Microbially mediated phosphatization in the Neoproterozoic Doushantuo Lagerstätte, South China

2005 ◽  
Vol 176 (4) ◽  
pp. 355-361 ◽  
Author(s):  
Benoìt Hubert ◽  
J. Javier Álvaro ◽  
Jun-Yuan Chen
Keyword(s):  
South China ◽  
Globular Clusters ◽  
Carbonate Precipitation ◽  
Elemental Mapping ◽  
Pore Filling ◽  
Low Concentrations ◽  
Dispersive System ◽  
Clear Peak ◽  
Geochemical Studies ◽  
Algal Thalli

Abstract Detailed petrographic and geochemical studies of pore-filling cements and replaced (epigenic) membranes of some organic-walled microorganisms preserved in the Neoproterozoic Doushantuo Lagerstätte (China) are based on an energy dispersive system (EDS) of elemental mapping attached to backscattered MEB. Their microcrystalline apatite (collophane) occurs predominantly as phosphatized microbial pseudomorphs: phosphatic crusts of chasmolithic bio-films (or microstromatolites) and globular clusters occur lining intraparticular porosities. Three major pre-compactional cement types are identified on algal thalli, embryos and vase-shaped microfossils: epigenic collophane (by replacement of membranes), polyphasic filling of collophane and crystalline apatite and fluorapatite within intraparticular porosities (some of them microbially mediated), and latest carbonate precipitation filling the remaining intraparticular porosities (preserved at present as dedolomitized calcite). P2O5 concentration has a clear peak in the microbial pseudomorphs and uniformly low concentrations elsewhere, whereas MgO, Na2O, K2O and SiO2 show a slight increase in concentration through successive cements. These geochemical trends evidence a slight change of pore fluids accompanied by a final rise in pH, presumably following the main interval of decay, which favoured precipitation of CaCO3 postdating that of apatite.

scholarly journals Study of the component composition of organic matter of the East Pre-Caucasian basin rocks based on the results of lithological, petrophysical and geochemical studies

Georesursy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 66-72
Author(s):  
R.S. Khisamov ◽  
Natalia Skibitskaya ◽  
Nikita Samokhvalov ◽  
Kazimir Kovalenko ◽  
Oleg Navrotsky
Keyword(s):  
Organic Matter ◽  
Component Composition ◽  
Separate Determination ◽  
Weight Concentration ◽  
Kerogen Type ◽  
Low Concentrations ◽  
Close Relationship ◽  
Geochemical Investigation ◽  
Geochemical Studies

This study introduces results of lithological, petrophysical and geochemical investigation of Lower Cretaceous (K1) and Middle Jurassic (J2a-b) rocks of East Pre-Caucasian basin. According to pyrolytic and bituminological studies method of separate determination of kerogen and bitumen concentration been developed. In accordance with this method differentiation of organic matter components in different lithotypes of rocks been described. Also relationship between bitumen and kerogen concentrations been revealed. The majority of samples have poor to fair organic richness and poor source potential. Kerogen type is commonly presented by type III and stages of maturity characterized by stages PC3 to MC3. Bitumen compounds have low concentrations of asphaltenes and aromatic hydrocarbons and mainly contains light and heavy resins. Based on petrophysical and geochemical studies a close relationship between the concentration of organic carbon and the weight concentration of potassium nuclides was obtained. This relationship indicates that kerogen in the sediments under consideration is associated with clay minerals, which is also confirmed by the mineral composition of the rocks.

