Filters: Tags: Geochronology (X)138 results (81ms)
Visualization of luminescence excitation-emission timeseries: Palaeoclimate implications from a 10,000 year stalagmite record from Ireland
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...
Geologic context, age constraints, and sedimentology of a Pleistocene volcaniclastic succession near Mount Spurr volcano, south-central Alaska
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...
Heat flow variations in a deep borehole near Sept-Iles, Quebec, Canada: Paleoclimatic interpretation and implications for regional heat flow estimates
This digital geologic map summarizes all available geologic information for the Tetilla Peak quadrangle located immediately southwest of Santa Fe, New Mexico. The geologic map consists of new polygon (geologic map units) and line (contact, fault, fold axis, dike, flow contact, hachure) data, as well as point data (locations for structural measurements, geochemical and geochronologic data, geophysical soundings, and water wells). The map database has been generated at 1:24,000 scale, and provides significant new geologic information for an area of the southern Cerros del Rio volcanic field, which sits astride the boundary of the Espanola and Santo Domingo basins of the Rio Grande rift.The quadrangle includes the...
Data tables related to geology and gold mineralization in the Richardson district, east-central Alaska
This report describes the results of geologic mapping and sample analysis from the Richardson district, east-central Alaska.
These data are U-Pb sensitive high-resolution ion microprobe (SHRIMP) geochronology data from quartz porphyry dikes for the study of the Butte mining district, U.S.A. Results of the study are described and interpreted in Lund and others (2018).
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...
Cassiterite (SnO2), a main ore mineral in tin deposits, was collected by multiple Russian geologists or obtained from museum collections in both the USA and Russia and dated at the U.S. Geological Survey. The dated samples represent four different mining districts spanning the entire country from the village of Pitkäranta in the west (31° E Longitude) to the Merekskoe Deposit in the Russian Far East (134°E Longitude). The samples were recovered from a variety of host deposit types that range from the Proterozoic to Phanerozoic. Cassiterite (in the form of mounted loose grains) was prepared and analyzed for direct age dating on a laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) system at the...
U-Pb data for: In situ LA-ICPMS U-Pb dating of cassiterite without a known-age matrix-matched reference material: Examples from worldwide tin deposits spanning the Proterozoic to Tertiary
This dataset accompanies the publication, 'In situ LA-ICPMS U-Pb dating of cassiterite without a known-age matrix-matched reference material: Examples from worldwide tin deposits spanning the Proterozoic to Tertiary', published in Chemical Geology (https://doi.org/10.1016/j.chemgeo.2018.03.008), which reports a LA-ICPMS analytical procedure for dating cassiterite, a main ore mineral in tin deposits, with no need for an independently dated matrix-matched cassiterite standard.
In 2016, with National Park Service support, several previously undated plutons were sampled in Glacier Bay National Park and Preserve along the west side of Glacier Bay for age determinations. Geochronologic analyses were conducted to determine the ages of the plutonic rocks in the Glacier Bay area. Five samples were collected by Frederic Wilson (USGS Alaska Science Center), from Dundas Bay and Geikie Inlet, and dated by laser ablation-inductively coupled plasma mass spectrometry U-Pb methods. The dates obtained ranged from approximately 112-118 Ma, indicating that these samples are younger than the Saint Elias plutonic suite (ca. 160 Ma-130Ma), which runs along the same trend as the sampled rocks to the south.
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.
Data release for cosmogenic beryllium-10 exposure ages of moraine boulders in the Stura Valley, Maritime Alps, northwestern Italy
This report summarizes the cosmogenic beryllium-10 (10Be) geochronologic results from boulders deposited on moraines in the Stura Valley of the Maritime Alps, the southwestern most extent of the European Alpine mountain chain, northwestern Italy. Within this report are detailed the methodologies used to collect samples of whole rock, determine the concentrations of cosmogenic 10Be in purified quartz isolated from those samples, and use those nuclide concentrations to calculate surface exposure ages. This report should be used as supplementary material for any publication(s) that uses the nuclide concentrations and/or ages reported herein. This version supersedes all previous age estimates and reports.
Photoluminescence Imaging of Whole Zircon Grains on a Petrographic Microscope—An Underused Aide for Geochronologic Studies
The refractory nature of zircon to temperature and pressure allows even a single zircon grain to preserve a rich history of magmatic, metamorphic, and hydrothermal processes. Isotopic dating of micro-domains exposed in cross-sections of zircon grains allows us to interrogate this history. Unfortunately, our ability to select the zircon grains in a heavy mineral concentrate that records the most geochronologic information is limited by our inability to predict internal zonation from observations of whole zircon grains. Here we document the use of a petrographic microscope to observe and image the photoluminescence (PL) response of whole zircon grains excited under ultraviolet (UV) light, and the utility of this PL...
This location is part of the Arizona Mineral Industry Location System (AzMILS), an inventory of mineral occurences, prospects and mine locations in Arizona. Cochise742 is located in T20S R23E Sec 34 ALL in the Hay Mountain - 7.5 Min quad. This collection consists of various reports, maps, records and related materials acquired by the Arizona Department of Mines and Mineral Resources regarding mining properties in Arizona. Information was obtained by various means, including the property owners, exploration companies, consultants, verbal interviews, field visits, newspapers and publications. Some sections may be redacted for copyright. Please see the access statement.
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.
Geologic Map of the Mound Spring Quadrangle, Nye and ClarkCounties, Nevada, and Inyo County, California
The Mound Spring quadrangle, the southwestern-most 7.5'quadrangle of the area of the Las Vegas 1:100,000-scalequadrangle, is entirely within the Pahrump Valley, spanning theNevada/California State line. New geologic mapping of thepredominantly Quaternary materials is combined with new studiesof gravity and geochronology in this quadrangle. Elevenpredominantly fine-grained units are delineated, including playasediment, dune sand, and deposits associated with several cyclesof past groundwater discharge and distal fan sedimentation.These units are intercalated with 5 predominantly coarse-grainedalluvial-fan and wash gravel units mainly derived from the SpringMountains. The gravel units are distinguished on the basis...
Ar/Ar data are reported from eight samples of white mica separated from rock samples collected along the Austroalpine-Pennine boundary in the Central Alps of Switzerland. These samples were collected as part of a Caltech PhD study to examine the tectonic history of this boundary and these argon geochronology data represent one small part of the study. Data are reported from these eight samples together with standards that were irradiated together in the Denver USGS TRIGA reactor. Data from the samples were collected by incremental infrared laser heating of individual grains and analysis by multi-collector mass spectrometry. The reported data have been corrected for blanks, radioactive decay, and interfering nucleogenic...
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...