AN EQUATION FOR THE DETERMINATION OF IRON-METEORITE COOLING RATES

The Goldstein-Short graph for the determination of ironmeteorite cooling rates from kamacite bandwidths and Ni concentrations has been approximated by the equation: log CR = ?2.040 log BW — 8.940 log Ni + 8.700 where the cooling rate, CR, is in units of°K/m.y., the bandwidth, BW, in units of mm, and Ni concentration is in weight percent. The equation reproduces the Goldstein-Short values to within ±7% within the Ni concentration range 7 to 14%, which includes most octahedrites. The discrepancy between the graphical or analytical cooling-rate estimations and those estimated from microprobe data is a factor of 2.1 at 1σ.