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Showing 1 to 20 of 22 for “"U-Pb dating"”.
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High-precision U/Pb dating of the Cenomanian-Turonian boundary Kaiparowits Plateau, Utah
… the Kaiparowits Plateau, Utah were dated using U/Pb geochronology. The Cenomanian-Turonian boundary is constrained to be 94.040 ± 0.029/0.098/0.14 Ma, in agreement with recent astrochronologic studies of the same time period. This research will help improve the calibration of the astronomical time …
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U-Pb dating of granites from the Charlotte belt of the southern Appalachians
New U-Pb zircon ages from plutons in the Charlotte belt of the southern Appalachians have provided evidence of Cambro-Ordovician and Siluro-Devonian magmatic activity. Several U-Pb zircon ages of Cambro-Ordovician plutons predate their Rb-Sr whole rock ages by as much as 60 m.y., suggesting a post …
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U-Pb geochronology of the Acasta Gneiss Complex in Northwest Canada
… in age from 4.03-3.6 Ga, as determined by U-Pb dating of zircons (Bowring and Williams 1999). U-Pb dating of xenocrystic cores in these zircons indicates a cryptic record of continental crust older than 4.0 Ga. In this study, zircons were selected and characterized from thirteen samples of …
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Uranium-Lead dating of hominid fossil sites in South Africa
… that are complex in terms of their stratigraphy. Dating methods previously applied at the caves include faunal, palaeomagnetic, electron-spin resonance and cosmogenic isotope methods. These have been unable to give conclusive ages to the fossils. South African hominids are therefore poorly dated …
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Archean detrital zircons in the Proterozoic Vishnu Schist of the Grand Canyon, Arizona : implications for crustal architecture and Nuna reconstructions
U-Pb dating of 1035 detrital zircons from twelve spatially-distributed samples of the Paleoproterozoic Vishnu Schist reveals a bimodal 207Pb/ 206Pb age probability diagram with peaks at 1.8 Ga and 2.5 Ga. Surprisingly, only 13% of detrital zircon ages overlap with the published depositional age …
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Zircon crystallization patterns from U-Th dates inform U-Pb estimates of volcanic eruption ages
U-Pb dating of zircons provides time constraints on events from 4.5 Ga to < 1Ma by measuring the timing of zircon crystallization. Absolute uncertainties on U-Pb zircon dates are significant enough to obscure zircon crystallization and complicate estimating the relationship between zircon …
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Characterization and chronology of refractory inclusions (CAIs) in the CV3 chondrite NWA 4502
… Rb-Sr and uranium) compositions as well as U-Pb ages of five coarse-grained igneous inclusions (Type A CAIs 1 and 4a, Type B CAIs 5, 6 and 7) from the CV chondrite North West Africa (NWA) 4502 the second largest CV chondrite so far after Allende. At a mineralogical level, NWA 4502 is rather …
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Characterization and chronology of refractory inclusions (CAIs) in the CV3 chondrite NWA 4502
… Rb-Sr and uranium) compositions as well as U-Pb ages of five coarse-grained igneous inclusions (Type A CAIs 1 and 4a, Type B CAIs 5, 6 and 7) from the CV chondrite North West Africa (NWA) 4502 the second largest CV chondrite so far after Allende. At a mineralogical level, NWA 4502 is rather …
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Palaeoenvironments and position of the Precambrian–Cambrian boundary within the lower Vanrhynsdorp Group of South Africa: sedimentary facies analysis, U-Pb series zircon geochronology and micropalaeontology
… discovered in the Vanrhynsdorp Group. Through U-Pb dating of detrital zircons using LA-ICP-MS, radiometric ages for the middle part of the Vanrhynsdorp Group (Besonderheid Formation) were obtained in a preliminary study of this project. The radiometric data, yielding a maximum depositional age of …
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The geochemistry and geochronology of the barby formation in the sinclair area, Southern Namibia
… although some alkaline rocks are present. U-Pb dating and Lu-Hf isotopic microbeam analyses were made on zircon and baddeleyite grains from four samples using cathodoluminescent images. A Barby rhomb porphyry sample gives an U-Pb baddeleyite age of 1217 ±2 Ma and a Barby felsic tuff has an …
