Evaluating the sulfur isotopic composition of biodegraded petroleum: The case of the Western Canada Sedimentary Basin     

Sabine Méhay  Pierre Adam  Isabelle Kowalewski  Pierre Albrecht 《Organic Geochemistry》2009,40(4):531-545

The sulfur isotopic composition (δ³⁴S) of petroleum is believed to be affected mainly by sulfur incorporation reactions into the sedimentary organic matter during the early diagenesis. However, secondary processes could affect the original δ³⁴S of oil under the effect of thermal maturity or of the microbial activity of biodegraded reservoirs. In this study, the different processes that may affect the δ³⁴S of in-reservoir oils were assessed based on the sulfur content and isotopes of a series of oil and core samples coming from various reservoirs of the Lower Cretaceous Mannville Group, Western Canada Sedimentary Basin (WCSB). Based on the molecular study, these samples appear to have reached various levels of maturity and biodegradation, ranging from 0 to 6.5 on the biodegradation scale of Peters and Moldowan. In addition, mixing of organic matter coming from different source rocks was identified based on the comparison with extensive correlation studies performed in the WCSB.Investigation of the δ³⁴S shows a trend that seems a priori correlated to the level of biodegradation. However, a careful interpretation of molecular and sulfur isotope data leads to the conclusion that the observed δ³⁴S variations have rather to be ascribed to contributions of oils generated by various source rocks. Alternatively, variations of δ³⁴S could neither be related to maturity differences nor to kinetic effects during organic sulfur compounds biodegradation. In the case of some specific core samples showing a common origin based on biomarker study, δ³⁴S variations might not be related to different sources but to secondary sulfur incorporation/exchange processes occurring within the reservoir. These processes would involve reduced sulfur species from bacterial sulfate reduction formed in situ or migrated into Mannville reservoirs. This hypothesis is supported by laboratory experiments showing sulfur exchange/incorporation under plausible conditions for shallow reservoirs.  相似文献   

Molecular and isotopic characterization of organic samples from the wreck of the Saint-Etienne merchant ship (XVIIIth century): Identification of pitch,fat, hair and sulfur     

Armelle Charrié-Duhaut  Jacques Connan  Mike Darnell  Jorge Spangenberg  Ewa Szymczyk  Adry Bissada  Pierre Albrecht 《Organic Geochemistry》2009,40(5):647-665

The wreck U Pezzo, excavated within the Saint Florent Gulf in northern Corsica was identified as the pink, Saint Etienne, a merchant ship which sank on January 31, 1769. In order to determine the composition of organic materials used to coat the hull or to waterproof different parts of the pink, a study of several samples, using molecular biomarker and carbon isotopic analysis, was initiated. The results revealed that the remarkable yellow coat, covering the outside planks of the ship’s bottom under the water line, is composed of sulfur, tallow (of ox and not of cetacean origin) and black pitch which corresponds to a mixture called “couroi” or “stuff”. Onboard ropes had been submitted to a tarring treatment with pitch. Hairs mixed with pitch were identified in samples collected between the two layers of the hull or under the sheathing planking. The study also provides a key model for weathering of pitch, as different degrees of degradation were found between the surface and the heart of several samples. Accordingly, molecular parameters for alteration were proposed. Furthermore novel mixed esters between terpenic and diterpenic alcohols and the free major fatty acids (C_14:0, C_16:0, C_18:0) were detected in the yellow coat.  相似文献   

U–Pb dating, Hf-isotope characteristics and trace-REE-patterns of zircons from Medet porphyry copper deposit, Bulgaria: implications for timing, duration and sources of ore-bearing magmatism     

Irena Peytcheva  Albrecht von Quadt  Franz Neubauer  Martin Frank  Rossen Nedialkov  Christoph Heinrich  Strashimir Strashimirov 《Mineralogy and Petrology》2009,96(1-2):19-41

Precise U–Pb geochronology, Hf isotope compositions and trace element distributions in zircons are combined in the present study to define the timing and sources of the magmatism forming the Medet porphyry copper deposit, Bulgaria. ID-TIMS U–Pb-zircon dating demonstrates that ore-bearing magmatism extended for less than 1.12 Ma. As inferred from the field relationships, it started with the intrusion of a quartz-monzodiorite at 90.59?±?0.29 Ma followed by granodiorite porphyries at 90.47?±?0.30 and 90.27?±?0.60 Ma and by crosscutting aplite dykes at 90.12?±?0.36 Ma. These units were overprinted by potassic alteration and host economic copper-(Mo–Au) mineralization. The main magmatic–hydrothermal activity ceased after that, and a later quartz-granodiorite porphyry dyke, dated at 89.26?±?0.32 Ma, only contains an uneconomic quartz–pyrite mineralization. Assimilation of Lower Paleozoic rocks with a mantle to mantle–crust signature is characteristic of the fertile magma in the Medet deposit, as defined by positive ?-Hf values of the inherited zircons. The positive Ce-anomalies and the higher Eu/Eu* ratios of the zircons in the mineralized Cretaceous rocks of Medet deposit argue for crystallization from a generally more oxidized magma compared to the later quartz-granodiorite porphyry dyke. A change in paleostress conditions occurred during the intrusion of the Medet pluton and its dykes. The initial stage reveals E–W extension associated with N–S compression, whereas the younger granodiorite dyke was emplaced during subsequent N–S extension. The large-scale switch of the extensional stress regime during the mineralization was favourable for ore deposition by channelling the fluids and increasing the effective permeability.  相似文献   

