Oil-generation kinetics for organic facies with Type-II and -IIS kerogen in the Menilite Shales of the Polish Carpathians

The Menilite Shales (Oligocene) of the Polish Carpathians are the source of low-sulfur oils in the thrust belt and some high-sulfur oils in the Carpathian Foredeep. These oil occurrences indicate that the high-sulfur oils in the Foredeep were generated and expelled before major thrusting and the low-sulfur oils in the thrust belt were generated and expelled during or after major thrusting. Two distinct organic facies have been observed in the Menilite Shales. One organic facies has a high clastic sediment input and contains Type-II kerogen. The other organic facies has a lower clastic sediment input and contains Type-IIS kerogen. Representative samples of both organic facies were used to determine kinetic parameters for immiscible oil generation by isothermal hydrous pyrolysis and S₂ generation by non-isothermal open-system pyrolysis. The derived kinetic parameters showed that timing of S₂ generation was not as different between the Type-IIS and -II kerogen based on open-system pyrolysis as compared with immiscible oil generation based on hydrous pyrolysis. Applying these kinetic parameters to a burial history in the Skole unit showed that some expelled oil would have been generated from the organic facies with Type-IIS kerogen before major thrusting with the hydrous-pyrolysis kinetic parameters but not with the open-system pyrolysis kinetic parameters. The inability of open-system pyrolysis to determine earlier petroleum generation from Type-IIS kerogen is attributed to the large polar-rich bitumen component in S₂ generation, rapid loss of sulfur free-radical initiators in the open system, and diminished radical selectivity and rate constant differences at higher temperatures. Hydrous-pyrolysis kinetic parameters are determined in the presence of water at lower temperatures in a closed system, which allows differentiation of bitumen and oil generation, interaction of free-radical initiators, greater radical selectivity, and more distinguishable rate constants as would occur during natural maturation. Kinetic parameters derived from hydrous pyrolysis show good correlations with one another (compensation effect) and kerogen organic-sulfur contents. These correlations allow for indirect determination of hydrous-pyrolysis kinetic parameters on the basis of the organic-sulfur mole fraction of an immature Type-II or -IIS kerogen.     

Laboratory condensation of refractory dust in protosolar and circumstellar conditions

In order to better understand condensation processes that took place in the solar nebula and to evaluate the effect of kinetics on the condensed matter, we have built an experimental apparatus for studying condensation of multi-elemental refractory gases at high-temperature and low-pressure. The condensation of a Mg-Si-rich gas, with solar interelement ratios of Ca, Al, Mg and Si, and of a Ca-Al-rich gas under a total pressure of ∼4 × 10⁻³ bar at temperatures from 1045 to 1285 °C and for run times of 4-60 min results in direct formation of crystalline oxides or silicates such as corundum, spinel, anorthite, melilite, Al-diopside, forsterite and enstatite. The mineralogy of the condensates, close to that predicted at equilibrium, varies with the duration of an experiment and the temperature of condensation. The chemical reactions between gas and condensates are rapid enough to attain a steady state in less than one hour. The condensation results in chemical fractionation of the gas, i.e. a depletion of the gas in refractory elements at high temperature. Finally, besides revealing the textures of refractory crystals, which condense from a gas of complex chemical composition, this study shows that certain phases, such as spinel, have favored kinetics of condensation. Our experimental results confirm that refractory inclusions in primitive meteorites could have formed by condensation from a hot nebular gas. Similarly, we confirm that crystalline grains can condense at high temperature in the outflows of evolved stars. In both cases, our results indicate that kinetic processes certainly influence grain mineralogy. Kinetic processes must thus be taken into account in modeling the pressure-temperature conditions of circumstellar environments.     

Diagenesis and fracturing of Paleocene–Eocene carbonate turbidite systems in the Ionian Basin: The example of the Kelçyra area (Albania)

The Kelçyra area is emplaced in a foreland fold-and-thrust belt (FFTB), characterized by a westward thrusting with the Triassic evaporites as the major décollement level. Several secondary features related with this evolution, like backthrusting, folding, duplex structures, evaporite diapirism are present. During the FFTB evolution, the study area has been subjected to several fracturing events with associated stages of fluid migration. During the pre-deformational stage, complex textures such as crack-and-seal features most likely reflect expulsion of overpressured fluids. These fluids were dominantly host-rock buffered. Within the post-deformational stage, a meteoric fluid caused cementation and development of a karst network during a period of emergence after the thrust emplacement. Subsequently, Mg calcite reprecipitated in the more stable carbonate phase calcite and dolomite, which filled part of the karts network. The latter is finally dedolomitized and locally partially dissolved by a second meteoric fluid flow, which greatly increased the secondary porosity.     