Ediacaran Acanthomorphic Acritarchs and Other Microfossils from Chert Nodules of the Upper Doushantuo Formation in the Yangtze Gorges Area, South China

2014 ◽  
Vol 88 (S72) ◽  
pp. 1-139 ◽  
Author(s):  
Pengju Liu ◽  
Shuhai Xiao ◽  
Chongyu Yin ◽  
Shouming Chen ◽  
Chuanming Zhou ◽  
...  
Keyword(s):  
South China ◽  
Doushantuo Formation ◽  
Systematic Treatment ◽  
East European ◽  
Northern India ◽  
Systematic Paleontology ◽  
First Occurrence ◽  
Biostratigraphic Subdivision ◽  
Multicellular Organisms ◽  
Algal Thalli

Silicified microfossils preserved in chert nodules of the Doushantuo Formation in the Yangtze Gorges area of South China have great potential to improve the biostratigraphic subdivision and correlation of the Ediacaran System. This potential can be realized only if solid taxonomy is available. However, a systematic treatment of these microfossils (particularly acanthomorphic acritarchs) is lacking, greatly limiting their biostratigraphic potential. This paper presents the systematic paleontology of silicified microfossils from upper Doushantuo Formation (Member III) chert nodules at three sections in the Yangtze Gorges area. More than 90 species of microfossils are described, including 66 named taxa of acanthomorphs, seven named taxa of sphaeromorphs, 12 taxa of cyanobacterial filaments and coccoids, four taxa of algal thalli, and two species of tubular microfossils. Several acritarch species, includingAppendisphaera clavan. sp.,Mengeosphaera grandispinan. sp.,M. stegosauriformisn. sp.,Leiosphaeridia, and possiblySinosphaera rupina, are shown to be multicellular organisms, consistent with the proposition that some Ediacaran acritarchs may be diapause eggs of early animals. This study supports the view that theTianzhushania spinosaacanthomorph biozone is unique to the lower Doushantuo Formation in South China (and perhaps its equivalent in northern India) and that Ediacaran acanthomorph assemblages from Australia, Siberia, and East European Platform are younger than theTianzhushania spinosabiozone. It is proposed that the first occurrence ofHocosphaeridium anozos, a species with easily recognizable morphology and wide taphonomic and geographic distributions, be used to define the second Doushantuo acanthomorph biozone succeeding theTianzhushania spinosabiozone. New taxa described in this paper include three new genera (Bispinosphaeran. gen.;Yushengian. gen.; andGranitunican. gen.) and 40 new species:Appendisphaera?brevispinan. sp.,A. clavan. sp.,A.?hemisphaerican. sp.,A. longispinan. sp.,A. setosan. sp.,Bispinosphaera peregrinan. gen. n. sp.,Crinita paucispinosan. sp.,Ericiasphaera densispinan. sp.,Hocosphaeridium dilatatumn. sp.,Knollisphaeridium denticulatumn. sp.,K. longilatumn. sp.,K. obtusumn. sp.,K. parvumn. sp.,Mengeosphaera angustan. sp.,M. bellulan. sp.,M.cf.bellulan. sp.,M. constrictan. sp.,M.?cuspidatan. sp.,M.?gracilisn. sp.,M. grandispinan. sp.,M. latibasisn. sp.,M. miniman. sp.,M. spicatan. sp.,M. spinulan. sp.,M. stegosauriformisn. sp.,M. triangularisn. sp.,M. uniformisn. sp.,Sinosphaera asteriformisn. sp.,Tanarium acusn. sp.,T. elegansn. sp.,T. longitubularen. sp.,T.?minimumn. sp.,T. obesumn. sp.,T. variumn. sp.,Urasphaera fungiformisn. sp.,U. nuptan. sp.,Yushengia ramispinan. gen. n. sp.,Granitunica mcfaddeniaen. gen. n. sp.,Osculosphaera arcelliformisn. sp., andO. membraniferan. sp.

INFLUENCE OF ORGANIC MATTER ON Re-Os DATING OF SULFIDES: INSIGHTS FROM THE GIANT JINDING SEDIMENT-HOSTED Zn-Pb DEPOSIT, CHINA

2021 ◽  
Author(s):  
Shiqiang Huang ◽  
Yucai Song ◽  
Limin Zhou ◽  
David L. Leach ◽  
Zhaoshan Chang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Inductively Coupled Plasma ◽  
Elemental Mapping ◽  
Bacterial Reduction ◽  
Inductively Coupled ◽  
Hydrocarbon Reservoir ◽  
Low Concentrations ◽  
Icp Ms ◽  
Plasma Mass Spectrometry ◽  
Two Stages

