Grant-in-Aid for Scientific Research C. An early stage of the present project, developmental efforts for Re-Os analyses were made. The Re mass spectrometry was usually disturbed by filament blank, but finally successful measurements were attained. However, the contribution of filament Re is still large, and our efforts must be given to reduce such effect. The Re-Os dating method were applied to several kinds of samples such as Permian Akasaka limestones, late Jurassic mudstones from Tamba group, Miocene mudstones from Shimane Prefecture, present-day river and marine sediments. Those data indicate two important aspects: 1 Most of the limestones and mudstones undergone severe thermal event during diagenetic processes are not suitable for Re-Os dating.
The rhenium and osmium contents and the isotopic compositions of osmium in a ratios vary sufficiently as to make the Re/Os dating-method applicable.
Rhenium—osmium dating is a form of radiometric dating based on the beta decay of the isotope Re to Os. This normally occurs with a half-life of Rhenium—osmium dating is carried out by the isochron dating method. Isochrons are created by analysing several samples believed to have formed at the same time from a common source. The Re-Os isochron plots the ratio of radiogenic Os to non-radiogenic Os against the ratio of the parent isotope Re to the non-radiogenic isotope Os.
The stable and relatively abundant osmium isotope Os is used to normalize the radiogenic isotope in the isochron. A good example of an application of the Re-Os isochron method is a study on the dating of a gold deposit in the Witwatersrand mining camp, South Africa. Rhenium and osmium were strongly refractory and siderophile during the initial accretion of the Earth which caused both elements to preferentially enter the Earth’s core.
Re tends to enter the melt phase incompatible while Os remains in the solid residue compatible. In this regard, the Re—Os system to study the geochemical evolution of mantle rocks and in defining the chronology of mantle differentiation is extremely helpful. Peridotite xenoliths which are thought to sample the upper mantle sometimes contain supra-chondritic Os-isotopic ratios. This combination of radiogenic Os that was created by decay of Re and nonradiogenic melts helps to support the theory of at least two Os-isotopic reservoirs in the mantle.
osmium isotopes rhenium
They formed 3. Other ancient continents, such as in southern Africa or Siberia, have long been known to have diamonds almost as old, but none that have been so precisely dated. This conclusion documents one of the oldest known examples of modern plate tectonics.
“Direct radiometric dating of hydrocarbon deposits using rhenium-osmium isotopes”. Science (), , D Selby, RA Creaser, and MG Fowler.
A method of radiometric dating based on the decay of rhenium Re to osmium Os , with a half-life of 4. Access to the complete content on Oxford Reference requires a subscription or purchase. Public users are able to search the site and view the abstracts and keywords for each book and chapter without a subscription. Please subscribe or login to access full text content.
Canadian diamonds found to be oldest on Earth
Over the years, Chemostrat has expanded the services on offer to now include more advanced isotopic techniques that so far have been used only in academia. The information presented below briefly outlines how Chemostrat is utilising two of these techniques, i. Re and Os become concentrated in the organic, hydrogenous fraction of organic rich shales, thus the time when the shale was deposited can be dated.
Use of Rhenium-Osmium (Re-Os) Isotope for Direct Dating of Organic-Rich Rocks and Hydrocarbons/Oils in Petroleum Geology: A Review.
In order to resolve the controls on the distribution of these elements, chemical and isotope mapping of MoS 2 grains from representative porphyry copper-molybdenum deposits were performed using electron microprobe and nano-scale secondary ion mass spectrometry.
Dissecting the Re-Os molybdenite geochronometer
A newly acquired mass spectrometer MI by the Mass Spectrometry Laboratory will be adapted to determine rhenium and osmium isotope concentrations using negative thermal ionization mass spectrometry NTIMS. We describe the principle of the Re-Os dating technique and the thermal ionization phenomena which lead to high precision isotope analysis on NTIMS. Bahcall JN, Theory of Bound-State Beta Decay.
