古海洋研究中的地球化学新指标

有机地球化学与微量元素地球化学古环境指标及其相关的同位素指标已成为追溯古全球变化与古海洋生物地球化学演化的有力工具。从古环境替代指标的示踪原理和应用的角度，综述了有孔虫碳同位素、有机地球化学整体指标、生物标志化合物、单体有机分子同位素、微量元素等在古海洋古环境研究中的应用及相关的研究动态与进展。指出古海洋研究正从以恢复古海洋的物理参数（温度、盐度、古洋流等）为主，向着揭示古水团演化、古生产力、古营养状况、碳贮库及碳循环等古生物地球化学演化过程方向纵深发展。     

陆相盆地古生产力研究现状

古生产力是指地质历史时期生物在能量循环过程中固定能量的速率。陆相盆地古生产力的研究包括古生产力的大小及其组成研究两个方面。目前主要通过有机碳、生物硅和生物标志化合物等指标来评估陆相盆地古生产力的大小;通过生物标志化合物指标,包括正烷烃、萜类、甾类分子标志化合物等指标来研究陆相盆地古生产力的组成。陆相盆地古生产力的定量化研究比较欠缺,仅在有机碳、生物硅及生物标志化合物指标方面建立了数学模型,且多是对海相盆地古生产力指标的直接沿用;而在色素、湖相碳酸盐等具陆相特点的指标方面仅见部分定性研究。在地学应用方面,以陆相盆地古生产力研究为基础的地球生物学方法,在正演陆相烃源岩的形成过程研究中具有良好的前景。     

有机碳和有机分子碳同位素的地球化学意义

有机碳和有机分子碳同位素组成的研究不仅在沉积地层对比，油－油，油－源对比研究方向发挥了独特作用，而且在古气候，古环境研究方面更具有广阔的应用剪影。开展对全球气候变化及全球碳循环有重要意义的有机碳碳同位素组成及分布研究和对生物演化，恢复古生态，古环境有重要意义的化石及沉积物中有机分子的碳同位素成及分布研究已势在必行。     

蓟县剖面元古宙沉积物(1.8～0.85Ga)中的生物标志化合物特征

报道了蓟县剖面长达 10亿年的元古宙沉积物中生物标志化合物的组成和分布特征。结果表明 ,剖面样品具有基本类似的生物标志化合物组成 ,其中 ,特征的长链类异戊二烯化合物 ( >C2 0 )可能起源于元古宙燕山古海中的喜盐等古细菌 ,而 18 和 19 降松香 8,11,13 三烯则可能具有藻类起源。通过对生物标志化合物的组成分布特征与剖面各期古环境和古生物资料的对比 ,从分子的角度确证了古燕山盆地在其元古宙演化的各个时期环境与生物群落的转变     

南海北部17937岩心四万年来古环境变化的分子有机地球化学记录

以分子有机地球化学为手段对南海北部四万年来的古环境古气候研究表明, U₃₇k’-SST表层水温在冰期、间冰期平均范围分别为27℃和24℃, LGM与全新世温差达4.5℃; 以高分子量烷烃所代表的陆源物质输入和长链不饱和酮化合物所代表的海洋初级生产力都呈现冰期高、间冰期低特征, 表明冰期时陆源物质输入的增加和海洋表层生产力的提高; 正构烷烃C₃₁/C₂₇记录了南方大陆的植被由冰期时草本植物占优势向间冰期时木本植物占优势的转变.说明南海在末次冰期以来气候的不稳定性, 和海陆生态系统对气候变化的响应以及分子有机地球化学在古环境古气候研究中的巨大潜力.      

湖相沉积物有机地球化学在古环境研究中的应用

湖相沉积物中的有机质蕴含着丰富的地球化学信息,是古环境研究中必要的基础资料之一。文章综述了近年来湖相沉积物有机地球化学在古环境研究中的应用,结果表明:1在应用有机地球化学信息探讨古环境时,首先要根据有机质组成特征区分其来源,不同来源的有机质,其地球化学特征存在差异;2有机质碳同位素(δ13Corg)是研究古气候变化的常用指标,在区分暖湿、暖干、冷湿、冷干气候类型时需结合沉积物中总有机质丰度(TOC)、总有机氮丰度(TN)、自生碳酸盐氧同位素(δ18O)等资料;3脂肪酸不饱和度可作为恢复古环境温度的定性指标,UK37和UK37'在定量恢复古湖水表层温度中有较好的应用效果,TEX86有望应用在古湖水表层温度的重建;4生物标志化合物可较好地区分沉积物中有机质的来源、沉积水体的盐度及氧化还原性。可见,有机地球化学是研究古环境常用且有效的技术手段,多项有机地球化学参数相互验证能够更精确地重建古环境并预测其演化趋势。     

