Energy related studies utilizing K-feldspar thermochronology. Progress performance report, 1990--1993

Technical Report · Sat May 01 04:00:00 EDT 1993

DOI:https://doi.org/10.2172/10146243· OSTI ID:10146243

Two distinct sources of information are available from a {sup 40}Ar/{sup 39}Ar step-heating experiment: the age spectrum and Arrhenius plot. Model ages are calculated from the flux of radiogenic argon ({sup 40}Ar*) (assuming trapped argon of atmospheric composition) relative to the reactor produced {sup 39}Ar evolved during discrete laboratory heating steps. With the additional assumption that the {sup 39}Ar is uniformly distributed within the sample, we can infer the spatial distribution of the daughter product. ne associated Arrhenius plot, derived by plotting the diffusion coefficient (obtained from the inversion of the 39{sup Ar} release function assuming a single domain) against the inverse temperature of laboratory heating, are a convolution of the parameters which characterize the individual diffusion domains (whether these be dictated by varying length scale, energetics, etc.). However, many and perhaps Most {sup 40}Ar/{sup 39}Ar age spectra for slowly cooled alkali feldspars are significantly different from model age spectra calculated assuming a single diffusion-domain size. In addition, Arrhenius plots calculated from the measured loss of {sup 39}Ar during the step heating experiment show departures from linearity that are inconsistent with diffusion from domains of equal size. By extending the single diffusion-domain closure model (Dodsontype) to apply to minerals with a discrete distribution of domain sizes, we obtained an internally consistent explanation for the commonly observed features of alkali feldspar age spectra and their associated Arrhenius plots.

• Research Organization: California Univ., Los Angeles, CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG03-89ER14049
• OSTI ID: 10146243
• Report Number(s): DOE/ER/14049--4; ON: DE93013137
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000
AGE ESTIMATION
ARGON 39
ARGON 40
ARRHENIUS EQUATION
EARTH CRUST
FELDSPARS
GEOSCIENCES
HISTORICAL ASPECTS
PROGRESS REPORT
TEMPERATURE MEASUREMENT