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Showing 1 to 19 of 19 for “"Zircon ages"”.
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Pre-Grenville ages of basement rocks in central Virginia: a model for the interpretation of zircon ages
… old and may be as old as 1870 m.y. A concordant zircon from the Lovingston gneiss indicates that intense regional metamorphism occurred at least 913 m.y. ago. The Rockfish granodiorite, in Nelson County, Virginia, intruded these older basement rocks 820 ± 20 m.y. ago and appears to be coeval with …
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U/Pb Zircon Ages of Plutons from the Central Appalachians and GIS-Based Assessment of Plutons with Comments on Their Regional Tectonic Significance
… SIMS (secondary ion mass spectrometry) U/Pb ages of zircons were obtained for ten plutons (Leatherwood, Rich Acres, Melrose, Buckingham, Diana Mills, Columbia, Poore Creek, Green Springs, Lahore and Ellisville) within Virginia. These plutons are distinct chemically, isotopically, and show an …
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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 Duluth Complex and related hypabyssal intrusions: investigating the emplacement history of a large multiphase intrusive complex related to the 1.1 Ga Midcontinent Rift.
… not, however, resolve differences in emplacement ages within and between major intrusive units due to a small 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 …
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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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Early Laramide Magmatism in Southern Arizona U-Pb Geochronology of Key Igneous Units and Implications for the Timing of Regional Porphyry Copper Mineralization
… has been loosely constrained by early K-Ar ages and cross-cutting field relationships; in many districts early Laramide volcanic rocks host much of the porphyry mineralization, but the genetic relationship between intrusive and extrusive units in multiple districts remains poorly understood. …
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The tectonic evolution of the Southern Granulite Terrane of India and its role in the amalgamation of Gondwana.
… alternatively, the Cauvery Shear Zone). The U-Pb zircon geochronology of the orthopyroxene-bearing orthogneisses (charnockites) in the northern part of Madurai Block yielded Neoarchaean and Cryogenian (ca.2.7 - 2.5 Ga and 795 ± 17 Ma) crystallization ages with metamorphic overprinting at ca. 535 …
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Space-Time Analysis of Magmatism: Evidence for a Early Cryogenian Plume Track in Eastern Laurentia
… in an extensional setting. In this study U/Pb zircon ages of several plutons were determined using secondary ion mass spectrometry. The ages suggest two episodes of magmatism. An older episode (739 to 745 Ma) of magmatism includes White Oak Creek, Suck Mountain, and Amisville plutons. The …
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Mineral Ridge: A Late Cretaceous Orogenic Gold System in the Miocene Silver Peak-Lone Mountain Metamorphic Core Complex
… granites at Mineral Ridge yield U/Pb zircon ages of 91.7+/-0.3 Ma and 89.9+/-0.5 Ma and likely derive from crustal melts during peak metamorphism. Hydrothermal monazite in gold-bearing quartz veins yielded a U/Pb age of 76.0+/-1.8 Ma, indicating veins are unrelated to granites and …
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Fluid Release During Eclogite Formation, North Qaidam Terrane, Western China
… the availability of fluid, which could promote zircon recrystallization, and therefore zircon ages may be likely to record spikes in fluid release rates along the P-T path. The spikes in fluid release rates could promote the migration of fluids long distances, increase fluid pressures that …
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Mineralogy and provenance of the TiO₂ - ilmenite heavy mineral sand deposit of Nataka
… by ilmenite (50.91 wt. %), with additional zircon and rutile (9.96 and 3.52 wt. % respectively). The total heavy minerals comprise about 5% volume, of which 2 % are valuable heavy minerals making up about 445 Mt (million tonnes) probable resources. This study focuses on the mineralogical …
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Mesozoic tectonics of the Maria fold and thrust belt and McCoy basin : an examination of polyphase deformation and synorogenic response
… from macroscopic to microscopic scale, U-Pb zircon ages and Ar-Ar hornblende and biotite ages from key areas in the Maria Fold and Thrust Belt and McCoy Basin to resolve kinematics and timing of polyphase deformation events related to the Mesozoic Cordilleran Orogeny in southeastern …
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Stratigraphy and Tectonics: Multi-Disciplinary Evaluation of Tectonic Models For the Eastern and Southern Continental Margins of North America
… The distribution of single-grain detrital-zircon ages collected from the Upper Ordovician through upper Mississippian sandstones records the sedimentary response to Taconic, Acadian and Alleghanian phases of orogenesis. This analysis suggests the Late Ordovician accretion of Dahlonega …
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Origin and Tectonic Evolution of Gondwana Sequence Units Accreted to the Banda Arc: A Structural Transect through Central East Timor
… the active Banda Arc. Our field studies and U/Pb zircon age analysis helped assign most units to either Asian or Australian affinity. Detrital zircon from uplifted Banda forearc units (Asian affinity) have U/Pb ages as young as 80 Ma (Standley and Harris, in press). In contrast, analysis of …
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Characterization of pentlandite-bearing quartz veins of Kambalda, Western Australia
… constraints are delimited through hostrock U-Pb zircon ages and deformation event ages available in literature. The results of this study are principally important in building on knowledge of crustal fluids that are capable of mobilizing and consequently precipitating Ni minerals such as …
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Geology of the Bottle Lake Complex, Maine
… but geochronologic studies using Pb-Pb zircon ages do not display a clear age difference. The granite of Passadumkeag River is, as judged by the field relations, the youngest pluton in the Complex. This granite is also the most heterogeneous body as expressed by petrography, mineral …
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Integrating in situ Geochronology and Metamorphic Petrology: An Example from the Gruf Complex, European Central Alps
… 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 mineral thermometry, thermobarometric modeling, and trace element geochemistry to elucidate the P-T-time (P-T-t) evolution of …
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INNOVATIVE AND CONVENTIONAL APPROACHES TO DETRITAL ZIRCON PROVENANCE ANALYSIS: LOOKING TO THE PAST, PRESENT, AND FUTURE
… tool in our understanding paleo-fluvial drainages, erosion of landscapes, paleogeographic reconstructions, and regional geologic and tectonic histories. Here, we examine the utility of multiple provenance analysis techniques through their application to paleo, modern, and synthetic detrital …
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Tektonometamorphe Entwicklung von Scherzonen im präkambrischen Basement Südindiens
… Ga) show late Archaean average crustal residence ages. With respect to their LIL-, Nb-depleted tonalitic nature and Nd-model ages, these rocks resemble the neighbouring Nilgiri granulites. Mylonitic gneisses and granulite remnants from the BSZ yielded a Sm-Nd-whole rock-age of 2520 ± 150 Ma …