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Sample records for catagenesis

  1. Differences in bitumen and kerogen-bound fatty acid fractions during diagenesis and early catagenesis in a maturity series of New Zealand coals

    DEFF Research Database (Denmark)

    Glombitza, Clemens; Mangelsdorf, Kai; Horsfield, Brian

    2016-01-01

    differences in the fatty acid composition between bitumen and kerogen-bound acids, both in the short (fatty acid range. The compositions of these two acid fractions changed independently as a function of maturation. This points to the long and short chain fatty acids in bitumen......Oxygen-bearing functional groups, in particular the carboxylic groups of acids and esters, are mainly responsible for the chemical reactivity of sedimentary organic matter. We have studied kerogen and bitumen fractions from a coalification series from the New Zealand Coal Band covering the rank...... range from 0.28% to 0.80% vitrinite reflectance. We investigated the composition of fatty acids separated from the bitumen, and compared this to the distribution of kerogen-bound fatty acids (esters) obtained after selective chemical degradation of the macromolecular organic matter. We found remarkable...

  2. Maturation related changes in the distribution of ester bound fatty acids and alcohols in a coal series from the New Zealand Coal Band covering diagenetic to catagenetic coalification levels

    Energy Technology Data Exchange (ETDEWEB)

    Glombitza, C.; Mangelsdorf, K.; Horsfield, B. [German Research Cemter of Geoscience GFZ, Potsdam (Germany)

    2009-10-15

    Several lignites and coals of low to moderate maturation levels from the New Zealand Coal Band were investigated using alkaline ester cleavage experiments to reveal compositional changes of ester bound components during increasing maturation. Ester bound alcohols are found to be present in highest amounts in the very immature lignite samples but show a rapid decrease during early diagenesis. Ester bound fatty acids also show an initial exponential decrease during diagenesis but reveal an intermittent increase during early catagenesis before decreasing again during main catagenesis. This was related to the short chain fatty acids. To obtain a maturity related signal and to eliminate facies related scattering in the amounts of fatty acids in the coal samples, the carbon preference index of fatty acids (CPIFA) parameter is introduced. For the long chain fatty acids the CPIFA decreases with increasing maturity. During diagenesis, the same trend can be observed for the short chain fatty acids but the intermittent increase in the amounts of short chain fatty acids is also accompanied by high CPIFA values. This indicates less altered organic biomass at this maturation level and is in contrast to the mature CPIFA signal of the long chain fatty acids of the same samples. Thus could be due to extremely different amounts of short and long chain fatty acids in the original source organic matter or it could due to the incorporation of immature bacterial biomass from deep microbial communities containing C{sub 16} and C{sub 18} fatty acids as main cell membrane components. Deep microbial life might be stimulated at this interval by the increasing release of thermally generated potential substrates from the organic matrix during early catagenesis. The high amounts of alcohols in the immature lignite samples are also visible in the alkene distribution from the open system pyrolysis experiments of the organic matrix before and after saponification.

  3. Maturation-related changes in the distribution of ester-bound fatty acids and alcohols in a coal series from the New Zealand Coal Band covering diagenetic to catagenetic coalification levels

    DEFF Research Database (Denmark)

    Glombitza, Clemens; Mangelsdorf, Kai; Horsfield, Brian

    2009-01-01

    A rank series of lignites and coals of low to moderate maturation levels (vitrinite reflectance (R0): 0.27–0.8%) from the New Zealand Coal Band were investigated using alkaline ester cleavage experiments to reveal compositional changes of ester bound components (fatty acids and alcohols) during...... increasing maturation. Ester bound alcohols are found to be present in highest amounts in the very immature lignite samples (R0: 0.27–0.29%), but show a rapid decrease during early diagenesis. Ester bound fatty acids also show an initial exponential decrease during diagenesis, but reveal an intermittent...... containing C16 and C18 fatty acids as main cell membrane components. Deep microbial life might be stimulated at this interval by the increasing release of thermally generated potential substrates from the organic matrix during early catagenesis. In contrast to the fatty acids, the high amounts of alcohols...

  4. Représentation chimique de la structure des kérogènes et des asphaltènes en fonction de leur origine et de leur degré d'évolution Chemical Modeling of the Structure of Kerogens and Asphaltenes As a Function of Their Origin and Evolution Stage

    Directory of Open Access Journals (Sweden)

    Behar F.

    2006-11-01

    Full Text Available Dans cet article nous proposons des modèles de structures chimiques de kérogènes et d'asphaltènes de roche. Nous avons choisi de représenter les kérogènes appartenant aux trois types classiques de matières organiques aux stades d'évolution suivants : - début de la diagenèse sensu-stricto; - début de la catagenèse (formation de l'huile; - fin de la catagenèse (formation du gaz. Les asphaltènes représentés correspondent à la phase de formation de l'huile. Nous avons tenu compte des données d'analyse obtenues sur des échantillons naturels : analyse élémentaire, microscopie électronique, RMN 13C, thermogravimétrie, analyse fonctionnelle, dégradation par pyrolyse. Afin d'obtenir une représentation chimique ayant une valeur statistique suffisante, nous avons choisi une masse moléculaire de 25 000 environ, identique pour les trois kérogènes au début de la diagenèse, et une masse de 8000 environ pour les asphaltènes associés. Nous avons ensuite dessiné à l'échelle moléculaire les structures correspondantes. This paper proposes models for the chemical structures of kerogens and asphaltenes from rocks. The kerogens belonging to the three conventional types of organic matter are represented in the following stages of evolution: (1 beginning of diagenesis sensu stricto,(2 beginning of catagenesis (formation of oil, and (3 end of catagenesis (formation of gas. The asphaltenes represented here correspond to the phase of oil formation. Models are based on analytical data obtained on natural samples, i. e. elemental analysis, electron microscopy, 13C NMR, thermogravimetry, functional analysis and pyrolysis. To get enough statistical value for the chemical modelling, a same molecular mass of about 25 000 was chosen for the three kerogens at the beginning of diagenesis. A molecular mass of about 8000 was chosen for the related asphaltenes. The chemical structures were then constructed at the molecular scale.

