Meteorite Phosphates Show Constant 176Lu Decay Rate Since 4557 Million Years Ago

The use of radioactive decay of 176Lu to 176Hf to study the evolution of the Earth requires a precise and accurate value for the 176Lu decay constant. Recent determinations of this decay constant by age comparison to the more precisely calibrated U-Pb isotopic system produced internally consistent but discrepant values between terrestrial minerals and meteorites. New highly radiogenic Lu-Hf data for phosphate minerals from Richardton (ordinary chondrite) and Acapulco (primitive achondrite) yield decay constant values of 1.864 × 10-11 ± 0.016 × 10 -11 and 1.832 × 10-11 ± 0.029 × 10 -11 year-1, respectively, identical to the value determined from terrestrial minerals