T -distributed Random Fields: A Parametric Model for Heavy-tailedWell-log Data1

Histograms of observations from spatial phenomena are often found to be more heavy-tailed than Gaussian distributions, which makes the Gaussian random field model unsuited. A T-distributed random field model with heavy-tailed marginal probability density functions is defined. The model is a generalization of the familiar Student-T distribution, and it may be given a Bayesian interpretation. The increased variability appears cross-realizations, contrary to in-realizations, since all realizations are Gaussian-like with varying variance between realizations. The T-distributed random field model is analytically tractable and the conditional model is developed, which provides algorithms for conditional simulation and prediction, so-called T-kriging. The model compares favourably with most previously defined random field models. The Gaussian random field model appears as a special, limiting case of the T-distributed random field model. The model is particularly useful whenever multiple, sparsely sampled realizations of the random field are available, and is clearly favourable to the Gaussian model in this case. The properties of the T-distributed random field model is demonstrated on well log observations from the Gullfaks field in the North Sea. The predictions correspond to traditional kriging predictions, while the associated prediction variances are more representative, as they are layer specific and include uncertainty caused by using variance estimates.     

韧性剪切变形对岩石地球化学行为的制约——以北阿尔金巴什考供韧性剪切带为例

韧性剪切变形对岩石地球化学行为的制约一直是地质学家们探讨的课题。本文以构成北阿尔金红柳沟——拉配泉俯冲碰撞杂岩带与北阿尔金地块边界的巴什考供斜向逆冲型韧性剪切带为例，通过对韧性剪切带内花岗岩变形前后不同变形强度构造岩的地球化学组成进行对比，确定等比线斜率，探讨韧性变形对岩石体积和成分变异的影响。计算结果表明，在糜棱岩化过程中，糜棱岩化花岗岩体积亏损21％，花岗质糜棱岩体积亏损31％。质量平衡计算结果和等比线图表明，韧；陛剪切作用导致SiO2，流失量最大，A12O3、K2O及Ba、Rb、Sr等都有不同程度的丢失，显示出较强的活动性，MnO、P2O5、Sc位于等比线上或附近，表现出相对的稳定性。岩石中活动组分的变异是流体渗滤作用引起的，不活动组分的变异是体．积亏损造成的。     

Characterization and migration of atmospheric REE in soils and surface waters

Rainwater and snow collected from three different sites in France (Vosges Mountains, French Alps and Strasbourg) show more or less similar shapes of their REE distribution patterns. Rainwater from Strasbourg is the most REE enriched sample, whereas precipitations from the two mountainous, less polluted catchments are less REE enriched and have concentrations close to seawater. They are all strongly LREE depleted.Different water samples from an Alpine watershed comprising snow, interstitial, puddle and streamwater show similar REE distributions with LREE enrichment (rainwater normalized) but MREE and HREE depletion. In this environment, where water transfer from the soil to the river is very quick due to the low thickness of the soils, it appears that REE in streamwater mainly originate from atmospheric inputs. Different is the behaviour of the REE in the spring- and streamwaters from the Vosges Mountains. These waters of long residence time in the deep soil horizons react with soil and bedrock REE carrying minerals and show especially significant negative Eu anomalies compared to atmospheric inputs. Their Sr and Nd isotopic data suggest that most of the Sr and Nd originate from apatite leaching or dissolution. Soil solutions and soil leachates from the upper soil horizons due to alteration processes strongly depleted in REE carrying minerals, have REE distribution patterns close to those of lichens and throughfall. Throughfall is slightly more enriched especially in light REE than filtered rainwater probably due to leaching of atmospheric particles deposited on the foliage and also to leaf excretion.Data suggest that Sr and Nd isotopes of the soil solutions in the upper soil horizons originate from two different sources: 1) An atmospheric source with fertilizer, dust and seawater components and 2) A source mainly determined by mineral dissolution in the soil. These two different sources are also recognizable in the Sr and Nd isotopic composition of the tree’s throughfall solution. The atmospheric contributions of Sr and Nd to throughfall and soil solution are of 20 to 70 and 20%, respectively. In springwater, however, the atmospheric Sr and REE contribution is not detectable.     