  5. Petrology and diagenetic history of the upper shale member of the Late Devonian–Early Mississippian Bakken Formation, Williston Basin, North Dakota

    Science.gov (United States)

    Neil S. Fishman,; Sven O. Egenhoff,; Boehlke, Adam; Lowers, Heather

    2015-01-01

    The organic-rich upper shale member of the upper Devonian–lower Mississippian Bakken Formation (Williston Basin, North Dakota, USA) has undergone significant diagenetic alteration, irrespective of catagenesis related to hydrocarbon generation. Alteration includes precipitation of numerous cements, replacement of both detrital and authigenic minerals, multiple episodes of fracturing, and compaction. Quartz authigenesis occurred throughout much of the member, and is represented by multiple generations of microcrystalline quartz. Chalcedonic quartz fills radiolarian microfossils and is present in the matrix. Sulfide minerals include pyrite and sphalerite. Carbonate diagenesis is volumetrically minor and includes thin dolomite overgrowths and calcite cement. At least two generations of fractures are observed. Based on the authigenic minerals and their relative timing of formation, the evolution of pore waters can be postulated. Dolomite and calcite resulted from early postdepositional aerobic oxidation of some of the abundant organic material in the formation. Following aerobic oxidation, conditions became anoxic and sulfide minerals precipitated. Transformation of the originally opaline tests of radiolaria resulted in precipitation of quartz, and quartz authigenesis is most common in more distal parts of the depositional basin where radiolaria were abundant. Because quartz authigenesis is related to the distribution of radiolaria, there is a link between diagenesis and depositional environment. Furthermore, much of the diagenesis in the upper shale member preceded hydrocarbon generation, so early postdepositional processes were responsible for occlusion of significant original porosity in the member. Thus, diagenetic mineral precipitation was at least partly responsible for the limited ability of these mudstones to provide porosity for storage of hydrocarbons.

  6. Organic geochemistry of oils and condensates in the Kekeya field, southwest depression of the Tarim Basin (China)

    Energy Technology Data Exchange (ETDEWEB)

    Maowen Li; Snowdon, L.R. [Geological Survey of Canada, Calgary (Canada); Renzi Lin; Peirong Wang [Jianghan Petroleum Institute, Hubei (China); Yongsheng Liao; Peilong Li [Shengli Petroleum Administrative Bureau, Shandong (China)

    1999-07-01

    This study shows that the oils and condensates in the Kekeya Field in the Tarim Basin, NW China, belong to a single family, most likely derived from marine shale source rocks deposited under oxic-suboxic conditions with mixed terrigenous and algal-bacterial organic inputs. The maturity data clearly indicate that the paraffinic condensates were not formed by thermal cracking of oil during late catagenesis (R{sub o} > 1.2%). Both the oils and condensates were generated within the normal oil window, whereas addition of gaseous hydrocarbons from a separate source resulted in migration fractionation and hence spuriously high heptane indices. Age specific biomarkers show that the oils and condensates were not generated from the Mesozoic-Cenozoic strata, but from the Carboniferous-Permian sections. 1D basin modelling results are consistent with this interpretation, suggesting that the Mesozoic-Eocene strata are currently immature with respect to hydrocarbon generation and expulsion. Deep-seated faults may have provided routes for upward fluid migration at the time of active deformation during several pulses of the Himalayan orogeny. The favoured targets for further petroleum exploration in front of the Kunlun Mountains include the deep structures within the Carboniferous-Permian strata for indigenous petroleum accumulations and anticlines and stratigraphic traps within the Mesozoic-Cenozoic sections that are cut by deep-seated thrust faults where secondary petroleum accumulations most likely occurred. (author)

  7. Resins and asphaltenes: evolution as a function of organic-matter type and burial

    Energy Technology Data Exchange (ETDEWEB)

    Castex, H. (Institut Francais du Petrole, 92 - Rueil-Malmaison (France))

    Elemental analysis was used to investigate 151 resins and 175 asphaltenes extracted from rocks from several basins. It was shown that: resins have higher mean carbon and hydrogen values as well as a lower C/H ratio than asphaltenes. Resins thus have a more aliphatic and or more alicyclic structure. On the other hand, asphaltenes contain more sulfur, oxygen and nitrogen. Different types of organic matter are revealed by an H/C, O/C diagram. Their chemical evolution with burial is characterized by a decrease in hydrogen, oxygen and sulfur contents. Proton nuclear magnetic resonance (NMR) and infrared spectroscopy (IRS) were used to follow the structural evolution of resins and asphaltenes coming from different types of organic matter (algal, marine and terrestrial) buried at increasing depths. NMR can be used to compute several structural parameters such as Fsub(A) aromaticity and the degree of sigma substitution of the aromatic system. These data were completed by infrared spectroscopy. Variations in the intensity of bands: decrease of aliphatic C-H and of C = O fonctions; increase of aromatic C-H and C = C are related to both the type of organic matter and its catagenesis.

