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Showing 1 to 20 of 35 for “"U-Pb geochronology"”.
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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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Paleogeography of Western North America: Insights from Detrital Zircon U-Pb Geochronology and Hf Isotope Geochemistry
… using modern analytical techniques including U-Pb geochronology and Hf isotope geochemistry of detrital zircons, as well as, geologic mapping and paleocurrent analysis. The Neoproterozoic through Pennsylvanian Yukon-Tanana terrane (YTTs) in the Coast Mountains of southeastern Alaska, the …
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High-precision U/Pb geochronology of large igneous provinces and mass extinctions : testing coincidence and causation
… are coupled with the latest techniques in U/Pb geochronology to generate highprecision age models which are used to evaluate the relative timing of (1) the end- Permian mass extinction, which is the most severe in the Phanerozoic, and the Siberian Traps LIP, which is the largest continental …
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Statistical considerations in high precision U-Pb geochronology, with an application to the tectonic evolution of the North Cascades, Washington
… of geologic problems that may be addressed by U-Pb geochronology is governed by the precision to which U-Pb dates can be measured, expressed as their estimated uncertainties. Accurate and precise knowledge of both the value and uncertainty of an isotopic date are imperative to its correct …
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Early Laramide Magmatism in Southern Arizona U-Pb Geochronology of Key Igneous Units and Implications for the Timing of Regional Porphyry Copper Mineralization
… This investigation presents new U-Pb in zircon ages on key igneous units across southern Arizona to constrain the onset of early Laramide magmatism and to compare the timing of mineralization in several key mining districts with these early events. The objectives of this …
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High precision U/Pb geochronology on the Cenomanian Dakota Formation, Utah : implications for paleobotany and the transgression of the Western Interior Seaway preceding Oceanic Anoxic Event 2
… Utah localities have a weighted mean 206Pb/238U date of 97.656±0.082 Ma, while the samples taken from Henrieville, Utah have weighted mean 206Pb/238U dates of 95.170 0.056 Ma and 94.941±0.032 Ma. Based on an analysis of stratigraphic, paleontological, and geochronological data, the Dakota …
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U-Pb geochronology of the Duluth Complex and related hypabyssal intrusions: investigating the emplacement history of a large multiphase intrusive complex related to the 1.1 Ga Midcontinent Rift.
… number of dated samples. New high-precision U-Pb baddeleyite and zircon ages from five mafic intrusions related to the Duluth Complex builds on the work of Paces and Miller (1993). Ages from three intrusions that span the entire range of Duluth Complex layered series intrusive activity indicate …
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Fluid flow and deformation history of the Denver basin, CO region: fluid inclusions, U-Pb geochronology and isotope geochemistry of calcite-filled fracture cements in the Niobrara Formation
… and geochemical analyses including: LA-ICP-MS U-Pb geochronology, fluid inclusion microthermometry, stable isotope, and strontium isotope analysis. Samples were obtained from the Albert Kurtz well in the Wattenberg field, CO. Results obtained from several fracture fill types (e.g., …
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U-Pb geochronology and structural geology across major shear zones of the Southern granulite terrain of India and organic carbon isotope stratigraphy of the Gondwana coal basins of India : their implications for Gondwana studies
… of southernmost India, using field geology and U-Pb geochronology. Because Peninsular India occupied a central position in Gondwana, this work bears on reconstruction models of central Gondwana between circa 600 Ma and 200 :f1,a. The second part of the thesis (Chapter 6) tests the use of organic …
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Integrating in situ Geochronology and Metamorphic Petrology: An Example from the Gruf Complex, European Central Alps
… many researchers have used accessory mineral U-Pb geochronology to date (U)HT metamorphic events. However, it is not always clear to what part of the pressure-temperature (P-T) path the ages relate. Using an in situ approach, this study combines accessory mineral U-Pb geochronology with single …
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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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Geochemistry, Geothermobarometry and Geochronology of High-Pressure Granulites and Implications for the Exhumation History of Ultrahigh-Pressure Terranes: Dulan, Western China
… are 750–880 °C and 14–17 kbar. Zircon U-Pb geochronology, REE patterns and Ti-in-zircon thermometry indicate an increase in temperature from ~800 °C (449 Ma) to ~900 °C (418 Ma). This temperature increase could explain the presence of granulite leucosomes and tonalites (419 Ma) …
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Geochemical Constraints of Porphyry Cu Deposits-Forming Magmas in Sonora, Mexico
… Using zircon trace-element geochemistry, U–Pb geochronology, and thermobarometry, I assess the magmatic conditions under which PCDs and barren rocks formed, and identify key proxies, such as REE anomalies, H₂O content, and oxidation state, that distinguish fertile magmas from barren magmatic …
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Sediment-hosted Zn-Pb-Ag (+ Cu) deposits in the Mount Isa region: An epigenetic approach to mineralisation
… Australia, contains numerous sediment-hosted Zn-Pb-Ag-Cu deposits. Previous research on these deposits has resulted in two contrasting metallogenic models: (1) Zn-Pb-Ag mineralisation was formed during the deposition of the host Urquhart Shale at ca. 1655 Ma and was overprinted by Cu …
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Tertiary Sediments of the Big Hole Valley and Pioneer Mountains, Southwestern Montana: Age, Provenance, and Tectonic Implications
… alluvial channels, and rare fluvial deposits. U-Pb geochronology of detrital zircons and air-fall tuffs indicates the presence of Oligocene to Middle Miocene sedimentary rocks outcropping at the surface. Though the presence of detrital muscovite in several outcrops indicates derivation from the …
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Tertiary Sediments of the Big Hole Valley and Pioneer Mountains, Southwestern Montana: Age, Provenance, and Tectonic Implications
… alluvial channels, and rare fluvial deposits. U-Pb geochronology of detrital zircons and air-fall tuffs indicates the presence of Oligocene to Middle Miocene sedimentary rocks outcropping at the surface. Though the presence of detrital muscovite in several outcrops indicates derivation from the …
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Integrating high-precision U-Pb geochronologic data with dynamic models of earth processes
… behavior and/or initial conditions of the U-Pb system and provides an effective means of exploring the parameters that influence a calculated date. The record provided by geochronologic data is then coupled with models to quantitatively determine rates of geologic process on Earth. This …
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Geochemistry and Basin Analysis of Laramide Rocky Mountain Basins
… it uses the sedimentology, detrital zircon U-Pb geochronology, and isotope paleoaltimetry of early Eocene sedimentary strata to constrain the tectonic setting, paleogeography and paleoclimate of the Wind River basin. Annual and seasonal variation in ancient riverwater δ¹⁸O reconstructed from …
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Sedimentary basin evolution and structural compartmentalization in the northernmost Andes : Eastern Cordillera and Magdalena Valley, Colombia
… lateral variations. New detrital zircon U-Pb geochronological data across the unconformity reveals stepwise provenance changes in response to the transition from post-extensional (thermal) to foreland basin (flexural) subsidence. The latest Cretaceous to late Eocene shift from Andean …
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Chemical, isotopic, and temporal variations during crustal differentiation : insights from the Dariv Igneous Complex, Western Mongolia
… crystallization through high precision U-Pb geochronology of zircon from the Dariv Igneous Complex. Evolution from a basaltic melt to a silica-rich monzonitic melt in the Dariv Igneous Complex occurred in <300 ka. If rates of fractional crystallization are primarily a function of cooling, …
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