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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.

Tectonic and climate evolution could be well archived in deep-water stratigraphy. Based on newly acquired high-resolution two-dimensional (2-D) multichannel seismic profiles and multibeam bathymetry, together with Ocean Drilling Program/International Ocean Discovery Program (ODP/IODP) data, this study investigated the late Miocene–Quaternary deep-water seismic stratigraphy, sedimentary evolution, and responses to regional tectonic and climatic variations at the northeastern margin of the South China Sea. The late Miocene–Quaternary stratigraphy consists of three units (i.e., SU-1, SU-2, and SU-3 from bottom to top) that are dated to 10.5–6.5 Ma (stage 1), 6.5–0.9 Ma (stage 2), and 0.9 Ma–present (stage 3), respectively. SU-1 is dominated by sheeted drifts with slight thickness variation, but SU-2 and SU-3 mainly consist of mounded, lenticular contourite drifts and channel-like moats. This suggests that the bottom currents intensified from stage 1 to stage 2, which was probably caused by the sill uplifting at the Luzon Strait under the influence of tectonic collision between the Luzon arc and Eurasia since ca. 6.5 Ma. SU-2 and SU-3 are separated by a basinwide high-amplitude seismic reflection, across which the average sedimentation rate shows a dramatic increase from ~28 m/m.y. in SU-2 to ~144 m/m.y. in SU-3. The high sediment supply since 0.9 Ma could be linked to the mid-Pleistocene climate transition, which resulted in abundant rainfall that promoted the Taiwan orogen to contribute more sediments to the South China Sea. This study indicates that the deep-water stratigraphy recorded the tectonic collision around the sole deep-water gateway (i.e., Luzon Strait) and mid-Pleistocene climate transition event at the northeastern South China Sea margin, which has important implications for understanding the relationships among the tectonic, paleoclimatic, paleoceanographic, and deepwater sedimentary processes in the largest marginal basin of the western Pacific Ocean.

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.

Cold seeps are pervasive along the continental margin worldwide, and are recognized as hotspots for elemental cycling pathway on Earth. In this study, analyses of pore water geochemical compositions of one ~400 cm piston core (S3) and the application of a mass balance model are conducted to assess methane-associated biogeochemical reactions and uncover the relationship of methane in shallow sediment with gas hydrate reservoir at the Makran accretionary wedge off Pakistan. The results revealed that approximately 77% of sulfate is consumed by the predominant biogeochemical process of anaerobic oxidation of methane. However, the estimated sulfate-methane interface depth is ~400 cm below sea floor with the methane diffusive flux of 0.039 mol/(m2·a), suggesting the activity of methane seepage. Based on the δ13CDIC mass balance model combined with the contribution proportion of different dissolved inorganic carbon sources, this study calculated the δ13C of the exogenous methane to be −57.9‰, indicating that the exogenous methane may be a mixture source, including thermogenic and biogenic methane. The study of pore water geochemistry at Makran accretionary wedge off Pakistan may have considerable implications for understanding the specific details on the dynamics of methane in cold seeps and provide important evidence for the potential occurrence of subsurface gas hydrate in this area.

Authigenic carbonates of the northern Okinawa Trough have been shown to be contributed by both sulfate- and Fe-driven anaerobic oxidation of methane (SD-AOM and Fe-AOM, respectively); however, the microorganisms involved remain poorly constrained. To better understand the types and roles of microorganisms in specific biological methane oxidation processes, authigenic carbonates collected from the northern Okinawa Trough at water depths between ∼540 m and 700 m were studied using petrographic, mineralogical, elemental, and lipid biomarker analyses. The carbonate minerals were primarily aragonite, high-magnesium calcite, low-magnesium calcite, or dolomite. The extremely low δ13C values of bulk carbonates (−59.2‰), molecular fossils of anaerobic methane oxidizing archaea (ANME; −131‰), and sulfate-reducing bacteria (SRB; −77‰) indicated that the authigenic carbonates formed as products of AOM. Biogenic methane was confirmed to be the main carbon source for all carbonates, whereas bio-degraded oil and hydrothermal input complemented carbon sources, as revealed by the occurrence of unresolved complex mixture, strongly enriched As and Sb, and their correlations with Fe/Al. Combined with enriched δ18O values (as high as +5‰), the methane fluids were suggested to derive from the dissociation of gas hydrates. ANME-2 and a mixture of ANME-1 and ANME-2 were identified for the two calcitic carbonates, respectively, as revealed by their specific biomarker patterns. The relatively higher contents of 13C-depeleted isoprenoids and SRB−related fatty acids, strong Mo enrichment, and biological debris in both calcite- and aragonite-dominated carbonates reflect precipitation driven by SD-AOM in a shallow sulfate-methane transition. For other seep carbonates, low amounts of 13C-depeleted isoprenoids and the near absence of crocetane suggest dominance of the ANME-1 assemblage. The extremely low amounts and non-13C-depleted iso-/anteiso-C15:0 fatty acids (−27‰) in the dolomite-containing carbonates indicate the decoupling of ANME and SRB. These carbonates were most likely formed below or at the bottom of the sulfate-methane transition and included contributions from Fe-AOM, as indicated by the low Mo content, occurrence of dolomite and siderite, and decreased δ56Fe values with increasing Fe/Al ratios.

