Organic Gases in Fluid Inclusions of Ore Minerals and Their Constraints on Ore Genesis: A Case Study of the Changkeng Au-Ag Deposit, Guangdong, China

The newly discovered Changkeng Au-Ag deposit is a new type of sediment-hosted precious metal deposit. Most of the previous researchers believed that the deposit was formed by meteoric water convection. By using a high vacuum quadrupole gas mass spectrometric system, nine light hydrocarbons have been recognized in the fluid inclusions in ore minerals collected from the Changkeng deposit. The hydrocarbons are composed mainly of saturated alkanes C1-4 and unsaturated alkenes C2-4 and aromatic hydrocarbons, in which the alkanes are predominant, while the contents of alkenes and aromatic hydrocarbons are very low. The Σalka/Σalke ratio of most samples is higher than 100, suggesting that those hydrocarbons are mainly generated by pyrolysis of kerogens in sedimentary rocks caused by water-rock interactions at medium-low temperatures, and the metallogenic processes might have not been affected by magmatic activity. A thermodynamic calculation shows that the light hydrocarbons have reached chemical equilibrium     

Hydrocarbon degradation potential of autochthonous bacteria from the Yellow River delta soil

Microbial remediation potential to crude oil-contaminated soils in the Yellow River delta was assessed. Hydrocarbons degradaters were isolated from the soil samples obtained from the Yellow River delta. A selected mixed microbial consortium （MYRD-1） and two individual isolates （YRD-3 and YRD-4） were further tested for optimal performance and degradation of different hydrocarbons. The results demonstrated that the optimal crude oil biodegradation conditions for the mixed microbial consortium were at temperature of 28 ℃, salt concentration of 15‰, and pH of 8, and the optimal C/N/P ratio was found to be 70 ： 3 ： 1. Isolate YRD-3 could only use n-alkanes （C8, C12 and C16） as the sole source of carbon and YRD-4 could transform only naphthalene and phenanthrene. The optimal performance conditions for both isolates were at salt concentration of 20‰, and pH of 7, and C/N/P ratio of 80 ： 5 ： 1, but the temperature for YRD-3 was 24 ℃ and 28 ℃ for YRD-4. Capacity to transform hydrocarbons for the mixed microbial consortium and both isolates could be improved in a liquid medium supplemented using a mixture of alkanes and/or aromatic hydrocarbons （naphthalene and phenanthrene）, but the transformation of different substrates by MYRD-1 was higher than both isolates, showing the importance of mixed bacteria （microbial community） in hydrocarbon degradation.     

Light Hydrocarbons in Fluid Inclusions and Their Constraints on Ore Genesis: A Case Study of the Songxi Ag (Sb) Deposit, Eastern Guangdong, China

The Songxi deposit is a newly discovered large Ag (Sb) deposit. By using a suite of high-vacuum quadrupole gas mass spectrometer systems, the authors have recognized many kinds of light hydrocarbons in fluid inclusions of minerals. These hydrocarbons are mainly composed of C1-C4 saturated alkanes, while the contents of C2-C4 unsaturated alkenes and aromatic hydrocarbons are quite low, suggesting that the metallogenic processes have not been affected by magmatic activities. Chemical equilibrium studies show that these hydrocarbons may be a mixture of organic gases generated by microorganism activity and those by thermal cracking of type-n kerogens (kukersite) in sedimentary host rocks, and the former may constitute more than two-thirds, implying that microorganism might have played an important role in the metallogenesis. The equilibrium temperature of the latter is about 300℃, which is much higher than the geothermal temperature at the estimated depth of metallogenesis. Thus, the light hydrocarbons gen     

Compositional characteristics and geochemical significance of light hydrocarbons for crude oils in Tarim Basin, China

