2020
31. A unique Fe-rich carbonate chimney associated with cold seeps in the Northern Okinawa Trough, East China Sea
- Author
-
Luning Shang, Xianrong Zhang, Xijie Yin, Helong Wei, Yunbao Sun, Huang Wei, Zhilei Sun, Xunhua Zhang, and Lei Xu
- Subjects
Great Oxygenation Event ,Clathrate hydrate ,Mineralogy ,Aquatic Science ,engineering.material ,Oceanography ,Cold seep ,Carbon cycle ,chemistry.chemical_compound ,chemistry ,Anaerobic oxidation of methane ,engineering ,Carbonate ,Chimney ,Pyrite ,Geology - Abstract
The East China Sea is an important marginal sea of the Western Pacific Ocean, from which natural gas hydrate sample has not been acquired so far. Recently, copious carbonate chimneys have been discovered in turbidite deposits in the olistostrome zone located on the west slope of the northern section of Okinawa Trough. Here, the petrology, geochemistry and chronology of an iron-rich carbonate chimney were characterized, confirming a close relationship between its formation and the dissociation of natural gas hydrate beneath the chimney in OT. A distinctive relationship has been observed between goethite and total carbonate contents along with a negative correlation between Fe and Ca contents. Conversely, abundant Fe accumulated on carbonate substrate by mineralized microorganisms. The δ 13 C values of the chimney wall were from −27.56 to −43.66‰ (average: −37.18‰, V-PDB), implying anaerobic oxidation of methane (AOM) as a predominant controlling factor on carbonate precipitation. As no pyrite and organic residues were identified in the iron-rich chimney, it was assumed that AOM was coupled to the iron reduction reaction at least to some extent during the chimney growth owing to the local deficiency of sulfate supply. The δ 56 Fe values of bulk chimney wall (ranging from −0.316‰ to −0.023‰, average −0.134‰) suggest mass and isotope exchanges between the chimney and ambient environment during its growth history, whereas the enrichment of δ 18 O of the carbonate implies these carbonate sourcing from hydrate dissociation underlying our sampling site. This assumption has been supported by a distinct bottom simulation reflector (BSR) and a well-developed fault system beneath the sampling site. This is the first report of cold seepage inside the OT and the identified iron-dependent AOM has shed a new light to the Carbon cycle related to the marine methane oxidation, particularly before the Great Oxidation Event ~2.45 Ga ago.
- Published
- 2015
32. Formation of Fe–Mn–Si oxide and nontronite deposits in hydrothermal fields on the Valu Fa Ridge, Lau Basin
- Author
-
Zhilei Sun, Zhiqiang Chen, Xijie Yin, Qunhui Yang, G.P. Glasby, Jiwei Li, and Huaiyang Zhou
- Subjects
Lau Basin ,Precipitation (chemistry) ,Oxide ,Geochemistry ,Mineralogy ,Geology ,Nontronite ,Isotopes of oxygen ,Hydrothermal circulation ,chemistry.chemical_compound ,chemistry ,Chemical composition ,Earth-Surface Processes ,Hydrothermal vent - Abstract
Hydrothermal Fe–Mn–Si oxides and nontronite are pervasive in the Hine Hina, Vai Lili and Mariner hydrothermal fields along the central Valu Fa Ridge, Lau Basin. Morphometric and mineralogical analyses reveal that the iron-rich filaments are the most important constituents of these Fe–Mn–Si oxide deposits. Both the morphologies and chemical composition of the filaments indicate that neutrophilic Fe-oxidizing bacteria have played a key role in the formation of these deposits. A key process of the formation of these deposits is the creation of a complicated filamentous network in which a series of metabolic activities and passive sorption and nucleation processes occur. The precipitation of dissolved Si in unsaturated and saturated states leads to a “two-generation” growth model in the hydrothermal vents. The precipitation of amorphous opal occurs in a relatively narrow temperature range (41.1–42.9 °C) based on oxygen isotope analyses, indicating a fast precipitation rate of opal-A when conductive cooling of the hydrothermal fluid occurrs. Patchy nontronite in the Mariner fields is a product of the direct precipitation from hydrothermal fluids at a temperature of ∼87.9 °C, whereas the scattered nontronite at the Hine Hina field is the product of the replacement of hydrothermal Fe–Si oxides at a temperature of ∼46.2 °C.
