Fission Track Dating Stephanie Owens July 27, 2006 Nuclear and Radiochemistry Summer School 2006

Performed on etchable, transparent solids: Minerals, glass, petrified wood, sediment, meteorites Comparable to the K-Ar dating method Fission tracks were first observed in mica in 1962 Provides cooling age of a material NOT absolute age Tracks form as a result of spontaneous fission, usually 238 U Introduction

Materials

Assumptions Uranium must be homogenous throughout the sample and greater than 0.1 ppm. Lattice structure of the solid must be intact excluding track damage. Chemical weathering must not cause loss of tracks or uranium. Induced fission tracks of 235 U must not significantly contribute to total tracks. 238 U is most significant fission species. The decay constant for spontaneous fission of 238 U is known.

Track Formation

Calculation of Age Decay constant for spontaneous fission Density of 238 U fission tracks Density of 235 U induced fission tracks Track densities of the sampleTrack densities of the standard

Materials and Time Range

Seafloor Spreading

Meteorites 244 Pu

Fission Track Dating Stephanie Owens July 27, 2006 Nuclear and Radiochemistry Summer School 2006