A natural pyrolysis experiment — hopanes from hopanoic acids?

The formation or generation of hopanes are important processes during both the natural heating of organic-rich sediments and laboratory pyrolysis experiments. Molecular maturity parameters as well as the amounts (ng/g rock) of the C₃₁ hopanes and C₃₀–C₃₂ hopanoic acids were quantified in a Jurassic silty shale horizon (Isle of Skye, Scotland) as a function of distance from an igneous intrusion. The maturity profiles of the homohopanes and the hopanoic acids are comparable. There is also a correlation between the decreasing amounts of C₃₀–C₃₂ hopanoic acids and concomitant increases in C₂₉–C₃₁ hopanes suggesting that free hopanoic acids could be one potential source of hopanes in this particular horizon. Other possible sources could include hopanoic acids that are bound into the macromolecular fraction.     

海湾扇贝性腺发育的生物学零度

采用数理统计的方法，对１９９１～１９９２年海湾扇贝控温促熟实验的有关数据进行分析。得到海湾扇贝在青岛地区性腺发育的生物学零度为６．６℃，产卵的有效积温为１７８．９℃。     

Physiological differences in the growth and maturation of Eisenia bicyclis and Ecklonia cava gametophytes in Korea

The objective of this study was to examine the eff ects of temperature and light intensity on growth of female gametophytes of Eisenia bicyclis and Ecklonia cava and responses of these female gametophytes to Fe addition and daylength. Female gametophytes of each species were cultured at four temperatures (10, 15, 20, and 25°C) and under a combination of four light intensities (10, 20, 40, and 80 μmol photons/(m^2 ·s)) with two temperatures (15 and 20°C for E i . bicyclis;20 and 25°C for E c . cava ) to clarify their optimal growth conditions. Growth and maturation of female gametophytes of these two species under a combination of five Fe-EDTA concentrations (0, 1, 2, 4, and 8 μmol/L) and three daylengths (10, 12, and 14 h) were also examined. The growth of E i . bicyclis gametophyte was maximal at approximately 15–20°C, 20 μmol photons/(m^2 ·s), Fe-EDTA concentration of 8 μmol/L and daylengths of 12–14 h. While E c . c ava gametophytes showed optimal growth at approximately 20–25°C, 20 μmol photons/(m^2 ·s), Fe- EDTA concentration of 8 μmol/L and daylength of 14 h. Maturation of gametophytes was enhanced at Fe-EDTA concentration of 4 μmol/L for E i . bicyclis and at 2 μmol/L for E c . c ava . In conclusion, optimal growth temperatures and Fe-EDTA concentrations for maturation of E i . bicyclis and E c . c ava gametophytes were diff erent. Higher optimal growth temperature for E c . c ava gametophytes may contribute to its wider geographical distribution compared to E i . bicyclis which has restricted habitats in Korea. This suggests that addition of Fe ion could be used to recover beds of these two species in barren grounds of Korea.     

石油系统Re-Os同位素体系封闭性研究进展

Re-Os同位素定年在石油生成及富有机质沉积岩的绝对定年方面取得了良好的应用效果,并且石油的Os同位素初始值还可以作为油源示踪的指标。分析了Re-Os同位素定年方法在富有机质体系中应用的原理,探讨了影响同位素体系封闭性的各种因素,指出熟化作用、生物降解及水洗作用、脱沥青作用不会影响Re-Os同位素体系的封闭性,而硫酸盐热化学还原作用、成矿流体作用及幔源岩浆混染会扰动Re-Os同位素体系。目前石油系统中Re-Os同位素研究存在的主要问题可归结为2个方面:1石油系统有机质中Re-Os同位素的地球化学行为;2Re-Os同位素年龄的精度及其指示意义。对于这2个方面,开展有机相及现代海藻与Re-Os同位素相关性的研究将有助于了解Re和Os在有机质中的具体富集形式;对控制Re-Os同位素分馏的因素(如沉积环境及有机质类型)的研究将会有助于鉴别哪些地层以及什么样的样品能用来进行Re-Os定年。     

