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.
Canadian Journal of Earth Sciences
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.
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.
Reos pyrite dating
The Kerman copper belt in Iran contains a number of important porphyry copper deposits, including Sarkuh and Iju. Molybdenite Re-Os isotope dating of the Sarkuh and Iju porphyry copper deposits shows that mineralization occurred at Compared with the previous Re-Os dating of molybdenite in the region, it is revealed that Cu mineralization was an ongoing process in an arc setting during the Miocene.
The available zircon dates of the granitic rocks from the Sarkuh
Ore minerals are chalcopyrite, pyrite, galena, sphalerite and siderite. Re-Os dating of molybdenite yielded a weighted average age of ± Ma, which.
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.
Why Is Joe Rogan So Popular?
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
Abstract—Re-Os isotopic analyses of a single organic-rich sedimentary rock unit (ORS) of known deposi- date for further evaluating the Re-Os geochronometer in ORS. 3. The Re and Os contents of diagenetic pyrite nodules associated.
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].
The Campo del Cielo refers to a group of iron meteorites or to the area where they were found situated on the border between the provinces of Chaco and Santiago del Estero, 1, kilometers mi northwest of Buenos Aires, Argentina. Pallasites, a rare type of stony-iron meteorite, consist of olivine grains embedded in an iron-nickel metal matrix. If you are testing a potential meteorite with a magnet, first ensure that the magnet is not attached to any other metallic objects, then attach it to a piece of string.
The same is true for airplane parts and car parts, motorcycle parts all are found in the desert and other isolated areas now. With this information, we estimate the costs an These meteorites are composed of olivine crystals, similar to the piece of 4 Vesta that Ian Nicklin discussed above, that are embedded in a larger mass of iron-nickel.
U-Th-Pb dating and high-precision Re-Os ages for molybden- ite from the thermal-stage minerals (molybdenite, chalcopyrite, pyrite, ga- lena, sphalerite, and.
The study area is located at the southern end of the Gorouol greenstone belt, northwestern Niger. This region contains significant deposits of Copper and Molybdenum hosted in intrusive rocks metamorphosed in the green shale facies. This deposit was previously considered a porphyry system of Copper Cu and Molybdenum Mo without having been the subject of advanced research. The objective of this study is to confirm or refute this hypothesis and to date the mineralisation in an absolute manner in order to readjust the mineralising episode in the history of the West African Craton.
The methodology used within the framework of this study is the isotopic dating by the Re-Os method carried out on the pyrites of the host rock. This age range represents the West African Craton scale to an episode of magmatic accretion. During this accretion, the subduction phenomena between the Crusts Oceanic and Continental would have been favourable for the formation of the Cu and Mo mineralisation of Kourki. Abdou, H. Bonnot, D. Bory Kadey, D. Chalamet, M. Saint Martin, et I.
Dissecting the Re-Os molybdenite geochronometer
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.
Pyrite Os and Re concentrations range between and ppb The first attempt to date molybdenite from the Bagdad ore deposit was reported.
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.
Mirnejad, H. Economic Geology, 4. ISSN
In-situ LA-ICP-MS trace elemental analyses of magnetite and Re–Os dating of pyrite: the Tianhu hydrothermally remobilized sedimentary Fe deposit, NW China.
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.
Research (Crustal Re-Os Geochronology)
The Baishan Mo Re deposit is located in the eastern section of the eastern Tianshan orogenic belt, NW China. The deposit has a grade of % Mo and a high.
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
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.
To address this need, we applied Re-Os pyrite dating to the world class Irankuh Zn-Pb deposit, Iran. The Irankah deposit is located in the thrust.
A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. The word ‘concretion’ is derived from the Latin con meaning ‘together’ and crescere meaning ‘to grow’. Concretions form within layers of sedimentary strata that have already been deposited. They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock.
This concretionary cement often makes the concretion harder and more resistant to weathering than the host stratum. There is an important distinction to draw between concretions and nodules. Concretions are formed from mineral precipitation around some kind of nucleus while a nodule is a replacement body.
Descriptions dating from the 18th century attest to the fact that concretions have long been regarded as geological curiosities.