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。      

川中地区大安寨段分子标志物异常组合及其地球化学意义

在川中地区大安寨段烃源岩抽提物中检测出丰富的重排藿烷系列、重排补身烷系列、重排甾烷系列及C26+长链三环萜烷系列的分子标志物组合.结合烃源岩的有机质来源、沉积环境、热演化程度特征,探讨上述甾烷、萜烷分布特征指示的地质地球化学意义.结果表明:重排类化合物与C26+长链三环萜烷系列存在着某些相同的富集途径,重排藿烷系列富集...     

银根-额济纳旗盆地原油的发现及其主要地球化学特征

在银根－额济纳旗盆地东部查干凹陷和西部路井凹陷首次发现了轻质低硫成熟原油，其饱和烃含量在80％以上，非烃和沥青质含量低；饱和烃和芳烃成熟度参数表明它们均为成熟原油，其成熟度相当于镜质相反射率Ro0.8%-1.1%阶段，是生油高峰阶段的产物。原油全油碳同位素δ^13C值小于－31‰。生物标志物中类异戊二烯含量较高，植烷与姥鲛烷均势；查干凹陷原油三环萜烷含量高于五环萜烷，而路井凹陷原油三环萜烷含量相对较低；两原油中均含有较高的Ts,C29Ts,C30重排藿烷和伽马蜡烷，藿烷为主，C32以上升藿烷含量极低；孕甾烷含量较高，尤其是查干凹陷原油；甾烷中以C29甾烷为主，约占50％，C27和C28甾烷基本均势，异胆甾烷含量高于胆甾烷；重排甾烷含量低，甾烷的含量与萜烷含量相当，这些特征表明原油是典型的湖相原油，其主要的烃源岩是下白垩统湖相源岩而非侏罗系煤系烃源岩。     

黔北地区下志留统龙马溪组烃源岩生物标志物

应用气相色谱和色谱-质谱分析技术,对黔北地区下志留统龙马溪组烃源岩的甾烷和萜烷进行测试分析。结果表明,正构烷烃为后单峰型,主峰碳为C22～C30,Pr/Ph值为0.48～0.64,Pr/nC17为1.35～4.22,Ph/nC18为0.92～0.97。甾烷中,具孕烷系列的异常高值,C27、C28和C29呈规则甾烷"V"字型分布(C27C28C29),具明显的C27优势,甾烷/藿烷比值为0.57～0.71。萜烷类中具三环萜烷高值,低升藿烷,高伽马蜡烷指数特征。成熟度方面,OPE1,Ts/(Ts+Tm)分布在0.42～0.48之间,C3122S/(S+R)值为0.6～0.66,C29ββ/(ββ+αα)在0.56～0.58之间,反映出龙马溪期具明显的水体分层和高还原环境。有机质主要来源于浮游水生生物和藻类,并经历了一定的生物降解过程。烃源岩的热演化已进入高成熟-过成熟阶段。     

松花粉热降解甾族分子生物标志化合物及其热演化特征

松花粉热模拟实验饱和烃馏分中检出大量的甾族系列生物标志化合物,包括甾烯酮、甾烯、规则甾烷、异构化甾烷、重排甾烷、4-甲基甾烷及孕甾烷,芳烃馏分中还检出芳构化甾烷,从而提供了该类生物标志物植物花粉来源的直接证据.甾族化合物模拟温度150℃时开始断裂出来,250～350℃时达到排出高峰,400℃时含量急剧下降,500℃以后因强烈地热降解而无法检出. 250℃模拟样品中的甾族化合物以甾烯丰度最高,还检出了大量的甾烯酮和规则甾烷.它们都是以C29和C28两个碳数为主,且表现出C29>>C28的特点,每个碳数均以ααα20(R S)两种构型成对出现和相对丰度20R>20S为主要特征.300℃样品中检出C29重排甾烯,350℃时甾烯被大量还原,达到规则甾烷形成的高峰.400℃以后的样品除检出ααα(20R 20S)构型的生物甾烷外,αββ构型异构化甾烷可明显检出,而且也可检出相对丰度较高的C29和C28αβ重排甾烷.规则甾烷的ααα20R构型向20S构型的转化,也随热模拟温度的升高逐渐增强.450℃和500℃的高温模拟样品中检出了较明显的孕甾烷和甲基孕甾烷C21和C22.此外,松粉低温热模拟样品的芳烃馏份中检出单、三芳甾烷.     

