The ultramafic massif at Raobazhai in North Dabie is located in the suture zone between the Yangtze craton and North China craton. The Re-Os isotope compositions of the massif are used to decipher the origin and tectonics of the ultramafic rocks involved in continental subduction and exhumation. Fifteen samples were collected from five drill holes along the main SE-NW axis of the Raobazhai massif. Major and trace element compositions of the samples show linear correlations between MgO, Yb and Al2O3. This suggests that the massif experienced partial melting with variable degrees and is from fertile to deplete in basaltic compositions. Nine selected samples were analyzed for Re-Os isotope compositions. Re contents range from 0. These indicate that the massif is a piece of continental lithospheric mantle with variable depletion. During Triassic subduction of the Yangtze craton beneath the North China craton, part of the wedge of subcontinental lithospheric mantle was intruded into the subduction belt, and then exhumed to crustal level together with the subducted crustal plate after ultrahigh pressure metamorphism at mantle depths. This ancient lithospheric mantle is now exposed as an orogenic peridotite massif.
Timing and tempo of the Great Oxidation Event
University of Quebec at Chicoutimi ; M. Chinese Academy of Sciences ; B. Current research topics include:
dating of the Devonian–Mississippian time-scale boundary using the Re–Os black shale geochronometer. Geology 33, –]. This may suggest fairly constant and low global continental weathering rates during the Late Devonian, although in view of the.
Here we report that eleven typical Besshi-type deposits yielded Re-Os isochron ages around Ma We infer that intense mid-ocean ridge hydrothermal and volcanic activity in the Late Jurassic produced huge sulphide deposits and large emissions of CO2 gas, leading to global warming and a stratified Panthalassa Ocean with anoxic deep seas that favored preservation of sulphides in the pelagic environment.
Ocean anoxic events OAEs are recorded by the ubiquitous presence of organic carbon—rich sedimentary rocks such as black mudstone and shale, which are stable under anoxic conditions 1 , 2 , 3. The presence of these rocks in pelagic deep-sea sedimentary successions in accretionary complexes is considered especially strong evidence for ancient OAEs on a global scale 2 , 3 , 4 , because pelagic deep-sea sediments far away from continents provide us representative information on open ocean environments.
Similarly, sulphide minerals are redox-sensitive and easily dissolve in seawater under oxygenated conditions 5 , 6 , 7. In the oxygenated pelagic deep-sea of open oceans such as the modern Pacific and Atlantic, seafloor hydrothermal sulphide deposits are rapidly dissolved or replaced by Fe-oxide or oxyhydroxide minerals 6 , 7 , and thus are not generally preserved. Hence, the presence of massive sulphide deposits, formed and preserved on an ancient pelagic deep-sea floor and now found in accretionary complexes, can be regarded as a powerful indicator of an OAE.
Our study involved the well-known copper-bearing sulphide deposits distributed along the Sanbagawa metamorphic belt of southwest Japan, a Cretaceous accretionary complex 8 , 9. Classified as Besshi-type deposits, these large strata-bound stratiform sulphides were deposited within a limited stratigraphic range, perhaps only a few stratigraphic horizons, in a belt of outcrops more than km long 10 Fig. Besshi-type deposits are recognised throughout the world in rocks of Early Proterozoic to Paleogene age 11 , More than Besshi-type deposits, including the type locality, have been documented in the Sanbagawa metamorphic belt Fig.
These were a major source of copper during the development of modern Japan over approximately three centuries until the s.
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A practical method for determination of molybdenite Re-Os age by inductively coupled plasma- mass spectrometry 3 digestion Y. Go to our Instructions for using Copyright Clearance Center page for details. Authors contributing to RSC publications journal articles, books or book chapters do not need to formally request permission to reproduce material contained in this article provided that the correct acknowledgement is given with the reproduced material.
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Tectonic implications from Re–Os dating of Mesozoic molybdenum deposits in the East Qinling–Dabie orogenic belt Molybdenite Re–Os dating method is a powerful tool for the precise age determination of ore deposits (cf. pyrite and minor chalcopyrite, galena, and sphalerite. The.
Doctoral thesis, Durham University. Auriferous quartz veins and mylonitic shear zones cross cut Archean granitoids ca. Lu-Hf zircon results provide evidence for ca. A greenschist facies metamorphic mineral assemblage overprints all of the magmatic phases and U-Pb dating of syn-metamorphic titanite hosted by a foliated Archean granitoid at ca. The majority of mineralization is hosted by a network of brittle-ductile and mylonitic shear zones, which record evidence for transpressional deformation of triclinic, or lower order, symmetry.
Relacement of igneous feldspar plagioclase and K feldspar with intrinsically weaker phyllosilicates, during sericitization of the granitic wall rock, created the ideal conditions for strain localization and locally may have led to the onset of crystal plastic deformation processes. Continued feedback between fluid, rock and deformation generated interconnected networks of weak mylonitic shear zones that are subject to reactivation.
