云南禄劝地区泥盆系油苗地球化学特征及地质意义

随着四川盆地海相常规天然气和页岩气勘探开发的成功,新区、新层系的油气勘探逐渐提上议程。云南地区泥盆系泥页岩在局部地区广泛分布,有机质丰度较高,但钻井工作很少,研究较为薄弱,油气富集情况不明。通过野外调查,在云南禄劝地区中泥盆统华宁组发现了液态油苗。有机地球化学分析表明:油苗与中泥盆统华宁组三段的泥灰岩亲缘关系较好;中泥盆统华宁组三段的泥灰岩整体沉积于强还原—还原环境,生烃母质主要为藻类等低等水生生物,也有来自高等植物的贡献,已处于成熟阶段,具有较强的油气生成能力,生烃能力与Ⅱ₁型烃源岩相当;康滇古陆西缘泥盆系泥灰岩有过生油气过程,生成的原油以饱和烃和芳香烃为主,且保存条件好的情况下,具有一定的页岩油气和常规油气勘探前景。      

热模拟实验中煤岩及壳质组饱和烃萜类系列化合物地球化学特征

通过对塔里木盆地煤岩与壳质组热模拟实验可溶有机物的色—质分析,煤岩和壳质组三环二萜烷具有低丰度、窄碳数（C19～C26）特征,且三环二萜烷主要来源于煤岩结构中具有三环萜骨架前身物的断裂释放。藿烷C31和C32-αβ22S/22（S+R）随着热模拟温度升高呈增加趋势,表明该地球化学参数是较好的热成熟度指标;αββ藿烷可以用来反映煤岩的热演化程度,且ββ构型向βα构型转化时需要一定能量;煤岩在未熟到成熟热演化过程中,藿烷具有ββ<βα<αβ的热稳定性。壳质组萜烷系列化合物的地球化学参数（以17β（H）三降藿烷、C29βα-藿烷、C31αβ22S/22（S+R））表明壳质组热演化史比煤岩有迟豫效应。      

Organic geochemistry in Precambrian research

Cherts, shales, and carbonates containing small amounts of organic matter occur throughout the Precambrian sedimentary record. The oldest known organic-rich sediments have been dated at > 3,000 million years. Knowledge of the composition, origin, and fate of the organic content of these rocks relates to many facets of Precambrian earth history. Apart from its primary paleobiological significance, organic geochemical research is also concerned with problems in atmospheric and hydrospheric evolution, sedimentation, diagenesis, metamorphism, and ore genesis.Precambrian organic geochemistry to date has rested on the premise that ancient life process can be profitably studied at a chemical level, as well as by examination of the morphological fossils of conventional paleontology. A decade of intensive research on selected Precambrian carbonaceous and bituminous sediments has been made possible by the refinement of analytical techniques (notably gas chromatography and mass spectrometry) which are now capable of detecting and characterizing the minute quantities of complex organic mixtures found in geological materials. It has resulted in the development of criteria which allow discrimination between indigenous and adventitious organic matter. A diverse array of stable organic compounds has been isolated from Precambrian sedimentary rocks. The compounds, termed chemical fossils, are thought to be derived from ancestral microorganisms and as such have contributed to the formulation of the biological marker concept. Despite reports of possible abiotic occurrences, a biological origin for most of the organic matter preserved in Precambrian rocks (whether sedimentary or metamorphic) now appears likely.The possibility of secondary emplacement from migrating formation fluids means that an indigenous chemical fossil need not have been syngenetic with the deposition of its host sediment. No conclusive test of Precambrian age as yet exists for these compounds. The bulk of the organic material (kerogen) in Precambrian rocks is insoluble in organic and aqueous solvents. For this reason, kerogen is almost certainly both indigenous and syngenetic, but clarification of its chemical structure must await the development of new analytical procedures. The nature and extent of the modification that the soluble and insoluble organic fractions have undergone during late diagenesis and incipient metamorphism is still virtually unknown. Correlation of chemical fossils with specific biogenic precursor compounds, or a particular type of primitive organism, therefore remains equivocal. So also comparison of the organic geochemical facies of one sediment with that of another may be complicated by differences in their thermal history and mineralogy.Recent interest in the possible involvement of living and decayed microorganisms in the genesis of certain Precambrian Fe, U, Au, Cu, Pb, and Zn metal deposits signals the beginning of an important new phase in organic geochemical studies.     