James M. Day, D. Graham Pearson, Larry J. We present new Re—Os isotope data for the intrusion, together with PGE and trace element abundances, and oxygen and Sm—Nd isotope data on samples that include local crustal materials, layered series peridotites, stratiform chromitites, marginal and roof zone rocks, and the Muskox Keel feeder dyke. HSE and fluid-immobile trace element abundance variations are consistent with relative compatibilities expected for cumulate rocks.
The most radiogenic Os and unradiogenic Nd isotope compositions occur in the Muskox marginal and roof zones. The most significant process causing Os and Nd isotope variations in the layered series of the intrusion is crustal contamination of mantle-derived magma batches feeding individual cyclic units. This process may be directly responsible for formation of chromitite horizons within the intrusion.
Parental magmas were probably derived from a mantle source unaffected by long-term, large-scale melt depletion, with no appreciable input from recycled crust and lithosphere, or putative core contributions. A long-standing debate in geology has been the relative roles played by the Earth’s crust and mantle in generating the geochemical signatures of large igneous provinces LIPs , and the influence these reservoirs have in the formation of mineral deposits in magmatic systems.
Layered intrusions are central for addressing these issues, because they record periods of magmatic activity intimately associated with LIPs, and generally host precious metal mineralization within the system. Application of the Re—Os isotope system to these problems has allowed effective discrimination of crustal and mantle signatures, because Re and Os track the behaviour of the platinum-group element [PGE; Os, Ir, Ru, Rh, Pt, Pd—with Re and Au collectively termed highly siderophile elements HSE ] enrichments more faithfully than lithophile isotope systems e.
Lambert et al. Furthermore, in contrast to the less than Myr snapshot provided by ocean island basalts, LIP magmatism has occurred over much of Earth history, providing important constraints on the secular evolution of the terrestrial mantle.
America; West of Shetlands oilfields. Selby’s research has developed a unique geochemical toolbox using rhenium, osmium, platinum and palladium that constrain more accurate geological models leading to better reserve predictions. The toolbox provides previously unavailable geological time constraints and source identification of resources e. The underpinning research carried out by Selby TOTAL Reader in Petroleum Geoscience, appointed and his research group at Durham University from appointment to present addresses longstanding academic industry-related issues concerning the development of subsurface Earth resources.
Emplacement of the Muskox intrusion occurred early in the Mackenzie event and has been precisely dated using baddeleyite–zircon U–Pb dating.
Re and Os are redox-sensitive and organophilic, and can be enriched in potential hydrocarbon source rocks, tar sands, crude oil, and bitumen. Re-Os geochronology of these organic-rich samples has the potential for direct dating the time frame of hydrocarbon formation, migration or charge within a petroleum system. Here, we review some major reported case studies on the Re-Os geochronology of oil and gas reservoirs over the last decade. Filling the above knowledge gaps requires a comprehensive academia-industry collaboration, which is critical step to accomplish a valuable application guide for the petroleum industry end-users on using the Re-Os isotope system to directly date petroleum systems.
Research (Crustal Re-Os Geochronology)
This report presents the results of rhenium-osmium Re-Os isotope analysis performed on 11 organic-rich and radiogenic shale samples from the following Devonian and Jurassic formations in central and northern Alberta:. Current detailed stratigraphic work at the AGS includes an effort to resolve uncertainties regarding the age and stratigraphic position of a number of stratigraphic units, based on precise isotope dating. Recent advances in dating organic-rich shales using the Re-Os isotope system have allowed us to date important hydrocarbon source rocks in the Western Canada Sedimentary Basin.
All rhenium and osmium isotopic measurements were made on a VG plasma Quad facility The application of Re-Os isotope system to the tracing and dating of.
