Argon Geochronology Active
This project supports the USGS argon geochronology laboratory in Denver. The USGS 40Ar/39Ar geochronology laboratory is a state-of-the-art research facility for determining absolute ages of minerals and rocks. The 40Ar/39Ar laboratory contributes critical geochronology to individual USGS research projects and to partners in academia and other Federal agencies. This laboratory develops methodology for small and difficult sample analysis often at the limits of existing mass spectrometer technology.
Science Issue and Relevance
The 40Ar/39Ar Method: 40Ar/39Ar geochronology is an experimentally robust and versatile method for constraining the age and thermal history of rocks. Such information is extremely valuable for understanding a variety of geological processes including the formation of ore deposits, mountain building and history of volcanic events, paleo-seismic events, and paleo-climate. The 40Ar/39Ar isotopic dating method has evolved into the most commonly applied geochronological method, and can be applied to many geological problems that require precise and accurate time and temperature control.
Methodology to Address Issue
This project provides partial support for the USGS argon geochronology laboratory in Denver. The USGS 40Ar/39Ar geochronology laboratory is a state-of-the-art research facility for determining absolute ages of minerals and rocks. The 40Ar/39Ar laboratory contributes critical geochronology to individual USGS research projects and to partners in academia and other Federal agencies. This facility houses necessary equipment for sample preparation and analysis, including high-sensitivity noble gas mass spectrometers and ultraviolet (UV) and infrared (IR) lasers. The versatility of the 40Ar/39Ar method permits determining the timing of processes and events such as igneous intrusions and extrusions, ore mineralization and hydrothermal fluid circulation, metamorphic cooling and exhumation, mineral formation and recrystallization, and shallow crustal faulting. Scientists are dependent on the geochronologist for data and interpretations to determine these parameters. This laboratory develops methodology for small and difficult sample analysis often at the limits of existing mass spectrometer technology.
Below are other science projects associated with this project.
Below are data releases associated with this project. Visit USGS Geochron - a database of geochronologic and thermochronologic dates and data.
Below are publications associated with this project.
Recent, slow normal and strike-slip faulting in the Pasto Ventura region of the southern Puna Plateau, NW Argentina
Mauritania – A greenfields exploration opportunity in northwestern Africa
Igneous activity, metamorphism, and deformation in the Mount Rogers area of SW Virginia and NW North Carolina: A geologic record of Precambrian tectonic evolution of the southern Blue Ridge Province
Constraints on the history and topography of the Northeastern Sierra Nevada from a Neogene sedimentary basin in the Reno-Verdi area, Western Nevada
Geophysical expression of elements of the Rio Grande rift in the northeast Tusas Mountains - Preliminary interpretations
40Ar∗ loss in experimentally deformed muscovite and biotite with implications for 40Ar/39Ar geochronology of naturally deformed rocks
Lifetime of an ocean island volcano feeder zone: Constraints from U-Pb dating on coexisting zircon and baddeleyite, and 40Ar/39Ar age determinations, Fuerteventura, Canary Islands
40Ar* loss in experimentally deformed muscovite and biotite with implications for 40Ar/39Ar geochronology of naturally deformed rocks
Exhumation history of the NW Indian Himalaya revealed by fission track and 40Ar/39Ar ages
Vertical movements of ocean island volcanoes: Insights from a stationary plate environment
Beyond Colorado's Front Range - A new look at Laramide basin subsidence, sedimentation, and deformation in north-central Colorado
Episodic swell growth inferred from variable uplift of the Cape Verde hotspot islands
In addition to the USGS National Cooperative Geologic Mapping Program and the Geosciences and Environmental Change Science Center, below are partners associated with this project.
- Overview
This project supports the USGS argon geochronology laboratory in Denver. The USGS 40Ar/39Ar geochronology laboratory is a state-of-the-art research facility for determining absolute ages of minerals and rocks. The 40Ar/39Ar laboratory contributes critical geochronology to individual USGS research projects and to partners in academia and other Federal agencies. This laboratory develops methodology for small and difficult sample analysis often at the limits of existing mass spectrometer technology.
Science Issue and Relevance
The 40Ar/39Ar Method: 40Ar/39Ar geochronology is an experimentally robust and versatile method for constraining the age and thermal history of rocks. Such information is extremely valuable for understanding a variety of geological processes including the formation of ore deposits, mountain building and history of volcanic events, paleo-seismic events, and paleo-climate. The 40Ar/39Ar isotopic dating method has evolved into the most commonly applied geochronological method, and can be applied to many geological problems that require precise and accurate time and temperature control.