  8. Geochemical markers of soil anthropogenic contaminants in polar scientific stations nearby (Antarctica, King George Island).

    Science.gov (United States)

    Prus, Wojciech; Fabiańska, Monika J; Łabno, Radosław

    2015-06-15

    The organic contamination of Antarctic soils and terrestrial sediments from nearby of five polar scientific stations on King George Island (Antarctica) was investigated. Gas chromatography-mass spectrometry (GC-MS) was applied to find composition of dichloromethane extracts of soil and terrestrial sediments. The presence of geochemical markers, such as n-alkanes, steranes, pentacyclic triterpenoids, and alkyl PAHs, their distribution types, and values of their ratios indicates the predominating source of organic fossil fuels and products of their refining rather than from the natural Antarctic environment. Fossil fuel-originated compounds well survived in conditions of Antarctic climate over long times thus enabling to characterize geochemical features of source fossil fuel identified as petroleum expelled from kerogen II of algal/bacterial origins deposited in sub-oxic conditions and being in the middle of catagenesis. Both microbial activity and water leaching play an important role in degradation of terrestrial oil spills in the Antarctica climate, and petroleum alteration occurs lowly over long periods of time. Synthetic anthropogenic compounds found in terrestrial Antarctica sediments included diisopropylnaphthalenes, products of their sulfonates degradation in paper combustion, and organophosporus compounds used as retardants and plasticizers.

  9. Thermal stability of ladderane lipids as determined by hydrous pyrolysis

    Science.gov (United States)

    Jaeschke, A.; Lewan, M.D.; Hopmans, E.C.; Schouten, S.; Sinninghe, Damste J.S.

    2008-01-01

    Anaerobic ammonium oxidation (anammox) has been recognized as a major process resulting in loss of fixed inorganic nitrogen in the marine environment. Ladderane lipids, membrane lipids unique to anammox bacteria, have been used as markers for the detection of anammox in marine settings. However, the fate of ladderane lipids after sediment burial and maturation is unknown. In this study, anammox bacterial cell material was artificially matured by hydrous pyrolysis at constant temperatures ranging from 120 to 365 ??C for 72 h to study the stability of ladderane lipids during progressive dia- and catagenesis. HPLC-MS/MS analysis revealed that structural alterations of ladderane lipids already occurred at 120 ??C. At temperatures >140 ??C, ladderane lipids were absent and only more thermally stable products could be detected, i.e., ladderane derivatives in which some of the cyclobutane rings were opened. These diagenetic products of ladderane lipids were still detectable up to temperatures of 260 ??C using GC-MS. Thus, ladderane lipids are unlikely to occur in ancient sediments and sedimentary rocks, but specific diagenetic products of ladderane lipids will likely be present in sediments and sedimentary rocks of relatively low maturity (i.e., C31 hopane 22S/(22S + 22R) ratio 0.5). ?? 2008 Elsevier Ltd.

  10. A Study of Porphyrins in Petroleum Source Rocks

    Energy Technology Data Exchange (ETDEWEB)

    Huseby, Berit

    1996-12-31

    This thesis discusses several aspects of porphyrin geochemistry. Degradation experiments have been performed on the Messel oil shale (Eocene, Germany) to obtain information on porphyrins bound or incorporated into macromolecular structures. Thermal heating of the preextracted kerogen by hydrous pyrolysis was used to study the release of porphyrins and their temperature dependent changes during simulated diagenesis and catagenesis. Selective chemical degradation experiments were performed on the preextracted sediment to get more detailed information about porphyrins that are specifically bound to the macromolecular structures via ester bonds. From the heating experiments, in a separate study, the porphyrin nitrogen content in the generated bitumens was compared to the bulk of organic nitrogen compounds in the fraction. The bulk nitrogen contents in the generated bitumens, the water phase and the residual organic matter was recorded to establish the distribution of nitrogen between the kerogen and product phases. Porphyrins as biomarkers were examined in naturally matured Kimmeridge clay source rocks (Upper Jurassic, Norway), and the use of porphyrins as general indicators of maturity was evaluated. Underlying maturity trends in the biomarker data was investigated by Partial Least Squares analysis. Porphyrin as indicators of depositional conditions was also addressed, where the correlations between the (amounts) abundance of nickel and vanadyl porphyrins were mapped together with other descriptors that are assumed to be indicative of redox depositional conditions. 252 refs., 28 figs., 4 tabs.

  11. Transition metal catalysis in the generation of petroleum and natural gas. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Mango, F.D.

