Cosmic-ray-produced V⁵⁰and K⁴⁰in the iron meteorite Aroos

Abstract

The abundances of V60 and K40 in the iron meteorite Aroos have been determined by means of mass-spectrometric techniques. It was found earlier [Voshage and Hintenberger, 1959; Honda, 1959] that potassium separated from iron meteorites is enriched in K40 which is produced in cosmic-ray-induced spallation reactions. However, the absolute content of cosmogenic K40 has not yet been obtained accurately by massspectrometric measurements. The content of vanadium in iron meteorites is unknown. Goldschmidt [1954] estimates a value of <5 ppm in the iron-nickel phase, while the troilite phase shows a considerably higher value. Recent studies on stable and radioactive cosmic-ray-produced nuclides [Arnold, Honda, and Lal, 1961; Honda and Arnold, 1961] permit an estimation of the abundance of cosmogenic V50 in the iron meteorite Aroos. Assuming a production rate of 100 atoms/min kg and an exposure age of 600 m. y. [Heymann and Schaeffer, 1961], we obtain a value of 3 ppb V50. If the total vanadium content is <5 ppm, the enrichment of V50 should easily be detectable.