Four massive brecciated, chimney-like, and slender pipe network carbonate samples(JA-4, JA-5, JX-8 and BG-12) were collected from southwestern Taiwan, which were suggested to have formed as a result of anaerobic oxidi...Four massive brecciated, chimney-like, and slender pipe network carbonate samples(JA-4, JA-5, JX-8 and BG-12) were collected from southwestern Taiwan, which were suggested to have formed as a result of anaerobic oxidization of methane(AOM). Considering that the environmental conditions of the carbonates precipitation and the sources of carbon and organic matter need to be further declared, molecular fossils and compound-specific carbon isotopic investigations of the carbonates were conducted in this study. According to lipid biomarkers of 2,6,10,15,19-pentamethyleicosane(PMI) and squalane diagnostic to methanotrophic archaea, as well as the extremely low δ^(13)C values(as low as -1^(13).4‰) detected in samples JA-4, JA-5 and JX-8, these carbonates were revealed to be a result of AOM. Based on the varied δ^(13)C values of characteristic archaea biomarkers in specific samples, biogenic methane was proposed to be responsible for the formation of samples JA-4 and JA-5, whereas a mixed carbon source of ^(13)C-depleted methane and ^(13)C-enriched residual CO_2 from methanogenesis was suggested for the carbonate of JX-8 due to the co-occurrence of a highly positive δ^(13) C_(carb) value(+8‰) and a moderate ^(13)C depletion of PMI. The low content of AOM-related biomarkers and the absence of indicators for ANME-2 suggested that these carbonates were formed in weak seep settings. By comparison, no typical lipid biomarkers for methanotrophic archaea was detected in carbonate BG-12. The short-chain and long-chain n-alkanes accounted for 30% and 45% of all hydrocarbons, respectively, with a CPI value of 1.2, suggesting that the n-alkanes were derived from both marine organisms and terrestrial inputs. A low thermal maturity could be revealed by the incomplete equilibrium value of the C^(31)αβ 22S/(22S+22R) ratio(0.5), and the carbonate BG-12 was probably deposited in a suboxic condition indicated by a value of Pr/Ph ratio(2.5).展开更多
U-bearing sandstones from the Dongsheng deposit in Ordos Basin contain abundant C15-C18 fatty acids. The fatty acids may have been derived from modern and ancient organisms including organisms from the intervals of U ...U-bearing sandstones from the Dongsheng deposit in Ordos Basin contain abundant C15-C18 fatty acids. The fatty acids may have been derived from modern and ancient organisms including organisms from the intervals of U mineralization. A certain amount of i15:0, a15:0, a17:0 fatty acids coexist with small amounts of i17:1ω7c and 10me16:0, characteristic biomarkers of Desulfovibrio and Desulfobacter sp., respectively. This indicates the existence of sulfate-reducing bacteria (SRB) in the sandstones. The presence of sulfur-oxidizing bacteria (SOB), such as Beggiatoa and Thioploca, is indicated by significant amounts of 16:1ω7c and 18:1ω7c fatty acids. The existence of the SRB in the deposit, as inferred from the fatty acids, is consistent with results from fossilized microorganisms and isotopic compositions of ore-stage pyrite. This suggests that the environment may have been favorable for the SRB to grow since ore formation (9.8-22 Ma). The bacteria may have degraded hydrocarbons directly, or indirectly utilized hydrocarbons degraded by oxic microbes in the deposits. This process may have produced 12C-rich calcite and prominent baseline humps of unresolved complex mixtures (UCM), and 25-demethylated hopanes and tricyclic terpanes. The existence of sulfur-oxidizing bacteria and sulfate-reducing bacteria in the deposit may have resulted in bacterial sulfate reduction to sulfide, re-oxidization of the sulfide to sulfate and subsequent reduction of the sulfate to sulfide. This assertion is supported by ore-stage pyrite with δ34S values as low as-39.2‰, and the lightest sulfate (about 11‰) measured during the Phanerozoic, a difference of more than 46‰.展开更多
