Methane seep in the Shenhu area of the South China sea using geochemical and mineralogical features

Zhang, Qinyi; Wu, Daidai; Jin, Guangrong; Xu, Xinliang; Yang, Chao; Liu, Lihua

doi:10.1016/j.marpetgeo.2022.105829

Cited by 6 publications

(6 citation statements)

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“…Intense AOM promotes the combination of oversaturated HCO 3 − with metal ions and leads to the precipitation of carbonate minerals (Baker and Burns, 1985). TOC and IC were higher at the Haima sampling sites than at other cold seep areas in the SCS (Li et al, 2018b;Zhuang et al, 2019;Zhang et al, 2022b). TOC and IC can indicate the geochemical processes of methane seepage activity, as explained in recent studies on the long history of cold seep evolution in the Haima (Zhang et al, 2022a;Dan et al, 2023).…”

Section: Geochemical Characteristics Of Different Habitats In the Hai...mentioning

confidence: 53%

Microbial communities and mineral assemblages in sediments from various habitats at the Haima Cold Seep, South China Sea

Liang,

Feng,

Kong

et al. 2023

Front. Mar. Sci.

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Cold seeps create diverse habitats in the deep sea and play an important role in the global carbon cycling. Anaerobic oxidation of methane (AOM) and biogenic mineralization are essential carbon pathways of methane and carbon transformation in cold seeps, however, the effects of habitat heterogeneity on the processes are still poorly understood. In this study, we investigated the microbial communities and mineral assemblages at distinct habitats in the Haima cold seep and their relationships with environmental factors. These habitats were classified as methane seep site (MS), seep-free faunal habitat (FH), and control site (CS). Bacterial communities were significantly different among the three habitats. ANME-3 archaea, Sulfurovum bacteria, and mineralization-associated microbes (e.g., Campylobacterales) were detected in high relative abundances at ROV2. Mineralogical analysis revealed abundant calcite minerals at the seep site, indicating that authigenic carbonate minerals were formed at highly active seep. Multivariate statistical analysis demonstrated that the concentrations of SO42–, Ca2+, and Mg2+ were significantly correlated with the presence of calcite minerals and bacterial communities. These results suggested that AOM-accompanied authigenic carbonate formation is an important factor influencing the mineral assemblages in seep habitats. This finding improves our understanding of marine microbial carbon cycling.

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Section: Geochemical Characteristics Of Different Habitats In the Hai...mentioning

confidence: 53%

Microbial communities and mineral assemblages in sediments from various habitats at the Haima Cold Seep, South China Sea

Liang,

Feng,

Kong

et al. 2023

Front. Mar. Sci.

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“…Except for the individual crystal, pyrite microcrystals are mostly found assembled as framboids [37]. [38][39][40][41][42], octahedral form [8,38,[43][44][45], pyritohedral form [12,38,43,[45][46][47], and intermediate [13,33,44,48,49] [38][39][40][41][42], octahedral form [8,38,[43][44][45], pyritohedral form [12,38,43,[45][46][47], and intermediate [13,33,44,48,49] under different marine environments, among which (O6,C5,C6,I1,I5,P5,P6) are BSE images, (O1-O5, C1-C4,I2-I4,I6,P1-P4) are SE images.…”

Section: Shape Of Single Crystal Of Pyritementioning

confidence: 99%

“…Figure 2. The scanning electron micrographs of euhedral pyrite in cubic form[38][39][40][41][42], octahedral form[8,38,[43][44][45], pyritohedral form[12,38,43,[45][46][47], and intermediate[13,33,44,48,49] under…”

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The Morphological Characteristics of Authigenic Pyrite Formed in Marine Sediments