    1997-01-21

    This project originated on the premise that natural gas could be formed catalytically in the earth rather than thermally as commonly believed. The intention was to test this hypothetical view and to explore generally the role of sedimentary metals in the generation of light hydrocarbons (C1 - C9). We showed the metalliferous source rocks are indeed catalytic in the generation of natural gas. Various metal compounds in the pure state show the same levels of catalytic activity as sedimentary rocks and the products are identical. Nickel is particularly active among the early transition metals and is projected to remain catalytically robust at all stages of catagenesis. Nickel oxide promotes the formation of n-alkanes in addition to natural gas (NG), demonstrating the full scope of the hypothetical catalytic process: The composition of catalytic gas duplicates the entire range of natural gas, from so-called wet gas to dry gas (60 to 95+ wt % methane), while gas generated thermally is consistently depleted in methane (10 to 60 wt % methane). These results support the view that metal catalysis is a major pathway through which natural gas is formed in the earth.

  12. Transition metal catalysis in the generation of petroleum and natural gas. Final report, September 1, 1992--October 31, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Mango, F.D.

    1997-01-21

    This project originated on the premise that natural gas could be formed catalytically in the earth rather than thermally as commonly believed. The intention was to test this hypothetical view and to explore generally the role of sedimentary metals in the generation of light hydrocarbons (C1 - C9). We showed the metalliferous source rocks are indeed catalytic in the generation of natural gas. Various metal compounds in the pure state show the same levels of catalytic activity as sedimentary rocks and the products are identical. Nickel is particularly active among the early transition metals and is projected to remain catalytically robust at all stages of catagenesis. Nickel oxide promotes the formation of n-alkanes in addition to natural gas (NG), demonstrating the full scope of the hypothetical catalytic process. The composition of catalytic gas duplicates the entire range of natural gas, from so-called wet gas to dry gas (60 to 95+ wt % methane), while gas generated thermally is consistently depleted in methane (10 to 60 wt % methane). These results support the view that metal catalysis is a major pathway through which natural gas is formed in the earth.

  13. The relationship between dolomitization and organic matter occurrence in Lower Paleozoic carbonate in the Ordos Basin

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on observations on the core and surface sections of Lower Paleozoic carbonate in the Ordos Basin, petrography research and measurements of TOC, TOS , Ro, XRD, and comparative study with dolomite in modern Coorong Lake, it has been revealed that: (i)dolomitization may occur in micrite limestone, gypsum-halite and argillaceous sandstone, and it can be divided into three types: sedimentary penecontemporaneous-early diagenesis, late diagenesis of deep burial and catagenesis of uplift period. However, the crystal cell of the second type less than 35 μ m in size is most closely associated with gas pool; (ii) the highest content of organic matter (OM) is produced in samples from the argillic dolomite which may be formed by argillaceous fluid through gypsum-halite; (iii) in the evolution process from penecontemporaneous dolomite into stoichiometric dolomite, the crystal order of dolomite and the porosity of its host rock tend to increase, which is favorable to the formation of an available migration network. When the power of the fluid is high enough, the network is mainly favorable to the migration and transport of heat, but when the power of the fluid goes down, the network system is favorable, due to its large space, to OM deposition in it.

  14. Characterization of oil source strata organic matter of Jurassic age and its contribution to the formation of oil and gas deposits

    Science.gov (United States)

    Pronin, Nikita; Nosova, Fidania; Plotnikova, Irina

    2013-04-01

    Within the frames of this work we carried out comprehensive geochemical study of high-carbon rocks samples taken from the three segments of the Jurassic system - from the lower (Kotuhtinskaya suite), from the medium (Tyumenskaya suite) and from the upper (Vasyuganskaya, Georgievskaya and the Bazhenovskaya suites), all within the north-eastern part of the Surgut oil and gas region. Altogether we investigated 27 samples. The complex study of the organic matter (OM) of these strata included the following: chloroform extraction of bitumen, the determination of the group and element composition, gas chromatography (GC) and gas chromatomass-spectrometry (GC/MS). These methods allow giving high quality assessments of the potential oil and gas source strata and thus identifying the possible oil and gas generating strata among them, ie, those strata that could be involved in the formation of oil and gas within the area. As a result of this work we identified various biomarkers that allow characterizing each oil and gas source strata under the study in the open-cast of the Jurassic system: 1. Kotuhtinskaya Suite. The build-up of this suite took place in the coastal marine weakly reducing conditions. In their composition these deposits contain some highly transformed humus organic matter (gradation of catagenesis MK3). 2. Tyumenskaya Suite. Accumulation of OM in these deposits occured mainly in the coastal marine environment with the influx of a large number of terrestrial vegetation in the basin of deposition. As for the type of agents - it is a humus or sapropel-humus OM with a rich content of continental organics. Source type of this OM is mixed - bacterial and algal. OM of the rocks of Tyumenskaya suite is situated in the area of high maturity (stage of catagenesis at MK3 level). 3. Vasyuganskaya Suite. In this case the accumulation of OM occurred mainly in the laguna (lake-delta) weak-reduction close to oxidative conditions with the influx of bacterial matter and the

  15. Closed pyrolyses of the isoprenoid algaenan of Botryococcus braunii, L race: geochemical implications for derived kerogens

    Science.gov (United States)

    Behar, F.; Derenne, S.; Largeau, C.