Methodology to Address Issue
This project provides partial support for the USGS argon geochronology laboratory in Denver. The USGS 40Ar/39Ar geochronology laboratory is a state-of-the-art research facility for determining absolute ages of minerals and rocks. The 40Ar/39Ar laboratory contributes critical geochronology to individual USGS research projects and to partners in academia and other Federal agencies. This facility houses necessary equipment for sample preparation and analysis, including high-sensitivity noble gas mass spectrometers and ultraviolet (UV) and infrared (IR) lasers. The versatility of the 40Ar/39Ar method permits determining the timing of processes and events such as igneous intrusions and extrusions, ore mineralization and hydrothermal fluid circulation, metamorphic cooling and exhumation, mineral formation and recrystallization, and shallow crustal faulting. Scientists are dependent on the geochronologist for data and interpretations to determine these parameters. This laboratory develops methodology for small and difficult sample analysis often at the limits of existing mass spectrometer technology.
- Science
Below are other science projects associated with this project.
- Data
Below are data releases associated with this project. Visit USGS Geochron - a database of geochronologic and thermochronologic dates and data.
Filter Total Items: 19No Result Found - Publications
Below are publications associated with this project.
Filter Total Items: 66Recent, slow normal and strike-slip faulting in the Pasto Ventura region of the southern Puna Plateau, NW Argentina
Recent normal and strike-slip faulting on the Puna Plateau of NW Argentina has been linked to lithospheric foundering, gravitational spreading, plate boundary forces and a decrease in crustal shortening from north to south. However, the timing, kinematics and rate of extension remain poorly constrained. We focus on the Pasto Ventura region (NW Argentina) located on the southern Puna Plateau and reAuthorsRenjie Zhou, Lindsay M. Schoenbohm, Michael CoscaMauritania – A greenfields exploration opportunity in northwestern Africa
No abstract available.AuthorsCliff D. Taylor, E. D. Anderson, D. C. Bradley, G. Beaudoin, Michael A. Cosca, Robert G. Eppinger, Gregory L. Fernette, Carol A. Finn, Michael J. Friedel, Stuart A. Giles, Richard J. Goldfarb, John D. Horton, Gregory K. Lee, Erin E. Marsh, Jeffrey L. Mauk, Holly A. Motts, M. Y. Ould El Joud, S. Ould Soueidatt, A. Ould Taleb Mohamed, Barnaby W. RockwellIgneous activity, metamorphism, and deformation in the Mount Rogers area of SW Virginia and NW North Carolina: A geologic record of Precambrian tectonic evolution of the southern Blue Ridge Province
Mesoproterozoic basement in the vicinity of Mount Rogers is characterized by considerable lithologic variability, including major map units composed of gneiss, amphibolite, migmatite, meta-quartz monzodiorite and various types of granitoid. SHRIMP U-Pb geochronology and field mapping indicate that basement units define four types of occurrences, including (1) xenoliths of ca. 1.33 to ≥1.18 Ga age,AuthorsRichard P. Tollo, John N. Aleinikoff, Roland Mundil, C. Scott Southworth, Michael A. Cosca, Douglas W. Rankin, Allison E. Rubin, Adrienne Kentner, Christopher A. Parendo, Molly S. RayConstraints on the history and topography of the Northeastern Sierra Nevada from a Neogene sedimentary basin in the Reno-Verdi area, Western Nevada
Neogene (Miocene–Pliocene) sedimentary rocks of the northeastern Sierra Nevada were deposited in small basins that formed in response to volcanic and tectonic activity along the eastern margin of the Sierra. These strata record an early phase (ca. 11–10 Ma) of extension and rapid sedimentation of boulder conglomerates and debrites deposited on alluvial fans, followed by fluvio-lacustrine sedimentaAuthorsJames Trexler, Patricia Cashman, Michael CoscaGeophysical expression of elements of the Rio Grande rift in the northeast Tusas Mountains - Preliminary interpretations
New interpretations of the nature of the Rio Grande rift and pre-existing rocks in the northeast Tusas Mountains region are derived from new and existing gravity and aeromagnetic data. 12-15 mGal amplitude gravity lows are interpreted to mainly reflect large thicknesses of the upper Oligocene to upper Miocene, syn-rift Los Pinos Formation and possibly significant amounts of the Eocene El Rito FormAuthorsBenjamin J. Drenth, Kenzie J. Turner, Ren A. Thompson, V. J. Grauch, Michael A. Cosca, John Lee40Ar∗ loss in experimentally deformed muscovite and biotite with implications for 40Ar/39Ar geochronology of naturally deformed rocks