泥炭分子化石单体碳氢同位素的古气候意义

为了查明泥炭分子化石记录的古植被状况与古植物学分析结果的差异，并进一步探讨这些分子化石所记录的古气候信息，本文利用气相色谱仪(CC)、气相色谱—质谱联用仪(GC—MS)、气相色谱—燃烧-同位素比质谱仪(GC-C-IRMS)、气相色谱-热转换—同位素比质谱仪(CC—TC—IRMS)详细分析了一个40cm(约220年)长的泥炭岩芯中的分子化石及其单体碳、氢同位素组成。正构烷烃分子化石的主峰化合物(C23)及其碳、氢同位素组成与温度有很好的对应关系，工业革命以来化石燃料的燃烧效应也在单体碳同位素上反映出来。这些结果反映了泥炭分子化石具有很好的古气候和古环境意义。     

应用生物标志化合物参数判识古沉积环境

本文应用分子有机地球化学方法研究了中国陆相沉积盆地22个代表性样品,试图确认陆相沉积物的古环境。样品包括白垩纪至第三纪的油页岩、页岩、泥岩和芒硝。根据地质和地球化学资料判断,所研究的样品均为湖相沉积物。按盐度可划分为淡水、半咸水或淡水和高盐度水或咸水三种环境的沉积物。对沉积样品抽提物的脂肪烃组分进行了色谱分析和色谱-质谱分析,并在质量色谱图上测得无环烷烃和环烷烃化合物的相对丰度及有关参数。     

中元古界沉积物中典型分子标志化合物及其地质意义

分子标志化合物在前寒武纪古海洋生命演化和古环境的研究中发挥着越来越重要的作用。在华北克拉通宣隆坳陷中元古界下马岭组黑色页岩中检测到一系列典型分子标志化合物,其特征表现为明显的“UCM”鼓包,高丰度的甲基支链烷烃、C₂₄四环萜烷、C₁₉-C₂₀13β（H）,14α（H）-三环萜烷、13α（正烷基）-三环萜烷系列以及四类重排藿烷化合物,甾烷系列化合物的缺失,其组成特征及其地质意义明显不同于显生宙沉积物。甾烷系列化合物缺失可能是异养微生物转化和降解的结果,不能否定真核藻类在14亿年前古海洋的局部繁盛,但生物群落仍以原核生物为主。     

第九届“侯德封矿物岩石地球化学青年科学家奖”简讯

20 0 2年 6月 2日 ,经中国矿物岩石地球化学学会第九届“侯德封矿物岩石地球化学青年科学家奖”评选委员会评审 ,共评选出 6名获奖人。中国地质大学地球科学学院谢树成教授榜上有名。谢树成请奖的项目是“生物标志化合物在全球变化研究中的应用”。其主要学术成就如下。 1从青藏高原海拔 70 0 0 m的雪冰中检测出系列痕量有机分子 ,这些分子不仅灵敏地记录了人类活动的污染物 ,而且证实了青藏高原夏季风和冬季风的活动 ,以及雪冰这一全球变化重要载体中的有机分子所具有的古气候意义。 2确立了泥炭中某些有机分子的单体氢同位素值与古温度有…     

Biomarker Compounds as Indicators of Paleoenvironments

In an attempt to assess the paleoenvironments of terrestrial sediments,some twenty-two representa-tive Chinese non-marine sediment samples were studied using the molecular organic geochemistry method.The sediment samples stuied include oilshale,shale,mudstone and glauber salt from Tertiary to Cretaceous in age.Judging from geological/geochemical data and paleosalinity data,the samples studied are of lacustrine sedimentary origin and can be divided into three different types:fresh water,brackish and saline/hypersaline lake sediments.The aliphatic fractions were separated from the extracts of the samples and analysed by means of GC and GC/MS instruments,giving a number of parameters such as relative abundances of alkanes and cycloalkanes as shown in the mass chromatograms.     

Tertiary deltaic and lacustrine organic facies: comparison of biomarker and kerogen distributions

Biological marker and kerogen compositional data in Tertiary deltaic and lacustrine settings were compared and contrasted. The two settings are represented by (a) coals and organic-carbon-rich shales in a ick deltaic sequence from the Far East, constituting three distinct organic facies, and (b) humic coals and spropelic oil shales in a restricted intermontane (freshwater) lacustrine sequence from western Montana (U.S.A.), constituting two distinct organic facies. Wedistinguish the organic facies in each depositional setting by systematic differences in gross compound class distributions, kerogen and infrared spectral characteristics, molecular character of pyrolyzates, sterane carbon number distribution and sterane/hopane ratios. The kerogens of the three deltaic organic facies are characterized by varying quantities of vitrinite, resinite, sporinite, cutinite and fluorescent amorphinite. Triterpane distributions reveal numerous terrigenous compounds, including oleanane, oleanenes and unidentified C₃₀ (presumably) resin-derived components. The two organic facies of the freshwater lacustrine setting are distinguishedased upon either a vitrinite or an alganite/fluorescent amorphinite predominance in the kerogen. Numerous characteristics facies-related markers are also present, including dehydroabietane (land plant resins) and 4-methylsteranes (perhaps from freshwater dinoflagellate input). The available molecular and petrographic data are evaluated, and characteristics are proposed for distinguishing five organic facies of these two depositional settings. The successful simultaneous use of molecular geochemistry and organic petrography in this study provides a format for refining the organic facies concept.     

