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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...
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Cook Inlet has been recognized as the second-largest petroleum province in Alaska, second only to the North Slope. The south-central Tyonek Quadrangle is an area of significant geologic interest because it is the only location in Cook Inlet where the entire producing stratigraphy of the basin is exposed on the surface. Additionally, this area encompasses the structural boundary between the forearc basin and its sediment source rocks. To better understand the petroleum system and the geologic relationships between the exhumed arc intrusive rocks and adjacent Cenozoic stratigraphy of the Cook Inlet forearc basin, during the summer of 2010 the Alaska Division of Geological & Geophysical Surveys conducted a federally-funded...
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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...
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Mineral Resources Section personnel from the Alaska Division of Geological & Geophysical Surveys (DGGS) carried out a geologic field survey, including mapping and sampling, in the eastern part of the Bonnifield mining district in the Fairbanks A-1 and A-2 and the Healy D-1 and D-2 quadrangles, Alaska, from June 16 through July 18, 2008. The fieldwork provides basic information critical to building an understanding of Alaska's geology and is part of an integrated program of airborne geophysical surveys followed by geologic mapping. Specifically, this work provides geologic context for geophysical surveys conducted in 2006. Interpretation and synthesis of this data has been presented in professional and trade meetings....
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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...
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Geologists from the Alaska Division of Geological & Geophysical Surveys (DGGS) and the University of Alaska Fairbanks (UAF) carried out geologic field surveys, including bedrock mapping and sampling, in the Alaska Highway Corridor from 2006 through 2010. The fieldwork provides basic information critical to building an understanding of Alaska's geology and is part of a broader, integrated program that includes airborne geophysical surveys, bedrock and surficial mapping, a mineral-resource assessment, a geologic-hazards assessment, and other geological studies. This publication contains descriptive, location, and analytical information for samples collected in the Mount Hayes, Tanacross, and Nabesna quadrangles, Alaska,...
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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...
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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.
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Re-analyses of sample pulps and bulk rejects from historic USBM rock and heavy-mineral-concentrate samples were conducted by the Alaska Division of Geological & Geophysical Surveys (DGGS) as part of the State of Alaska's Strategic and Critical Minerals Assessment project, which is designed to evaluate Alaska's potential for these resources. The objective of this resource assessment is to expand the state's geochemical database by obtaining and publishing modern, quantitative geochemical analyses for historic USBM samples, where available. Highlights of this re-analysis project include heavy mineral concentrates with up 7,220 ppm Sn, 5,870 ppm Cr, and 17,000 ppm Mn.
Tags: Aluminum, Antimony, Arsenic, Barium, Basalt, All tags...
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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...
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This data file presents 40Ar/39Ar step-heating geochronology results for a granite sample from the Livengood mining district. The Livengood area is a historically productive placer mining area approximately 80 road miles north of Fairbanks, Alaska. This data is a component of a geologic map and accompanying report that synthesizes recently collected and previously published agency and industry geologic data in a 1:50,000-scale comprehensive geologic map to build a better understanding of the geology and mineral-resource potential of the Livengood area.
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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,...
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...
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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.
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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...
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This geologic map and report depicts portions of the Livengood B-3, B-4, C-3, and C-4 quadrangles. The Livengood area is a historically productive placer mining area approximately 80 road miles north of Fairbanks, Alaska. This report synthesizes recently collected and previously published agency and industry geologic data in a 1:50,000-scale comprehensive geologic map to build a better understanding of the geology and mineral-resource potential of the Livengood area. It expands and updates the Alaska Division of Geological & Geophysical Surveys (DGGS) Preliminary Interpretive Report (PIR) 2004-3 with the addition of new DGGS mapping and drillhole data from ITH, and integrates previously published DGGS surficial...
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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...
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Geologists from the Alaska Division of Geological & Geophysical Surveys (DGGS) Mineral Resources Section conducted four weeks of helicopter-supported mapping and fieldwork from June 26 through July 24, 2013. The Styx River project in the Lime Hills C-1 Quadrangle was part of the State-funded Airborne Geophysical/Geological Mineral Inventory (AGGMI) program as part of the State's Strategic Minerals Assessment Project, an initiative designed to evaluate Alaska's potential for rare-earth elements, PGEs, and other similarly supply-challenged resources. The Styx River project area has active and ongoing mineral exploration for deposit types including porphyry copper/molybdenum/gold, reduced intrusion-related gold, and...
Tags: Alaska Range, Aluminum, Antimony, Arsenic, Barium, All tags...
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Mineral-resources personnel from the Alaska Division of Geological & Geophysical Surveys (DGGS) carried out a helicopter-supported geological and geochemical resource assessment project in the Beaver, Bettles, Livengood, and Tanana quadrangles from June 23 through August 5, 2012. The objectives of DGGS's resource assessment are to improve the trace-element geochemical coverage of selected watersheds; to obtain modern, quantitative geochemical analyses; to understand the petrogenesis of the granites; and to better document established mineral occurrences. Stream-sediment, pan-concentrate, and rock sampling were conducted as part of the State's Rare Earth Elements and Strategic Minerals Assessment project, which is...
Tags: Aluminum, Antimony, Arsenic, Augen Gneiss, Barium, All tags...
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In 2012, the State of Alaska established its Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), to evaluate Alaska's statewide potential for SCM resources. The project is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. For decades, the Ray Mountains area of west-central Alaska has been explored for its potential mineral resources. To further assess the rare-earth-element (REE) potential of the State-selected and top-filed lands in the Ray Mountains area, mineral-resource geologists at DGGS carried out a helicopter-supported geological and...
