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Twenty-two igneous and metamorphic rock samples were collected in a 20-km-long swath centered on the Alaska Highway between Tetlin Junction, Alaska, and the Canada border. Igneous and metamorphic rock samples were submitted to the Apatite to Zircon, Inc. laboratory (A2Z), where zircon U-Pb age analysis, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), was performed by Paul O'Sullivan. The 15 felsic plutonic rock samples and one gabbro sample yield Cretaceous zircon U-Pb weighted-mean ages ranging from 95.7 Ma to 106.2 Ma. Zircons from a metadiorite yield a Triassic weighted-mean age of about 241.9 Ma. Metamorphic zircons from two samples with felsic igneous protoliths yield Mississippian...
Tags: Age Dates,
Alaska Highway Corridor,
Analyses and Sampling,
Bedrock,
Bedrock Geology, All tags...
Detrital Zircon,
Geochronology,
Geology,
Igneous Rocks,
Isotopes,
Metamorphic Rocks,
Nabesna Quadrangle,
Tanacross Quadrangle,
U-Pb,
geoscientificInformation, Fewer tags
A physiographically prominent, approximately 40 square km plateau lies roughly 20 km east of Mount Spurr volcano, northwestern Cook Inlet region, Alaska, and comprises the preserved remnant of a volcaniclastic succession, designated in this study as map unit Qvc. Although this readily mappable package of volcaniclastic rocks has been recognized in numerous studies during the past five decades, uncertainties regarding its age and origin have persisted. We describe the general characteristics of the volcaniclastic plateau, provide new age constraints for deposits, present lithofacies descriptions and interpretations of the volcaniclastic strata, and synthesize our observations and lithofacies analysis to propose an...
Tags: Age Dates,
Alluvial,
Alluvial Deposits,
Bedrock,
Bedrock Geology, All tags...
Capps Glacier,
Debris Flow,
Debris Flow Deposit,
Depositional Environment,
Depositional Environments,
Detrital Zircon,
Facies Analysis,
Geochronology,
Geological Process,
Geology,
Lahar,
Lahar Runout Flow,
Liquefaction,
Mount Spurr,
Paleoenvironment,
Paleogeography,
STATEMAP Project,
Sediment Transport,
Sedimentary,
Sedimentary Rocks,
Sedimentation,
Sedimentology,
Tyonek Quadrangle,
U-Pb,
Volcaniclastics,
geoscientificInformation, Fewer tags
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
Kasatochi is a small, isolated island volcano in the center of the Aleutian Island chain. It consists of a roughly circular cone approximately 3 km in diameter with a lake-filled central crater that is 1.2 km in diameter and extends from the highest point on the island to sea level. The oldest unit recognized is a thick series of mid-Pleistocene glaciovolcanic deposits consisting of autobrecciated lava, lahars, and volumetrically minor lava masses that we believe to have been emplaced underneath a regional ice cap. This unit is unconformably overlain by several massive Holocene lavas, above which lies a thick sequence of latest-Holocene pyroclastic deposits likely deposited during the crater-forming eruption. The...
Tags: Active Volcanoes,
Age Dates,
Aleutian Arc,
Aleutian Islands,
Alluvial Deposits, All tags...
Analyses,
Analyses and Sampling,
Basalt,
Bedrock,
Bedrock Geology,
Caldera,
Chemistry,
Colluvium,
Erosion,
Fan,
Geochemical Data,
Geochemistry,
Geochronology,
Geologic,
Geologic Hazards,
Geologic Map,
Geological Process,
Geology,
Geomorphology,
Hazards,
Historic Eruption,
Igneous,
Kasatochi,
Lava Flow,
Mineralogy,
Petrographic,
Petrography,
Petrology,
Pumice,
Pyroclastics,
Rockfall,
Rocks,
Sample Location,
Slope Instability,
Slump,
Soils,
Surface,
Surficial,
Talus,
Tephra,
Topography,
Ultramafic,
Uplift,
Volcanic,
Volcanic Ash,
Volcanic Eruption,
Volcanic Rocks,
Volcaniclastics,
Volcanoes,
Volcanology,
geoscientificInformation, Fewer tags
We report U-Pb zircon geochronology results for one metavolcanic and one metaplutonic rock sample from the Mount Hayes A-6 Quadrangle of central Alaska. These samples are representative of rock units assigned to the Clearwater terrane of Jones and others (1987), a sequence of greenschist-grade metavolcanic and metasedimentary rocks of poorly constrained age and tectonic origin. Our results indicate a crystallization age of 277.33 +/- 11.84 Ma for a felsic metavolcanic rock, and a 268.05 +/- 11.64 Ma crystallization age for a granitic metaplutonic unit intruding the former.
Tags: Age Dates,
Analyses,
Analyses and Sampling,
Analytical Lab Results,
Bedrock, All tags...