北部湾盆地沟鞭藻类分子化石的分布及成因

北部湾盆地流沙港组二段湖相烃源岩是盆地的主力烃源岩,其中检测到甲藻甾烷和三芳甲藻甾烷,以及丰富的4-甲基甾烷等重要分子化石。通过对北部湾盆地北部地区古近系流二段烃源岩的元素地球化学和有机地球化学特征等分析,研究了富有机质页岩的古氧化还原条件和古盐度,并进行甾类生物标志物对比,探讨了甲藻甾烷,三芳甲藻甾烷和C₃₀-4-甲基甾烷分布特征及其与沟鞭藻的成因关系。研究结果表明:流二段底部富有机质页岩中的C₃₀-4-甲基甾烷和三芳甲藻甾烷丰度呈负相关关系,表明弱还原的淡水—微咸水沉积条件可能不适宜甲藻甾烷和三芳甲藻甾烷的形成,而可以形成高丰度的C₃₀-4-甲基甾烷。油页岩中高丰度的C₃₀-4-甲基甾烷与其较高的成熟度有密切的关系。     

Organic geochemical studies of a Messinian evaporitic basin, northern Apennines (Italy)—II Isoprenoid and n-alkyl thiophenes and thiolanes

Series of n-alkyl and isoprenoid thiophenes and thiolanes, most of which have not been previously reported, have been identified in an extract from a Messinian (Upper Miocene) marl layer deposited under hypersaline, euxinic conditions. The identifications were based on mass spectra and Chromatographic data of synthesized reference compounds and on comparison of mass spectra, relative retention times and response on the FPD. Their specific structures and their distribution patterns show similarities with those of the alkanes. Inorganic sulphur is therefore considered to be incorporated into specific lipid moieties from (archae)bacterial and/or algal input during diagenesis. A biosynthetic origin of these compounds is also possible, however. The organic sulphur compounds encountered are thought to be indicators of a hypersaline depositional environment.     

Baccharane (18,19-secolupane): A rare triterpenoid skeleton widespread in Triassic sediments and petroleum from the Adriatic Basin

Baccharane (18,19-secolupane) 1, a triterpenoid skeleton seldom encountered in living organisms, has been characterized together with 17βH-des-E-lupane 2, one of its minor degradation products, in Italian Triassic sediment and crude oil samples from the Adriatic Basin by synthesis of standards.Reports of baccharane-derived triterpenoids in the field of natural products are scant and up to now restricted to terrestrial plants (angiosperms and ferns). In this regard, sedimentary baccharane derivatives may indicate a continental contribution (ferns?) to fossil organic matter; but they may also represent a contribution of as yet undetermined marine microorganisms, as has been proposed for dammarenes and dammaranes. Alternatively, they could be the bio/geochemical transformation products of biosynthetically closely related precursors such as lupane- or dammarane-type triterpenoids.The apparently restricted occurrence of baccharane derivatives in geological samples (up to now detected only in Triassic sediments of the Adriatic Basin) confers upon these compounds great value as correlation parameters and possibly as source indicators.     

加拿大阿萨巴斯卡地区Mildred泥炭柱脂类化合物的组成特征

利用气相色谱-质谱联用仪(GC-MS)系统地分析了阿萨巴斯卡地区Mildred泥炭柱37个样品的脂类化合物,研究了它们的组成特征及可能来源。结果表明,样品中检出的正构烷烃、正烷酮、正烷醛、正烷醇、脂肪酸和脂肪酸甲酯均由高碳数化合物构成,并具明显的奇碳或偶碳优势,GC-MS质量色谱图中甾类和萜类极性化合物呈现显著的高峰。根据泥炭分子地球化学分析,Mildred泥炭柱沉积有机质主要来源于原地堆积的高等植物,苔藓类、水生植物对泥炭有机质也有一定程度的贡献,其中松柏、杜鹃花科等木本植物、莎草科草本植物以及泥炭藓类是主要的成炭植物。萜类和甾类极性化合物的分布存在明显差异,萜类化合物主要集中于剖面的上部,其形成与泥炭藓类植物存在联系;甾类化合物来源不具专属性,多与高等植物的输入有关,也可能是受微生物的改造作用而形成。     