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Tectonic-erosion interactions : insights from the paleo-drainage of the Brahmaputra River
… in the foreland basin. Sediment depositional dating of two sedimentary sections is performed using magnetostratigraphy, apatite fission-track and luminescence dating. Provenance analysis using zircon and apatite U-Pb dating allows the reconstruction of the Miocene-Quaternary paleo-drainage of …
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GEOCHEMISTRY AND PETROGRAPHY OF SPELEOTHEMS FROM TURKEY AND IRAN: PALAEOCLIMATE AND DIAGENESIS
… proxies, and precisely dated by Uranium Series dating. As U/Th dating is only viable for samples up to approximately 700 kyr of age, U/Pb dating must be used to date older samples. In this study, U/Pb methods were used to date an aragonite layer in a speleothem from Iran, following the use of …
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Provenance, geochronology and sedimentary characteristics of the Campanian M1 Sandstone, Napo Formation, Oriente Basin, Ecuador
… setting of the M1 Sandstone. Detrital zircon U-Pb dating was applied to 24 core samples from across the entire Oriente Basin; most samples were from accepted M1 Sandstone horizons, but some were taken from levels thought to be the basal Tena Sandstone. Probability density plot (PDP) curves …
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Genesis and structure of the San Albino orogenic gold deposit, NW Nicaragua with implications for Mesozoic tectonic and metallogenic processes
… analysis of structural orientations, and U-Pb zircon geochronology of dike samples. Drill core logging and open pit mapping provided key observational constraints, helping to delineate pre- to syn-mineralization structure, such as isoclinal folds and mylonitic textures in schistose host …
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Deep-marine depositional systems of the western North Atlantic: Insights into climate and passive-margin evolution
… the two datasets is remarkably similar, validating the relationship of sortable silt with current velocity in the deep ocean. Chapter two leverages sortable silt to investigate the long-term evolution of the Deep Western Boundary Current in the North Atlantic, targeting contourite drifts …
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Zircon Geochronology of Ash Beds in the Marcellus Shale of the Appalachian Basin
… from the ash layers are suitable for SIMS U-Th-Pb geochronology due to their resistant behavior against weathering and ability to record age of the eruptions.;A total of 24 Tioga ash layers within cores of the Middle Devonian Marcellus and Onondaga from six wells located in West Virginia and …
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The Global Detrital Zircon Database: Quantifying the Timing and Rate of Crustal Growth
… the database where grains were dated with both U-Pb and Hf isotopes. The Hf isotope model ages suggest that the majority of detrital zircons U-Pb ages reflect crustal recycling events that generated granitic magmatism, as most grains exhibited Hf isotope ages that are much older than the …
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Buffalo Canyon: An Oligocene Greisen-Like Intrusion-Related Gold Deposit in the Union Mining District, Nye County, Nevada
… from diorite to granodiorite and granite. U-Pb dating of zircons by LA-ICPMS has revealed distinct intrusive events in the Jurassic, Cretaceous, and Oligocene. Metaluminous, biotite-pyroxene diorite stocks to porphyritic granodiorite dikes have been dated at 162.03 + 0.91 Ma and 158.72 + 0.94 …
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Geochemical and Geochronological Constraints on the Origin and Evolution of Rocks in the Active Woodlark Rift of Papua New Guinea
… chapter uses a panoply of geochronological (U-Pb zircon) and geochemical (Lu-Hf and Sm-Nd isotopes, trace/REEs, and major elements) tools to investigate the origin the major lithostratigraphic units in the Woodlark Rift. Important findings in this chapter include the establishment of a tectonic …
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Controls on the geometry, stratigraphic distribution and quality of coals of Middle to Upper Jurassic strata in eastern Australia
… and palynologic data, combined with precise U-Pb dating of volcanic sediments and basin subsidence studies. Zircon from twenty-eight tuffs in 12 wells across the Surat and Clarence- Moreton Basins were dated using the high-precision chemical abrasion thermal ionization mass spectrometry …
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