银额盆地查干凹陷原油地化特征及油源对比

银额盆地东部查干凹陷首次发现轻质低硫成熟原油，其饱和径含量在90％以上，成熟度相当于镜煤反射率Ro1．0％左右，是生油高峰阶段的产物；原油全碳同位素δ^13C值－31．1‰。原油生物标志物中类异戊二烯含量较高，植烷与姥皖烷均势；三环萜烷含量高于五环萜烷；含有较高的TS C29、Ts、C30重排藿烷、伽马蜡烷；藿烷中以C50藿烷为主，C32以上升藿烷含量极低；孕甾烷含量高；甾烷中以C29甾烷为主，C27甾烷含量也较高，异胆甾烷含量高于胆甾烷；重排甾烷含量低；甾烷的含量与萜烷含量相当，是典型的湖相原油。已发现的天然气中甲烷含量达80％，为湿气。原油和源岩生物标志物组成特征分析对比表明下白垩统巴音戈壁组源岩是主要油源岩。生物标志物特征示原油具有一定的运移效应。     

塔里木盆地台盆区原油甾、萜烷浓度与热稳定性

对塔里木盆地台盆区未遭受生物降解的138个原油样品进行甾、萜烷定量分析,展示原油甾、萜烷浓度随成熟度变化特征。C23三环萜烷/(C23三环萜烷+C₃₀藿烷)值与甾、萜烷浓度图版显示各类甾、萜烷具有不同的热稳定性。依据热稳定性的差异将甾、萜烷分为3类:第1类包括Tm、C₂₉藿烷和C₃₀藿烷等五环三萜烷,随成熟度增高,这类化合物浓度降低较快,具有相对较低的热稳定性;第2类既包括Ts、C₂₉Ts和C₃₀重排藿烷等五环三萜烷,也包括C27和C₂₉规则甾烷各异构体,随成熟度增高,这类化合物浓度降低较慢,具有中等热稳定性;第3类包括C27重排甾烷、C21甾烷和C23三环萜烷,随成熟度增高,这类化合物浓度先增高、后降低,降低速率低于前2类化合物,表明其热稳定性相对较高。在常用的甾、萜烷成熟度指标中,Ts/(Ts+Tm)、C₂₉Ts/(C₂₉Ts+C₂₉藿烷)和C₃₀重排藿烷/(C     

鄂尔多斯盆地姬塬-西峰地区原油地球化学特征及油源分析

采用色谱-质谱(GC-MS)、裂解-色谱-质谱(Py-GC-MS)、色谱-同位素比值质谱(GC-IRMS)等方法,系统地分析了鄂尔多斯盆地南部姬塬与西峰地区原油的地球化学特征,重新确定了原油成熟度及对应源岩的形成环境.分析表明,单体碳同位素组成偏轻,介于-30‰～-33‰之间.原油饱和烃馏分中五环三萜烷含量较高;藿烷以C30藿烷占优势,C29藿烷次之;含较高的18α(H)-30-降新藿烷(C29Ts);C30重排藿烷和伽马蜡烷含量较低;规则甾烷含量高并以C29甾烷为主,含一定的孕甾烷、升孕甾烷和重排甾烷;芳烃馏分中富含萘、菲系列化合物;沥青质裂解产物中芳基类异戊二烯烃含量很低.原油成熟度相当于镜质组反射率0.82%左右,是烃源岩在生油高峰阶段的产物.油源分析表明,该区原油主要来源于三叠系长7段泥岩,有机质形成于水体较深、淡水湖相沉积环境.     