Abstract This study evaluates the effect of organic matter impurities on pyrite Re-Os dating, using the giant Jinding sediment-hosted Zn-Pb deposit in China as an example. The Jinding deposit is hosted in a Paleocene evaporite dome that was a hydrocarbon reservoir before mineralization. Pyrite in Jinding formed in two stages: pre-ore (py1) and syn-ore (py2). Two types of py1 are recognized, organic matter-free and organic matter-bearing. The organic matter-free py1 contains homogeneously distributed low concentrations of Re (<2.5 ppb) that yields an isochron age of 51 ± 1 Ma (mean square of weighted deviates [MSWD] = 3.2). This date is interpreted to be the age of py1 formation. The organic matter-bearing py1 contains organic matter inclusions trapped during py1 growth and synchronous with bacterial reduction of sulfate. Elemental mapping with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) shows that the organic matter inclusions have Re signals 1 to 4 orders of magnitude higher than those of pyrite, revealing that organic matter is the major host for Re. Such pyrite separates contain 37 to 1,145 ppb Re. The Re-Os data of organic matter-bearing py1 yield an isochron age of 72.9 ± 0.5 Ma (MSWD = 0.2). This age is older than the actual py1 formation age of 51 ± 1 Ma but overlaps with previously dated bitumen Re-Os isochron age of 68 ± 5 Ma at Jinding, indicating that organic matter inclusions can significantly influence the Re-Os dates of pyrite and likely other sulfides. This study demonstrates that in order to date sulfides formed in organic-rich environments using the Re-Os method, it is necessary to determine the distribution of Re in samples using detailed petrography and LA-ICP-MS trace element mapping plus spot analysis.

Origin, tectonic environment and age of the Bibole banded iron formations, northwestern Congo Craton, Cameroon: geochemical and geochronological constraints

2021 ◽  
pp. 1-19
Author(s):  
Arlette Pulcherie Djoukouo Soh ◽  
Sylvestre Ganno ◽  
Lianchang Zhang ◽  
Landry Soh Tamehe ◽  
Changle Wang ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Atmospheric Oxygen ◽  
Banded Iron Formations ◽  
True Negative ◽  
Low Concentrations ◽  
Heavy Rare Earth Elements ◽  
Geochronological Constraints ◽  
Geochemical Studies ◽  
Iron Formations

Abstract The newly discovered Bibole banded iron formations are located within the Nyong Group at the northwest of the Congo Craton in Cameroon. The Bibole banded iron formations comprise oxide (quartz-magnetite) and mixed oxide-silicate (chlorite-magnetite) facies banded iron formations, which are interbedded with felsic gneiss, phyllite and quartz-chlorite schist. Geochemical studies of the quartz-magnetite banded iron formations and chlorite-magnetite banded iron formations reveal that they are composed of >95 wt % Fe2O3 plus SiO2 and have low concentrations of Al2O3, TiO2 and high field strength elements. This indicates that the Bibole banded iron formations were not significantly contaminated by detrital materials. Post-Archaean Australian Shale–normalized rare earth element and yttrium patterns are characterized by positive La and Y anomalies, a relative depletion of light rare earth elements compared to heavy rare earth elements and positive Eu anomalies (average of 1.86 and 1.15 for the quartz-magnetite banded iron formations and chlorite-magnetite banded iron formations, respectively), suggesting the influence of low-temperature hydrothermal fluids and seawater. The quartz-magnetite banded iron formations display true negative Ce anomalies, while the chlorite-magnetite banded iron formations lack Ce anomalies. Combined with their distinct Eu anomalies consistent with Algoma- and Superior-type banded iron formations, we suggest that the Bibole banded iron formations were deposited under oxic to suboxic conditions in an extensional basin. SIMS U–Pb data indicate that the Bibole banded iron formations were deposited at 2466 Ma and experienced metamorphism and metasomatism at 2078 Ma during the Eburnean/Trans-Amazonian orogeny. Overall, these findings suggest that the studied banded iron formations probably marked the onset of the rise of atmospheric oxygen, also known as the Great Oxidation Event in the Congo Craton.