The effects of deformation on radiogenic argon (40Ar∗) retentivity in mica are described from high pressure experiments performed on rock samples of peraluminous granite containing euhedral muscovite and biotite. Cylindrical cores, ∼15 mm in length and 6.25 mm in diameter, were drilled from granite collected from the South Armorican Massif in northwestern France, loaded into gold capsules, and welAuthorsMichael Cosca, Holger Stunitz, Anne-Lise Bourgiex, John P. LeeLifetime of an ocean island volcano feeder zone: Constraints from U-Pb dating on coexisting zircon and baddeleyite, and 40Ar/39Ar age determinations, Fuerteventura, Canary Islands
High-precision isotope dilution thermal ionization mass spectrometry (IDTIMS) UPb zircon and baddeleyite ages from the PX1 vertically layered mafic intrusion Fuerteventura, Canary Islands, indicate initiation of magma crystallization at 22.10 0.07 Ma. The magmatic activity lasted a minimum of 0.52 Ma. 40Ar/39Ar amphibole dating yielded ages from 21.9 0.6 to 21.8 0.3, identical within errors to theAuthorsJames Allibon, Maria Ovtcharova, Francois Bussy, Michael Cosca, Urs Schaltegger, Denise Bussien, Eric Lewin40Ar* loss in experimentally deformed muscovite and biotite with implications for 40Ar/39Ar geochronology of naturally deformed rocks
The effects of deformation on radiogenic argon (40Ar∗) retentivity in mica are described from high pressure experiments performed on rock samples of peraluminous granite containing euhedral muscovite and biotite. Cylindrical cores, ∼15 mm in length and 6.25 mm in diameter, were drilled from granite collected from the South Armorican Massif in northwestern France, loaded into gold capsules, and welAuthorsM. Cosca, H. Stunitz, A.-L. Bourgeix, J.P. LeeExhumation history of the NW Indian Himalaya revealed by fission track and 40Ar/39Ar ages
New fission track and Ar/Ar geochronological data provide time constraints on the exhumation history of the Himalayan nappes in the Mandi (Beas valley) — Tso Morari transect of the NW Indian Himalaya. Results from this and previous studies suggest that the SW-directed North Himalayan nappes were emplaced by detachment from the underthrusted upper Indian crust by 55 Ma and metamorphosed by ca. 48–4AuthorsMicha Schlup, Albrecht Steck, Andrew Carter, Michael Cosca, Jean-Luc Epard, Johannes HunzikerVertical movements of ocean island volcanoes: Insights from a stationary plate environment
Uplift reconstructions based on the Cape Verde's geological record provide a unique opportunity to study the long-term isostatic movements associated with hotspot activity on a stationary plate environment. The archipelago is considered stationary with respect to its melting source so the hotspot-driven isostatic effects affecting the ocean islands are expected to be enhanced. In this study, Ar–ArAuthorsRicardo Ramalho, George Helffrich, Michael A Cosca, D. Vance, D. Hoffman, Daniela N. SchmidtBeyond Colorado's Front Range - A new look at Laramide basin subsidence, sedimentation, and deformation in north-central Colorado
This field trip highlights recent research into the Laramide uplift, erosion, and sedimentation on the western side of the northern Colorado Front Range. The Laramide history of the North Park-Middle Park basin (designated the Colorado Headwaters Basin in this paper) is distinctly different from that of the Denver basin on the eastern flank of the range. The Denver basin stratigraphy records the tAuthorsJames C. Cole, James H. Trexler, Patricia H. Cashman, Ian M. Miller, Ralph R. Shroba, Michael A. Cosca, Jeremiah B. WorkmanEpisodic swell growth inferred from variable uplift of the Cape Verde hotspot islands
On the Beagle voyage, Charles Darwin first noted the creation and subsidence of ocean islands1, establishing in geology’s infancy that island freeboard changes with time. Hotspot ocean islands have an obvious mechanism for freeboard change through the growth of the bathymetric anomaly, or swell2, on which the islands rest. Models for swell development indicate that flexural9, thermal2,3 or dynamicAuthorsR. Ramalho, G. Helffrich, M. Cosca, D. Vance, D. Hoffmann, D.N. Schmidt - Web Tools
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- Partners
In addition to the USGS National Cooperative Geologic Mapping Program and the Geosciences and Environmental Change Science Center, below are partners associated with this project.