After the detection of the 1,20,21-C29 long-chain triol in some sediments and freshwater pteridophytes, in this study a new homologous long-chain triol, 1,3,4-C27-29, is detected for the first time in the Site4B core ...After the detection of the 1,20,21-C29 long-chain triol in some sediments and freshwater pteridophytes, in this study a new homologous long-chain triol, 1,3,4-C27-29, is detected for the first time in the Site4B core sediment in the northern South China Sea. The hydroxyl location and length of the carbon chain of this newly discovered triol differ from those of 1,20,21-C29 triol. The test results of its molecular distribution and individual carbon isotope reveal that 1,3,4-C29triol has a good correlation with n-C26-30 even carbon-numbered long-chain fatty alcohols, with R2 （n=68） values of 0.905, 0.929 and 0.903, respectively, and its carbon isotope composition, at -32.3%o_1.9%o, is similar to that of rt-C26.30, at -29.13%o^0.87%o, -32.98%o^1.28%o, and -32.98%o^1.28%o. 1,3,4-C29 triol from the Site4B core sediment and terrigenous long-chain fatty alcohol （n-C26.34） show highly consistent distribution trends in the entire section; thus, the former could serve as a proxy indicator of the terrigenous input. Considering that the 1,20,21-C29 triol in previous research belongs to Azolla, which are fresh water pteridophytes, the 1,3,4-C27-29 triol identified in this study might have similar biogenetic derivation. Thus, determination of its biogenic area and growing environment could provide potential organic geochemical evidence supporting the terrigenous input and source in the northern South China Sea.展开更多
This study investigated the composition of long-chain alkyl diols, triols, sec-alcohols, hydroxyl acids, and other hydroxylated compounds in Azolla imbricata and compared the organic alcohol components of Azolla filic...This study investigated the composition of long-chain alkyl diols, triols, sec-alcohols, hydroxyl acids, and other hydroxylated compounds in Azolla imbricata and compared the organic alcohol components of Azolla filiculoides, Azolla microphylla, and South China Sea （SCS） sediments in order to investigate the possible indication of Azolla being the biological source of diols and triols in SCS sediment. Large amounts of diols, monohydroxy acids, and sec-alcohols with internal hydroxy groups at ω20 were detected in the three types of Azolla. Among these, 1,ω20-diol and ω20-hydroxy acid exhibited strong even-odd predominance distribution, whereas co20-sec-alcohol exhibited strong odd-even predominance distribution. In addition, small amounts of diols, triols, and dihydroxy acids with internal hydroxy groups at 9, 10 or ω9, ω 10 were detected, among which the chain length of C29 was predominate. Compounds having similar structures as those in Azolla reflected a similar biosynthetic pathway： ω20-hydroxy acid exhibiting even-odd predominance distribution is decarboxylated to ω20-sec-alcohol exhibiting odd-even predominance distribution and converted to 1, ω20-diol with even-odd predominance distribution by acyl reduction; ω9,ω10-hydroxy acid is converted to 1,20,21（1, ω9, ω10）-triol by acyl reduction, and then converted to 9,10-diol by hydrogenation and dehydration. The alcohol components in A. imbricata were clearly not the biological source of 1,13/1,14/1,15-C28, 30, 32 diols and 1,3,4-C27.29 triols in the SCS sediment. Certain marine diatoms might be the source of 1,14-C28.30 diol in inshore sediment, but the biological source of diols and triols in the SCS sediment requires further investigation.展开更多