Chronological and geochemical studies of granite and enclave in Baimashan pluton, Hunan, South China

2007 ◽  
Vol 50 (11) ◽  
pp. 1606-1627 ◽  
Author(s):  
WeiFeng Chen ◽  
PeiRong Chen ◽  
HongYe Huang ◽  
Xing Ding ◽  
Tao Sun
Keyword(s):  
South China ◽  
Geochemical Studies

Origin of early Cambrian black-shale-hosted barite deposits in South China: Mineralogical and geochemical studies

2015 ◽  
Vol 106 ◽  
pp. 79-94 ◽  
Author(s):  
Shanchu Han ◽  
Kai Hu ◽  
Jian Cao ◽  
Jiayong Pan ◽  
Fei Xia ◽  
...  
Keyword(s):  
Black Shale ◽  
South China ◽  
Early Cambrian ◽  
Geochemical Studies

scholarly journals An Areal Assessment of Subseafloor Carbon Cycling in Cold Seeps and Hydrate-Bearing Areas in the Northern South China Sea

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Yanping Zhang ◽  
Min Luo ◽  
Yu Hu ◽  
Hongbin Wang ◽  
Duofu Chen
Keyword(s):  
Organic Matter ◽  
South China Sea ◽  
Carbon Cycling ◽  
South China ◽  
Northern South China Sea ◽  
Continental Margins ◽  
Cold Seeps ◽  
Carbonate Precipitation ◽  
Organic Matter Degradation ◽  
China Sea

Gas hydrates, acting as a dynamic methane reservoir, store methane in the form of a solid phase under high-pressure and low-temperature conditions and release methane through the sediment column into seawater when they are decomposed. The seepage of methane-rich fluid (i.e., cold hydrocarbon seeps) fuels the chemosynthetic biota-inhabited surface sediments and represents the major pathway to transfer carbon from sediments to the water column. Generally, the major biogeochemical reactions related to carbon cycling in the anoxic marine sediments include organic matter degradation via sulfate reduction (OSR), anaerobic oxidation of methane (AOM), methanogenesis (ME), and carbonate precipitation (CP). In order to better understand the carbon turnover in the cold seeps and gas hydrate-bearing areas of the northern South China Sea (SCS), we collected geochemical data of 358 cores from published literatures and retrieved 37 cores and corresponding pore water samples from three areas of interest (i.e., Xisha, Dongsha, and Shenhu areas). Reaction-transport simulations indicate that the rates of organic matter degradation and carbonate precipitation are comparable in the three areas, while the rates of AOM vary over several orders of magnitude (AOM: 8.3-37.5 mmol·m-2·yr-1 in Dongsha, AOM: 12.4-170.6 mmol·m-2·yr-1 in Xisha, and AOM: 9.4-30.5 mmol·m-2·yr-1 in Shenhu). Both the arithmetical mean and interpolation mean of the biogeochemical processes were calculated in each area. Averaging these two mean values suggested that the rates of organic matter degradation in Dongsha (25.7 mmol·m-2·yr-1) and Xisha (25.1 mmol·m-2·yr-1) are higher than that in Shenhu (12 mmol·m-2·yr-1) and the AOM rate in Xisha (135.2 mmol·m-2·yr-1) is greater than those in Dongsha (27.8 mmol·m-2·yr-1) and Shenhu (17.5 mmol·m-2·yr-1). In addition, the rate of carbonate precipitation (32.3 mmol·m-2·yr-1) in Xisha is far higher than those of the other two regions (5.3 mmol·m-2·yr-1 in Dongsha, 5.8 mmol·m-2·yr-1 in Shenhu) due to intense AOM sustained by gas dissolution. In comparison with other cold seeps around the world, the biogeochemical rates in the northern SCS are generally lower than those in active continental margins and special environments (e.g., the Black sea) but are comparable with those in passive continental margins. Collectively, ~2.8 Gmol organic matter was buried and at least ~0.82 Gmol dissolved organic and inorganic carbon was diffused out of sediments annually. This may, to some extent, have an impact on the long-term deep ocean carbon cycle in the northern SCS.

