Filters: Tags: Gneiss (X) > partyWithName: Alaska Division of Geological & Geophysical Surveys (X) > partyWithName: Benowitz, J.A. (X)

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40Ar/39Ar data from the Tok River area, Tanacross A-5 and A-6 quadrangles and adjoining areas, eastern Alaska Range This report presents 40Ar/39Ar step-heating geochronology results for igneous and metamorphic rocks from the Alaska Division of Geological & Geophysical Surveys' (DGGS) geologic mapping project in the Tanacross A-5 and A-6 quadrangles and adjoining areas. Our results indicate the Hona granodiorite pluton intruded the area in the Late Cretaceous between 76 and 71 Ma. We determined Cretaceous metamorphic ages from 126 to 121 Ma for hornblende, biotite, sericite and muscovite from multiple samples of upper greenschist to amphibolite grade rocks. This is consistent with regional argon results that imply this area is in the upper plate of the Yukon Tanana Terrane (Hansen and Dusel-Bacon, 1998). Basaltic andesite dikes... Tags: 40Ar/39Ar, Amphibolite, Analyses, Analyses and Sampling, Analytical Lab Results, All tags... Analytical Results, Basalt, Bedrock, Crystals, Exploration, Faulting, Geochronology, Geologic, Geology, Gneiss, Granite, Granodiorite, Greenschist, Hornblende, Igneous, Isotopes, Metamorphic, Metamorphic Rocks, Metamorphism, Methods, Mica, Mineral Composition, Mineral Prospect, Mineralogy, Minerals, Muscovite, Noah Prospect, Plagioclase, Plutonic, Rocks, Sample Location, Sericite, Shalosky Prospect, Tanacross Quadrangle, Tok, Tok Mining District, Tok River, geoscientificInformation, Fewer tags