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40Ar/39Ar analyses were performed on igneous rocks from the Ray Mountains area of west-central Alaska. The plutonic samples have ages from about 89 Ma to 109 Ma, while the volcanic samples show ranges from about 30 Ma to 64 Ma. The three volcanic samples fall into two age groups: the younger sample, a basalt, has an age of about 30 Ma, while the two older, rhyolitic samples fall between 58 Ma and 64 Ma. Analyses were performed by the University of Alaska Fairbanks Geochronology Laboratory, and results were reported by Paul Layer and Jeff Benowitz. Products included in this data release are: a summary of sample collection method; the laboratory report, analytical data tables and associated metadata; and plots of...
Tags: 40Ar/39Ar,
Age Dates,
Analyses,
Analyses and Sampling,
Analytical Lab Results, All tags...
Analytical Results,
Ar-Ar,
Bedrock,
Bedrock Geology,
Bettles Quadrangle,
Geochronology,
Geology,
Lab Methods,
Mineral Assessment,
Mineral Deposit,
Mineral Resources,
Ray Mountains,
Sample Location,
Strategic and Critical Minerals Assessment Project,
geoscientificInformation, Fewer tags
This data release presents zircon U-Pb LA-ICP-MS geochronology from igneous rocks exposed in a coastal exposure at Ursus Head, Iliamna C-2 Quadrangle. Sills and dikes exposed in a coastal exposure at Ursus Head are deformed within the Bruin Bay fault zone. Common dikes intruding late Triassic Kamishak Formation strata composing the hanging-wall of the Bruin Bay fault are cut by numerous small-scale, low-angle, bedding-parallel, and high angle contractional faults. Sample 09MAW006A collected from one of many dikes deformed in the fault zone produced a uni-modal distribution of zircon ages of with a weighted mean of 206.92 +/-0.96 (2 sigma, n=47) and an MSWD of 1.1. Sample 09BG020C collected from a sill of more mafic...
Tags: 40Ar/39Ar,
Age Dates,
Analyses,
Analyses and Sampling,
Analytical Lab Results, All tags...
Analytical Results,
Ar-Ar,
Bedrock,
Bedrock Geology,
Contact Point,
Cook Inlet,
Cook Inlet Basin,
Fault Displacement,
Geochronology,
Geologic,
Geology,
Igneous,
Iliamna Quadrangle,
Isotopes,
Lab Methods,
Lead,
Methods,
Naknek,
Plagioclase,
Rocks,
Sample Location,
Stratigraphy,
Structural Geology,
Structure,
Tectonics,
U-Pb,
Uranium,
Ursus Head,
Volcanic,
Volcanic Rocks,
Zircon,
geoscientificInformation, Fewer tags
This DGGS Raw Data File presents 40Ar/39Ar age dating results for selected igneous rocks encountered in the Styx River area of the western Alaska Range. Crystallization ages on biotite and hornblende from plutonic rocks range from about ~60 to ~63 Ma, while a sericite alteration age in plutonic rocks altered by a dike swarm also is around ~63 Ma. Sericite alteration associated with a copper-molybdenum porphyry ranges from ~10 to ~11 Ma. Analyses were performed by the University of Alaska Fairbanks Geochronology Laboratory, and results were reported by Paul Layer and Jeff Benowitz. This data release includes the following products: a summary of sample collection methods, the laboratory report, analytical data tables...
Tags: 40Ar/39Ar,
Age Dates,
Airborne Geophysical Survey,
Alaska Range,
Analyses and Sampling, All tags...
Analytical Results,
Ar-Ar,
Bedrock Geology,
Copper,
Economic Geology,
Faults,
Fracturing,
Geochronology,
Geology,
Gold,
Hornblende,
K-Feldspar,
Lab Methods,
Lime Hills Quadrangle,
Mica,
Mineral Deposit,
Mineral Prospect,
Mineralogy,
Minerals,
Mining,
Mining Claims,
Molybdenite,
Muscovite,
Ore Deposit Model,
Plutonic Rocks,
Plutons,
Polymetallic Vein,
Porphyry,
Pyrite,
Pyrrhotite,
Quartz,
Sample Location,
Sericite,
Sericite Alteration,
Styx River,
Volcanic Rocks,
geoscientificInformation, Fewer tags
This report presents 40Ar/39Ar step-heating geochronology results for igneous and metamorphic rocks from the Alaska Division of Geological & Geophysical Surveys' (DGGS) Wrangellia Mineral Assessment project, part of a multi-year effort focusing on improving the publicly available geoscientific information for the western Wrangellia terrane. The samples described in this report were selected and analyzed to improve our understanding of the geology and structural history of the Wrangellia Mineral Assessment project area. A metagabbro rock sample returned a Late Triassic crystallization age consistent with regional ages for Nikolai Greenstone-related magmatism; however, the two amphibole separates ages do not overlap,...
Tags: 40Ar/39Ar,
Analyses,
Analyses and Sampling,
Analytical Lab Results,
Analytical Results, All tags...
