Abstract
Strontium isotopic composition is a potentially powerful tracer in studies of kimberlitic rocks but the results from even the most carefully collected and stringently prepared bulk‐rock samples are still hampered by contamination and alteration effects. Here we describe a LA‐MC‐ICP‐MS technique which can obtain accurate, high precision Sri ratios from 50–150 μm kimberlitic groundmass perovskite without requiring time‐consuming mineral separation procedures. Since perovskite is a robust magmatic phase with an extremely low Rb/Sr ratio, the effects of late‐stage crustal contamination, post‐emplacement alteration and age correction are minimised and results are more representative of primary melt compositions, while additionally preserving powerful grain‐scale spatial and textural information. We demonstrate that the adopted protocol overcomes isobaric interferences from Kr+, Rb+, Er2+ and Yb2+, and that Ca dimers and Ca argides do not detectably affect the quality of 87Sr/86Sr ratios produced. To illustrate the utility of the technique, contrasting bulk‐rock and in situ perovskite results from eleven Proterozoic kimberlites are documented.
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