scholarly journals THE FIRST EVIDENCE OF LATE DEVONIAN GRANITOID MAGMATISM IN THE NORTHEASTERN FLANK OF THE SOUTH MONGOLIA–KHINGAN OROGENIC BELT

2021 ◽  
pp. 65-76
Author(s):  
Y.V. Smirnov ◽  
◽  
A.A. Sorokin ◽  
N.M. Kudryashov ◽  
◽  
...  
Keyword(s):  
Continental Margin ◽  
Orogenic Belt ◽  
Late Devonian ◽  
The South ◽  
Granitoid Magmatism ◽  
Margin Setting ◽  
Low Concentrations ◽  
History Of ◽  
Northeastern Flank ◽  
Geochemical Studies

The results of geochemical, U-Pb geochronological, Sm-Nd isotopic-geochemical studies of granites of the Medvedka Massif in the northern part of the Nora–Sukhotino terrane are presented. It has been found that these granites are of 378 ± 3 Ma in age. It was shown that these granites are characterized by the presence of ferruginous silicates, high iron index (FeO*/(FeO*+MgO)), low concentrations of Al2O3, CaO, MgO, high contents of Nb, Ga, Y, deficiency of Sr, Eu, positive values of εNd(t) (+3.0...+4.1), and high values of the ratio Y/Nb. In total, this indicates that the granites of the Medvedka massif are related to A2-type granites. The Late Devonian hastingsite-biotite granites of the Medvedka Massif most likely reflect evidence of the transform continental margin setting in the history of the formation of the South Mongolian – Khingan orogenic belt.

scholarly journals Characterization of the Composition and Biological Activity of the Venom from Vespa bicolor Fabricius, a Wasp from South China

Toxins ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 59
Author(s):  
Yong-Hua Wu ◽  
Yu Zhang ◽  
Dan-Qiao Fang ◽  
Jing Chen ◽  
Jing-An Wang ◽  
...  
Keyword(s):  
South China ◽  
Anaerobic Bacteria ◽  
Clinical Importance ◽  
Biological Properties ◽  
Inflammatory Activity ◽  
Raw 264.7 Cells ◽  
Antiproliferative Effects ◽  
Low Concentrations ◽  
Cytotoxicity Studies ◽  
Allergenic Activity

We analyzed, for the first time, the major components and biological properties of the venom of Vespa bicolor, a wasp from South China. Using HPLC and SDS-PAGE, combined with LC–MS/MS, MALDI-TOF-MS, and NMR data to analyze V. bicolor venom (VBV), we found that VBV contains three proteins (hyaluronidase A, phospholipase A1 (two isoforms), and antigen 5 protein) with allergenic activity, two unreported proteins (proteins 5 and 6), and two active substances with large quantities (mastoparan-like peptide 12a (Vb-MLP 12a), and 5-hydroxytryptamine (5-HT)). In addition, the antimicrobial activity of VBV was determined, and results showed that it had a significant effect against anaerobic bacteria. The minimum inhibitory concentration and minimum bactericidal concentration for Propionibacterium acnes were 12.5 µg/mL. Unsurprisingly, VBV had strong antioxidant activity because of the abundance of 5-HT. Contrary to other Vespa venom, VBV showed significant anti-inflammatory activity, even at low concentrations (1 µg/mL), and we found that Vb-MLP 12a showed pro-inflammatory activity by promoting the proliferation of RAW 264.7 cells. Cytotoxicity studies showed that VBV had similar antiproliferative effects against all tested tumor cell lines (HepG2, Hela, MCF-7, A549, and SASJ-1), with HepG2 being the most susceptible. Overall, this study on VBV has high clinical importance and promotes the development of Vespa bicolor resources.

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