Tags: Base Metals, Batholith, Bedrock, Bettles Quadrangle, Cerium, All tags...


map background search result map search result map Preliminary bedrock geologic map data for the eastern Bonnifield mining district, Fairbanks and Healy quadrangles, Alaska Geology of Kasatochi volcano, Aleutian Islands, Alaska Geochemical major-oxide, minor-oxide, trace-element, and rare-earth-element data from rocks and streams sediments collected in 2012 in the Ray Mountains area, Beaver, Bettles, Livengood, and Tanana quadrangles, Alaska Analyses of historic U.S. Bureau of Mines rock and heavy mineral concentrate samples for geochemical trace-element and rare-earth element data--Ray Mountains and Kanuti-Hodzana uplands area, Alaska Major-oxide, minor-oxide, and trace-element geochemical data from rocks collected in the Alaska Highway corridor, Mount Hayes, Tanacross, and Nabesna quadrangles, Alaska, in 2006, 2008, 2009, and 2010 Major-oxide, minor-oxide, and trace-element geochemical data from rocks in the Styx River area, Lime Hills C-1 Quadrangle, Lime Hills, McGrath, Talkeetna, and Tyonek quadrangles, Alaska Zircon U-Pb age data, Alaska Highway Corridor, Tanacross and Nabesna quadrangles, Alaska Geochemical major-oxide, minor-oxide, trace-element, and rare-earth-element data from rock samples collected in 2013 in the Ray Mountains area, Bettles A-1 and A-6 quadrangles, Alaska 40Ar/39Ar data, Ray Mountains area, Bettles Quadrangle, Alaska Major-oxide and trace-element geochemical data from rocks collected in 2010 in the Tyonek Quadrangle, Alaska Zircon U-Pb age data, Ray Mountains area, Bettles Quadrangle, Alaska U-Pb zircon age data from meta-igneous rocks in the Clearwater Mountains, Mount Hayes A-6 Quadrangle, Alaska 40Ar/39Ar data from rocks collected in the 2015 Wrangellia mineral assessment project area, Mount Hayes A-5, Mount Hayes B-6, and Talkeetna Mountains D-2 quadrangles, Alaska U-Pb and Lu-Hf isotope, age, and trace-element data from zircons at four sites in the western Alaska Range and Talkeetna Mountains, Alaska Zircon U-Pb and 40Ar/39Ar results from dikes collected within the Bruin Bay fault zone, lower Cook Inlet Geologic map of the Circle mining district, Alaska Geologic context, age constraints, and sedimentology of a Pleistocene volcaniclastic succession near Mount Spurr volcano, south-central Alaska Geologic map of portions of the Livengood B-3, B-4, C-3, and C-4 quadrangles, Tolovana mining district, Alaska Geologic map of portions of the Livengood B-3, B-4, C-3, and C-4 quadrangles, Tolovana mining district, Alaska Zircon U-Pb and 40Ar/39Ar results from dikes collected within the Bruin Bay fault zone, lower Cook Inlet Geology of Kasatochi volcano, Aleutian Islands, Alaska Geologic context, age constraints, and sedimentology of a Pleistocene volcaniclastic succession near Mount Spurr volcano, south-central Alaska U-Pb zircon age data from meta-igneous rocks in the Clearwater Mountains, Mount Hayes A-6 Quadrangle, Alaska Geochemical major-oxide, minor-oxide, trace-element, and rare-earth-element data from rock samples collected in 2013 in the Ray Mountains area, Bettles A-1 and A-6 quadrangles, Alaska Preliminary bedrock geologic map data for the eastern Bonnifield mining district, Fairbanks and Healy quadrangles, Alaska Zircon U-Pb age data, Ray Mountains area, Bettles Quadrangle, Alaska 40Ar/39Ar data, Ray Mountains area, Bettles Quadrangle, Alaska Geologic map of portions of the Livengood B-3, B-4, C-3, and C-4 quadrangles, Tolovana mining district, Alaska Major-oxide and trace-element geochemical data from rocks collected in 2010 in the Tyonek Quadrangle, Alaska Geologic map of the Circle mining district, Alaska Analyses of historic U.S. Bureau of Mines rock and heavy mineral concentrate samples for geochemical trace-element and rare-earth element data--Ray Mountains and Kanuti-Hodzana uplands area, Alaska Major-oxide, minor-oxide, and trace-element geochemical data from rocks in the Styx River area, Lime Hills C-1 Quadrangle, Lime Hills, McGrath, Talkeetna, and Tyonek quadrangles, Alaska 40Ar/39Ar data from rocks collected in the 2015 Wrangellia mineral assessment project area, Mount Hayes A-5, Mount Hayes B-6, and Talkeetna Mountains D-2 quadrangles, Alaska Zircon U-Pb age data, Alaska Highway Corridor, Tanacross and Nabesna quadrangles, Alaska Geochemical major-oxide, minor-oxide, trace-element, and rare-earth-element data from rocks and streams sediments collected in 2012 in the Ray Mountains area, Beaver, Bettles, Livengood, and Tanana quadrangles, Alaska Major-oxide, minor-oxide, and trace-element geochemical data from rocks collected in the Alaska Highway corridor, Mount Hayes, Tanacross, and Nabesna quadrangles, Alaska, in 2006, 2008, 2009, and 2010 U-Pb and Lu-Hf isotope, age, and trace-element data from zircons at four sites in the western Alaska Range and Talkeetna Mountains, Alaska