Trace element microanalysis in iron meteorites by laser ablation ICPMS

A laser ablation microanalysis system has been developed that can analyze t race elements with a sensitivity in time ppb range, using a CETAC LSX-200 l aser ablation system with a Finnigan Element. This capability has been appl ied to a set of iron meteorites to demonstrate the laser microprobe's analy tical capability for the determination of platinum group elements (PGEs) wi th a spatial resolution of similar to 20 mu m, comparable to that of dynami c secondary ion mass spectrometry (SIMS), The laser is shown to provide an accurate means of solid sampling for magnetic sector inductively coupled pl asma mass spectrometry (ICPMS), allowing the determination of bulk metal co mposition, chemical zoning within the sample, and depth profiling. Recovery of the chemical zoning in taenite lamellae was achieved for Ru, Rh, and Pd , which was not previously possible using SIMS, The methods presented here show that magnetic sector ICPMS can be successfully coupled to a laser abla tion system, providing the advantages of higher sensitivity of the sector i nstrument, low background count rates (<0.1 counts/s), and flat-topped spec tral peaks, while minimizing tradeoff against the speed of data acquisition required to handle the transient signals from the laser ablation system.