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. Furthermore, as Re and Os have been inherited from the source rocks, Os isotopes can be employed to correlate an oil with its source. Despite this application mainly being associated with the economic extraction of minerals, it can be employed by the oil and gas industry to date the formation of disseminated sulphide minerals within basement rocks and so the basement itself. Moreover, when these minerals are found in fractures it can be used to provide a minimum date for when the fracture network was open. Re-Os Radiogenic Isotope Dating Methods and Applications 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. Establishing when organic shales were deposited 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.
Top9. Re-Os isotopic analysis opened a new approach to dating sedimentary rocks
A suite of pyroxenites from the Beni Bousera peridotite massif, northern Morocco, have been analysed for Re—Os and Lu—Hf isotopic compositions. In general, the Nd—Hf isotope compositions of the pyroxenites lie close to the mantle array. As with the Sm—Nd and Rb—Sr systems, parent—daughter and isotopic ratios for the Lu—Hf system have been recently decoupled by a partial melting event associated with transfer of the massif from mantle to crust. The near-solidus extraction of a siliceous melt from the pyroxenites is also a possible explanation for the orthopyroxene-rich margins to numerous pyroxenite layers, via reaction with peridotite.
Pyroxenite Os isotope compositions are much more radiogenic than their host peridotites.
This work has resulted in major advancements in the direct isotopic dating of crustal sulfide minerals, petroleum source-rocks, and natural hydrocarbons, using Re-.
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. Our results show a heterogeneous distribution of , Re and Os isotopes in MoS 2 , and that both Re and Os isotopes are not decoupled as previously thought. We conclude that Re and Os are structurally bound or present as nanoparticles in or next to molybdenite grains, recording a complex formation history and hindering the use of microbeam techniques for Re-Os molybdenite dating.
Our study opens new avenues to explore the effects of isotope nuggeting in geochronometers. Ore deposits are the main source of metals for society, and their efficient and sustainable exploration requires a precise understanding of the factors that control their distribution within the upper crust. Rhenium is radioactive and decays to radiogenic Os by beta emission.
The Re-Os system follows the law of radioactivity where the total number of Os atoms in the sample at the present time is equal to the number of atoms of Os incorporated in the sample at the time of mineral formation and the Os atoms produced by decay of the Re parent radionuclide. Due to their chalcophile affinity and behavior during partial melting of the mantle, Re and Os will be concentrated in sulphide phases usually at low ppb and ppt levels, respectively.
Research (Crustal Re-Os Geochronology)
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.
Re–Os geochronology underpins dating of materials from meteorites, the mantle, and metallic ore deposits. Furthermore, both Re and Os are redox-sensitive.
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. N2 – Re and Os are redox-sensitive and organophilic, and can be enriched in potential hydrocarbon source rocks, tar sands, crude oil, and bitumen.
AB – Re and Os are redox-sensitive and organophilic, and can be enriched in potential hydrocarbon source rocks, tar sands, crude oil, and bitumen. Overview Fingerprint. Abstract Re and Os are redox-sensitive and organophilic, and can be enriched in potential hydrocarbon source rocks, tar sands, crude oil, and bitumen. Keywords Re-Os isotope dating oil-oil and oil-source rock correlations petroleum reservoir progress challenge.
Copyright remains with the author s or their institution s. Permission for reuse free in most cases can be obtained from RightsLink. The Shimadong porphyry Mo deposit is located in eastern Yanbian, in the eastern part of the north margin of the North China craton, northeastern China.
Top9. Re-Os isotopic analysis opened a new approach to dating sedimentary rocks. Updated,05, Researcher Qu W.J. and his team from the National.
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.
Dissecting the Re-Os molybdenite geochronometer
Geochronology involves understanding time in relation to geological events and processes. Geochronological investigations examine rocks, minerals, fossils and sediments. Absolute and relative dating approaches complement each other. Relative age determinations involve paleomagnetism and stable isotope ratio calculations, as well as stratigraphy.
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.
Specifically, exactly when, how and where do resources, such as oil and copper, form in rocks? Analytical and technological advances, developed in part by research at Durham, have permitted the use of previously challenging geochemical methods to help answer old, but critically important geological questions. Selby, his research group and international collaborations 6 PhD students, 2 post-doctoral researchers, United States and Canada Geological Survey research staff; Prof.
As a direct result, Selby’s research has defined and enhanced the precision and understanding of Re-Os and Pd-Pt analytical protocols and elemental behaviour in rocks and minerals. This has improved our understanding of genetic models for both mineral and hydrocarbon systems . In impact terms, the outcome yields critical necessary data required for exploration programmes [Section 4]. Ultimately Selby’s research has shown that the Re-Os system can be applied much more widely than previously thought and has placed Durham at the forefront in the use of this novel research tool both academically and through industry.
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.
Goals This proposed work will extend laser ablation resonance ionization spectrometry LARIMS from the previously demonstrated rubidium-strontium Rb-Sr geochronology system to four other radiogenic systems, enabling in-situ, concordant age determinations to be made on extraterrestrial bodies in the solar system. Advantages include providing an independent test of concordance, while expanding the potential range of samples that can be successfully measured.
Testing for concordance is important because individual isotopic dating systems can be biased by a variety of factors. These biases are frequently distinct for different radiometric systems. Objectives This proposal addresses the important NASA goal to understand the history and evolution of the solar system. The time of key events in solar system history are poorly constrained by current samples, giving impetus to future missions with sample return and in-situ landed dating measurements.
An issue for in-situ radiometric measurements is the desire for testing concordance, i.
Geochronology and Isotopes
The age dating strategy depends on the type of formation magmatic, metamorphic or sedimentary , the sample composition and the age of formation. The concentration of the mother and daughter isotopes, as well as the apparent age can be determined with high precision. In many cases, however, the determined age may not be the real age of the geological event. The apparent age may be affected by the post-depositional or post-formation history of the rocks.
Natural contamination of chemical sediments with detrital material can also affect the results of dating of diagenesis.
The Re-Os isotope system, based on its unusual qualities, has been widely used on the dating and tracing in the geoscience and geochemistry. As a reflection.
While whole-rock peridotite Re-Os isotopic signatures are the core of such investigations, the Re-Os dating of individual peridotite minerals—base metal sulfides BMS and platinum group minerals PGM —that are the main hosts for Re and Os in the mantle peridotites came into play two decades ago. This is, however, not a rule of thumb as clear evidence of crust-mantle age decoupling also exist. As such, they are the mantle equivalents of crustal zircons. Abrajano, T. Sulfide petrology of the critical zone of the Acoje massif.
Contributions to Mineralogy and Petrology, , 64— Ackerman, L. Geochimica et Cosmochimica Acta, 73, — Geochimica et Cosmochimica Acta, , — Alard, O.