Organic geochemistry of Recent equatorial deltaic sediments

The organic matter of recent deltaic sediments cored in the Mahakam delta, East Kalimantan, has been studied before and after physical fractionation into sands >50 μm, silts 5–50 μm and clays <5 μm. Both the lipid and non-lipid components have been investigated.Weight, carbon and nitrogen fractionation budgets were used to define three types of samples, depending on coarse particle contributions to the total amount of organic matter: a = a first type with more than 50% of the O.M. in the coarse particles, high C/N ratios and O.M. content, b = an intermediary type with medium C/N ratios and O.M. content, each fraction having quite the same O.M. content, c = a third type with less than 5% of the whole O.M. in the sands and the lowest C/N ratios and O.M. content.Concerning the global organic characteristics of the fractions, a systematic increase of C/N ratios occurs when going from clays to sands; the finer the fraction is, the more nitrogenous the compounds are. This enrichment in nitrogen is related to a persistent high rate of hydrolysable material either for argillaceous organic matter-poor sediments or for the clay fractions of all types of samples. Conversely, the type (a) coarse sediments, in particular the sandy components were resistant to acid hydrolysis with burial.Concerning the geochemical markers signatures of granulometric fractions, the distribution patterns of n-alkanes and n-fatty acids are characterized by the predominance of high molecular weight compounds >C₂₂. Carbon preference index (CPI) values are higher in the sands and silts, reflecting their enrichment in continentally-derived vegetation debris. For type (c), the fractionation revealed markers of microbial activity within the clay fractions. For all types of samples, we observed an increase with burial of the n-alkane and n-fatty acid concentrations, particularly in the clay fractions, suggesting possibly a better preservation and/or affinity of lipids with the finest fractions.     

Organic Geochemistry of Lead—Zinc Polymetallic Dposits,Northern Guangdong

The characters of organic matter in rocks and ores in the Fankou and Dabaoshan deposits are systematically studied with regard to their implications for mineralization.The results show that kerogens in this area faaa mainly into the plutonism field in Van Krevelen‘s diagram.Reflectivity of the organic substance was measured to be 3.06%(Fankou)and 1.67%(Dabaoshan),corresponding to the paleo-geotemperatures of 232℃ and 184℃ respectively.The same types of porphyrins and hydrocarbons were recognized in the rocks and ores and hydrocarbon-bearing inclusions are widespread in quartz and calcite,particularly in Dabaoshan,It is thought that the orgain matter must have played a critical role in diagenesis and metallization in these deposits and that the hydrothermal solution was most likely to be the type of water-oil hot brine.     

Application of organic petrology and geochemistry to coal waste studies

Coal wastes produced during mining activities are commonly deposited in nearby dumps. These wastes mostly composed of minerals and variable amounts (usually 20-30%) of organic matter start to weather immediately after deposition. Oxidation of the organic matter can lead to self heating and self combustion as a result of organic and mineral matter transformations. The degree of alteration depends on the properties of the wastes, i.e., the maceral and microlithotype composition of the organic matter and its rank.Alteration of wastes also depends on the heating history, i.e., the rate of heating, final heating temperature, duration of heating, and the degree of air access. Although air is probably necessary to initiate and drive the heating processes, these usually take place under relatively oxygen depleted conditions. With slow heating, color of organic matter particles changes, irregular cracks and oxidation rims develop around edges and cracks, and bitumen is expelled. As a result, massive and detritic isotropic and strongly altered organic matter forms. On the other hand, higher heating rates cause the formation of devolatilization pores, oxidation rims around these pores and along cracks, vitrinite-bands-mantling particles, and bitumen expulsions.Organic compounds generated from the wastes include n-alkanes, iso-alkanes, alkylcyclohexanes, acyclic isoprenoids, mainly pristane, phytane and, in some cases, farnesane, sesquiterpanes, tri- and tetracyclic diterpanes, tri- and pentacyclic triterpanes, and steranes, polycyclic aromatic hydrocarbons (mostly with two- to five rings, rarely six rings), and phenols. The compounds formed change during the heating history. The fact that phenols are found in dumps where heating has not yet been completed, but are absent in those where heating ceased previously suggests the presence of water washing. The organic compounds formed may migrate within the dumps. However, when they migrate out of the dumps, they become a hazard to environment.This paper is a review on transformations of organic matter (both maceral composition and reflectance and chemical composition) in coal wastes deposited in coal waste dumps. Immediately after deposition the wastes are exposed to weathering conditions and sometimes undergo self heating processes.     

