Electron probe determination of trace elements in olivine

Evaluation of the error of computations using analysis results requires knowing the error of determining the analyte. The necessity of limiting the error of computations conditions the value of the permissible error of determining the concentration: it should not exceed a certain predetermined limit. In particular, such a requirement is made for determining a component by the content of which the temperature of rock formation is calculated in a mineral. This study demonstrates derivation of a formula for quantitation limit C_lim of an analyte. Relations have been obtained connecting C_lim, the detection limit C_min, and the relative standard deviation V of the element quantitation. The equations connecting metrological characteristics allowed identifying the required analysis conditions and their practicability. The characteristics of the methodology for quantitation of Na₂O, Al₂O₃, CaO, Cr₂O₃ и MnO in the olivines of depleted peridotites have been identified using microanalyzer JXA‐8100, with the accelerating voltage of 20 kV and the probe current of 400 nA. The count rate per measurement was 10 s in the line and background positions. The number of measurements per quantitation was 25. Under these conditions, C_min of the aforementioned oxides does not exceed 9 ppmw for 1σ‐criterion. For V = 0.1, C_lim is within the range of 45–100 ppmw. The example of an ‘aluminum’ geothermometer serves to demonstrate that electron probe micro analysis may ensure the error required for calculating the temperature by the content of trace elements. Copyright © 2014 John Wiley & Sons, Ltd.