Kerogen-mineral reactions at raised temperatures in the presence of water

Kerogen has been artificially matured under “hydrous pyrolysis” conditions in the presence of various minerals in order to investigate the influence of the latter on the organic products. In addition to three clay minerals (montmorillonite, illite, kaolinite), calcium carbonate and limonite were also employed as inorganic substrates. Kerogen (Type II) isolated from the Kimmeridge Blackstone band was heated in the presence of water and a 20-fold excess of mineral phase at two different temperatures (280 and 330°C) for 72 hr. Control experiments were also carried out using kerogen and water only and kerogen under anhydrous conditions. This preliminary study describes the bulk composition of the pyrolysates with detailed analyses of the aliphatic hydrocarbon distributions being provided by gas chromatography and combined gas chromatography-mass spectrometry.In the 280°C experiments, considerably more organic-soluble pyrolysate (15% by weight of original kerogen) was produced when calcium carbonate was the inorganic phase. At 330°C, all samples generated much greater amounts of organic-soluble products with calcium carbonate again producing a large yield (40% wt/wt). Biomarker epimerisation reactions have also proceeded further in the 330°C pyrolysate formed in the presence of calcium carbonate than with other inorganic phases. Implications of these and other observations are discussed.     

Organic matter maturation under the influence of a deep intrusive heat source: A natural experiment for quantitation of hydrocarbon generation and expulsion from a petroleum source rock (Toarcian shale, northern Germany)

Four shallow boreholes were drilled in the Hils syncline, northern Germany, in order to determine quantitatively the amount of hydrocarbons generated and expelled during maturation of a typical kerogen-type-II-bearing source rock. The holes penetrated the carbonceous Lias shales (Posidonia shale, Lower Toarcian) and part of the adjacent Dogger α and Lias δ mudstones. The maturity of the organic matter in the cores recovered ranges from immature (0.48% R̄₀) to overmature 1.45% R̄₀) due to location of the Hils syncline in the vicinity of the Vlotho Massif, which is deep-seated intrusive body. Facies variations of the Lias within the short geographical distances in the study area are negligible.Organic matter mass balance calculations were based on detailed organic geochemical analyses of residual material in the Lias shales (kerogen, bitumen etc.) and on the evidence of a uniform initial composition of these sediments in the study area. Dead carbon determinations supported this latter criterion but were not used as a parameter in the calculations.About 50% of the initial kerogen was transformed into oil, gas and inorganic compounds during the vitrinite reflectance increase from 0.48 to 0.88% R̄_o and only marginally more during the maturity increase from 0.88 to 1.45% R̄_o. Only a small portion of the generated material remained in the source rock even at a relatively early stage of generation (0.68% R̄_o). Expulsion efficiency of oil plus gas reached a value of 86% at the end of the main generation stage (0.88% R̄_o).     

Burial history of Palaeozoic strata in Belgium as revealed by conodont colour alteration data and thickness distributions

Thickness distributions of Devono-Carboniferous formations and their relationship to conodont colour alteration indices (CAIs) from over 500 sample locations in Belgium and northern France have been studied to reconstruct the thermal alteration and burial history of Palaeozoic rocks. The depositional centre during Eifelian through Visean times was located in the subsiding southern part of the Dinant Basin, forming a thick sedimentary pile of probably more than 3.5 km. In order to explain conodont CAIs chiefly resulting from Upper Carboniferous sedimentation, two different depositional centres are considered, giving rise to approximately 4.5 km of sediment in the central part of the Dinant and Namur Basins. As a consequence of the northward shifting Variscan fold belt, the Upper Carboniferous succession in the southern part of the Dinant Basin and in the Rocroi area was reduced or absent. Conodont CAIs together with other thermal alteration data from the Condroz Massif indicate that this area was a structural high for most of the Devonian. The Brabant Massif was probably covered with approximately 1.5–2.0 km of Upper Carboniferous sediments in the south and less than 1.0 km in the central and northern parts. In the central Campine Basin Viséan strata could have been buried by 3.5–4.5 km of Upper Carboniferous rocks.     

华北克拉通北缘中—新元古界构造-热演化:来自锆石(U-Th)/He年龄的约束

由于复杂的构造沉积史和缺乏有效古温标,华北克拉通北缘燕辽裂陷带中—新元古界热史研究很薄弱,造成古老烃源岩成熟演化过程一直存在争议.研究利用锆石(U-Th)/He热定年技术探讨了燕辽裂陷带自中元古代以来的构造-热演化史,并分析了中元古界两套烃源岩成熟演化期次.燕辽裂陷带中—新元古界单颗粒锆石(U-Th)/He年龄均小于地...