    1995-07-01

    Algaenans, i.e., highly aliphatic, nonhydrolysable, insoluble macromolecular constituents, have been identified in a number of microalga cell walls and their selective preservation shown to play a major role in the formation of numerous kerogens. All the algaenans so far examined comprise a network of long polymethylenic chains, except for the L race of Botryococcus braunii. The resistant macromolecular material isolated from the latter, termed PRB L, is based on C 40 isoprenoid chains with a lycopane-type skeleton. Recent comparative studies of PRB L and of Botryococcus-derived sediments provided the first example of kerogen formation via the selective preservation of an "isoprenoid" algaenan. The present study is concerned with PRB L pyrolyses in sealed gold tubes under various temperature/time conditions (260-350°C, 0.5-69 h). For the conversion rates thus obtained, ranging from 30 to 100%, a complete mass balance of the different families of pyrolysis products was established; most of the C 1 to C 40 pyrolysate constituents were identified and the abundances of the above compounds and their variations with conversion progress were determined. This study thus allowed us (1) to derive further information about PRB L chemical structure (location of the ether bridges, contribution of linear chains and their relationships with the C 40 isoprenoid ones), (2) to determine the behaviour of this isoprenoid algaenan to thermal stress (timing of the formation of the different groups of products then released, nature of the primary cleavages, origin and mode of formation of the secondary products, and further degradations), and (3) to show, in connection with previous studies, that PRB L-derived kerogens should exhibit pronounced differences relative to standard type I kerogens, the latter being based on polymethylenic chains, regarding not only the structure of the generated products but also the timing of oil generation (upward shift of the catagenesis zone).

  16. Paleoenvironmental and source rock assessment of black shales of Pennsylvanian Age, Powder River and northern Denver basins

    Energy Technology Data Exchange (ETDEWEB)

    Clayton, J.L.; King, J.D.; Lubeck, C.M.; Leventhal, J.S.; Daws, T.A.

    1988-07-01

    Thin Middle Pennsylvanian (Desmoinesian) organic-rich black shales (cumulative thickness < 50 ft) underlie much of the northern Denver basin and southeastern Powder River basin. In the Powder River basin, these shales are part of the middle member of the Minnelusa Formation. During Desmoinesian time, the present area of the southeastern Powder River basin and Nebraska was a shallow, at times highly saline, restricted sea. In contrast, in the present area of northeastern Colorado, black shales were deposited in a marine environment with normal salinity that was probably continuous with the Mid-Continent Pennsylvanian sea. Assessment of the paleoenvironment has been carried out using organic geochemical parameters. Shales deposited in the restricted basin setting contain abundant porphyrins (25,000-30,000 ppm relative to total extractable organic matter) and significant quantities of aryl isoprenoids. The aryl isoprenoid compounds (1) are evidence for the presence of the sulfur bacteria families Chlorobiaceae and possibly Chromatiaceae and (2) indicate that euxinic conditions existed in the water column. High ratios of sulfur to carbon in the shales support this interpretation. In contrast, extracts from black shale in the normal sea to the south contain lower porphyrin concentrations (generally less than 1000 ppm) and aryl isoprenoids are minor constituents or are absent. Sulfur/carbon ratios in these latter shales are similar to those observed for normal marine shales (that is, not euxinic conditions). Other paleoenvironmental indicators (sterane composition, alkane distribution) are consistent with these observations. Bulk organic matter in the black shales from both environments is type II and has good source potential for generation of liquid hydrocarbons during catagenesis. Pyrolysis yields of 50 kg/MT (50,000 ppm) are common, and in some shales, yield is 100 kg/MT (100,000 ppm).

  17. Dissolved Black Carbon in the Southern Ocean along CLIVAR section I6S

    Science.gov (United States)

    Paeng, J.; Dittmar, T.

    2008-12-01

    Thermogenic matter ("black carbon", BC) is abundant in the environment. BC is produced during catagenesis in earth's crust and is also a residue of fossil fuel and biomass burning. Because of its refractory character, BC accumulates in soils and sediments and sequesters carbon from active cycles. Previous studies found indications that BC might be a significant component also in marine dissolved organic matter (DOM). However, the available information on black carbon in DOM is extremely rare up to now. The objective of this study is to quantify BC in marine DOM and identify the source and dynamics of dissolved BC for a major oceanic region. Detailed depth profiles were sampled along 30º E from South Africa to Antarctica at 1º intervals on CLIVAR section I6S. Dissolved BC was isolated from approximately 250 seawater samples via a new solid phase extraction method. Fused aromatic ring systems as a molecular tracer for BC were quantified in these samples. For this purpose, the samples were oxidized with nitric acid and the reaction products of fused ring systems analyzed as benzene-polycarboxylic acids with HPLC. BC concentrations were very stable throughout the water column and along the North-South section, ranging between 500 and 700 nM BC. The molecular composition of benzene-polycarboxylic acids indicates a relatively small number of fused aromatic rings per molecule. Similar structures were observed preciously in riverine and also petroleum-derived DOM. The homogenous distribution of BC in all water masses indicates conservative behavior of BC in the ocean, and turnover rates which are far longer than oceanic turnover rates. The stable character of dissolved BC and its abundance in the ocean has major implications for our understanding of global biogeochemical cycles.