巢湖地区二叠系栖霞组和三叠系南陵湖组石灰岩生物标志物特征与生烃潜力——以平顶山和马家山剖面为例

对安徽巢湖地区平顶山和马家山剖面下二叠统栖霞组和下三叠统南陵湖组进行了地层沉积特征及暗色石灰岩生烃潜力的综合分析,并对这两个层位的样品进行了饱和烃生物标志物特征研究。结果表明,两个层位的石灰岩都属于有效烃源岩,均具有一定的生烃潜力。南陵湖组石灰岩饱和烃以高丰度的长链三环萜烷、重排藿烷、重排甾烷为特征,表明其形成于偏弱氧化的沉积环境。栖霞组沉积期水体能量相对较低,受陆源物质影响明显,栖霞组石灰岩萜烷系列为常规的分布模式,但其甾烷成熟度参数明显低于平衡值,认为高的热演化程度是造成栖霞组石灰岩20S/(20S+20R)-ααα-C29甾烷值和ββ/(ββ+αα)-C29甾烷值"倒转"的主要原因。     

松辽盆地梨树断陷原油高碳数三环萜烷分布特征及主控因素

对梨树断陷71个湖相原油样品的饱和烃和芳烃进行了气相色谱和色谱—质谱(GC-MS)分析,根据其生物标志化合物组合特征的差异将梨树断陷的原油划分为三种类型,不同成因类型的原油样品中三环萜烷的分布特征差异明显,其中Ⅰ类原油三环萜烷的浓度明显高于Ⅱ类原油,而Ⅱ类原油Σ三环萜烷/17α(H)-藿烷比值明显高于Ⅰ类原油,但不同类型原油中均存在较高含量的高碳数三环萜烷(C₂₈TT-C₂₉TT),其相对百分含量均高于低碳数三环萜烷(C₁₉TT-C₂₀TT、C₂₁TT、C₂₃TT)。从沉积环境、母质来源和成熟度三方面对高碳数三环萜烷的主控因素进行了探讨,结果表明,梨树断陷不同类型原油的母质来源都是以细菌及低等水生生物为主,(C₂₈TT-C₂₉TT)/17α(H)-藿烷与伽马蜡烷指数有一定的正相关性,说明偏还原性的咸水环境是高碳数三环萜烷富集的次要影响因素。就该研究区而言,Σ三环萜烷/17α(H)-藿烷比值与成熟度参数Ts/(Ts...     

Gas-solid molecular structure differences

Molecular geometries for a variety of classes of compounds are discussed. Where available, the structures of free molecules are compared with those in the crystal. Information inferred about intermolecular interactions are augmented with observations on structural consequences of dimerization and complex formation. Examples include substituted benzenes, sulfones, siloxane derivatives, metal halides, group four dihalides, tetrahaloaluminates, and donor-acceptor complexes.     

The molecular composition of ambers

Bulk (elemental composition, IR, CP/MAS ¹³C NMR) and molecular (GC-MS) analyses have been performed on a series of ambers and resins derived from different locations (Dominican Republic, Philippines, Canada, Israel, New Zealand, Chile) having diverse botanical affinities (Araucariaceae, Hymenaea) and variable age (from Holocene to Early Cretaceous). No major differences have been observed from the elemental composition and the spectroscopic data; however, the molecular analyses of the solvent extractable fraction show that a specific mixture of components is present in each sample. These are mainly diterpenoid products that in general are also found abundantly in the higher plants from which the ambers and resins originate. Nevertheless, a direct relationship between major terpenoid constituents in fossil resins and precursor plant materials can only be established for the younger samples.Irrespective of the geographical or botanical origin of the ambers and resins, several common age-dependent molecular transformation trends can be recognized: (1) progressive loss of olefinic bonds (especially those located in exocyclic positions), (2) decrease of functionalized products, and (3) increasing proportion of aromatized components. However, even in the samples of older age (Cretaceous) the degree of aromatization is very low when compared with that of other higher-plant related materials such as fossilized woods or low rank coals. This indicates that maturation must involve essentially olefin polymerization processes instead of extensive aromatization.     