Structure and kinematics of the Jungfrau syncline, Faflertal (Valais, Alps), and its regional significance     

Thomas Krayenbuhl  Albrecht Steck 《Swiss Journal of Geoscience》2009,102(3):441-456

The formation and structural evolution of the Jungfrau syncline is described, based on excellent outcrops occurring in the Lötschental, in the Central Alps of Switzerland. The quality of the outcrops allows us to demonstrate that the External Massifs of the Swiss Alps have developed due to internal folding. The Jungfrau syncline, which separates the autochtonous Gastern dome from the Aar massif basement gneiss folds, is composed of slivers of basement rocks with their Mesozoic sedimentary cover. In the Inner Faflertal, a side valley of the Lötschental, the 200 m thick syncline comprises four units, the Gastern massif with a reduced Mesozoic sedimentary cover in a normal stratigraphic succession, two units of overturned basement rocks with their Mesozoic sedimentary cover, and the overturned lower limb of the Tschingelhorn gneiss fold of the Aar massif with lenses of its sedimentary cover. Stratigraphy shows that the lower units, related to the Gastern massif, are condensed and that the upper units, deposited farther away from a Gastern paleo-high, form a more complete sequence, linked to the Doldenhorn Meso-Cenozoic basin fill. The integration of these local observations with published regional data leads to the following model. On the northern margin of the Doldenhorn basin, at the northern fringe of the Alpine Tethys, the pre-Triassic crystalline basement and its Mesozoic sedimentary cover were folded by ductile deformation at temperatures above 300 °C and in the presence of high fluid pressures, as the Helvetic and Penninic nappes were overthrusted towards the northwest during the main Alpine deformation phase. The viscosity contrast between the basement gneisses and the sediments caused the formation of large basement anticlines and tight sedimentary synclines (mullion-type structures). The edges of basement blocks bounded by pre-cursor SE-dipping normal faults at the northwestern border of the Doldenhorn basin were deformed by simple shear, creating overturned slices of crystalline rocks with their sedimentary cover in what now forms the Jungfrau syncline. The localisation of ductile deformation in the vicinity of pre-existing SE-dipping faults is thought to have been helped by the circulation of fluids along the faults; these fluids would have been released from the Mesozoic sediments by metamorphic dehydration reactions accompanied by creep and dynamic recrystallisation of quartz at temperatures above 300 °C. Quantification of the deformation suggests a strain ellipsoid with a ratio (1+ e₁ / 1+ e₃) of approximately 1000. The Jungfrau syncline was deformed by more brittle NW-directed shear creating well-developed shear band cleavages at a late stage, after cooling by uplift and erosion. It is suggested that the external massifs of the Alps are basement gneiss folds created at temperatures of 300 °C by detachment through ductile deformation of the upper crust of the European plate as it was underthrusted below the Adriatic plate.  相似文献   

High resolution imaging of Pluto and Charon with the Faint Object Camera of the Hubble Space Telescope     

R. Albrecht 《Earth, Moon, and Planets》1995,70(1-3):207-212

Images of the Pluto-Charon system were obtained with the Faint Object Camera (FOC) of the Hubble Space Telescope (HST) with the aim of determination of radii, fluxes, and albedos. The resolution of the already diffraction limited images was further improved by image restoration, yielding indications of surface albedo distributions which are qualitatively consistent with models derived from observations of Pluto-Charon mutual eclipses.Based on Observations with the NASA-ESA Hubble Space Telescope, which is operated by AURA, Inc., under NASA contract NAS 5-26555.  相似文献   

Alpine and pre-Alpine magmatism in the root-zone of the western Central Alps   总被引：1，自引：0，他引：1  

R. L. Romer  U. Schärer  Albrecht Steck 《Contributions to Mineralogy and Petrology》1996,123(2):138-158

 The highest grade of metamorphism and associated structural elements in orogenic belts may be inherited from earlier orogenic events. We illustrate this point using magmatic and metamorphic rocks from the southern steep belt of the Lepontine Gneiss Dome (Central Alps). The U-Pb zircon ages from an anatectic granite at Verampio and migmatites at Corcapolo and Lavertezzo yield 280–290 Ma, i.e., Hercynian ages. These ages indicate that the highest grade of metamorphism in several crystalline nappes of the Lepontine Gneiss Dome is pre-Alpine. Alpine metamorphism reached sufficiently high grade to reset the Rb-Sr and K-Ar systematics of mica and amphibole, but generally did not result in crustal melting, except in the steep belt to the north of the Insubric Line, where numerous 29 to 26 Ma old pegmatites and aplites had intruded syn- and post-kinematically into gneisses of the ductile Simplon Shear Zone. The emplacement age of these pegmatites gives a minimum estimate for the age of the Alpine metamorphic peak in the Monte Rosa nappe. The U-Pb titanite ages of 33 to 31 Ma from felsic porphyritic veins represent a minimum-age estimate for Alpine metamorphism in the Sesia Zone. A porphyric vein emplaced at 448±5 Ma (U-Pb monazite) demonstrates that there existed a consolidated Caledonian basement in the Sesia Zone. Received: 23 May 1995/Accepted: 12 October 1995  相似文献   