Organic geochemistry of the Vindhyan sediments: Implications for hydrocarbons

The organic geochemical methods of hydrocarbon prospecting involve the characterization of sedimentary organic matter in terms of its abundance, source and thermal maturity, which are essential prerequisites for a hydrocarbon source rock. In the present study, evaluation of organic matter in the outcrop shale samples from the Semri and Kaimur Groups of Vindhyan basin was carried out using Rock Eval pyrolysis. Also, the adsorbed low molecular weight hydrocarbons, methane, ethane, propane and butane, were investigated in the near surface soils to infer the generation of hydrocarbons in the Vindhyan basin. The Total Organic Carbon (TOC) content in shales ranges between 0.04% and 1.43%. The S₁ (thermally liberated free hydrocarbons) values range between 0.01–0.09 mgHC/gRock (milligram hydrocarbon per gram of rock sample), whereas the S₂ (hydrocarbons from cracking of kerogen) show the values between 0.01 and 0.14 mgHC/gRock. Based on the T_max (temperature at highest yield of S₂) and the hydrogen index (HI) correlations, the organic matter is characterized by Type III kerogen. The adsorbed soil gas, CH₄ (C₁), C₂H₆ (C₂), C₃H₈ (C₃) and nC₄H₁₀, (nC4), concentrations measured in the soil samples from the eastern part of Vindhyan basin (Son Valley) vary from 0 to 186 ppb, 0 to 4 ppb, 0 to 5 ppb, and 0 to 1 ppb, respectively. The stable carbon isotope values for the desorbed methane (δ¹³C₁) and ethane (δ¹³C₂) range between −45.7‰ to −25.2‰ and −35.3‰ to −20.19‰ (VPDB), respectively suggesting a thermogenic source for these hydrocarbons. High concentrations of thermogenic hydrocarbons are characteristic of areas around Sagar, Narsinghpur, Katni and Satna in the Son Valley. The light hydrocarbon concentrations (C₁–C₄) in near surface soils of the western Vindhyan basin around Chambal Valley have been reported to vary between 1–2547 ppb, 1–558 ppb, 1–181 ppb, 1–37 ppb and 1–32 ppb, respectively with high concentrations around Baran-Jhalawar-Bhanpur-Garot regions (Kumar et al., 2006). The light gaseous hydrocarbon anomalies are coincident with the wrench faults (Kota – Dholpur, Ratlam – Shivpuri, Kannod – Damoh, Son Banspur – Rewa wrench) in the Vindhyan basin, which may provide conducive pathways for the migration of the hydrocarbons towards the near surface soils.     

松辽盆地基底浅变质岩的有机地球化学特征

松辽盆地基底石炭-二叠系地层处于浅变质阶段.岩石有机地球化学分析表明,有机碳含量 0.05%～ 2.08%,氯仿沥青" A"含量 0.000 3%～ 0.002 9%, MAB抽提物含量 0.001 2%～ 0.002 8%, H/C摩尔比 0.10～ 0.52, Ro范围 2.98%～ 4.16%.随成熟度的增加,可溶有机质含量以及干酪根 H/C摩尔比降低.按岩石抽提物的正构烷烃分布和生物标志化合物的分布可把样品分为两类,第一类样品中正构烷烃分布呈偶碳优势,伽马蜡烷丰度高、 C28甾烷丰度高,反映高盐度环境菌、藻有机质的贡献;第二类样品中正构烷烃分布呈奇碳优势,伽马蜡烷丰度低、 C29甾烷丰度高,反映陆源植物为主要生源的沉积特征.     