The origin of giant molecular clouds

The parameters of molecular clouds formed via the Parker instability with dominant radiative losses are estimated. In this scenario, the cloud parameters (such as their mean densities and masses) should depend on galactocentric radius. This dependence is determined mainly by radial variations of the gas metallicity and the flux of heating radiation in the Galaxy. Due to the development of the interchange mode of the Parker instability, the angular momentum of the clouds will not necessarily be parallel to the galactic rotation axis.     

Methanol and other molecular tracers of outflows and dense gas in the molecular cloud G345.01+1.79

The results of SEST millimeter observations of the molecular cloud G345.01+1.79 are presented. Spectra of CH₃OH, SO₂, SiO, HCO⁺, C¹⁸O, C³³S, C³⁴S, HCN, and DCN lines have been obtained. Mapping of the cloud in CH₃OH, SiO, and C³⁴S lines indicates that the maximum integrated intensity in the SiO and C³⁴S lines and in low-excitation CH₃OH transitions coincide with the northern group of methanol masers, while the corresponding maximum for high-excitation CH₃OH transitions coincides with the southern methanol-maser group. The physical parameters are estimated from the quasi-thermal CH₃OH lines under the large-velocity-gradient approximation, and their distribution on the sky derived. The density and temperature are higher toward the southern group of methanol masers than in the northern group. This may indicate that star formation is in an earlier stage of evolution in the northern than toward the southern group. A maser component can be distinguished in 14 (of 71) CH₃OH lines. We have detected for the first time weak, probably maser, emission in the CH₃OH lines at 148.11, 231.28, 165.05, 165.06, and 165.07 GHz. A blue wing is clearly visible in the CH₃OH, SiO, C¹⁸O, and SO₂ lines. The emission in this wing is probably associated with a compact source whose velocity is characteristic of the CH₃OH maser emission in the southern group of masers.     

Applications of molecular fossils in lacustrine stratigraphy

Biomarkers, or the so-called molecular fossils, are used tentatively in the Eogene lacustrine stratigraphy study in the Jiyang Sub-basin. Notwithstanding the fact that unidentified microfossils or amorphism and acritarchae are widely distributed in lacustrine source rocks, molecular fossils are useful to identify the sources. It is helpful to reconstruct the palaeo-enviroment, palaeo-ecosystem and compartmentalize the stratigraphic sequence by using molecular fossils with which the existence and types of microbes including bacteria, archaea and certain algae can be identified.     

Calculation of molecular weights of humic substances from colligative data: Application to aquatic humus and its molecular size fractions

A rigorous mathematical expression for the dependence of colligative properties on acid dissociation of water soluble humic substances is presented. New data for number average molecular weights of a river derived humic material and its gel permeation Chromatographic fractions are compared with $\text{M}\text{?}{}_{\mathrm{n}}$ values obtained by a reevaluation of previously published experimental observations on soil and water fulvic acids. The results reveal a remarkable similarity of fulvic acids from widely different sources with respect to number-average molecular weight.     

Masers in the cool molecular cloud L 379

We present the results of monitoring the H₂O masers in the IR sources IRAS 18265-1517 and IRAS 18277-1516 associated with the cool molecular cloud L 379, which contains high-velocity bipolar molecular jets. The sources were observed in the 1.35 cm H₂O line using the 22-m radio telescope of the Pushchino Radio Astronomy Observatory (Russia) during 1991–2004. We detected H₂O maser emission from IRAS 18265-1517 at radial velocities of 17.8 and 18.4 km/s, virtually coincident with the velocity of the molecular cloud derived from CO-line observations (18.4 km/s). The maser emission towards the other source, IRAS 18277-1516, was at higher velocities than the central velocity of the CO molecular cloud. The H₂O maser spots are most likely associated with a redshifted region of CO emission. Cyclic variability of the integrated H₂O maser emission that may be related to cyclic activity of the central star was detected for IRAS 18277-1516. The strongest and most long-lived component (V_LSR ≈ 20.6 km/s) displays a radial-velocity drift, which could be due to deceleration of a dense clump of matter (maser condensation) in the circumstellar medium during the descending branch of a strong flare. We found numerous emission features for both IRAS 18265-1517 and IRAS 18277-1516, providing evidence for fragmentation of the medium surrounding their central objects.     