The East Asian Monsoon (EAM) is a regional factor affecting the East Asian climate and the oceanographic processes of the marginal seas along the Western Pacific. Finding proxies for the EAM intensity and reconstructing the interannual and interdecadal variations of the EAM using high-resolution records are necessary to improve our understanding of the EAM’s role in the global climate system and for predicting climate change. In this paper, high-resolution sedimentary records of sedimentary core C0702 obtained from the inner continental shelf of the East China Sea were comprehensively analyzed using a laser particle size analyzer, an ItraxTM core scanner, and a 210Pb and 137Cs radionuclide analyzer to explore potential proxies for the East Asian Winter Monsoon (EAWM). By combining the obtained results with instrumental observations of the EAM, we established a quantitative formula for the EAWM, which enables to reconstruct the evolution trend of the EAWM during the past 130 years. The sensitive grain-size component F2, with a grain-size range of 14.35–230 µm, and principal component PC1 of the sedimentary deposits of the East China Sea inner shelf can be used as EAWM proxies. The evolution of EAWM in 1880–1950 could be roughly divided into two stages: a weak EAWM period from 1882 to 1900 and a strong EAWM period from 1900 to 1945. This study improves our understanding of the variations in the EAWM on interannual and interdecadal temporal scales.

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.

Seafloor pockmarks are important indicators of submarine methane seepages and slope instabilities. In order to promote the understanding of submarine pockmarks and their relationship with sediment instabilities and climate changes, here we summarize the research results of pockmarks in the spatio-temporal distributions and shaping factors. Most of pockmarks occur along active or passive continental margins during the last 25 kyr B.P.. Circular and ellipse are the most common forms of pockmarks, whereas pockmarks in a special crescent or elongated shape are indicators of slope instabilities, and ring-shape pockmarks are endemic to the gas hydrate zones. Further researches should be focused on the trigger mechanism of climate changes based on the pockmarks in the high latitudes formed during the deglaciation periods, and the role of gas hydrates in the seafloor evolution should be elucidated. In addition, the feature of pockmarks at their early stage (e.g., developing gas chimneys and gas driving sedimentary doming) and the relations between pockmarks and mass movements, mud diapirs could be further studied to clarify the influences of rapid methane release from submarine sediments on the atmospheric carbon contents.

Aerobic methane (CH4) oxidation plays a significant role in marine CH4 consumption. Temperature changes resulting from, for example, global warming, have been suggested to be able to influence methanotrophic communities and their CH4 oxidation capacity. However, exact knowledge regarding temperature controls on marine aerobic methane oxidation is still missing. In this study, CH4 consumption and the methanotrophic community structure were investigated by incubating sediments from shallow (Bohai Bay) and deep marine environments (East China Sea) at 4, 15, and 28 °C for up to 250 days. The results show that the abundance of the methanotrophic population, dominated by the family Methylococcaceae (type I methanotrophs), was significantly elevated after all incubations and that aerobic methane oxidation for both areas had a strong temperature sensitivity. A positive correlation between the CH4 oxidation rate and temperature was witnessed in the Bohai Bay incubations, whereas for the East China Sea incubations, the optimum temperature was 15 °C. The systematic variations of pmoA OTUs between the Bohai Bay and East China Sea incubations indicated that the exact behaviors of CH4 oxidation rates with temperature are related to the different methanotrophic community structures in shallow and deep seas. These results are of great significance for quantitatively evaluating the biodegradability of CH4 in different marine environments.