Due to the importance of the Gloeocapsomorpha Prisca(G.prisca)-enriched source rocks,which belong to Kukersite-type source rocks in the Lower Paleozoic Ordovician strata,it has received great attentions during the pet...Due to the importance of the Gloeocapsomorpha Prisca(G.prisca)-enriched source rocks,which belong to Kukersite-type source rocks in the Lower Paleozoic Ordovician strata,it has received great attentions during the petroleum exploration as to whether there are the Kukersite-type source rocks developed in the major hydrocarbon source strata of the Upper and Middle Ordovician in the Tarim Basin.Using pyrolysis-gas chromatography-mass spectrography to analyse kerogens from source rocks in the limemud mound with moderate maturity,study reveals that there are the Kukersite-type source rocks in the Ordovician strata of the Tarim Basin.The pyrolysis products showed a low content of>n-C19normal alkanes with a significant odd-even predominance between n-C13and n-C17,long-chain alky substituted alkylbenzene and alkylthiophene isomers and distinctive distribution of 5-Nalkyl-1,3-Benzenediol and its homologous.Based on the geographic environment characteristics of G.Prisca,the molecular distributions of crude oil from the Lower Paleozoic petroleum systems in the Tarim Basin and characteristics of kerogen pyrolysis products from the Middle and Upper Ordovician source rocks,the results suggested that it is less possible to develop the G.Prisca-enriched Kukersite-type source rocks in the major hydrocarbon source rocks in the Middle and Upper Ordovician strata in the Tarim Basin.However,the benthic macroalga and planktonic algae-enriched source rocks are the main contributors.展开更多
文摘异戊二烯类甘油二烷基甘油四醚脂类化合物(isoprenoid Glycerol dialkyl glycerol tetraethers,isoGDGTs)在海洋奇古菌(Thaumarchaeota)中广泛存在,其结构对温度变化的敏感性使其成为广受欢迎的古气候与古温度重建材料。在北冰洋和西太平洋气候以及黑潮等多种因素的影响下,冲绳海槽中部成为研究全新世以来古海洋和古气候变化的天然实验室。本文通过研究C14柱状沉积物的GDGTs组成、含量变化特征及其延伸的86个碳原子的四醚指标(tetraether index of tetraethers consisting of 86 carbons,TEX86H),分析冲绳海槽中部的GDGTs来源,并定量计算C14柱状沉积物记录的海洋表面温度(seasurfacetemperature,SST),从而探讨8.2ka以来冲绳海槽中部古温度变化的驱动机制。通过甲烷指数和支链/异戊二烯类指标等,我们确认isoGDGTs主要来自于氨氧化古菌,适用于古温度重建。距今8.2ka以来,TEX86H SST的变化范围是21.6~27.2℃。冲绳海槽中部SST主要受到西热带太平洋、低纬度冬季日晒量的影响;TEX86H指标记录的温度上升趋势与东亚夏季风强度的减弱不一致。7.4—6.6ka冷事件广泛存在于冲绳海槽的SST记录中,但只在TEX86H数据中显示较大幅度的降低(~5℃),我们推测可能受到Kikai-Akahoya火山灰(~7.3ka)的影响。
基金supported by Qingdao National Laboratory for Marine Science and Technology(No.QNLM2016ORP0210)the NSF of China(No.41473080 and 41673029)
文摘Four massive brecciated, chimney-like, and slender pipe network carbonate samples(JA-4, JA-5, JX-8 and BG-12) were collected from southwestern Taiwan, which were suggested to have formed as a result of anaerobic oxidization of methane(AOM). Considering that the environmental conditions of the carbonates precipitation and the sources of carbon and organic matter need to be further declared, molecular fossils and compound-specific carbon isotopic investigations of the carbonates were conducted in this study. According to lipid biomarkers of 2,6,10,15,19-pentamethyleicosane(PMI) and squalane diagnostic to methanotrophic archaea, as well as the extremely low δ^(13)C values(as low as -1^(13).4‰) detected in samples JA-4, JA-5 and JX-8, these carbonates were revealed to be a result of AOM. Based on the varied δ^(13)C values of characteristic archaea biomarkers in specific samples, biogenic methane was proposed to be responsible for the formation of samples JA-4 and JA-5, whereas a mixed carbon source of ^(13)C-depleted methane and ^(13)C-enriched residual CO_2 from methanogenesis was suggested for the carbonate of JX-8 due to the co-occurrence of a highly positive δ^(13) C_(carb) value(+8‰) and a moderate ^(13)C depletion of PMI. The low content of AOM-related biomarkers and the absence of indicators for ANME-2 suggested that these carbonates were formed in weak seep settings. By comparison, no typical lipid biomarkers for methanotrophic archaea was detected in carbonate BG-12. The short-chain and long-chain n-alkanes accounted for 30% and 45% of all hydrocarbons, respectively, with a CPI value of 1.2, suggesting that the n-alkanes were derived from both marine organisms and terrestrial inputs. A low thermal maturity could be revealed by the incomplete equilibrium value of the C^(31)αβ 22S/(22S+22R) ratio(0.5), and the carbonate BG-12 was probably deposited in a suboxic condition indicated by a value of Pr/Ph ratio(2.5).
