Tatsuo Nozaki and Dr. This result supports the ideas of previous studies, indicating that there is a large age gap hiatus in the geologic record of million years and a wide distribution of the Cambrian beds in the Hitachi area. It is expected to provide an important age constraints to reconstruct the initial tectonic history of the Japanese Islands. Besshi- and Kuroko-type sulfide deposits widely distributed in the Japanese Islands are classified as one of the volcanogenic massive sulfide deposits. Figure 1: Principles of the Re-Os isotope dating method. Figure 3: Photomicrographs of Fudotaki and Fujimi sulfide ores under reflected light. These sulfide ores are dominated by pyrite with some amounts of chalcopyrite, sphalerite, pyrrhotite, galena, marcasite and barite. We could not obtain the Re-Os isochron having good linearity from the Fujimi sulfide ores which include much more amounts of sphalerite and pyrrhotite than the Fudotaki sulfide ores. Scale bar is 0. Figure 4: Re-Os isochron diagram for the Fudotaki sulfide ores.
Mirnejad, H. Economic Geology, 4. ISSN Full text is not posted in this repository. Consult Related URLs below.
These unique characteristics explain why Re-Os molybdenite dating as seen for example for Au in arsenian pyrite and Os-Ir alloys in laurite.
E-mails: marapita1 yahoo. E-mails: mapabarros yahoo. E-mail: orestes. E-mail: mcnaughton curtin. E-mail: malc. Hydrothermal monazite grains formed during the Au mineralization event occur as fine anhedral crystals filling fractures or as isolated grains associated with Ag, Au, molybdenite, barite, pyrite, galena, and sphalerite.
The investigation of epigenetic carbonate-hosted Pb-Zn deposits from China and Europe in the Eastern and Western orogens of the Tethyan Domain, have provided a new perspective on the range of processes operating in this deposit class globally. However, improved metallogenic models require new constraints on the timing of mineralization throughout the Domain.
Mineralization is hosted by the Goushfil Main Fault and adjacent dolomitized limestones.
in the field of fault-rock dating, fault mechanics, Re–Os pyrite–chalcopyrite. systematics and Early Paleoproterozoic C isotopic fluctuations and. geodynamics.
Vernon, R. Precambrian Research , , pp. In the Archaean basement rocks of the Assynt and Gruinard terranes of the mainland Lewisian Complex in NW Scotland, a regional suite of quartz-pyrite veins cross-cut regional Palaeoproterozoic Badcallian, ca. The quartz veins are overprinted by amphibolite-greenschist facies Laxfordian deformation fabrics ca. The almost orthogonal orientation of the quartz veins NE-SW to the Scourie dykes NW-SE are incompatible and must result from distinct paleostress regimes suggesting they are related to different tectonic events.
Sulphur isotope analysis suggests that the sulphur associated with the pyrite is isotopically indistinguishable from primitive mantle. The presence of the ca. The absence of the veins in the Rhiconich Terrane is consistent with the suggestion that it was not finally amalgamated to the Assynt Terrane until the Laxfordian. Skip to main content Accessibility information. Site tools A-Z Lists.
Seven Re- Os ages were determined for molybdenite and pyrite samples from two well-dated Precambrian intrusions in Fennoscandia to examine the sustainability of the Re-Os chronometer in a metamorphic and metasomatic setting. Using a new Re decay constant 1. These two localities contain some of the oldest and youngest plutonic activity in Fennoscandia and are associated with newly discovered economic Au mineralization Ilomantsi, Finland and a Cu-Mo prospect Kabeliai, Lithuania.
The slightly younger age suggests the introduction of Cu-Mo mineralization by a later phase of the Kabeliai magmatic system. This is a preview of subscription content, log in to check access. Rent this article via DeepDyve. Reprints and Permissions.
Danny Hnatyshin, Robert A. Creaser, Jamie J. Wilkinson, Sarah A. Gleeson; Re-Os dating of pyrite confirms an early diagenetic onset and extended duration of mineralization in the Irish Zn-Pb ore field. Geology ; 43 2 : —
Structural characteristics and Re–Os dating of quartz-pyrite veins in the Lewisian Gneiss Complex, NW Scotland: evidence of an early.
A Nature Research Journal. The origin of giant, sedimentary rock-hosted copper-cobalt Cu-Co provinces remains contentious, in part due to the lack of precise and reliable ages for mineralisation. As such, no consensus has been reached on the genetic model for ore formation, and the relationships between tectonism, palaeo-fluid circulation and mineralisation.
Here, we link the timing of Cu-Co mineralisation in the Central African Copperbelt to compressional tectonics during the Lufilian Orogeny by using new ca. The initial Os isotope composition of carrolite is compatible with the leaching of Os and Cu -Co from Mesoproterozoic Cu sulphide deposits hosted in fertile basement.
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organic matter, titanium oxides, iron hydroxides, pyrite and clay minerals Re–Os dating of the Kurišková U–Mo deposit (Slovakia).
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precise and accurate single mineral Re-Os dating of molybde-. Corresponding rSa4S values for pyrite (%0) and molybdenite ( %o), which.
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.
The Yamansu iron deposit, hosted in submarine volcanic rocks, is located in the Aqishan-Yamansu Fe-Cu metallogenic belt of eastern Tianshan, Xinjiang. New pyrite Re-Os, and pyroxene diorite intrusion ages and the chemistry of magnetite constrain the origin of the deposit. The Yamansu orebodies display banded or lenticular forms and sharp contacts with marble and garnet skarn. Pyrite associated with magnetite from hydrothermal massive ores has a Re-Os isochron age of However, the pyroxene diorite age
Re-Os dating of auriferous pyrite from the Zhenyuan super-large gold deposit in Ailaoshan gold belt, Yunnan Province,. Southwestern China. SHI GuiYong1,3.
Understanding the distribution of parent Re and radiogenic daughter Os isotopes in molybdenite is critical in interpreting isotopic measurements because it can compromise the accurate determination and interpretation of mineralization 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.
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. However, molybdenite MoS 2 the most common molybdenum ore mineral constitutes a particular case within sulphide minerals because it contains high Re in the ppm range and Os at ppb levels , but almost no initial or common Os, hence all Os in molybdenite is of radiogenic origin i.
These unique characteristics explain why Re-Os molybdenite dating using the whole mineral approach is currently the most widely used single mineral geochronometer in ore deposits, where reliable crystallization ages have been obtained by the direct measurement of Re and Os concentrations in the mineral. Although the potential of molybdenite as a single-mineral geochronometer was recognized years ago 6 , 7 , initial studies were hampered by spurious ages that were interpreted as open system behavior of the isotopic system 8 , 9.