济阳坳陷古近纪沟鞭藻分子化石的分布与控制因素

济阳坳陷古近纪沟鞭藻化石十分丰富,沟鞭藻为有机质富集层的形成作出了重要贡献。三芳甲藻甾烷和甲藻甾烷是沟鞭藻及其祖先在古代沉积物中两种重要的存在形式,并且它们几乎专一性地由沟鞭藻提供。研究发现,沟鞭藻的不同属种,德弗兰藻属、多刺甲藻属、渤海藻类等,均可以提供丰富的三芳甲藻甾烷和甲藻甾烷,但是三芳甲藻甾烷和甲藻甾烷对沉积环境的变化具有不同的响应。在淡水、半咸水、咸水等不同水介质条件下,三芳甲藻甾烷指数稳定分布在0.50～0.96之间,高丰度的三芳甲藻甾烷与地层中丰富的沟鞭藻化石相一致,因而三芳甲藻甾烷是指示沟鞭藻输入的有效分子化石。甲藻甾烷的丰度与古沉积环境存在密切关系,高盐环境有利于甲藻甾烷的形成和保存,随着盐度的降低甲藻甾烷指数在0.04～0.74这样一个较大的范围内变化,其发育程度与有机质沉降过程中和成岩作用早期遭受的微生物降解作用有关,强烈的生物降解不利于甲藻甾烷的保存。     

Geochemical Characteristics of Crude Oils from Zao-V Oil Measures in Shenjiapu Oilfield

The geochemical characteristics of crude oils from Zao-V oil measures in the Shen-jiapu oilfield are systematically described in terms of the fractional composition of crude oils, GC characteristics of saturated hydrocarbon fraction of crude oils and the characteristics of their bio-markers. The deposifional environment, type and evolution of the biological source are also discussed. All pieces of evidence such as low saturated hydrocarbon fraction, high resin and asphalt, high isoprenoid alkane, weak odd-carbon number predominance ( CPI ranging from 1.23 to 1,29, OEP ranging from 1.14 to 1.16) and low sterane and terpane maturity parameters show these crude oils are immature oils. Low Pr/Ph ratios (0.66 -0.88) and high gammacer-ante/C31 hopane ratios ( 0.59 - 0.86 ) indicate the source rocks were formed in a slightly saline to brackish reducing lake depositional environment. Gas chromatographic characteristics of the saturated hydrocarbon fraction and the predominance of C30 hopane in terpane series and C29 sterane in sterane series indicate the biological source of the crude oils is composed mainly of bacterial and algal organic matter, and some algae are perhaps the main contributor of organic matter to the source rocks.     

辽河盆地煤系地层中特高含量的二萜类及其地质意义

从辽河盆地东部凹陷下第三系沙三段煤系烃源岩中检出了特高含量的海松烷,脱氢松香烷等三环二萜烷和扁枝烷等四环二萜烷类化合物,此外还检测到了奥利烯、乌散烯等罕见的三萜类。上述三类化合物尽管出现在同一套地层中,但它们的主要来源并不完全相同,其中三环二萜和四环二萜类分别以裸子植物和蕨类植物为主要来源,而五环三萜类则主要来源于被子植物。说明辽河盆地下第三系沙三段煤系地层中母质输入的多样性和复杂性。     

Organic geochemistry of impactites from the Haughton impact structure, Devon Island, Nunavut, Canada

Organic matter in impactites from the 24 km wide and 39 Ma old Haughton impact structure, Canadian High Arctic, is a mixture of fossil and modern biological components. The fossil component represents a conventional oil that was generated from Lower Palaeozoic marine source material before impact and permeates bedrock dolomites. Biomarker maturity parameters record the thermal effect of the mid-Tertiary impact. Maturity-influenced sterane, rearranged hopanoid, and triaromatic steroid ratios all increase towards the centre of the impact structure, where thermal alteration was greatest. The heating was probably dominated by an impact-related hydrothermal system, as such systems last long enough for kinetically-based thermal alteration to occur. Kinetically-related biomarker data suggest that the hydrothermal heating lasted for c. 5000 years. Biomarkers are also preserved in dolomite clasts within impact melt breccia, and indicate strong thermal alteration. Modern biological contamination of the rocks is responsible for the superposition of two geochemical signatures (which could be cyanobacteria, non-marine algae, or higher plant matter) onto the fossil component, but they can be recognized and distinguished. The data show that the impact structure system holds a record of both the pre-impact organic signature and the thermal signature of the impact, and thereby indicates that organic geochemistry is a valuable tool in documenting the response of rocks to impacts.