Ar-Ar,
Basalt,
Bedrock,
Bedrock Geology,
Copper,
Crystals,
Geochronology,
Geologic,
Geology,
Greenstone,
Hayes,
Hornblende,
Igneous,
Igneous Rocks,
Interpretation,
Lab Methods,
Methods,
Mica,
Mineral Composition,
Mineral Resources,
Mineralogy,
Minerals,
Mount Hayes Quadrangle,
Muscovite,
Plutonic Rocks,
Porphyry,
Resources,
Rocks,
Sample Location,
Strategic Minerals,
Strategic and Critical Minerals Assessment Project,
Stratigraphy,
Structural Geology,
Talkeetna,
Talkeetna Mountains,
Talkeetna Mountains Quadrangle,
Thrust,
Volcanic Rocks,
geoscientificInformation, Fewer tags
This publication contains previously unpublished geochemical analyses or re-analyses of lavas, magmatic inclusions, and a few gabbroic cumulate inclusions from Alaska volcanoes (Akutan, Augustine, Buzzard Creek, Dana, Douglas, Fourpeaked, Frosty, Great Sitkin, Iliamna, Kaguyak, Kiska, Okmok, Prindle Cone, Recheshnoi, Redoubt, Spurr, Ukinrek Maars, Vsevidof, Westdahl, Wrangell) collected by the authors and others over the past 35 years. It provides substantial data sets for three volcanoes (Vsevidof, Westdahl, and Douglas) for which little or no published data exist. All analyses were made by the GeoAnalytical laboratory at Washington State University in Pullman, WA. The ICP/MS data have been reduced using the 2006...
Tags: Adagdak,
Adak,
Akutan,
Analyses,
Analyses and Sampling, All tags...
Analytical Lab Results,
Analytical Results,
Augustine,
Augustine Volcano,
Basalt,
Bedrock,
Bogoslof,
Chemistry,
Colorado Creek,
Crater Peak,
Crystals,
Douglas,
Faris Peak,
Fourpeaked,
Frosty,
Frosty Peak,
Geochemical Data,
Geochemistry,
Geochronology,
Geologic,
Geology,
Glacier Creek,
Hayes,
Hazards,
Ice,
Iliamna,
Iliamna Volcano,
Jag Peak,
Juneau,
Kaguyak,
Kansas Creek,
Kasatochi,
Katmai,
Kiska,
Maars,
Mount Douglas,
Mount Peulik,
Mount Recheshnoi,
Mount Spurr,
Mount Wrangell,
Mount Zanetti,
Nikolski,
Okmok,
Okmok Caldera,
Pavlof,
Prindle Volcano,
Redoubt,
Redoubt Volcano,
Rhyolite,
Rocks,
Sample Location,
Spurr,
Tanana,
Tephra,
The Sisters,
Ukinrek,
Ukinrek Maars,
Uliaga,
Umnak Island,
Unimak,
Volcanic,
Volcanic Arc,
Volcanic Rocks,
Volcanoes,
Volcanology,
Vsevidof,
Westdahl,
Whittier,
Wrangell,
Yakutat,
geoscientificInformation, Fewer tags
40Ar/39Ar data from seven plutonic samples and one metamorphic sample collected during mineral assessment studies in 1991 show that various rock units in the Selawik Hills plutonic complex were emplaced in the order syenite/monzonite (nonfoliated, 106.6 ± 0.8 Ma; foliated, 101.7 ± 0.7 Ma; both on hornblende), followed by nepheline syenite (103.7 ± 0.8 Ma on hornblende) and then quartz monzonite (100.4 ± 3.7 Ma on biotite). 40Ar/39Ar data from Granite Mountain hornblendes yielded ages slightly older, but overlapping, those from Selawik Hills. In this suite, the silica-undersaturated phase appears to be younger (105.7 ±0.8 Ma) than the silica-saturated phase(s) (106.8 ± 0.8 Ma and 107.1 ± 0.8 Ma).
Tags: 40Ar/39Ar,
Age Dates,
Analytical Results,
Ar-Ar,
Candle Quadrangle, All tags...
Geochronology,
Granite,
Granite Mountain,
Hornblende,
Igneous Rocks,
Plutonic Rocks,
Selawik Quadrangle, Fewer tags
This report presents 40Ar/39Ar step-heating geochronology results for igneous and metamorphic rocks from the Alaska Division of Geological & Geophysical Surveys' (DGGS) Talkeetna Mountains C-4 Quadrangle and Adjoining Areas geologic mapping project. Hornblende-bearing gabbro returned a Late Triassic crystallization age consistent with regional results for Nikolai Greenstone-related magmatism. We determined Early Jurassic metamorphic ages for hornblende and sericite from two samples of upper greenschist to amphibolite grade metavolcanic rocks. Our results indicate that a granodiorite pluton intruding Wrangellia in the study area has a Middle Jurassic age consistent with the Talkeetna Arc, indicating that the Wrangellia...
Tags: 40Ar/39Ar,
Age Dates,
Analyses,
Analyses and Sampling,
Analytical Lab Results, All tags...