- Published
- 2012
33. Hydrothermal Fe–Si–Mn oxide deposits from the Central and South Valu Fa Ridge, Lau Basin
- Author
-
Huiqiang Yao, Shenxu Bao, Huaiyang Zhou, Zhixue Sun, Qunhui Yang, and Zhilei Sun
- Subjects
geography ,geography.geographical_feature_category ,Lau Basin ,Geochemistry ,Oxide ,Mineralogy ,Pyroclastic rock ,Pollution ,Hydrothermal circulation ,Isotopes of strontium ,chemistry.chemical_compound ,Volcano ,chemistry ,Geochemistry and Petrology ,Mössbauer spectroscopy ,Environmental Chemistry ,Seawater ,Geology - Abstract
A series of samples from the Hine Hina hydrothermal field (HHF) and the Mariner hydrothermal field (MHF) in the Central and Southern Valu Fa Ridge (VFR), Lau Basin were examined to explain the source origin and formation of the hydrothermal Fe–Si–Mn oxide deposits. The mineralogy was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Mossbauer spectroscopy, and energy-dispersive spectroscopy (EDS). For the Fe–Mn oxide crusts in the HHF, varying amounts of volcanic fragments and some seawater contributions were recognized, along with higher concentrations of Mn, Al, Co, Ni, Zn, Sr, Mo, elevated ∑REE and negative Ce anomalies. In contrast, the Si-rich oxide samples of the MHF were enriched in Cu, Pb and Ba, indicative of proximity to a hydrothermal jet. Moreover, conductive cooling of hydrothermal fluid evoked the Si-rich deposit formation in the MHF. The Sr, Nd and Pb isotope data provided further constraints regarding the source and formation of the Fe–Si–Mn deposits in the VFR by showing that the samples of the HHF are a mixture of three components, namely, hydrothermal fluid, seawater and volcanic materials, whereas the samples of the MHF were dominated by hydrothermal fluids. The seawater had a minor influence on the Nd isotope data, and the Pb isotope data exhibited a close association with the substrate rock and preformed volcaniclastic layers in this area. The occurrence of relatively high Mn/Fe ratios in the hydrothermal deposits of this area may be a good indicator of the propagating activities of the VFR over geological time.
- Published
- 2011
34. Metal sources of black smoker chimneys, Endeavour Segment, Juan de Fuca Ridge: Pb isotope constraints
- Author
-
Jiangtao Li, Huiqiang Yao, Jiwei Li, Guangqian Chen, Xiaotong Peng, Zhiqiang Chen, ZiJun Wu, Zhilei Sun, Huaiyang Zhou, and Shen-Xu Bao
- Subjects
Basalt ,geography ,geography.geographical_feature_category ,Stable isotope ratio ,Mineralogy ,Sediment ,Pollution ,Mantle (geology) ,Hydrothermal circulation ,Volcanic rock ,Igneous rock ,Geochemistry and Petrology ,Environmental Chemistry ,Chimney ,Geology - Abstract
Hydrothermal chimney sulfides, vent cap chimney samples, Fe-oxide and basalts from sediment-starving Juan de Fuca Ridge, in the Endeavour segment, exhibit a range of Pb isotope ratios ( 206 Pb/ 204 Pb = 18.658–18.769; 207 Pb/ 204 Pb = 15.457–15.566; 208 Pb/ 204 Pb = 37.810–38.276). The data array is not parallel to the northern hemisphere mantle reservoirs indicating a possible sediment component within the sulfides. By assuming that the potential end-member sediment component has a 207 Pb/ 204 Pb (15.70) similar to Middle Valley sediment, it is suggested the potential end-member sediment component may have 206 Pb/ 204 Pb = 18.90; 208 Pb/ 204 Pb = 38.82. Basalt-derived Pb for the Endeavour segment hydrothermal system involves about 50/50 leaching of E-MORB and T2-MORB. Detailed observations show the Mothra field derives more Pb from T2-MORB than the Main Endeavour field does. According to the binary mixing model, the results show little Pb ( NH 4 + , CH 4 and Br/Cl ratios in hydrothermal fluids are consistent with a sediment component within the segment. Reconciling the Pb isotope data with the chemistry data of hydrothermal fluids, it is suggested that the sediment component may be located in a lower temperature recharge zone where Pb could not be mobilized from the sediment.
- Published
- 2009
35. Characteristics of carbonate cements in sandstone reservoirs: A case from Yanchang Formation, middle and southern Ordos Basin, China
- Author
-
Zhixue, Sun, primary, Zhilei, Sun, additional, Hongjiang, Lu, additional, and Xijie, Yin, additional
- Published
- 2010
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