Characterization of a Natural Garnet Crystal as a Reference Material for Micro Analytical Determination of Trace Elements

Garnet has been widely used in igneous and metamorphic studies of a wide variety of rock types. It is particularly important in provenance studies to locate and assess kimberlites and lamproites during diamond exploration (Fedorowich, Jain et al. 1995). However, an international garnet reference material with well-characterized trace element compositions for in situ laser ablation ICPMS is not widely available. This study aims to characterize the concentrations of trace and ultra- trace elements in a natural garnet crystal, PHN1617, using both laser ablation ICP-MS and solution ICP-MS. LA-ICP-MS trace element mapping was used to confirm the homogeneity of the garnet crystal. Inter-laboratory comparison has been performed to obtain a consensus value for the trace element data. We conclude that the PHN1617 garnet can serve as a reference material or secondary reference material for micro-analytical applications. The use of Ni-in-garnet as a geothermometer for diamond exploration necessitates obtaining high quality Ni ICP-MS data. As such we have evaluated the effect of using Pt, Al, and Ni ICP-MS cones on Ni data quality. A variety of LA-ICP-MS standardization strategies, suited to garnet analysis, have also been investigated using NIST612 and other USGS glasses and these results are presented here. Fedorowich, J. S., et al. (1995). "TRACE-ELEMENT ANALYSIS OF GARNET BY LASER-ABLATION MICROPROBE ICP-MS." Canadian Mineralogist 33: 469-480.