An X-ray absorption fine structure and nuclear magnetic resonance spectroscopy study of gallium-silica complexes in aqueous solution

The influence of aqueous silica on gallium(III) hydrolysis in dilute (2 × 10⁻⁴ ≤ m_Ga ≤ 5 × 10⁻³) and moderately concentrated (0.02 ≤ m_Ga ≤ 0.3) aqueous solutions was studied at ambient temperature, using high resolution X-ray absorption fine structure (XAFS) and nuclear magnetic resonance (NMR) spectroscopies, respectively. Results show that, in Si-free acidic solutions (pH < 3), Ga is hexa-coordinated with oxygens of H₂O molecules and/or OH groups in the first coordination sphere of the metal. With increasing pH, these hydroxyl groups are progressively replaced by bridging oxygens (-O-), and polymerized Ga-hydroxide complexes form via Ga-O-Ga chemical bonds. In the 2.5-3.5 pH range, both XAFS and NMR spectra are consistent with the dominant presence of the Ga₁₃ Keggin polycation, which has the same local structure as A1₁₃. Under basic pH (pH > 8), Ga exhibits a tetrahedral coordination, corresponding to Ga(OH)₄⁻ species, in agreement with previous NMR and potentiometric studies. Major changes in Ga hydrolysis have been detected in the presence of aqueous silica. Ga is tetra-coordinated, both in basic and acid (i.e., at pH > 2.7) Si-bearing solutions (0.01 ≤ m_Si ≤ 0.2), and forms stable gallium-silicate complexes. In these species, Ga binds via bridging oxygen to 2 ± 1 silicons, with an average Ga-Si distance of 3.16 ± 0.05 Å, and to 2 ± 1 silicons, with an average Ga-Si distance of 3.39 ± 0.03 Å. These two sets of Ga-Si distances imply the formation of two types of Ga-silicate aqueous complex, cyclic Ga-Si_2-3 species (formed by the substitution of Si in its tri-, tetra- or hexa-cyclic polymers by Ga atoms), and chainlike GaSi_2-4 species (similar to those found for A1), respectively. The increase in the number of Si neighbors (a measure of the complex concentration and stability), in alkaline media, with increasing SiO₂(aq) content and decreasing pH is similar to that for A1-Si complexes found in neutral to basic solutions. At very acid pH and moderate silica concentrations, the presence of another type of Ga-Si complex, in which Ga remains hexa-coordinated and binds to the silicon tetrahedra via the GaO₆ octahedron corners, has also been detected. These species are similar to those found for Al³⁺ in acid solutions. Thus, as for aluminum, silicic acid greatly hampers Ga hydrolysis and enhances Ga mobility in natural waters via the formation of gallium-silicate complexes.     

Comparison between the Chile and Mexico triple junction areas substantiates slab window development beneath northwestern Mexico during the past 12-10 Myr

When combined with the Miocene-Recent volcanic record of Baja California, a parallel drawn between the Chile and Mexico triple junction areas substantiates slab window development beneath northwestern Mexico during the past 12-10 Myr. The slab-free zone manifestations challenge the notion that ridge subduction has not occurred beneath the southern Baja California peninsula. The geochemically distinctive rocks from the Santa Clara volcanic field of west-central Baja California, including coeval adakites and niobium-enriched basalt, are commonly inferred to signal partial melting of the subducting plate at shallow depths and relatively high temperatures, before slab dehydration occurs. Such PT conditions for slab melting have only been observed in association with spreading-ridge subduction. We propose that slab window development beneath southern Baja California and mainland Mexico (30° to 18°N) resulted from subduction of the East Pacific rise.     

新时期我国区域经济地理学发展问题初探

我国新时期的区域经济地理学在取得全面发展的同时，在理论体系，研究方法和实践领域等方面还需要进一步的发展，文章根据学习和实践区域经济地理学的体会，初步提出基础理论和应用理论，思维方法和技术方法等方面发展见解，并指出区域创新系统和国际经济技术合作等学科应注意拓展的重要实践领域，最后提出我国区域经济地理学科发展的建议。