Carbon-14 activities in recently fallen meteorites and Antarctic meteorites

This paper reports ¹⁴C measurements in meteorites using an extraction method which employs RF melting of samples as small as 0.1 g. A study of extraction of cosmic-ray-produced ¹⁴C in samples of Bruderheim gave ¹⁴C levels between 38 and 60 dpm/kg for samples which had been preheated in air between 250 and 700°C, with a mean value of 46.8 ± 1.4 dpm/kg. A range of values between 35 and 59 dpm/kg was found for other falls of saturated meteorites preheated to 500°C. The preheating step is shown to be effective in removing terrestrial carbon contamination. A series of samples previously dated by ⁸¹Kr as having ages of 120-310 kyrgave ¹⁴C levels of between <0.16 and 0.37 ± 0.10 dpm/kg. These levels are consistent with levels of in situ production by cosmic rays at the Earth's surface.