Objectives: To investigate the value of CT arterial enhancement fraction (AEF) in the post-processing technique of liver perfusion-like phase III enhanced CT scan in evaluating the degree of liver function impairment in patients with hepatitis B cirrhosis. Methods: The study included 85 patients with hepatitis B cirrhosis admitted to the Department of Radiology, The Affiliated Huai’an Hospital of Xuzhou Medical University from May 2018 to October 2020 were selected as the experimental group, and 71 patients with liver fibrosis during the same period were selected as the control group. All patients underwent routine liver CT phase III perfusion scan, and hepatic AEF (hAEF) and liver/spleen ratio (H/S) were compared between the two groups to analyze the differential value of hAEF and H/S for liver fibrosis and hepatitis B cirrhosis. Patients were divided into the mild group (Grade-A) and the severe group (Grade-B and C) according to Child-Pugh grading. hAEF and H/S values of the two groups were compared, and the evaluation value of AEF on the degree of impairment of hepatitis B cirrhosis was analyzed. Results: hAEF and H/S values of the experimental group were greater than those of the control group (P

As a powerful in situ detection technique, Raman spectroscopy is becoming a popular underwater investigation method, especially in deep-sea research. In this paper, an easy-to-operate underwater Raman system with a compact design and competitive sensitivity is introduced. All the components, including the optical module and the electronic module, were packaged in an L362 × Φ172 mm titanium capsule with a weight of 20 kg in the air (about 12 kg in water). By optimising the laser coupling mode and focusing lens parameters, a competitive sensitivity was achieved with the detection limit of SO42− being 0.7 mmol/L. The first sea trial was carried out with the aid of a 3000 m grade remotely operated vehicle (ROV) “FCV3000” in October 2018. Over 20,000 spectra were captured from the targets interested, including methane hydrate, clamshell in the area of cold seep, and bacterial mats around a hydrothermal vent, with a maximum depth of 1038 m. A Raman peak at 2592 cm−1 was found in the methane hydrate spectra, which revealed the presence of hydrogen sulfide in the seeping gas. In addition, we also found sulfur in the bacterial mats, confirming the involvement of micro-organisms in the sulfur cycle in the hydrothermal field. It is expected that the system can be developed as a universal deep-sea survey and detection equipment in the near future.

Deep-sea mussels are widely distributed in marine chemosynthetic ecosystems. Bathymodiolus platifrons and B. japonicus, occurring at both cold seeps and hydrothermal vents, have been reported to house exclusively methanotrophic symbionts in the gill. However, the comparison of microbiota associated with different tissues between these two species from two contrasting habitats is still limited. In this study, using B. platifrons and B. japonicus collected from the adjacent cold seep and hydrothermal vent environments, we sampled different tissues (gill, adductor muscle, mantle, foot, and visceral mass including the gut) to decipher the microbial community structure at the tissue scale by employing 16S rRNA gene sequencing strategy. In the gill of both seep mussels and vent mussels, the symbiont gammaproteobacterial Methylomonaceae was the predominant lineage, and methane oxidation was identified as one of the most abundant putative function. In comparison, abundant families in other tissues were Pseudomonadaceae and Enterobacteriaceae in seep mussels and vent mussels, respectively, which may get involved in element cycling. The results revealed high similarity of community structure between two mussel species from the same habitat. The gill showed distinctive bacterial community structure compared with other tissues within the same environment, while the gill communities from two environments were more similar. Remarkably structural variations of adductor muscle, mantle, foot, and visceral mass were observed between two environments. This study can extend the understanding on the characteristics of tissue-associated microbiota of deep-sea mussels from the adjacent cold seep and hydrothermal vent environments.

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

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.

The hadal zone represents one of the last great frontiers in modern marine science, and deciphering the provenance of sediment that is supplied to these trench settings remains a largely unanswered question. Here, we examine the mineralogical and geochemical composition of a sediment core (core CD-1) that was recovered from the southwestern margin of the Challenger Deep within the Mariana Trench. Major element abundances and rare-earth element patterns from these sediments require inputs from both terrigenous dust and locally sourced volcanic debris. We exploit a two-endmember mixing model to demonstrate that locally sourced volcanic material dominates the sediment supply to the Challenger Deep (averaging ∼72%). The remainder, however, is supplied by aeolian dust (averaging ∼28%), which is consistent with adjacent studies that utilized Sr-Nd isotopic data. Building on a growing database, we strengthen our understanding of Asian aeolian dust input into the northwestern Pacific, which ultimately improves our appreciation of sedimentation in, and around, the hadal zone.

