Accession Number : ADA258429
Title : Diffusion of Helium Isotopes in Silicate Glasses and Minerals: Implications for Petrogenesis and Geochronology.
Descriptive Note : Doctoral thesis,
Corporate Author : WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
Personal Author(s) : Trull, Thomas W
Report Date : Jun 1989
Pagination or Media Count : 402
Abstract : Helium mobility in geologic materials is a fundamental constraint on the petrogenetic origins of helium isotopic variability and on the application of radiogenic and cosmogenic helium geochronology. 3He and 4He volume diffusivities determined at 25-600 deg C in basaltic glasses by incremental- heating and powder storage experiments (using a diffusion model incorporating grain size and shape information to obtain high precision) are three to four orders of magnitude greater than for common cations. Diffusion in tholeiitic glass can be described by an Arrhenius relation with activation energy = 16.85 + or - .13 Kcal/mole and log D sub o = -2.37 + or - .06, although low temperature data are better described by a distribution of activation energies model. The best estimate for D at 0 deg C in tholeiitic glass is 5 + or - 2 x 10 to the - 16th power sq. cm/s, an order of magnitude higher than the results of Kurz and Jenkins (1981) but lower than suggested by Jambon, Weber and Begemann (1985).
Descriptors : *HELIUM , *PETROLOGY , CATIONS , TEMPERATURE , VOLUME , LOW TEMPERATURE , MOBILITY , MODELS , DISTRIBUTION , ENERGY , MAGMA , ACTIVATION ENERGY , OCEAN BOTTOM , SILICATES , SEA WATER , DIFFUSION , SHAPE , GRAIN SIZE , GLASS , BASALT , ESTIMATES , PRECISION , ISOTOPES
Subject Categories : Physical and Dynamic Oceanography
Geology, Geochemistry and Mineralogy
Distribution Statement : APPROVED FOR PUBLIC RELEASE