Light hydrocarbons, especially C7 isoalkanes, cyclopentanes, cyclohexanes and n-heptane in 540 oils from the Tarim Basin were studied systematically. The results suggested the K1 values [ （2-MH＋ 2,3-DMP）/（3-MH ＋ 2,4-DMP） ] of crude oils vary from a lowest value of 0.78, to a highest value of 1.54, but the K1 values of the majority of oil samples （80%） range from 0.90 to 1.20. However, the absolute contents of （ 2-methylhexane ＋ 2,3-dimethylpentane） and （ 3-methylhexane ＋ 2,4-dimethylpentane） in the total light hydrocarbons （ C4-C7 ） show a similar variation trend. The variation of K1 values of crude oils can suggest a typical sedimentary environment for source rocks. Therefore, according to the compositional characteristics of C7 light hydrocarbons in light of the steady-state catalytic hypothesis, nonmarine oils from the Yingmaili area and marine oils from the Tazhong uplift in the Tarim Basin were genetically classified.     

Geochemical characteristics and oil family classification of crude oils from the Markit Slope in the southwest of the Tarim Basin,Northwest China

Based on the chromatograms of oils and saturated hydrocarbons, biomarkers and stable carbon isotope analyses, the geochemical characteristics and oil family Classification of crude oils from the Markit Slope in the southwest of the Tarim Basin were investigated. The results showed that crude oils from the Markit Slope are divided into two oil family Classification. Oils collected from the Bashituo oilfield in the western part of the Markit Slope are characterized by high contents of tricyclic terpanes, pregnane, and homopregnane, low contents of garmmacerane (G/H<0.20), dibenzofuran, and methyl cyclohexane, and light stable carbon isotopic values (the δ13C values of satu-rated hydrocarbons and aromatic components are less than -34‰ and -32‰, respectively), with the distribution type of steranes being C27>>C28 -32‰ and -30.6‰, respectively), with the distribution type of steranes being C27>C28<相似文献   

Abiotic Hydrocarbons Generation Simulated by Fischer-Tropsch Synthesis under Hydrothermal Conditions in Ultra-deep Basins

FTT experiments with water as a hydrogen source and three types of possible carbon sources in the subsurface (diiron nonacarbonyl, siderite and formic acid, representing CO, CO2 and a simple organic acid, respectively) were carried out in this study. Our experimental results showed that n-alkanes with the highest carbon number of C33 were produced when CO was used as a carbon source (series A); a variety of polycyclic aromatic hydrocarbons (PAHs) were detected in series B with CO2 as a carbon source; gaseous hydrocarbons were also detected with formic acid added (series C). The different products in the three series showed that there were different hydrocarbon generation mechanisms and reaction processes with different carbon sources. The generation of long-chain n-alkanes in series A provided experimental support for the formation of abiogenic petroleum underground, which was of significance to early membranes on the Earth. PAHs in series B provide experimental support for the possibility of an abiotic source of reduced carbon on other planets. The carbon isotopes of gaseous hydrocarbons produced by CO exhibited a partial reversed order (δ13C1 < δ13C2 > δ13C3 > δ13C4 > δ13C5), while the gaseous hydrocarbons produced by CO2 and HCOOH showed a positive order (δ13C1 < δ13C2 < δ13C3 < δ13C4 < δ13C5). Based on these, the alkylene mechanism and the carbonyl insertion mechanism were used to reasonably explain these characteristics.     

Multi-parametric geochemical survey on evaluation of hydrocarbon potential of trap structure in a desert area: A case of TD-2 structure in the Tarim Basin,China

TD-2 structure is located in the eastern part of the Central Uplift zone of the Tarim Basin, China. It is a basement-uplift anticline-type structure confirmed by seismic and gravity prospecting, and it is expected to have good potential for oil and gas according to the analysis of regional geological evolution history. But further exploration such as drilling is suspended because of lacking direct geochemical information. Therefore, multi-parametric geochemical surveys, such as free hydrocarbons (C1-C5), acid hydrocarbons (C1-C5) and ?C, Hg of soil, were conducted. It is concluded in this paper that free hydrocarbons are obviously better than other geochemical parameters and could be used for evaluation of oil and gas potential of TD-2 structure in the desert area. Shapes of near-surface geochemical anomalies and geochemical characteristic parameters suggested that TD-2 structure was a dry gas-bearing structure at the early-middle dissipation stage. So TD-2 structure should have some promising potential for oil-gas. Multi-parametric geochemical survey provided important information for further drilling exploration.     

