(super 40) Ar/ (super 39) Ar and U/Pb dating of the Fish Canyonmagmatic system, San Juan volcanic field, Colorado; evidence for anextended crystallization history
Bachmann, O; Oberli, F; Dungan, M A; Meier, M; Mundil, R; Fischer, H (2007) (super 40) Ar/ (super 39) Ar and U/Pb dating of the Fish Canyonmagmatic system, San Juan volcanic field, Colorado; evidence for anextended crystallization history. Chemical Geology, vol.236, no.1-2, pp.134-166, 15 Jan 2007
| Authors | Bachmann, O; Oberli, F; Dungan, M A; Meier, M; Mundil, R; Fischer, H |
|---|---|
| Year | 2007 |
| Title | (super 40) Ar/ (super 39) Ar and U/Pb dating of the Fish Canyonmagmatic system, San Juan volcanic field, Colorado; evidence for anextended crystallization history |
| Source | Chemical Geology, vol.236, no.1-2, pp.134-166, 15 Jan 2007 |
| ISSN | 0009-2541 |
| GeoRef | 2007-058887 |
| Keywords | absolute age; Ar/Ar; calderas; Cenozoic; Colorado; crystallization;dates; eruptions; Fish Canyon Tuff; geochemistry; igneous rocks; LaGarita Caldera; magma chambers; magmas; magmatism; mass spectra;mineral assemblages; mineral composition; Nutras Creek Dacite;Oligocene; Pagosa Peak Dacite; Paleogene; petrography; processes;pyroclastics; rhyolites; San Juan volcanic field; spectra; TaylorCreek Rhyolite; Tertiary; thermal history; thermal ionization massspectra; tuff; U/Pb; United States; volcanic features; volcanicfields; volcanic rocks; volcanism; X-ray diffraction data |
| Notes | Includes appendices |
| DOI | 10.1016/j.chemgeo.2006.09.005 |
Abstract
The approximately 5000 km (super 3) Fish Canyon Tuff (FCT) is animportant unit for the geochronological community because itssanidine, zircon and apatite are widely used as standards for the(super 40) Ar/ (super 39) Ar and fission track dating techniques. Therecognition, more than 10 years ago [Oberli, F., Fischer, H. andMeier, M., 1990. High-resolution (super 238) U- (super 206) Pb zircondating of Tertiary bentonites and Fish Canyon Tuff; a test for age""concordance"" by single-crystal analysis. SeventhInternational Conference on Geochronology, Cosmochronology and IsotopeGeology. Geological Society of Australia Special Publication Canberra,27:74], of a > or =0.4 Ma age difference between the U-Pb zirconages and (super 40) Ar/ (super 39) Ar sanidine ages has, therefore,motivated efforts to resolve the origin of this discrepancy. Toaddress this controversial issue, we initially performed 37 U-Pbanalyses on mainly air-abraded zircons at ETH Zurich and nearly 200(super 40) !