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.

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

Research on the biomineralization in modern seafloor hydrothermal systems is conducive to unveiling the mysteries of the early Earth’s history, life evolution, subsurface biosphere and microbes in outer space. The hydrothermal biomineralization has become a focus of geo-biological research in the last decade, since the introduction of the microelectronic technology and molecular biology technology. Microorganisms play a critical role in the formations of oxide/hydroxides (e.g. Fe, Mn, S and Si oxide/hydroxides) and silicates on the seafloor hydrothermal systems globally. Furthermore, the biomineralization of modern chemolithoautotrophic microorganisms is regarded as a nexus between the geosphere and the biosphere, and as an essential complement of bioscience and geology. In this paper, we summarize the research progress of hydrothermal biomineralization, including the biogenic minerals, the microbial biodiversity, and also the interactions between minerals and microorganisms. In the foreseeable future, the research on hydrothermal biomineralization will inspire the development of geosciences and biosciences and thus enrich our knowledge of the Earth’s history, life evolution and even astrobiology. © 2019 China Geology Editorial Office.

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.

In an effort to assess the potential contamination and determine the environmental risks associated with heavy metals, 51 surface sediment samples (0–4 cm) were collected in the Zhoushan Islands coastal sea of the East China Sea (ECS). The heavy metal concentrations, grain size and total organic carbon (TOC) contents of these surface sediments were comprehensively analyzed. The results showed that the order of the average concentrations of heavy metals is Zn > Cr > Cu > Pb > As > Cd > Hg. Zn, Cr, Cd and Hg exhibit similar distribution and which derived from a common source, however, Cu, Pb and As present different distribution. The metal enrichment factor (EF) and geoaccumulation index (Igeo) values both suggest that Cu and Cd likely pose environmental risks. The results of this study could provide scientific data to authorities in charge of sustainable marine management.

In an attempt to investigate the nature and origin of mantle heterogeneities beneath the South Mid-Atlantic Ridge (SMAR), we report new whole-rock Sr, Nd, Pb, and Hf isotopic data from eight basalt samples at four dredge stations along the SMAR between 18&deg, S and 21&deg, S. Sr, Nd, and Pb isotopic data from SMAR mid-ocean ridge basalts (MORBs) at 18&ndash, 21&deg, S published by other researchers were also utilized in this study. The SMAR MORBs at 18&ndash, S feature the following ratio ranges: 87Sr/86Sr = 0.70212 to 0.70410, 143Nd/144Nd = 0.512893 to 0.513177, 206Pb/204Pb = 18.05 to 19.50, 207Pb/204Pb = 15.47 to 15.71, 208Pb/204Pb = 37.87 to 38.64, and 176Hf/177Hf = 0.283001 to 0.283175. The 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb, and 176Hf/177Hf ratios of these MORBs varied considerably along the SMAR axis. The variable compositions of the Sr&ndash, Nd&ndash, Pb&ndash, Hf isotopes, combined with the corresponding whole-rock major and trace elemental abundances reported in previous studies, suggest that the SMAR MORBs at 18&ndash, S were probably derived from a heterogeneous mantle substrate related to a mixture of depleted mantle (DM) materials with a small amount (but variable input) of HIMU (high-&mu, where &mu, = 238U/204Pb)- and enriched (EMII)-type materials. The HIMU-type materials likely originated from the proximal St. Helena plume and may have been transported through &ldquo, pipe-like inclined sublithospheric channels&rdquo, into the SMAR axial zone. The EMII-type materials possibly originated from a recycled metasomatized oceanic crust that may have been derived from the early dispersion of other plume heads into the subcontinental asthenosphere prior to the opening of the South Atlantic Ocean. In addition, the contributions of subducted sediments, continental crust, and subcontinental lithospheric mantle components to the formation of the SMAR MORBs at 18&ndash, S may be nonexistent or negligible.