Re-Examination of the Oil and Gas Origins in the Kekeya Gas Condensate Field, Northwest China–A Case Study of Hydrocarbon-Source Correlation Using Sophisticated Geochemical Methods

This work discussed the origins, alteration and accumulation processes of the oil and gas in the Kekeya gas condensate field based on molecular compositions, stable carbon isotopes, light hydrocarbons, diamondoid hydrocarbons and biomarker fingerprints. A comparison study is also made between the geochemical characteristics of the Kekeya hydrocarbons and typical marine and terrigenous hydrocarbons of the Tarim Basin. Natural gas from the Kekeya gas condensate field is derived from Middle–Lower Jurassic coal measures while the condensates are derived from Carboniferous–Permian marine source rocks with a higher maturity. In the study area, both natural gas and condensates have experienced severe water washing. A large amount of methane was dissolved into the water, resulting in a decrease in the dryness coefficient. Water washing also makes the carbon isotopic compositions of the natural gas more negative and partially reverse. Considering that the gas maturities are higher than once expected, gas generation intensity in the study area should be much stronger and the gas related to the Jurassic coal measures could promise a greater prospecting potential. As a result of evaporative fractionation, the Kekeya condensates are enriched in saturates and lack aromatics. Evaporative fractionation disguises the original terrigenous characteristics of the light hydrocarbons associated with the natural gas, making it appear marinesourced. Thus, alteration processes should be fully taken into consideration when gas–source correlations are carried out based on light hydrocarbons. With the condensates discovered in the study area all being "migration phase", the pre-salt Cretaceous and Jurassic reservoirs may promise great exploration potential for the "residual phase" hydrocarbons. This research not only is of significance for oil and gas exploration in the southwest Tarim Basin, but also sheds light on the oil/gas-source correlations in general.     

The Role of Organic Matter During Metal Enrichment in Permian Kupferschiefer of the Rudna Mine,Southwest Poland

The bulk composition of organic matter and saturated and aromatic hydrocarbons extracted from 16 samples collected from two Kuperschiefer profiles in the Rudna mine,Southwest Poland has been analyzed to study the role of organic matter during base metal enrichment in the Kupferschiefer shale.The results indicated that the extract yields and saturated hydrocarbon yields decreased with increasing base metal contents.GC and GC/MS analyses indicated that n -alkanes and alkylated aromatic compounds were depleted and may have served as hydrogen donators for thermochemical sulfate reduction.The enrichment of base metal is closely connected with the destruction of hydrocarbons.     

Conversion and degradation of crude oil by Bacillus SP3

The objective of this study is to demonstrate the basic characteristics of Bacillus SP3 and evaluate its effect on different crude oils. Strain SP3 is a motile, gram-positive, spore-producing rod that was isolated from a reservoir of the Shengli oil field in East China. The cells of strain SP3 grew at high temperatures up to 58℃ at the pH range of 5.5–8.5. Strain SP3 grew facultatively and could use different organic substrates, and produce some metabolites such as 4-hydroxy-4-methyl-2-pentanone, methyl-2-nitrogen benzene and 1, 2-benzenedicarboxylic acid bis ester. Laboratory studies have demonstrated that the strain converted and degraded different components and changed the physical and chemical properties of crude oils. Strain SP3 degraded crude oil and the growth of bacteria on crude oil resulted in loss of aromatic hydrocarbons, resins and asphaltenes. The bioconversion of crude oils would lead to an enrichment in lighter hydrocarbons and an overall redistribution of saturate hydrocarbons. The interactions of microorganisms with crude oils are variable, depending on the microbial species and the chemical compositions of crude oils.     

