Filters: Tags: 40Ar/39Ar (X)44 results (121ms)
New 40Ar-39Ar and detrital zircon U-Pb ages for the Upper Cretaceous Wahweap and Kaiparowits formations on the Kaiparowits Plateau, Utah: implications for regional correlation, provenance, and biostratigraphy
In order to better constrain the age and provenance of the Upper Cretaceous Wahweap and Kaiparowits formations in southern Utah, U-Pb SHRIMP ages were obtained for detrital zircons from three sandstone samples, in addition to the first 40Ar-39Ar age for the Wahweap Formation, obtained from a devitrified volcanic ash horizon (bentonite). The ash horizon, located 40Â m above the base of the Wahweap Formation, yields an age of 80.1Â Â±Â 0.3Â Ma. The new radiometric data improve upon previous biostratigraphic age estimates for the Wahweap Formation and indicate that the formation was deposited between approximately 81 and 76Â Ma. The youngest population of detrital zircons from the base of the Wahweap Formation clusters...
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...
Ar/Ar data are reported from minerals and rocks that were collected as part of a mineral resource investigation of the Tonopah, Divide, and Goldfield districts in Nevada. Data are reported from 92 samples and associated standards from eight separate neutron irradiations in the Denver USGS TRIGA reactor, including separated mineral grains and whole rocks. Data were collected by infrared laser heating of irradiated samples, either incremental heating or fusion, and analysis by multi-collector mass spectrometry. The reported data have been corrected for blanks, radioactive decay, and interfering nucleogenic reactions associated with sample irradiation.
This dataset accompanies planned publication 'Determining fault geometry through the transport-parallel distribution of thermochronometer cooling ages'. The Ar/Ar data is for samples that record the thermal history of the area. The geochronology provides time constraints for the thermal histories studied in the manuscript. Samples were collected from Nepal, overseen by Nadine McQuarrie (University of Pittsburgh), who sent them to the USGS Denver Argon Geochronology Laboratory for Ar/Ar analysis.
Bedrock geologic map of the Livengood SW C-3 and SE C-4 quadrangles, Tolovana mining district, Alaska
The Preliminary Interpretive Report 2004-3B, "Bedrock geologic map of the Livengood SW C-3 and SE C-4 quadrangles, Tolovana mining district, Alaska," is the bedrock geologic map of an approximately 123-square-mile area in the central Livengood Quadrangle, Alaska.
This report provides detailed (1:63,360-scale) mapping of the Tanana A-1 and A-2 quadrangles (500 square miles; equivalent to eight 7.5-minute quadrangles). The area is part of the Manley Hot Springs-Tofty mining districts and adjacent to the Rampart mining district to the south of the Tanana B-1 Quadrangle. This report includes detailed bedrock, surficial, structural, and stratigraphic data. Based on the resulting geologic maps, field investigations, and laboratory materials analyses, the report also includes derivative maps of geologic construction materials and geologic hazards. The Tanana A-1 and A-2 Quadrangles and surrounding area comprise several isolated mountainous ridges in the western Yukon-Tanana Upland...
Zircon U-Pb and 40Ar/39Ar results from dikes collected within the Bruin Bay fault zone, lower Cook Inlet
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...
Geologic map of portions of the Livengood B-3, B-4, C-3, and C-4 quadrangles, Tolovana mining district, Alaska
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.
This dataset accompanies planned publication 'Detrital record of the Late Oligocene – Early Miocene mafic volcanic arc in the Southern Patagonian Andes (~51°S) from single-clast geochronology and trace element geochemistry'. The Ar/Ar data is for samples that record the detrital sedimentary record of the basin. The geochronology provides time constraints for the sedimentation studied in the manuscript. Samples were collected from the Magallanes-Austral Basin, and collection was supervised by Julie Fosdick, who sent them to the USGS for Ar/Ar analysis.
Argon and geochemical data for: 40Ar/39Ar geochronology and petrogenesis of the Table Mountain Shoshonites, Golden, CO
This dataset accompanies publication '40Ar/39Ar geochronology and petrogenesis of the Table Mountain Shoshonites, Golden, CO', to be published in Rocky Mountain Geology, which analyzed lava flows on North and South Table Mountain in Golden, CO, for argon geochronology and geochemistry.
Argon data for: Elemental, isotopic, and geochronological variability in Mogollon-Datil Volcanic Province, New Mexico
This dataset accompanies publication 'Elemental, isotopic, and geochronological variability in Mogollon-Datil Volcanic Province archaeological obsidian, Southwestern New Mexico: Solving issues of inter-source discrimination', published in Geoarchaeology (https://dx.doi.org/10.1002/gea.21672), which studied the ability of isotopic and argon geochronologic analyses to discriminate between archaeological obsidian sources in the Mogollon-Datil volcanic province.
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...
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
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 map is the result of field investigations by DGGS in 1997 and 1998. This geologic map and report supersede the previously released Public Data File 99-24B, Preliminary interpretive bedrock geologic map of the Healy A-6 Quadrangle, southcentral Alaska. The current map has been updated to include mapping of areas adjacent to the Healy A-6 Quadrangle, newly interpreted bedrock units based on newly acquired analytical, paleontologic, and Ar40/Ar39 data. Ages for the rock units were modified. Field investigations were part of a two-year mapping program to provide geologic ground truth for airborne geophysical surveys flown by DGGS in the Chulitna region of southcentral Alaska during 1996.
This dataset accompanies planned publication '40Ar/39Ar geochronology of hydrothermal activity related to orogenic gold mineralization in the Klamath Mountains, California, U.S.A.'. The Ar/Ar data are for samples that record the mineralization of the area. The geochronology provides time constraints for the mineralization studied in the manuscript. Samples were collected from the Klamath Mountains by Ryan Taylor (U.S. Geological Survey, Geophysics, and Geochemistry Science Center), who sent them to the USGS Denver Argon Geochronology Laboratory for Ar/Ar analysis.
This dataset accompanies publication: Minor, S.A., Caine, J.S., Ruleman, C.A., Fridrich, C.J., Chan, C.F., Brandt, T.R., Morgan,L.E., Cosca, M.A., and Grauch, V.J.S., in prep, Geologic map of the Poncha Pass area, Chaffee, Fremont, and Saguache Counties, Colorado: U.S. Geological Survey Scientific Investigations Map (in revision), 2 plates, 27 ms. p, 1:24,000 scale.
This dataset accompanies publication 'A supervolcano and its sidekicks: A 100 ka eruptive chronology of the Fish Canyon Tuff and associated units of the La Garita magmatic system', in review in Geology, which analyzed eruptive products from the La Garita caldera.
Argon geochronology data for Multiproxy Cretaceous-Paleogene boundary event stratigraphy: an Umbria-Marche basin-wide perspective
This dataset accompanies publication 'Multiproxy Cretaceous-Paleogene boundary event stratigraphy: an Umbria-Marche basin-wide perspective'.
The Alaska Division of Geological & Geophysical Surveys (DGGS), in partnership with the U.S. National Cooperative Geologic Mapping Program, mapped approximately 450 mi2 of the Talkeetna Mountains region of central Alaska at 1:50,000 scale over the course of six weeks in 2014. This area contains significant exposures of Late Triassic mafic volcanics and gabbro sills that have been the focus of region-wide exploration for the Strategic and Critical platinum-group elements (PGEs). The area also exposes numerous inactive and possibly active faults which project through the area of proposed hydropower development. The resulting geologic map offers an improved understanding of the geology, structural history, and mineral...
Geologic map of portions of the Livengood B-3, B-4, C-3, and C-4 quadrangles, Tolovana mining district, Alaska
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...