  18. Phylogenetic analysis of HpnP reveals the origin of 2-methylhopanoid production in Alphaproteobacteria.

    Science.gov (United States)

    Ricci, J N; Michel, A J; Newman, D K

    2015-05-01

    Hopanoids are bacterial steroid-like lipids that can be preserved in the rock record on billion-year timescales. 2-Methylhopanoids are of particular interest to geobiologists because methylation is one of the few chemical modifications that remain after diagenesis and catagenesis. 2-Methylhopanes, the molecular fossils of 2-methylhopanoids, are episodically enriched in the rock record, but we do not have a robust interpretation for their abundance patterns. Here, we exploit the evolutionary record found in molecular sequences from extant organisms to reconstruct the biosynthetic history of 2-methylhopanoids using the C-2 hopanoid methylase, HpnP. Based on HpnP phylogenetic analysis, we find that 2-methylhopanoids originated in a subset of the Alphaproteobacteria. This conclusion is statistically robust and reproducible in multiple trials varying the outgroup, trimming stringency, and ingroup dataset used to infer the evolution of this protein family. The capacity for 2-methylhopanoid production was likely horizontally transferred from the Alphaproteobacteria into the Cyanobacteria after the Cyanobacteria's major divergences. Together, these results suggest that the ancestral function of 2-methylhopanoids was not related to oxygenic photosynthesis but instead to a trait already present in the Alphaproteobacteria. Moreover, given that early 2-methylhopane deposits could have been made solely by Alphaproteobacteria before the acquisition of hpnP by Cyanobacteria, and that the Alphaproteobacteria are thought to be ancestrally aerobic, we infer that 2-methylhopanoids likely arose after the oxygenation of the atmosphere. This finding is consistent with the geologic record-the oldest syngenetic 2-methylhopanes occur after the rise of oxygen, in middle Proterozoic strata of the Barney Creek Formation.

  19. Formation of nanoporous pyrobitumen residues during maturation processes within the Barnett Shale (Fort Worth Basin)

    Science.gov (United States)

    Bernard, S.; Wirth, R.; Schreiber, A.; Schulz, H.-M.; Horsfield, B.

    2012-04-01

    Hydrocarbon generation processes occur within organic-rich shales as a response to increases in thermal maturation. Shale gas reservoir quality is thought to be largely dependent on the extent to which solid organic material has been converted to pore space during catagenesis. Although pores may drastically vary in variety and abundance within differing shales, the occurrence of nanopores within organic particles has recently been documented for an important number of gas shale systems (i.e., Barnett, Haynesville, Utica, Eagle Ford, Woodford, Horn River, Marcellus, Posidonia …). However, despite their ubiquitous nature, the formation and the geochemical nature of these nanoporous organic compounds remain unclear. Here, we present the characterization of samples from the organic-rich Mississippian Barnett shale gas system (Fort Worth Basin, Texas, USA) at varying stages of thermal maturation. Using a combination of compositional organic geochemistry and spectromicroscopy techniques, including synchrotron-based scanning transmission X-ray microscopy (STXM - data collected using the CLS 10ID-1 STXM beamline) and transmission electron microscopy (TEM), we document a net increase in sample geochemical heterogeneity with increasing maturity. In addition to the presence of bitumen in samples of oil window maturity, very likely genetically derived from thermally degraded kerogen, the formation of nanoporous pyrobitumen has been inferred for samples of gas window maturity, likely resulting from the formation of gaseous hydrocarbons by secondary cracking of bitumen compounds. By providing in-situ insights into the fate of bitumen and pyrobitumen as a response to the thermal evolution of the macromolecular structure of kerogen, the present contribution constitutes an important step towards better constraining hydrocarbon generation processes occurring within unconventional gas shale systems.

  20. 贵州紫云上石炭统叶状藻礁灰岩的成岩作用%Diagenesis of the Upper Carboniferous Phylloid Algal Reef Limestone in Ziyun County,Guizhou

    Institute of Scientific and Technical Information of China (English)

    孙宝亮; 巩恩普; 李金梅; 关长庆; 张永利

    2012-01-01

    porosity in the reef limestone reduce to approximately zero.Preexisting cements were altered on the hydrocarbon composition and color,but the crystal fabrics unaltered.The color of isopachous bladed to columnar calcite cement changed from gray to white,and the color of botryoidal cement became more blackish due to hydrocarbon infiltration.A little isopachous bladed to columnar calcite cement were dissolved,leaving mouldic pores filled subsequently.Construction fracturing is one of the main types of diagenesis that took place during catagenesis stage.Rusty microcrystalline layers containing Fe2O3 lining the wall of some fractures,and vadose pisoids and ferrugineous crystal silt containing Fe2O3 deposited at the bottom of the cavities formed in the tectonic fractures,indicate that they formed in oxidizing vadose environments.Most fractures are filled with white or green bladed cement and clear coarse sparry calcite cement,the middle part of some fractures is filled with bitumen block.Nearly all twins in calcite filling fractures are thicker than 1μm,therefore it can be derived that the thick twins deformed at the temperature above 200℃.So the phylloid algal reef limestone was again buried deeper than 2.8km during catagenesis stage.This indicates that the Nanpanjiang Basin has undergone frequent elevation-subsidence.It might be a reason for that the phylloid algal reef limestone did not become oil and gas reservoirs that the pores of the phylloid algal reef limestone were occluded by burial cement.Only limestone that has large interconnected secondary pores generated during catagenesis stage could become oil and gas reservoirs in the Nanpanjiang Basin.

