High-precision /sup 40/Ar//sup 39/Ar ages of sanidine, biotite, hornblende, and plagioclase from the Fish Canyon Tuff, San Juan volcanic field, south-central Colorado
Sanidine, biotite, hornblende, and plagioclase from the Fish Canyon Tuff in the San Juan volcanic field of south-central Colorado have been analyzed by the /sup 40/Ar//sup 39/Ar age spectrum and total-fusion dating techniques to assess the temporal resolution for multiple, cogenetic minerals from a single sample. The McClure Mountain hornblende standard (MMhb-1), which has an adopted age of 519.4 Ma, was used as the neutron-fluence monitor in this study. Sanidine and biotite from the tuff yield replicate, concordant plateau and total-fusion ages. Hornblende yields a discordant age spectrum and also yields discordant plateau and total-fusion ages. The discordancy of the hornblende ages is probably due to inclusions and impurities in the mineral separate. Plagioclase yields no age plateau; total-fusion ages are somewhat younger than those of the sanidine and biotite. The best current age estimate for the Fish Canyon Tuff (relative to an adopted age of 519.4 Ma for MMhb-1) is 27.79 Ma, the mean of the plateau ages for the sanidine and the biotite. The data from these two minerals also suggest that a temporal resolution of about 140,000 years, approximately twice the analytical uncertainty, is possible in this age range. The potential of this procedure to determine the rates of some volcanic processes is obvious.
- Research Organization:
- Geological Survey, Reston, VA (USA)
- OSTI ID:
- 6454637
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
Similar Records
Age of the Peach Springs Tuff, southeastern California and western Arizona
[sup 40]Ar/[sup 39]Ar isotopic dates from the Cripple Creek gold-Telluride district, Colorado: Constraints on the timing of magmatism and mineralization
Related Subjects
580100 -- Geology & Hydrology-- (-1989)
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
AGE ESTIMATION
AMPHIBOLE
ARGON 39
ARGON 40
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOTITE
CHEMICAL COMPOSITION
CHEMISTRY
COLORADO
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FEDERAL REGION VIII
FELDSPARS
GEOCHEMISTRY
GEOLOGIC FORMATIONS
HORNBLENDE
ISOTOPE DATING
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
MICA
MINERALOGY
MINERALS
NORTH AMERICA
NUCLEI
RADIOISOTOPES
SILICATE MINERALS
STABLE ISOTOPES
TUFF
USA
VOLCANIC REGIONS
YEARS LIVING RADIOISOTOPES