Chang

2022

JMSE

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Pyrites are widely distributed in marine sediments, the morphology of which is applied as a proxy to infer the redox conditions of bottom water, and identify diagenetic stages and hydrocarbon leakage activities. In this review, the methods used for the morphological study of pyrite are summarized. The textural and size characteristics of euhedral pyrite and pyrite aggregates, as the formation and evolution mechanism of pyrite are discussed for their significance in reconstructing the geochemical environment. The morphological study of pyrite includes shape observation, size estimation, and surface feature analysis. Scanning electron microscope and optical microscope are the main methods for morphological observation; transmission electron microscope and scanning tunneling microscope are applicable to observe nanoscale morphological structures and crystal growth on the crystal surface, and X-ray computed tomography is capable of measuring pyrite size distribution at the scale of a micrometer. Under the marine sedimentary condition, the single crystal of pyrite appears in cube, octahedron, dodecahedron, and their intermediates, the size of which ranges from several nanometers to more than 100 µm. The morphology of euhedral pyrite is controlled by temperature, pH, the chemical composition of interstitial water, etc., and might have been experienced in later reformation processes. The pyrite aggregates occur as framboid, rod-like, fossil-infilling, etc., characterized by the comparatively large size of several microns to several millimeters. It is found that certain textures correspond with different formation mechanisms and geochemical environments. Particularly, under special geological conditions, for instance, the methane leakage and/or decomposition of gas hydrate, pyrite is anomaly enriched with morphological textures of massive framboid cluster, rod-like aggregates, etc., and framboid is found with a large mean diameter (>20 µm) and standard deviation (>10 µm). These typical features can be employed to ascertain the position of the paleo sulfate methane transition zone (SMTZ).

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“…Why this HGGHR could form and accumulate in the clay-dominated sediments remains unclear. Previous studies have indicated that the dynamic accumulation of a gas hydrate system may have occurred in the Shenhu area, as evidenced by migrated submarine channellevee systems where gas hydrates differentially precipitated (Zhang et al, 2020a), venting hydrate systems identified from seismic profiles (Liang et al, 2021), paleo-cold seeps indicated by authigenic carbonates and pore water anomalies (Lin et al, 2016;Deng et al, 2020;Hu et al, 2020;Zhang et al, 2022), and the coexistence of gas hydrates and free gas (Qian et al, 2018;Qin et al, 2020;Zhang et al, 2020b). The deep mud diapirs and gas chimneys in the Shenshu area are closely related to the gas hydrate accumulation (Chen et al, 2016;Su et al, 2016Su et al, , 2017Cheng et al, 2020), but how the diapirs/gas chimneys have shifted the BGHSZ, especially the influence of the associated diapiric faults on the gas migration and gas hydrate accumulation, remains unclear.…”

Section: Introductionmentioning

confidence: 99%

Dynamic accumulation of a high-grade gas hydrate system: insights from the trial production gas hydrate reservoir in the Shenhu area, northern South China Sea

Zhang,

Liang,

et al. 2024

Front. Mar. Sci.

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The ultimate enrichment level and quantity of gas hydrate resources are influenced by the dynamic process of accumulation and preservation. High-resolution 3-D seismic data, logging while drilling (LWD), pressured coring, and in situ testing were used to characterize the dynamic accumulation and preservation of the trial production high-grade gas hydrate reservoir (HGGHR) in the Shenhu area. Through seismic variance analysis and ant-tracking, we found that newly identified mud diapir-associated faults with three development stages controlled the migration and accumulation of gas hydrate and shifted the base of the gas hydrate stability zone (BGHSZ), resulting in dynamic accumulation and dissociation of gas hydrates. The recognized double bottom simulating reflectors (BSRs) were concluded to have been formed due to the shift of the BGHSZ caused by the variational equilibrium conditions. The interval between the double BSRs was inferred to be a disequilibrium zone where gas recycling occurred, contributing to the coexistence of gas hydrates and free gas and the dynamic formation of the HGGHR. Multiple gliding faults formed within the GHSZ in the late period have altered the HGGHR and control the present thickness and distribution of the gas hydrates and free gas in the hanging wall and footwall. Under the influence of geothermal fluids and the fault system associated with the mud diapir, the HGGHR experienced dynamic accumulation with three stages, including early accumulation, medium-term adjustment, and late alteration and preservation. We conclude that four factors affected the formation, distribution, and occurrence of the HGGHR: the geothermal fluids accompanying the deep mud diapir below the reservoir, the dual supply of thermogenic gas and biogenic gas, the recycling of hydrate gas beneath the BGHSZ, and the post-gas hydrate faults developed within the GHSZ. A geological model illustrating the dynamic formation of the trial production HGGHR was proposed, providing a reference for future exploration of HGGHRs with a great production potential in deepwater settings.

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Methane seep in the Shenhu area of the South China sea using geochemical and mineralogical features

Cited by 6 publications

References 93 publications

Microbial communities and mineral assemblages in sediments from various habitats at the Haima Cold Seep, South China Sea

Microbial communities and mineral assemblages in sediments from various habitats at the Haima Cold Seep, South China Sea

The Morphological Characteristics of Authigenic Pyrite Formed in Marine Sediments

Dynamic accumulation of a high-grade gas hydrate system: insights from the trial production gas hydrate reservoir in the Shenhu area, northern South China Sea

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