Organic geochemistry of Oxfordian carbon-rich sedimentary rocks of the Russian plate

The lithology and geochemistry of upper Oxfordian sedimentary rocks enriched in marine organic matter (OM) have been studied. These rocks occur as a persistent unit of Upper Jurassic rocks exposed on the right bank of the Unzha River in the Kostroma district. The OM was investigated in detail in both the carbon-rich rocks and their hosts. It was established that the OMs from the Oxfordian rocks are characterized by a low degree of thermal (catagenetic) maturity and their geochemical signature reflects specific features of synsedimentary and early diagenetic processes. Kerogen in the carbon-rich sedimentary rocks is markedly enriched in S_org, and its formation was related to the early diagenetic sulfate reduction (sulfurization of the lipid fraction of the initial OM). The composition of kerogen from the host clay is sharply distinct in many parameters. No derivatives of isorenieratene were revealed in the aromatic fraction of bitumen in the carbon-rich rocks. The Oxfordian carbonaceous rocks are distinguished by slightly enriched in S, Mo, V, and Ni. Anoxic conditions were unstable in the water column during the deposition of carbon-rich sediments (such conditions were probably episodic). The C_org-rich unit formed due to a short-term abrupt increase in the productivity of phytoplankton related to eutrophication of water, probably, as a result of the recycling and redistribution of biophile elements.     

安徽南陵—无为地区二叠系烃源岩有机地球化学特征

通过系统的野外剖面测量和样品采集,运用岩石热解、有机碳测试、有机显微组分镜检、气相色谱-质谱等对采集的样品进行分析测试,综合评价南陵—无为地区二叠系碳酸盐岩、煤和泥岩露头样品的有机质丰度、类型和成熟度,并分析有机质的来源及沉积环境。研究结果表明:栖霞组、孤峰组、龙潭组为有利烃源岩发育层段。其中栖霞组有机质类型为Ⅲ型,孤峰组为Ⅱ2型,有机质演化程度均处于高成熟阶段;龙潭组有机质类型为Ⅱ1型,处于成熟阶段。栖霞组烃源岩形成于受陆源影响的碳酸盐台地环境;孤峰组烃源岩形成于较深水的低能陆棚环境;龙潭组烃源岩形成于有陆源输入的滨岸环境。     

Early Cretaceous anoxic basin of the Russian Plate: Organic geochemistry

Compositions of organic matter in the bituminous shale accumulated under anoxic conditions and in the underlying clay deposited in aerated basin are noticeably different. Organic matter (OM) of the clay is depleted in hydrogen and kerogen of the clay during pyrolysis produces 2.5 times less aliphatic hydrocarbons than kerogen, which is separated from the bituminous shale, and dozens of times less sulfurous compounds, such as thiophenes and benzothiophenes. Accumulation of OM in the clay was primarily related to the direct inheritance of polymeric lipid biochemical components of the initial OM and lignin included in the higher plants. Changes of gas regime in the basin and sediments, expressed in the origin of anoxic conditions during the accumulation of bituminous shales, intensified the early diagenetic sulfuration and the consequent formation of sulfur- and hydrogen-rich kerogen in the shales. At the same time, less stable lipids and, possibly, carbohydrates were also conserved.Translated from Litologiya i Poleznye Iskopaemye, No. 1, 2005, pp. 25–34.Original Russian Text Copyright 2005 by Bushnev.     