Quartz veins are the other significant host for Au and possess geometries that imply mineralization occurred concurrently with episodic fluid pressure fluctuations. Re-Os molybdenite, pyrite and chalcopyrite geochronology ages record a protracted metallogenic history and provide evidence for at least two mineralizing events at ca. Each metallogenic event is represented in detail by a hydrothermal history that occurred at a time scale less than the resolution of the Re-Os method.
High precision U-Pb zircon ages for the Saza Granodiorite overlap with Re-Os ages and provide unequivocal evidence for magmatism concomitant with sulphidation, however the wide range of Re-Os sulphide ages precludes a genetic relationship between any individual intrusion and Au. The goldfield-wide metallogenic event at ca. Mesoproterozoic Re-Os ages ca.
Re-Os systematics of pyrite from the Bolcana porphyry copper deposit, Apuseni Mountains, Romania
Its orebodies are hosted in the Carboniferous Yiliu Formation volcanic-sedimentary cycle and occur as stratiform, stratoid and lenticular. Whether or not the stratabound ore belong to the volcanogenic massive sulfide VMS deposit remains unclear and controversial. In this paper, the whole rock geochemistry, trace elements in sphalerite, U-Pb zircon chronology and Pb isotopes were investigated, aiming to provide significant insights into the genesis and geodynamic setting of the Laochang deposit.
Lead isotope ratios of pyrite and sphalerite from the stratabound ore are This indicates a binary mixing of lead components derived from leaching between the host volcanic rock and mantle reservoir.
Minerals, an international, peer-reviewed Open Access journal. The gold-producing hydrothermal event is also recorded by Re–Os dating of molybdenite from the gold-bearing Mg-metasomatized metasedimentary and metavolcanic units at the Palokas prospect; a few kilometres from Rompas. The co-existence of siderite and pyrite was attributed.
Research Interests Re-Os isotope geochemistry, source rocks, hydrocarbons, and sulfides. Global metallogeny and ore genesis using absolute time as a correlation tool for dynamic, deep fluid-enhanced events associated with metal mobility and enrichment. Sequestration and release of metals in sedimentary rocks. Holistic interpretations for resource genesis relevant to 21st century exploration. Current Research CHRONOS , chronostratigraphy and correlations, Re-Os calibration of marine and terrestrial records; NSF , Re-Os geochemistry to test recurrent fluid flow in the crust, orogenic belts in central India; Twenty additional projects of years duration on topics covering 1 hydrocarbon maturation and migration through Re-Os isotope geochemistry, 2 Re-Os dating of molybdenite, pyrite and other sulfides, and 3 ore genesis and source to site processes.
Locations for this work span the globe, with a focus on Arctic regions. Stein is widely known for her solid understanding of all types of ore deposits and has visited, sampled, and dated many of these deposits globally. She started her career in the mineral industry, logging core and mapping underground — a muddy hands-on start that was pivotal to her success.
Redline Gold Skarn Deposits
Mass-production of Cambro-Ordovician quartz-rich sandstone as a consequence of chemical weathering of Pan-African terranes: Earth and Planetary Science Letters, , Formation and evolution of lateritic profiles in the middle Amazon basin:
iii. dating of alteration and mineralization using 40 Ar/ 39 Ar and Re-Os methods; and iv. development of a composite deposit model that incorporates both A. Pyrite crystals from N1 have granoblastic textures, as do most pyrite crystals in the.
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Top9. Re-Os isotopic analysis opened a new approach to dating sedimentary rocks
Residency of rhenium and osmium in a heavy crude oil. Geochimica et Cosmochimica Acta. Why terrestrial coals cannot be dated using the Re-Os geochronometer: International Journal of Coal Geology. Refining the Jurassic-Cretaceous boundary: Earth and Planetary Science Letters.
recent Re–Os dating of vein-hosted gold mineralization in the Meguma Zone of Nova Scotia. There is an obvious need for bet – such as pyrite, pyrrhotite, chalcopyrite and arsenopyrite. The only exception is the Re–Os geochronometer, based on the decay of Re to Os. This method has been used to.
Characteristics A block of electrolytically refined cobalt It is attacked by halogens and sulfur. It does not react with hydrogen gas H2 or nitrogen gas N2 even when heated, but it does react with boron , carbon , phosphorus , arsenic and sulfur. Green cobalt II oxide CoO has rocksalt structure. These halides exist in anhydrous and hydrated forms. Whereas the anhydrous dichloride is blue, the hydrate is red. Cobalt III fluoride, which is used in some fluorination reactions, reacts vigorously with water.
The principles of electronegativity and hardness—softness of a series of ligands can be used to explain the usual oxidation state of cobalt. One of the isomers determined was cobalt III hexammine chloride.