  1. Diagenetic and catagenetic products of isorenieratene: Molecular indicators for photic zone anoxia

    Science.gov (United States)

    Koopmans, Martin P.; Köster, Jürgen; Van Kaam-Peters, Heidy M. E.; Kenig, Fabien; Schouten, Stefan; Hartgers, Walter A.; de Leeuw, Jan W.; Sinninghe Damsté, Jaap S.

    1996-11-01

    A wide range of novel diagenetic and catagenetic products of the diaromatic carotenoid isorenieratene, a pigment of the photosynthetic green sulphur bacteria Chlorobiaceae, has been identified in a number of sedimentary rocks ranging from Ordovician to Miocene. Compound identification is based on NMR, mass spectrometry, the presence of atropisomers, and stable carbon isotopes. Atropisomers contain an axially chiral centre which, in combination with other chiral centres, results in two or more diastereomers that can be separated on a normal GC column. Chlorobiaceae use the reverse TCA cycle to fix carbon, so that their biomass is enriched in 13C. High 13C contents of isorenieratene derivatives therefore support their inferred origins. Isorenieratene derivatives include C 40, C 33, and C 32, diaryl isoprenoids and short-chain aryl isoprenoids with additional aromatic and/or S-containing rings. C 33 and C 32 compounds are diagenetic products of C 33 and C 32 “carotenoids” formed from isorenieratene during early diagenesis through expulsion of toluene and m-xylene, respectively. Cyclisation of the polyene acyclic isoprenoid chain can proceed via an intramolecular Diels-Alder reaction, followed by aromatisation of the newly formed ring. Sulphurisation is also an important process during early diagenesis, competing with expulsion and cyclisation. Sulphur-bound isorenieratane is released during progressive diagenesis, due to cleavage of relatively weak Ssbnd S and Csbnd S bonds. Cleavage of C-C bonds during aromatisation of newly formed rings and during catagenesis yields short-chain compounds. The inherent presence of a conjugated double bond system in carotenoids implies that similar diagenetic and catagenetic reactions can occur with all carotenoids. Chlorobiaceae live at or below the oxic/anoxic boundary layer and require both light and H 2S. The presence of isorenieratene or its diagenetic and catagenetic products in ancient sedimentary rocks and crude oils is

  2. Propriétés optiques de résidus de la pyrolyse kérogènes Optical Properties of Kerogen Pyrolysis Residues

    Directory of Open Access Journals (Sweden)

    Alpern B.

    2006-11-01

    Full Text Available On étudie l'évolution des propriétés optiques de trois kérogènes peu évolués au cours de leur pyrolyse sous azote en programmation de température. Le premier appartient à une série lacustre (Green River Shales, le second à une série marine (Toarcien du bassin de Paris, le troisième à une série deltaïque (Crétacé du Cameroun. On constate la ressemblance de l'évolution artificielle avec la catagenèse (évolution accompagnant l'enfouissement des sédiments. On observe dans les deux premiers kérogènes l'existence de particules ressemblant à de la vitrinite, mais dont les propriétés optiques évoluent différemment. On incite en conséquence à une grande prudence dans l'utilisati n du pouvoir réflecteur de telles particules pour localiser dans les séries lacustres et marines la zone de formation du pétrole. On note l'intérêt de mesurer le pour réflecteur de la grande masse du kérogène et de mettre son évolution en relation avec celle des autres propriétés physiques. This article examines the evolution of the optical properties of three immature kerogens during their pyrolysis in nitrogen ut programmed temperature. The first kerogen comes from a lacustrine series (Green River Shales, the second from a marine series (Tourcian from the Paris Basin, and the third from a deltaic series (Cretaceous from Cameroon. There is a resemblance in their artificial evolution with catagenesis (evolution accompanying the burial of the sédiments. The first two kerogens cari be seen to contain particles resembling vitrinite, although with optical properties which evolve differently. Therefore, great cure must be taken in using the reflecting power of such particules ta situate the petroleum forming zone in lacustrine and marines séries. It is important ta measure the reflecting power of the general mass of the kerogen and to compare its evolution with that of the other physical properties.

  3. In search of early life: Carbonate veins in Archean metamorphic rocks as potential hosts of biomarkers

    Science.gov (United States)

    Peters, Carl A.; Piazolo, Sandra; Webb, Gregory E.; Dutkiewicz, Adriana; George, Simon C.

    2016-11-01

    to - 4 ‰ and δ18OVPDB ranging from - 18 ‰ to - 12 ‰. Evidently, the migration and entrapment of hydrocarbons occurred after peak metamorphism under temperatures congruous with late catagenesis and from fluids of different compositions. The relatively high temperatures of vein formation and the known geotectonic history of the rocks analysed suggest a probable minimum age of 1.8 billion yrs (Paleoproterozoic). Our results demonstrate that post peak-metamorphic veins provide an exciting opportunity in the search for evidence of early life. The integration of petrological and organic geochemical techniques is crucial for any future studies that use biomarkers to reconstruct the early biosphere.