13C12C ratios of pleistocene mummified remains from beringia

During the Quaternary glacial episodes, when sea level was considerably lower, Asia and North America were linked by large extensions of circumarctic land (Beringia), which remained unglaciated. This land mass served not only as a biogeographical bridge for plants, animals, and humans, but also supported a biome very different from present tundra or boreal coniferous forests, which was dominated by steppes and a rich mammalian megafauna. Carbon stable isotope ratios of Beringian late Pleistocene mummified remains of bison, equids, mammoth, caribou, musk-ox, moose, woolly rhino, and other undetermined species, found preserved in permafrost, indicate that these megaherbivores fed exclusively on C₃ plants, and that C₄ grasses were not differentially ingested by bison, as previously suggested. Paleoclimatic constraints probably prevented the formation of a warm-season (C₄) guild during the later part of the growing season in the steppes of Beringia during the last glaciation.     

The system Ag-Sb-S from 600°C to 200°C

The system Ag-Sb-S was studied between 600°C and 200°C in evacuated silica glass tubes. Results from lower temperature runs require shifts in the stable tie-line configuration found by Barstad at 400°C. It is proposed that the configuration changes near 300°C, and that at 200°C the equilibrium assemblages correspond to those usually reported for minerals in ores. Most of the minerals of the system were synthesized. In addition, the synthetic phase Ag₇SbS₆ (antimony analogue of the arsenic mineral billingsleyite) is characterized, and the ease of its synthesis in the composition area bounded by argentite-pyrargyrite-sulfur suggests the probable existence of a mineral of this composition. The relatively common mineral stephanite (Ag₅SbS₄) was not formed as a synthetic product in the temperature range of this study. Combined DTA and X-ray data show that at 197±5°C stephanite decomposes in the absence of sulfur to form pyrargyrite plus argentite, whereas with excess sulfur the products are Sb-billingsleyite plus pyrargyrite. Pyrostilpnite (Ag₃SbS₃), the low temperature dimorph of pyrargyrite, is unstable above 192±5°C.

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Das ternäre System Silber-Antimon-Schwefel wurde zwischen 600° und 200°C untersucht und versucht, die Gleichgewichtszustände aller stabilen Phasen zu analogen natürlichen Mineralien in Beziehung zu setzen. Neben den Elementen wurden an binären Phasen Allargentum, Dyskrasit, Antimonit, Argentit bzw. Akanthit gefunden oder bestätigt. Auf dem pseudo-binären Schnitt Ag₂S-Sb₂S₃ liegen Pyrargyrit und Miargyrit, während eine als Mineral unbekannte ternäre Phase Ag₇SbS₆ (entsprechend dem natürlichen As-Analogon Billingsleyit) nur bei höherem Schwefelangebot beständig ist. Hier nicht synthetisch dargestellte Silber-Antimon-Sulfosalze liegen vermutlich unterhalb der 200°C-Grenze. So ließ sich mittels Differential-Thermo-Analyse und röntgenographischer Bestimmungsmethoden der inkongruente Zerfall von Stephanit in Argentit und Pyrargyrit bei 197±5°C bestimmen. Pyrostilpnit (Ag₃SbS₃) ist nur unterhalb 192±5°C beständig.

     

Carbon isotope and C/N ratios of suspended matter in rivers: an indicator of seasonal change in C4/C3 vegetation

A combination of δ ¹³C values with C/N ratios in suspended matter has been used to examine the seasonal relationship between C₄ and C₃ vegetation along the Loess Plateau, NW China. The C isotopic composition of suspended organic matter in rivers, together with C/N ratios can differentiate between soil and plant material, and can be used to estimate the relative contributions of soil organic C and plant litter to the suspended matter. The relationship between C isotopic composition and C/N ratios indicates that the samples are a mixture of two end members: (1) modern soils with relatively constant δ ¹³C values, low C content and low C/N ratios; (2) plant litter with varying δ ¹³C values, high C content and high C/N ratios. The results reflect the seasonal distribution of C₄/C₃ vegetation within the area studied, as part of the Loess Plateau. The abundance of C₄ grasses is about 20% for the current summer vegetation ecosystem in the eastern part of the Loess Plateau. Hence, the use of δ ¹³C values and C/N ratios of suspended matter in rivers and modern soil may be useful for reflecting seasonal distribution of C₄/C₃ vegetation in catchments. This could be a useful tool for distinguishing between catchments for GIS studies, and long term planning for ecological management of catchment areas.     