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-JC102)National Basic Research Program of China (2011CB808800)
文摘U-bearing sandstones from the Dongsheng deposit in Ordos Basin contain abundant C15-C18 fatty acids. The fatty acids may have been derived from modern and ancient organisms including organisms from the intervals of U mineralization. A certain amount of i15:0, a15:0, a17:0 fatty acids coexist with small amounts of i17:1ω7c and 10me16:0, characteristic biomarkers of Desulfovibrio and Desulfobacter sp., respectively. This indicates the existence of sulfate-reducing bacteria (SRB) in the sandstones. The presence of sulfur-oxidizing bacteria (SOB), such as Beggiatoa and Thioploca, is indicated by significant amounts of 16:1ω7c and 18:1ω7c fatty acids. The existence of the SRB in the deposit, as inferred from the fatty acids, is consistent with results from fossilized microorganisms and isotopic compositions of ore-stage pyrite. This suggests that the environment may have been favorable for the SRB to grow since ore formation (9.8-22 Ma). The bacteria may have degraded hydrocarbons directly, or indirectly utilized hydrocarbons degraded by oxic microbes in the deposits. This process may have produced 12C-rich calcite and prominent baseline humps of unresolved complex mixtures (UCM), and 25-demethylated hopanes and tricyclic terpanes. The existence of sulfur-oxidizing bacteria and sulfate-reducing bacteria in the deposit may have resulted in bacterial sulfate reduction to sulfide, re-oxidization of the sulfide to sulfate and subsequent reduction of the sulfate to sulfide. This assertion is supported by ore-stage pyrite with δ34S values as low as-39.2‰, and the lightest sulfate (about 11‰) measured during the Phanerozoic, a difference of more than 46‰.
基金In addition,gratitude is expressed to the National Natural Science Foundation of China(Grant Nos.41303067,41103043&41273022)Funds of Chinese Academy of Sciences for Key Topics in Innovation Engineering(Grant No.KGZD-EW-301)+2 种基金State Key Laboratory of Organic Geochemistry Open Research Fund(Grant No.OGL-201209)CNPC-CAS Science and Technology Cooperation Project(Grant No.2015A-4813)the international partnership project team of Innovation of the Chinese Academy of Sciences for providing financial support
文摘After the detection of the 1,20,21-C29 long-chain triol in some sediments and freshwater pteridophytes, in this study a new homologous long-chain triol, 1,3,4-C27-29, is detected for the first time in the Site4B core sediment in the northern South China Sea. The hydroxyl location and length of the carbon chain of this newly discovered triol differ from those of 1,20,21-C29 triol. The test results of its molecular distribution and individual carbon isotope reveal that 1,3,4-C29triol has a good correlation with n-C26-30 even carbon-numbered long-chain fatty alcohols, with R2 （n=68） values of 0.905, 0.929 and 0.903, respectively, and its carbon isotope composition, at -32.3%o_1.9%o, is similar to that of rt-C26.30, at -29.13%o^0.87%o, -32.98%o^1.28%o, and -32.98%o^1.28%o. 1,3,4-C29 triol from the Site4B core sediment and terrigenous long-chain fatty alcohol （n-C26.34） show highly consistent distribution trends in the entire section; thus, the former could serve as a proxy indicator of the terrigenous input. Considering that the 1,20,21-C29 triol in previous research belongs to Azolla, which are fresh water pteridophytes, the 1,3,4-C27-29 triol identified in this study might have similar biogenetic derivation. Thus, determination of its biogenic area and growing environment could provide potential organic geochemical evidence supporting the terrigenous input and source in the northern South China Sea.
