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.
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.
The hydrothermal mineral assemblage comprises sphalerite, galena, pyrite, minor chalcopyrite and sulfosalt minerals, together with dolomite, barite and abundant quartz. Nonetheless, vein and replacement pyrites from the Goushfil orebody yielded a 5-point isochron age of
The dominant sulphide is chalcopyrite accompanied by minor pyrite (chalcopyrite / pyrite = 5 / 1) and Re / Os molybdenite dates of 2 + 0. 6 and
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 : — Consequently, genetic models for ore formation are poorly constrained and remain controversial. Here we use Re-Os geochronology to show that ore-stage pyrite from the Lisheen deposit formed at Pyrite from the Silvermines deposit returns an age of These age determinations show that the much younger paleomagnetic ages reported for the Irish Zn-Pb deposits reflect remagnetization during the Variscan orogeny, a process that we suggest affects paleomagnetic dating more widely.
The Re-Os ages overlap with the ages of lower Carboniferous volcanic rocks in the Midlands, which are the product of magmatism that has been invoked as the driving force for hydrothermal activity. The relatively low initial Os ratios for both Lisheen 0. Shibboleth Sign In. OpenAthens Sign In. Institutional Sign In.
Reos pyrite dating
Mirnejad, H. Economic Geology, 4. ISSN Full text is not posted in this repository. Consult Related URLs below.
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.
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 hydrothermal monazite grains contain very low U, relatively low Th, and moderate Nd and La contents. Serrato et al.
The Amazon Craton AC was formerly considered a large Archean platform that underwent reworking and reactivation during the Proterozoic, with expressive anorogenic felsic magmatism Amaral , Almeida et al. Santos et al. In addition, exploration by mining companies resulted in thousands of surfaces and drill core samples for study Santos et al.
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Re-Os dating of pyrite confirms an early diagenetic onset and extended duration. 1 of mineralization in the Irish Zn-Pb orefield. 2. 3. Danny Hnatyshin. 1.
Abstract Abstract. These deposits are related to a Neogene andesitic volcanism.
Pyrite Re-Os age constraints on the Irankuh Zn-Pb deposit, Iran, and regional implications
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:.
Seven ReOs ages were determined for molybdenite and pyrite samples from two well-dated Precambrian intrusions in Fennoscandia to examine the.
The hydrothermal ore sequence, from early to latest, is: magnetite-hematite-pyrite, molybdenite, bornite-chalcopyrite-pyrite, pyrite-enargite to tennantite-tetrahedrite, covellite, gold. The presence of deep anhydrite vein infill indicates descending acid-sulfate water from shallow steam condensation.
The hydrothermal system is chemically characterized by a relatively narrow spectrum of elements enriched compared to bulk continental crust, i. Copper and Sb are enriched by a factor of 10 and 30, respectively. The arsenic budget is controlled by enargite and fahlore, although pyrite has a constant As abundance of around ppm. Arsenic, Sb and Hg correlate well fahlore control , while Au has no correlation with any other element.
This suggests that gold fixation is not controlled by any specific mineral, and that gold occurs as native gold. The gold content of pyrite, enargite and fahlore is below the analytical detection limit of the electron microprobe, i. Eight Mo-rich bulk rock samples define a Re-Os isochron age of Three Ar-Ar age data on deep potassic alteration and on alunite-altered rock are These ages overlap within error and define a combined age of
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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.
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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.
Dissecting the Re-Os molybdenite geochronometer
Here we use direct Rb-Sr dating of pyrite from Wulong gold deposit, and Frei, R., Nagler, T. F, Schonberg, R. and Kramers, J. () Re-Os, Sm-Nd, U-Pb, and.
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 Magnetite samples from different ores in the Yamansu deposit are suggested to have a magmatic-hydrothermal origin. Moreover, magmatic and hydrothermal magnetite samples show different characteristic normalized rare earth element REE and trace element patterns.