Development of Re-Os geochronology for crustal matrices has been ongoing since in the laboratory. This work has resulted in major advancements in the direct isotopic dating of crustal sulfide minerals, petroleum source-rocks, and natural hydrocarbons, using Re-Os isotopes. For sulfide minerals, Re-Os geochronology has direct application to the timing and duration of hydrothermal ore deposit formation. Some key papers include:. Systematic work, aimed at further evaluating the utility, robustness and cross-calibration of the Re-Os geochronometer to other dating methods, has also been a key research theme.
Using Re-Os isotopes to determine the deposition age of petroleum source-rock formation organic-rich shales is a major research theme, both in terms of technical development and application. This method has been applied to better understand the origins of global Oceanic Anoxic Events OAEs , the timing of shale deposition and correlation in Precambrian sedimentary basins and this rise of oxygen on Earth.
Re-Os isotopes in natural hydrocarbons is the third major research theme of the laboratory, again approaching this new field from both a systematic evaluation and application perspective. Re-Os isotopes natural hydrocarbons are directly related to source-rock Re-Os isotope character and in some cases Re-Os geochronology of hydrocarbons is possible. Research Crustal Re-Os Geochronology Development of Re-Os geochronology for crustal matrices has been ongoing since in the laboratory.
D Selby and RA Creaser. Canadian Centre for Isotopic Microanalysis.
Re and Os are redox-sensitive and organophilic, and can be enriched in potential hydrocarbon source rocks, tar sands, crude oil, and bitumen. Re-Os geochronology of these organic-rich samples has the potential for direct dating the time frame of hydrocarbon formation, migration or charge within a petroleum system. Here, we review some major reported case studies on the Re-Os geochronology of oil and gas reservoirs over the last decade.
Filling the above knowledge gaps requires a comprehensive academia-industry collaboration, which is critical step to accomplish a valuable application guide for the petroleum industry end-users on using the Re-Os isotope system to directly date petroleum systems.
Rhenium–osmium dating. Rhenium and Osmium were strongly refractory and siderophile during the initial accretion of the Earth which caused.
Official websites use. Share sensitive information only on official, secure websites. Re—Os geochronology of the lacustrine Green River Formation: Insights into direct depositional dating of lacustrine successions, Re—Os systematics and paleocontinental weathering Earth and Planetary Science Letters. By: Vivien M. Lacustrine sedimentary successions provide exceptionally high-resolution records of continental geological processes, responding to tectonic, climatic and magmatic influences.
These successions are therefore essential for correlating geological and climatic phenomena across continents and furthermore the globe. Producing accurate geochronological frameworks within lacustrine strata is challenging because the stratigraphy is often bereft of biostratigraphy and directly dateable tuff horizons. The rhenium—osmium Re—Os geochronometer is a well-established tool for determining precise and accurate depositional ages of marine organic-rich rocks. Lake systems with stratified water columns are predisposed to the preservation of organic-rich rocks and thus should permit direct Re—Os geochronology of lacustrine strata.
We present Re—Os systematics from one of the world’s best documented lacustrine systems, the Eocene Green River Formation, providing accurate Re—Os depositional dates that are supported by Ar—Ar and U—Pb ages of intercalated tuff horizons. Controls on uptake and fractionation of Re and Os are considered to relate mainly to depositional setting and the type of organic matter deposited, with the need to further understand the chelating precursors of Re and Os in organic matter highlighted.
Such insights enable us to evaluate fluctuations in continental climatic, tectonic and magmatic processes and provide the ability for chemostratigraphic correlation combined with direct depositional dates.
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rhenium-osmium (Re-Os) geochronology in pyrite-bitumen bearing However, the absolute dating of fault rock formation events remains a problematic issue.
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Thank you for your feedback. The information presented below briefly outlines how Chemostrat is utilising two of these techniques, i. Re and Os become concentrated in the organic, hydrogenous fraction of organic rich shales, thus the time when the shale was deposited can be dated. Furthermore, as Re and Os have been inherited from the source rocks, Os isotopes can be employed to correlate an oil with its source.
As a result, accurate and precise ages are difficult to determine for these successions, which hampers attempts to correlate successions across different regions.