The fission track record of Apennine Front KREEP basaltsWhitlockite grains in two Apennine Front KREEP soil fragments contain extremely high densities of fission tracks. A new method is described in which particle tracks are examined in an actinide-poor phase bordering an actinide-rich whitlockite phase. This method clearly distinguishes the fission track contributions from other track sources; e.g., Fe-group cosmic rays, spallation recoils, and dislocations. Observed track excesses, when corrected for U- and Th-related fission sources, are 4-20 times greater than the contribution from spontaneous fission of U-238 (based on an age of 4 b.y.), and probably represent a large and variable contribution from the fission of Pu-244. These fragments may have pre-Imbrium ages, underscoring the importance of KREEP as a constituent of the pre-mare lunar crust. Track excesses are not correlated with the U or Th contents of the whitlockite grains. This behavior suggests that Pu fractionates differently from U and Th in lunar igneous KREEP.
Document ID
19780062909
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Haines, E. L. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Weiss, J. R. (California Institute of Technology, Jet Propulsion Laboratory, Pasadena Calif., United States)
Hutcheon, I. D. (California, University Berkeley, Calif., United States)