⁴⁰Ar/³⁹Ar dating of terrestrial minerals with a continuous laser

Abstract

A new method of fusing samples for 40 Ar/ 39 Ar dating using a continuous argon‐ion laser is presented. Samples of hornblende, biotite, muscovite and slate were fused with a continuous laser and the results obtained agree with acres determined using our radio‐frequency (RF) fusion system. By varying the laser beam power level, it was possible to perform a step‐heating laser fusion of the slate which closely matched two RF step‐heating runs on the same material. Thus, not only does the continuous laser give an age‐microprobe capability, but it can routinely perform multi‐step heating experiments which are crucial to 40 Ar/ 39 Ar age interpretation.