In-situ micro-analysis of platinum and rare earths in ferromanganese crusts by laser ablation-ICP-MS (LAICPMS)

A 500 mJ Nd: YAG laser coupled to an inductively coupled plasma mass spectrometer (ICPMS) has been used for the direct determination of platinum (Pt) and the rare earth elements (REE) in concentration micro-profiles through ferromanganese crusts from the South Pacific. The instrument has been calibrated with briquetted powder pellets of U.S.G.S. reference materials NOD-A-1 and NOD-P-1. Linear calibration curves including the origin have been obtained for all elements of interest. An external calibration strategy has been developed which also accounted for variations in instrument response. The precision of the LA-ICP-MS measurements in this matrix has been 4–5% for platinum and <4% for the rare earths. Platinum concentrations have varied from 150 ng g^–1 to 500 ng g^–1 through the analysed microprofile. Two major peak areas in the platinum concentration profile have correlated roughly with cerium values and with changes in the normalised REE pattern: an enrichment of Pt coincides with a pronounced positive cerium anomaly and with an enrichment of the heavy REE relative to the light REE.