Accurate Determination of Ni, Ca and Mn in Olivine by EPMA and LA-ICP-MS

Phenocrystal olivines in mafic and ultramafic magmatic rocks are critical minerals for trace composition of primary mantle-derived magma and in turn to study composition and evolution of the mantle.We have developed two methods for accurate determination of Ni, Ca, Mn and other elements in olivine by EPMA and LA-ICP-MS.These elements are important indicators for the basalt source composition.The limits of detection for these elements are within the range of 7 to 57 (10-6) by using the proposed EPMA analytical method, which are lower than those of the routine EPMA method by a factor of 3-18.In this work, these elements in MPI-DING reference glasses (KL2-G (basalt), ML3B-G (basalt), StHs6/80-G (andesite) and T1-G (quartzdiorite)) were determined at a spatial resolution of 24μm by LA-ICP-MS.All the determined values of MPI-DING reference glasses agree within 8% with the reference values, and most of them agree within 5%, which demonstrated the accuracy of the established analytical methods.The EPMA and LA-ICP-MS were then successfully applied to the determination of Mg, Al, Ca, Ti, Cr, Mn, Fe, Co and Ni in olivine phenocrysts from Early Cretaceous Feixian (western Shandong) and Sihetun (western Liaonin) basalts in the North China craton.Most of the determined values in the same samples determined by EPMA and LA-ICP-MS agree within 10%.This demonstrates the accuracy of our developed EPMA and LA-ICP-MS methods.