Modelling the response of glaciers to a doubling in atmospheric CO2: a case study of Storglaciären, northern Sweden     

C. Schneeberger  O. Albrecht  H. Blatter  M. Wild  R. Hock 《Climate Dynamics》2001,17(11):825-834

To predict the evolution of glaciers in an enhanced greenhouse climate, results from a global climate model, a glacier melt/accumulation model, and a glacier flow model were combined. The method was applied to Storglaciären, a small well-studied glacier in northern Sweden. The difference between the present climate and a 2 × CO₂ climate around the year 2050 was extracted from a model experiment with the ECHAM4-T106 high resolution climate model for time slices at present and in 2050, using prescribed boundary conditions of sea surface temperature and sea-ice distribution, which are derived from a lower resolution transient run of the ECHAM4-T42/OPIC-coupled atmosphere ocean model between present and 2050. The local climatic conditions on the glacier for 2050 were obtained by adding the modelled local climate changes to the observed local present-day climate. The combination of the comprehensive models presented offers a tool to test and calibrate simplified models which are applicable to a much larger sample of glaciers. For the region of Storglaciären, the GCM projected temperature is found to increase most strongly during the winter months, but also shows a warming during the transition from spring to summer, and again between summer and fall, thus extending the melt season by three to four weeks. Precipitation, on the other hand, decreases by approximately 5% during May to September while there is a stronger increase of approximately 14% for the rest of the year. The consequent increase in winter accumulation on Storglaciären is more than compensated by the increase in ablation during the melt season. The glacier flow model predicts a 300 m retreat of the glacier terminus by the middle of the next century, and a loss of 30% of the present ice mass.  相似文献   

Improving Regional Seismic Event Location in China   总被引：1，自引：0，他引：1  

L.K. Steck  A.A. Velasco  A.H. CogbillL  H.J. Patton 《Pure and Applied Geophysics》2001,158(1-2):211-240

—?In an effort to improve our ability to locate seismic events in China using only regional data, we have developed empirical propagation path corrections and applied such corrections using traditional location routines. Thus far, we have concentrated on corrections to observed P arrival times for crustal events using travel-time observations available from the USGS Earthquake Data Reports, the International Seismic Centre Bulletin, the preliminary International Data Center Reviewed Event Bulletin, and our own travel-time picks from regional data. Location ground truth for events used in this study ranges from 25?km for well-located teleseimic events, down to 2?km for nuclear explosions located using satellite imagery. We also use eight events for which depth is constrained using several waveform methods. We relocate events using the EvLoc algorithm from a region encompassing much of China (latitude 20°–55°N; longitude 65°–115°E). We observe that travel-time residuals exhibit a distance-dependent bias using IASPEI91 as our base model. To remedy this bias, we have developed a new 1-D model for China, which removes a significant portion of the distance bias. For individual stations having sufficient P-wave residual data, we produce a map of the regional travel-time residuals from all well-located teleseismic events. Residuals are used only if they are smaller than 10?s in absolute value and if the seismic event is located with accuracy better than 25?km. From the residual data, correction surfaces are constructed using modified Bayesian kriging. Modified Bayesian kriging offers us the advantage of providing well-behaved interpolants and their errors, but requires that we have adequate error estimates associated with the travel-time residuals from which they are constructed. For our P-wave residual error estimate, we use the sum of measurement and modeling errors, where measurement error is based on signal-to-noise ratios when available, and on the published catalog estimate otherwise. Our modeling error originates from the variance of travel-time residuals for our 1-D China model. We calculate propagation path correction surfaces for 74 stations in and around China, including six stations from the International Monitoring System. The statistical significance of each correction surface is evaluated using a cross-validation technique. We show relocation results for nuclear tests from the Balapan and Lop Nor test sites, and for earthquakes located using interferometric synthetic aperture radar. These examples show that the use of propagation path correction surfaces in regional relocations eliminates distance bias in the residual curves and significantly improves the accuracy and precision of seismic event locations.  相似文献   

Faltung und Gangbildung im Gebiet der Eisenspatgrube “Ameise” bei Siegen     

Albrecht Giesecke 《International Journal of Earth Sciences》1955,44(1):326-344

Zusammenfassung Die Bildung des Spateisensteinganges von Grube Ameise fällt wahrscheinlich in das Ende der Faltung.Der Gang entwickelt sich aus einer Scherfläche, an der Abschiebungen stattfanden, die die Faltenachsen antithetisch verwerfen.  相似文献   

Untersuchungen über die «Optische Wolkendichte» und die Strahlungs-Absorption in Wolken     

Dr. Fritz Albrecht 《Pure and Applied Geophysics》1957,37(1):205-229

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