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.
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.
Re-Os Dating of Black Shales: Timing and Duration of Sedimentary Processes*. Judith L. Hannah. 1., Holly J. Stein. 1., Gang Yang. 1.
Degao Zhai, Anthony E. Economic Geology ; 5 : — Native gold is intergrown with molybdenite and pyrite in auriferous quartz veins hosted by a monzogranite-monzonite stock and locally by Proterozoic gneiss, thereby offering an excellent opportunity to directly date the mineralizing event. Uranium-Pb age determinations for zircon yielded ages for the monzogranite and monzonite of Numerous mafic to felsic dikes, which are crosscut by ore veins pre-ore , parallel to these veins possibly synore , or crosscut by them post-ore , were carefully examined and dated.
The age of mineralization was determined directly using the Re-Os method applied to molybdenite. A total of 19 molybdenite samples separated from auriferous quartz veins yielded widely differing Re-Os model ages of to Ma, and replicate analyses of individual samples also yielded widely differing ages.
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.
Both a deposition and migration age are recorded by separate Rhenium-Osmium (Re-Os) isochrons obtained from different phases within the same interval in.
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. Re—Os geochronology of the lacustrine Green River Formation: Insights into direct depositional dating of lacustrine successions, Re—Os systematics and paleocontinental weathering.
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 isotope system, based on its unusual qualities, has been widely used on the dating and tracing in the geoscience and geochemistry. As a reflection.
The Re-Os model ages for the molybdenites range between and Ma and apparently correspond to the early stages of metamorphism connected with pre-Variscan rift-related tectono-metamorphic events, which affected and recrystallized sedimentary CLM material rich in Mo-Th-Nb-REE. There is no geological evidence for the participation of fluids mobilized from host rocks in the formation of the CLM. Because the Re-Os chronometer in molybdenite is demonstrably stable through later Variscan facies metamorphism, the molybdenite chronometer has not been affected by subsequent thermal overprints associated with the Variscan orogeny.
Atencio D. Mineralogist 48, — Bingen B. Earth Planet. Earth Sci. Czech Geol. Craig J.
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. Here, we present the whole-rock major and trace elements, zircon U—Pb and Hf isotope data, and molybdenite Re—Os data for the Shimadong deposit.
Re-Os dating method was applied to the Kuroko ore deposits of the Hokuroku district, Japan. The Re and Os concentrations of four Kuroko, three Oko and one.
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. In contrast to cratonic eclogites, most pyroxenites analysed here and those reported in the literature lie close to the mantle Nd—Hf isotope array. The Nd—Sr—Pb—Hf isotopic compositions and stable isotope characteristics of these pyroxenites reflect signatures from recycled oceanic crust and sediment.
Hence, mixing of such material, if present within the convecting mantle, with peridotite, could account for some of the heterogeneity seen in oceanic basalts. Small amounts of pyroxenite incorporated into peridotite can also produce the radiogenic Os isotope signatures evident in the source of oceanic basalts. However, these observations alone do not require pyroxenite to be an integral part of the convecting upper-mantle magma source region. The spectrum of Nd, Hf and Os isotope compositions also makes them a suitable component to explain some of the isotopic characteristics of the source regions of ultrapotassic magmas.
Some recent models to explain the detailed major, trace element and isotopic systematics of mid-ocean ridge basalts MORB have advocated contributions from pyroxenites to the melting regime e. Prinzhofer et al. Because of their potential significance in such geodynamic and petrogenetic models, it is important to improve characterization of the elemental and isotopic systematics of pyroxenites.
Geochronology and Isotopes
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.
Dating mantle peridotites using Re-Os isotopes: The complex message from whole rocks, base metal sulfides, and platinum group minerals.
The Triassic collision between the North China and Yangtze Cratons which generated numerous granitoid intrusions such as the Shangcheng, Xingxian and Lingshan intrusions, and other small stocks, such as Tangjiaping, Dayinjian, Mushan and so on. Those shallow-emplaced granite porphyries are closely related to porphyry-skarn Mo and Mo-W deposites, forming the Dabie molybdenum metallogenic belt. Molybdenum deposits occur in the endo- and exocontact zones of the porphyry, include with three major types of Mo mineral systems, i.
The ore-forming ages of the molybdenum deposits in Dabie area are mainly cluster Request Permissions. Zhang, B. Zhang, X. Yuan and Q. Xiao: Qinling orogenic belt and continental dynamics Science Press, Beijing In Chinese. Ames, G.