陕北侏罗纪富油煤有机地球化学特征

富油煤的有机地球化学特征对研究其形成时期的古沉积环境和演化过程具有重要意义。以陕北地区侏罗纪延安组6个主采煤层为研究对象,运用煤质分析和气相色谱–质谱联用方法分析其有机地球化学特征。结果表明:陕北地区延安组主采煤的氯仿沥青“A”含量较高,饱芳比较低;正构烷烃呈单峰型分布,中链饱和烃占优势,Pr/nC₁₇、Ph/nC₁₈、Pr/Ph的值较高;C₂₈和C₂₉的规则甾烷和重排甾烷占主导地位。分析表明:陕北地区延安组主采煤层处于低热–成熟阶段,为富氢基质镜质体和壳质组生油的有利阶段;有机质来源以陆生高等植物为主并有部分水生生物混入,形成于贫氧的泥炭沼泽环境,且经历了较强的生物降解作用,为富氢组分的形成提供了有利的条件。      

Organic geochemistry of the Dongsheng sedimentary uranium ore deposits,China

Organic matter (OM) associated with the Dongsheng sedimentary U ore hosting sandstone/siltstone was characterized by Rock-Eval, gas chromatography–mass spectrometry and stable C isotope analysis and compared to other OM in the sandstone/siltstone interbedded organic matter-rich strata. The OM in all of the analyzed samples is Type III with Ro less than 0.6%, indicating that the OM associated with these U ore deposits can be classified as a poor hydrocarbon source potential for oil and gas. n-Alkanes in the organic-rich strata are characterized by a higher relative abundance of high-molecular-weight (HMW) homologues and are dominated by C₂₅, C₂₇ or C₂₉ with distinct odd-to-even C number predominances from C₂₃ to C₂₉. In contrast, in the sandstone/siltstone samples, the n-alkanes have a higher relative abundance of medium-molecular-weight homologues and are dominated by C₂₂ with no or only slight odd-to-even C number predominances from C₂₃ to C₂₉. Methyl alkanoates in the sandstone/siltstone extracts range from C₁₄ to C₃₀, maximizing at C₁₆, with a strong even C number predominance, but in the organic-rich layers the HMW homologues are higher, maximizing at C₂₄, C₂₆ or C₂₈, also with an even predominance above C₂₂. n-Alkanes in the sandstone/siltstone sequence are significantly depleted in ¹³C relative to n-alkanes in most of the organic-rich strata. Diasterenes, ββ-hopanes and hopenes are present in nearly all the organic-rich sediments but in the sandstone/siltstone samples they occur as the geologically mature isomers. All the results indicate that the OM in the Dongsheng U ore body is derived from different kinds of source materials. The organic compounds in the organic-rich strata are mainly terrestrial, whereas, in the sand/siltstones, they are derived mainly from aquatic biota. Similar distribution patterns and consistent δ¹³C variations between n-alkanes and methyl alkanoates in corresponding samples suggest they are derived from the same precursors. The OM in the organic-rich strata does not appear to have a direct role in the precipitation of the U ore in the sandstone, but an indirect role cannot be excluded. The OM in the U hosting sandstone shows a relatively low hydrogen index, presumably due to oxidation or radiolytic damage.     

羌塘盆地石炭—二叠系烃源岩地球化学特征讨论

长期以来,羌塘盆地烃源岩的研究一直限于中生代地层,而对其古生代地层生烃能力一直缺乏系统研究。针对这一问题,本文选择羌塘盆地石炭—二叠系8条剖面的暗色泥岩及碳酸盐岩样品,对其从有机质丰度、有机质类型和热演化程度等方面进行了有机地球化学特征的分析。研究发现,石炭—二叠系可能烃源岩类型包括泥岩和碳酸盐岩两种,其分布总体上受沉积相的控制,碳酸盐岩烃源岩可能为局限台地相发育的泥晶灰岩,而泥质烃源岩主要为三角洲及斜坡相发育的暗色泥岩及凝灰质泥岩。石炭—二叠纪泥岩有机碳含量较高,具有较好生烃能力,大多达到烃源岩标准,尤其是刻莫石炭系剖面及贡日二叠系剖面,大多为中等—好烃源岩。碳酸盐岩有机碳含量总体比较低,为非烃源岩。石炭—二叠系碳酸盐岩烃源岩有机质类型为Ⅱ1型,泥质烃源岩有机质类型主要为Ⅱ2-Ⅲ型。石炭—二叠系烃源岩热演化程度总体较高,除盆地东部刻莫石炭系剖面处在成熟阶段外,大都处在高成熟—过成熟阶段,非常有利于天然气的生成,具备良好的天然气勘探前景。