基金the National Natural Science Foundation of China(Grant Nos.41303067,41103043&41273022)the Chinese Academy of Sciences Knowledge Innovation Project(Grant No.KGZD-EW-301)the PetroChina-Chinese Academy of Sciences Science and Technology Cooperation Project(Grant No.2015A-4813)
文摘This study investigated the composition of long-chain alkyl diols, triols, sec-alcohols, hydroxyl acids, and other hydroxylated compounds in Azolla imbricata and compared the organic alcohol components of Azolla filiculoides, Azolla microphylla, and South China Sea （SCS） sediments in order to investigate the possible indication of Azolla being the biological source of diols and triols in SCS sediment. Large amounts of diols, monohydroxy acids, and sec-alcohols with internal hydroxy groups at ω20 were detected in the three types of Azolla. Among these, 1,ω20-diol and ω20-hydroxy acid exhibited strong even-odd predominance distribution, whereas co20-sec-alcohol exhibited strong odd-even predominance distribution. In addition, small amounts of diols, triols, and dihydroxy acids with internal hydroxy groups at 9, 10 or ω9, ω 10 were detected, among which the chain length of C29 was predominate. Compounds having similar structures as those in Azolla reflected a similar biosynthetic pathway： ω20-hydroxy acid exhibiting even-odd predominance distribution is decarboxylated to ω20-sec-alcohol exhibiting odd-even predominance distribution and converted to 1, ω20-diol with even-odd predominance distribution by acyl reduction; ω9,ω10-hydroxy acid is converted to 1,20,21（1, ω9, ω10）-triol by acyl reduction, and then converted to 9,10-diol by hydrogenation and dehydration. The alcohol components in A. imbricata were clearly not the biological source of 1,13/1,14/1,15-C28, 30, 32 diols and 1,3,4-C27.29 triols in the SCS sediment. Certain marine diatoms might be the source of 1,14-C28.30 diol in inshore sediment, but the biological source of diols and triols in the SCS sediment requires further investigation.
基金supported by the National Oil and Gas Special Fund of China(2011ZX05008-002-15)the National Natural Science Foundation ofChina(41172112)
文摘Due to the importance of the Gloeocapsomorpha Prisca(G.prisca)-enriched source rocks,which belong to Kukersite-type source rocks in the Lower Paleozoic Ordovician strata,it has received great attentions during the petroleum exploration as to whether there are the Kukersite-type source rocks developed in the major hydrocarbon source strata of the Upper and Middle Ordovician in the Tarim Basin.Using pyrolysis-gas chromatography-mass spectrography to analyse kerogens from source rocks in the limemud mound with moderate maturity,study reveals that there are the Kukersite-type source rocks in the Ordovician strata of the Tarim Basin.The pyrolysis products showed a low content of>n-C19normal alkanes with a significant odd-even predominance between n-C13and n-C17,long-chain alky substituted alkylbenzene and alkylthiophene isomers and distinctive distribution of 5-Nalkyl-1,3-Benzenediol and its homologous.Based on the geographic environment characteristics of G.Prisca,the molecular distributions of crude oil from the Lower Paleozoic petroleum systems in the Tarim Basin and characteristics of kerogen pyrolysis products from the Middle and Upper Ordovician source rocks,the results suggested that it is less possible to develop the G.Prisca-enriched Kukersite-type source rocks in the major hydrocarbon source rocks in the Middle and Upper Ordovician strata in the Tarim Basin.However,the benthic macroalga and planktonic algae-enriched source rocks are the main contributors.