Bedrock Geology,
Geochronology,
Geology,
Lab Methods,
Metamorphic Rocks,
Metavolcanic rocks,
Mount Hayes Quadrangle,
Orthogneiss,
Sample Location,
U-Pb,
Zircon,
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
U-Pb analyses were performed on igneous rocks from the Ray Mountains area of west-central Alaska. These new age analyses will allow us to better evaluate the geochronology of the granitic rocks that are the apparent source of the alluvial REE and tin resources. The plutonic samples have ages ranging from 98.0 +/- 0.9 Ma to 111.6 +/- 1.0 Ma. The sample location coordinates and analytical data tables associated with this report are available in digital format as comma-separated value (CSV) files.
Tags: Age Dates,
Analyses,
Analyses and Sampling,
Analytical Lab Results,
Analytical Results, All tags...
Bedrock,
Bedrock Geology,
Bettles Quadrangle,
Geochronology,
Geology,
Igneous Rocks,
Lab Methods,
Metals,
Mineral Assessment,
Mineral Deposit,
Mineral Resources,
Minerals,
Plutonic,
Polymetallic,
Rare Earth Elements,
Ray Mountains,
Sample Location,
Strategic and Critical Minerals Assessment Project,
Tin,
U-Pb,
Zircon,
geoscientificInformation, Fewer tags
This report provides detailed (1:63,360-scale) mapping of portions of U.S. Geological Survey Circle B-2 (1955), B-3 (1955), B-4 (1952), C-2 (1955), C-3 (1955), and C-4 (1952) quadrangles. The area is part of the Circle mining district and adjacent to the Fairbanks mining district. This report includes detailed geologic, structural, stratigraphic, and geochronologic data. Based on the resulting geologic maps, field investigations, and laboratory materials analyses, the project has also generated derivative maps of geologic construction materials and geologic hazards.
Tags: Aereal,
Aerial Photography,
Aeromagnetic Survey,
Age Dates,
Alaska, State of, All tags...
Alluvial Deposits,
Alluvium,
Amphibolite,
Ar-Ar,
Bedrock,
Bibliography,
Birch Creek,
C14,
Carbonates,
Circle Hot Springs,
Circle Mining District,
Circle Quadrangle,
Clastics,
Coal,
Colluvial Deposits,
Colluvium,
Conductivity Survey,
Conodonts,
Crooked Creek,
Electromagnetic Survey,
Fan,
Faulting,
Faults,
Fluvial,
Folding,
Fossils,
Geologic,
Geomorphology,
Glacial,
Glacial Deposits,
Glacial Drift,
Granite,
Hornblende,
Hornfels,
Igneous Rocks,
K-Ar,
Magnetite,
Major Oxides,
Mammoth Creek,
Mastodon Dome,
Metamorphic Grade,
Metamorphic Minerals,
Metamorphism,
Mineralogy,
Modal Analysis,
Petrography,
Plutonic,
Plutonic Hosted,
Porphyry,
Precious Metals,
Quartz,
Regional,
Regional Metamorphism,
Sample Location,
Sandstone,
Schist,
Sedimentary,
Structure,
Surficial,
Tectonics,
Terranes,
geoscientificInformation, Fewer tags
40Ar/39Ar data from plutonic, dike, and alteration samples collected during geologic mapping of the eastern part of the Bonnifield mining district geologic map area in parts of Fairbanks A-1 and Fairbanks A-2 and Healy D-1 and Healy D-2 quadrangles yield results indicating the plutons, dikes, and a gold-bearing quartz vein in the Bonnifield Map area range from 85 to 95 m.y.
Tags: 40Ar/39Ar,
Age Dates,
Alaska Range,
Alaska, State of,
Buzby prospect, All tags...
Chute Creek,
Denali Borough,
Dry Creek,
Dry Creek placer mine,
Dry Creek prospect,
Fairbanks Quadrangle,
Forgotten Creek,
Geochronology,
Geology,
Glacier Creek,
Glory Creek,
Glory Creek prospect,
Healy Quadrangle,
Kansas Creek,
Kansas Creek prospect,
LEA Creek prospect,
Newman Creek,
Newman Creek placer mine,
Red Mountain Creek,
Red Mountain Creek prospect,
Rogers Creek,
STATEMAP Project,
Sheep Creek,
Slate Creek,
Slide Creek,
Smog prospect,
Snow Mountain Gulch,
Threemile Creek,
WTF (Western Tundra Flats) prospect,
West Fork Little Delta River,
Wood River,
geoscientificInformation, Fewer tags
This Division of Geological & Geophysical Surveys (DGGS) Raw Data File presents U-Pb geochronology and Lu-Hf isotopic compositions, age-dating results, and additional trace-elemental composition of zircons from four granitoids sampled during investigations by DGGS geologists in the western Alaska Range and the Talkeetna Mountains. The purpose of the Lu-Hf and U-Pb isotopic study was to better understand the Jurassic through early Tertiary magmatic and tectonic evolution of the Alaska Range and the significance of that magmatism for the formation of metallic mineral deposits. The U-Pb isotopic data also serve to further refine the crystallization age of plutons, which were previously ambiguous in 40Ar/39Ar geochronology...