Long-term biogeochemical cycling in agroecosystems inferred from C, C and N

We investigated C and N cycling in long-term agroecological experiments initiated over 50 years ago at a cool, semi-arid site on the North American Great Plains. We used isotopes at natural abundance to trace C and N exchange between soils and plants in contrasting cropping systems. Both ¹³C and ¹⁴C indicated that the soil organic matter was isotopically distinct from current plant inputs, suggesting that recently added plant C was cycling independently of much of the soil C pool. For tracing recent C flows, bomb-¹⁴C was more sensitive than ¹³C, and increased more in high – than in low – yielding systems. Analysis of ¹⁵N in plant tissues, as an index of ¹⁵N in actively cycling soil N, suggested that biological and industrial N fixation both tended to decrease plant ¹⁵N, whereas livestock manure addition increased ¹⁵N abundance. Collectively, the data suggest that soil organic matter is kinetically heterogeneous, so that a majority of soil C and N inputs and outputs exchange with only the small pool of soil organic matter that is actively cycling. Consequently, recently photosynthesized C and deposited N may not readily enter the old, stable fractions of soil organic matter. Practices to retain CO₂ from the atmosphere and prevent leakage of reactive N to non-agricultural systems should therefore focus on management of this active pool.     

C/C++与FORTRAN混合编程技术及其应用研究

详细论述了C/C ++和FORTRAN混合编程技术 ,尤其是对动态连接库方法进行了重点介绍。将C/C ++和FORTRAN进行混合编程 ,一方面可以达到这两种语言优势互补的目的 ;另一方面可以再利用前人留下的大量成熟的FORTRAN程序 ,避免了重复编程和资源浪费 ,节约了大量编程时间。     

Die C14-Methode

Zusammenfassung Die Altersreichweite der C¹⁴-Datierung von pflanzlichen und tierischen Stoffen beträgt 50 000, allenfalls 70 000 Jahre. Die Datierungsunsicherheit beläuft sich auf mindestens ± 100 Jahre. Bei einem Alter bis zu etwa 10 000 Jahren spielen individuelle Unterschiede im Anfangsgehalt contemporärer organischer Substanzen eine gewisse Rolle. Geringfügige Verzerrungen der C¹⁴-Zeitskala sind möglich und zum Teil nachgewiesen. Bei höherem Alter spielen diese Abweichungen praktisch keine Rolle, dafür wächst die Gefahr der Altersfälschung durch eine kleine Verunreinigung mit jüngerem, sehr viel mehr C¹⁴ enthaltendem Material. Eine fälschliche Verjüngung kann in dem Zeitbereich über etwa 30 000 Jahren zwar nie mit Sicherheit ausgeschlossen werden, als Mindestalter sind die Ergebnisse aber selbst an der Reichweitengrenze äußerst zuverlässig und wertvoll.Einige Meßmethoden werden kurz erläutert. Die Ergebnisse und Möglichkeiten der Methode werden an einigen typischen Beispielen besprochen.     

C10TAB,C14TAB,C18TAB柱撑蒙脱石层间域有机柱排布研究

用十烷基三甲基溴化铵（C10TAB）、十四烷基三甲基溴化铵（C14TAB）和十八烷基三甲基溴化铵（C18TAB）制备有机柱撑蒙脱石,并对产物进行X射线衍射表征。研究结果表明：柱化剂的浓度和烷基季铵离子的性质能影响烷基季铵离子在蒙脱石层间的排布模式。在柱化剂浓度较低时易形成平卧排列,柱化剂达到一定浓度时石蜡型结构方能形成,且直链烷基越长,烷基季铵离子在蒙脱石层问越易形成石蜡型倾斜排列。在平卧结构向石蜡型结构转化过程中可出现多种排列共存。