FOSSIL TRACKS OF CHARGED PARTICLES IN MICA AND THE AGE OF MINERALS

Journal Article · Thu Aug 15 04:00:00 EDT 1963 · Journal of Geophysical Research (U.S.)

DOI:https://doi.org/10.1029/JZ068i016p04847· OSTI ID:4650642

Price, P B; Walker, R M

After a summary of what has been learned about the registration and development of charged particle tracks from previous accelerator and reactor experiments, observations on natural background tracks are described. Tracks can occur randomly throughout a sample and in clusters, which are usually, but not always, associated with an identifiable structural feature such as an inclusion. Track densities vary from an unobservably low value to >5 x 10/sup 4//cm/sup 2/. The tracks appear most frequently in biotites and phlogopites, less often in muscovites, and still less often in lepidolites. Various possible origins of the background tracks are discussed, and it was concluded that spontaneous fission of uranium impurities is the most likely source. If the tracks arise in this way, track counts before and after reactor irradiation give, in principle, a measure of the age of the mica specimens. Ages determined in this way for two specimens were in approximate agreement with geologic ages, thus giving strong experimental confirmation of the spontaneous fission origin of the tracks. The results also indicate that the time constant for track fading must be >10/sup 8/ years. The possible use of the new technique as an accurate method of dating mica samples is discussed. Track densities also give a measure of U concentrations, and values ranging from approximately 10/sup -8/ to 10/sup -11/ ntom fraction, exclusive of U in inclusions and grain boundaries, which shows that the solubility of U in mica is very small were found. Calculations also indicate that cosmic-ray- induced tracks should be found in certain specimens that have very low U concentrations and that have been at a depth less than that equivalent to 1 km of H/sub 2/O for long periods of time. The picture developed for mica applies equally well to other systems. (P.C.H.)

• Research Organization: General Electric Research Lab., Schenectady, N.Y.
• Sponsoring Organization: USDOE
• NSA Number: NSA-17-034132
• OSTI ID: 4650642
• Journal Information: Journal of Geophysical Research (U.S.), Journal Name: Journal of Geophysical Research (U.S.) Vol. Vol: 68; ISSN JGREA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

AGE ESTIMATION
ALUMINUM SILICATES
BACKGROUND
BIOTITE
CHARGED PARTICLES
COSMIC RADIATION
DISTRIBUTION
FISSION PRODUCTS
GEOLOGY, MINERALOGY, AND METEOROLOGY
IMPURITIES
IRON SILICATES
IRRADIATION
LEPIDOLITE
LITHIUM COMPOUNDS
MAGNESIUM SILICATES
MEASURED VALUES
MICA
MUSCOVITE
NEUTRON BEAMS
PARTICLE TRACKS
PHLOGOPITE
POTASSIUM SILICATES
QUANTITY RATIO
SOLUBILITY
URANIUM