Galaxies with anomalously high abundances of molecular hydrogen

A sample of 66 galaxies from the catalog of Bettoni et al. (CISM) with anomalously high molecular-to-atomic hydrogen mass ratios (M _mol/M _HI > 2) is analyzed. The sample galaxies do not differ systematically from the other galaxies in the catalog with the same morphological types, in terms of their photometric parameters, rotational velocities, dust contents, or the integrated masses of gas (for galaxies with the same linear sizes and disk angular momenta). This suggests that the overabundances of H₂ are due to the molecularization of HI. Galaxies with bars and active nuclei are found more frequently among galaxies with M _mol estimates in CISM. In a small fraction of cases, high M _mol/M _HI ratios are due to overestimation of M _mol due to overstimating of the conversion factor for the translation of CO-line intensities into the number of H₂ molecules along the line of sight. It is argued that the molecularization of the bulk of the gas mass could be due to the concentration of gas in the inner regions of the galactic disks and the resulting high gas pressures and relative low star-formation efficiencies, as is indeed observed in galaxies with high M _mol/M _HI ratios.     

Gas-phase molecular structure and energetics of anionic silicates

The gas-phase stabilities of linear, branched and cyclic silicates made of up to five silicon atoms were studied with density functional theory (DFT). The starting geometries for the DFT calculations at the B3LYP/6-311+G(2d,2p) level of theory were obtained from classical molecular dynamics simulations. We have observed that geometric parameters and charges are mainly affected by the degree of deprotonation. Charges on Si atoms are also influenced by their degree of substitution. The enthalpy of deprotonation of the neutral species was found to decrease with the size of the molecule, while the average deprotonation enthalpy of highly charged compounds increased with molecular size. Furthermore, the formation of rings in highly charged silicates is enthalpically preferred to chain growth. These observations result from two competing effects: the easier distribution of negative charge in silicates with low charge density and the strong intramolecular repulsions present in silicates with high charge density. As a consequence, highly charged silicates in the gas phase tend to be as small and as highly condensed as possible, which is in line with experimental observations from solution NMR.     

Animated molecular dynamics simulations of hydrated caesium-smectite interlayers

Computer animation of center of mass coordinates obtained from 800 ps molecular dynamics simulations of Cs-smectite hydrates (1/3 and 2/3 water monolayers) provided information concerning the structure and dynamics of the interlayer region that could not be obtained through traditional simulation analysis methods. Cs⁺ formed inner sphere complexes with the mineral surface, and could be seen to jump from one attracting location near a layer charge site to the next, while water molecules were observed to migrate from the hydration shell of one ion to that of another. Neighboring ions maintained a partial hydration shell by sharing water molecules, such that a single water molecule hydrated two ions simultaneously for hundreds of picoseconds. Cs-montmorillonite hydrates featured the largest extent of this sharing interaction, because interlayer ions were able to inhabit positions near surface cavities as well as at their edges, close to oxygen triads. The greater positional freedom of Cs⁺ within the montmorillonite interlayer, a result of structural hydroxyl orientation and low tetrahedral charge, promoted the optimization of distances between cations and water molecules required for water sharing. Preference of Cs⁺ for locations near oxygen triads was observed within interlayer beidellite and hectorite. Water molecules also could be seen to interact directly with the mineral surface, entering its surface cavities to approach attracting charge sites and structural hydroxyls. With increasing water content, water molecules exhibited increased frequency and duration of both cavity habitation and water sharing interactions. Competition between Cs⁺ and water molecules for surface sites was evident. These important cooperative and competitive features of interlayer molecular behavior were uniquely revealed by animation of an otherwise highly complex simulation output.