Tags: Age Dates,
Alaska Range,
Analyses,
Analyses and Sampling,
Analytical Lab Results, All tags...
Analytical Results,
Bedrock,
Geochemistry,
Geochronology,
Geologic,
Geology,
Geophysics,
Granite,
Hafnium,
Isotopes,
Lab Methods,
Lead,
Lime Hills Quadrangle,
Lutetium,
Methods,
Mineralogy,
Minerals,
Plutonic,
Plutons,
Resources,
Rocks,
STATEMAP Project,
Talkeetna Mountains,
Talkeetna Mountains Quadrangle,
Trace Elements,
U-Pb,
Uranium,
Zircon,
geoscientificInformation, Fewer tags
This map shows the distribution of surficial deposits and undifferentiated bedrock in parts of the Livengood C-3 and C-4 quadrangles, Tolovana mining district.
Tags: Aeolian,
Aerial Geology,
Age Dates,
Alluvial Deposits,
Alluvium, All tags...
C14,
Colluvial Deposits,
Colluvium,
Debris Flow,
Debris Flow Deposit,
Elliot Highway,
Eolian,
Floodplain,
Geomorphology,
Goldstream Creek,
Landslide,
Livengood,
Livengood Bench,
Livengood Creek,
Livengood Dome,
Livengood Mining District,
Livengood Quadrangle,
Money Knob,
Permafrost,
Permafrost and Periglacial,
Pingos,
Placer,
Placer Gold,
STATEMAP Project,
Slides,
Slope Instability,
Solifluction,
Surficial,
Surficial Geologic Map,
Surficial Geology,
Tailings,
Thawing Permafrost,
Thermokarst,
Trans-Alaska Pipeline,
geoscientificInformation, Fewer tags
This Alaska Division of Geological & Geophysical Surveys (DGGS) Raw Data File presents 40Ar/39Ar age dating results for a volcanic whole-rock sample, selected minerals from various metamorphic rocks and igneous dikes, and white mica from both metamorphic- and hydrothermal-mineralization-related veins encountered on the southern Seward Peninsula, as well as select minerals from one plutonic rock from Cape Denbeigh, eastern Norton Sound, Alaska. Cooling ages on glaucophane, barroisite, amphibole, paragonite, and biotite from metamorphic rocks range from 84 Ma to 209 Ma. The cooling age of white mica in a possible fault zone is 144 Ma. Cooling ages on late-stage metamorphic minerals (winchite and white mica) from veins...
Tags: 40Ar/39Ar,
Age Dates,
Ar-Ar,
Bendeleben Mountains,
Bendeleben Quadrangle, All tags...
Big Hurrah Mine,
Bluff (Place),
Cape Denbeigh,
Council,
Council Mining District,
Geochronology,
Koyuk Mining District,
Mineral Resources,
Nome,
Nome Mining District,
Nome Quadrangle,
Norton Bay Quadrangle,
Norton Sound,
STATEMAP Project,
Seward Peninsula,
Solomon 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) 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 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
Kasatochi is a small, isolated island volcano in the center of the Aleutian Island chain. It consists of a roughly circular cone approximately 3 km in diameter with a lake-filled central crater that is 1.2 km in diameter and extends from the highest point on the island to sea level. The oldest unit recognized is a thick series of mid-Pleistocene glaciovolcanic deposits consisting of autobrecciated lava, lahars, and volumetrically minor lava masses that we believe to have been emplaced underneath a regional ice cap. This unit is unconformably overlain by several massive Holocene lavas, above which lies a thick sequence of latest-Holocene pyroclastic deposits likely deposited during the crater-forming eruption. The...
Tags: Active Volcanoes,
Age Dates,
Aleutian Arc,
Aleutian Islands,
Alluvial Deposits, All tags...
Analyses,
Analyses and Sampling,
Basalt,
Bedrock,
Bedrock Geology,
Caldera,
Chemistry,
Colluvium,
Erosion,
Fan,
Geochemical Data,
Geochemistry,
Geochronology,
Geologic,
Geologic Hazards,
Geologic Map,
Geological Process,
Geology,
Geomorphology,
Hazards,
Historic Eruption,
Igneous,
Kasatochi,
Lava Flow,
Mineralogy,
Petrographic,
Petrography,
Petrology,
Pumice,
Pyroclastics,
Rockfall,
Rocks,
Sample Location,
Slope Instability,
Slump,
Soils,
Surface,
Surficial,
Talus,
Tephra,
Topography,
Ultramafic,
Uplift,
Volcanic,
Volcanic Ash,
Volcanic Eruption,
Volcanic Rocks,
Volcaniclastics,
Volcanoes,
Volcanology,
geoscientificInformation, Fewer tags
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