  4. Cement characteristics of the Upper Carboniferous phylloid algal reef limestone in Ziyun County, Guizhou Province%贵州紫云上石炭统叶状藻礁灰岩胶结物特征

    Institute of Scientific and Technical Information of China (English)

    孙宝亮; 巩恩普; 李金梅; 关长庆; 张永利

    2012-01-01

    phylloid algal thalli had high porosity and big pores, and marine botryoidal cement and isopachous acicular cement grew in the pores. During the early diagenetic stage, cementation supplied a great amount of cements, constructed rock framework, and consequently decided the features of the limestone rock. Blocky calcite spar and calcite microspar were formed in small pores, and radiating cement fans grew in big pores. During the epidiagenetic stage, extensive dissolution and cementation occurred. Vuggy or channel porosity was created by dissolution in the recharge area, and calcite precipitation was greatly increased in downflow areas. Meteoric phreaticcements include isopachous columnar calcite and blocky or equant calcite cement. Isopachous columnar cement is volumetrically more abundant. The porosity of the reef limestone was reduced dramatically through the early-stage cementation, so the reef limestone could prevent mechanical compaction. During the middle and late diage-netic stage, nearly all porosity was occluded by cements with low rates of fluid influx and efflux, and the remaining pores were filled with isopachous bladed cement and drusy or blocky calcite spar. Some preexisting cements were altered during the middle or late diagenetic stage, the color of isopachous bladed to columnar calcite cement changed from gray to white, and the color of botryoidal cement became more blackish due to hydrocarbon infiltration. Some isopachous bladed to columnar calcite cement could be dissolved, leaving mouldic pores filled subsequently and radiating cement fans formed simultaneously. Construction fracturing is one of the main types of diagenesis during the catagenesis stage. Rusty microcrystalline layers containing Fe2C>3 line the wall of some fractures, and vadose pisoids and ferrugineous crystal silt containing Fe2O3 are deposited at the bottom of the cavities formed in the tectonic fractures, which indicates that they were formed in oxidizing vadose environments. Late

  5. Organic geochemical study of domanik deposits, Tatarstan Republic.

    Science.gov (United States)

    Nosova, F. F.; Pronin, N. V.

    2010-05-01

    suggests a major marine phytoplankton contribution relative to terrigenous land plant source input. The marine affinity is evident from the relatively abundant C27 steranes, which are biomarkers for marine algal contribution to organic matter and low C29 sterane contens. In this present study, samples are dominated by 5α, 14α, 17α (H)-20R and 5β, 14α, 17α (H)-20R steranes (biological configuration). The ratios of 20S/(20S+20R) for αααC29 steranes and ββ/(αα + ββ) for 5α-C29 steranes in the samples, are 0.21 to 0.55 and to 0.12 to 0.50, respectively. The thermal maturity level, assessed by values of several biomarker parameters has been estimated to be within end of diagenesis/eginning of catagenesis and correspond to theoretical vitrinite values (R0) in the range 0.57-0.65%.

  6. Résines et asphaltènes : évolution en fonction des types de matière organique et de leur enfouissement Resins and Asphaltenes: Evolution As a Function of Organic-Matter Type and Burial

    Directory of Open Access Journals (Sweden)

    Castex H.

    2006-11-01

    several basins. It was shown that: (a Resins have higher mean carbon and hydrogen values as well as a lower C/H ratio than asphaltenes. Resins thus have a more aliphatic and or more alicyclic structure. On the other hand, asphaltenes contain more sulfur, oxygen end nitrogen. (b Sulfur and oxygen are not parameters enabling basins to be differentiated. (c Different types of organic matter are revealed by an H/C, O/C diagram. Their chemical evolution with burial is characterized by a decrease in hydrogen, oxygen and sulfur contents. Proton nuclear magnetic resonance (NMR and infrared spectroscopy (IRS were used to follow the structural evolution of resins and asphaltenes coming from different types of organic matter (algal, marine and terrestrial buried at increasing depths. NMR can be used to compute several structural parameters such as FA aromaticity and the degree of sigma substitution of the aromatic system. The FA factor seems to increase with burial and according to the type of organic matter, while sigma seems to decrease. These data were completed by infrared spectroscopy. The surface areas of the bands corresponding to the following functions were computed: (a OH in the 3700-2700 cm-1 range; (b carbonyl C-O around 1700 cm-1; (c aliphatic C-H at 2900, 2455 and 1380 cm-1; (d aromatic C-H at 1610 cm-1. Variations in the intensity of bands: (a decrease of aliphatic C-H and of C-O functions; (b increase of aromatic C-H and C-C are related to both the type of organic matter and its catagenesis.

  7. 腮腺肿瘤改良手术切口与传统手术切口的对比分析%Comparative study between modified technique of parotidectomy and traditional technique

    Institute of Scientific and Technical Information of China (English)

    谷爱玲

    2014-01-01

    test were checked clinically .A structured questionnaire was con-structed, sensation of the ear lobe and facial contour were in cooperated into the questionnaire .The data analysis were performed using SPSS Windows version 13.0 and were assessed by t -tests and Chi square tests .Results:There was no difference between two groups in salivary fistula and tumor recurrence(P >0.05).In MP group,the incidence of provisional facial paralysis,gustatory sweating syndrome, sense of lobulus auriculae and prosopo -catagenesis was significantly lower than those in TP group ( p<0.05) .Conclusion:The modified in cision of parotidectomy greatly reduce the disadvantages of the traditional technique .It should be better than conventional technique .