Application of Laser to Spot Analysis of Noble Gases in Primitive Meteorite

Abstract

A pulse Nd-YAG laser was applied to noble gas extraction from a small portion of primitive meteorite, Allende. Details of experimental methods using the laser microprobe have been described. The laser could make through-holes with diameters of 300 and 130μm by about 40 pulses with energy of 300 and 90 mJ/pulse in aperture-out and -in modes, respectively, in a thin plate of the Allende meteorite, 0.8 mm thick. Weights of fused material were estimated to be 200 and 40 μg for the pits produced in the aperture-out and -in modes, respectively, by approximating a cylindrical shape to the laser pits and the density of 3.5 g/cm³. The calculated noble gas compositions were compared with the reported values to examine outgassing efficiencies for noble gas elements from the laser pits. Heterogeneous distributions of radiogenic noble gases, ⁴He, ⁴⁰Ar, and ¹²⁹Xe, are compatible with previous observations.