Further Characterization of the RW-1 Monazite: A New Working Reference Material for Oxygen and Neodymium Isotopic Microanalysis

The oxygen (O) and neodymium (Nd) isotopic composition of monazite provides an ideal tracer of metamorphism and hydrothermal activity. Calibration of the matrix effect and monitoring of the external precision of monazite O-Nd isotopes with microbeam techniques, such as secondary ion mass spectrometry (SIMS) and laser ablation-multicollector-inductively coupled plasma-mass spectrometry (LA-MC-ICPMS), require well-characterized natural monazite standards for precise microbeam measurements. However, the limited number of standards available is impeding the application of monazite O-Nd isotopes. Here, we report on the RW-1 monazite as a potential new working reference material for microbeam analysis of O-Nd isotopes. Microbeam measurements by electron probe microanalysis (EPMA), SIMS, and LA-MC-ICPMS at 10-24 mu m scales have confirmed that it is homogeneous in both elemental and O-Nd isotopic compositions. SIMS measurements yield delta O-18 values consistent, within errors, with those obtained by laser fluorination techniques. Precise analyses of Nd isotope by thermal ionization mass spectrometry (TIMS) are consistent with mean results of LA-MC-ICPMS analyses. We recommend delta O-18 = 6.30 parts per thousand +/- 0.16 parts per thousand (2SD) and Nd-143/Nd-144 = 0.512282 +/- 0.000011 (2SD) as being the reference values for the RW-1 monazite.