Analytical Results,
Ar-Ar,
Bedrock,
Bedrock Geology,
Geochronology,
Geology,
Lab Methods,
Plutonic Rocks,
Plutons,
STATEMAP Project,
Sample Location,
Strategic and Critical Minerals Assessment Project,
Talkeetna Mountains Quadrangle,
Volcanic,
Volcanic Arc,
Volcanic Rocks,
geoscientificInformation, Fewer tags
This data release presents 40Ar/39Ar step-heating geochronology results from rocks collected roughly 7 km southwest of Contact Point, Iliamna B-3 Quadrangle. Samples obtained from a felsic dike intruding the principal Bruin Bay fault plane near Contact Point produced biotite and plagioclase 40Ar/39Ar ages of 36.5 +/- 0.8 Ma and 31.5+/-0.7 Ma, respectively. The age dates inform stratigraphic, structural, and geochronologic studies along the western margin of lower Cook Inlet basin. The accompanying report also presents zircon U-Pb LA-ICP-MS geochronology results for dikes near Ursus Head.
Tags: 40Ar/39Ar,
Age Dates,
Analyses,
Analyses and Sampling,
Analytical Lab Results, All tags...
Analytical Results,
Ar-Ar,
Bedrock,
Bedrock Geology,
Contact Point,
Cook Inlet,
Cook Inlet Basin,
Fault Displacement,
Geochronology,
Geologic,
Geology,
Igneous,
Iliamna Quadrangle,
Isotopes,
Lab Methods,
Lead,
Methods,
Plagioclase,
Rocks,
Sample Location,
Stratigraphy,
Structural Geology,
Structure,
Tectonics,
U-Pb,
Uranium,
Ursus Head,
Volcanic,
Volcanic Rocks,
Zircon,
geoscientificInformation, Fewer tags
40Ar/39Ar analyses of igneous rocks from the Alaska Highway corridor between Delta Junction and the Canada border show a range of Cretaceous ages from about 68 Ma to about 112 Ma. The 25 samples fall into two broad age groups. The younger group ranges from about 68 Ma to 73 Ma; the older group ranges from a minimum age of about 84 Ma to about 103 Ma. One sample, a mafic dike, yielded an older age of about 112 Ma.
Tags: 40Ar/39Ar,
Age Dates,
Alaska Highway Corridor,
Analyses and Sampling,
Analytical Lab Results, All tags...
Analytical Results,
Ar-Ar,
Bedrock,
Bedrock Geology,
Geochronology,
Geology,
Lab Methods,
Mount Hayes Quadrangle,
Nabesna Quadrangle,
Sample Location,
Tanacross Quadrangle,
geoscientificInformation, Fewer tags
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
This report presents 40Ar/39Ar step-heating geochronology results from a single outcrop of a mineralized near-trench intrusion exposed in a road cut near Whittier, Alaska. The outcrop is the best road-accessible occurrence of a Tertiary near-trench pluton in the region and is commonly visited by field trips, yet no prior geochronological data from this outcrop have been published. Two chronologically distinct intrusive bodies, the Paleogene Sanak-Baranof belt and the Eshamy-suite, are documented in the upper Cook Inlet area. Geochronological analysis of the two samples described in this report confirms that the Whittier road-cut intrusion and veins are coeval (53.0 +/- 0.3 Ma and 50.9 +/- 0.2 Ma, respectively) with...
Tags: 40Ar/39Ar,
Age Dates,
Analyses,
Analyses and Sampling,
Analytical Lab Results, All tags...
Analytical Results,
Ar-Ar,
Bedrock,
Bedrock Geology,
Geochronology,
Geologic,
Geology,
Igneous,
Igneous Rocks,
Isotopes,
Lab Methods,
Methods,
Mineralogy,
Rocks,
Sample Location,
Seward Quadrangle,
Volcanic Arc,
Volcanic Rocks,
Whittier,
geoscientificInformation, Fewer tags
This DGGS report presents 40Ar/39Ar age dating results from selected mafic to intermediate intrusions encountered during a geological and geochemical resource assessment project in the Gulkana, Healy, Mount Hayes, and Talkeetna Mountains quadrangles. Three intrusions returned mid-Cretaceous crystallization ages, while one olivine gabbro returned a Late Triassic crystallization age. Two altered or metamorphosed samples yielded Late Jurassic and Early Cretaceous ages. Analyses were performed by the University of Alaska Fairbanks Geochronology Laboratory, and results were reported by Paul Layer and Jeff Benowitz. Products included in this data release are: a summary of sample collection method; the laboratory report,...
Tags: 40Ar/39Ar,
Age Dates,
Amphitheater Mountains,
Analyses,
Analyses and Sampling, All tags...
Analytical Lab Results,
Analytical Results,
Ar-Ar,
Bedrock,
Bedrock Geology,
Geochronology,
Geology,
Gulkana Quadrangle,
Healy Quadrangle,
Lab Methods,
Metamorphism,
Mineral Assessment,
Mineral Deposit,
Mineral Resources,
Mount Hayes Quadrangle,
Platinum Group Elements,
Sample Location,
Skarn,
Strategic and Critical Minerals Assessment Project,
Talkeetna Mountains Quadrangle,
geoscientificInformation, Fewer tags
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