Microanalysis of Hornblende for Fluorine and Chlorine: Impact of Analytical Parameters on Accuracy and Detection Limits

The F and Cl contents in hornblende are critical for geological studies, but their accurate determination by electron probe microanalysis (EPMA) faces technical challenges. Existing “dual current” methods for major and trace elements are limited by instrumentation and data volume, and cannot meet large‐scale analytical needs. This study systematically evaluates EPMA parameters to establish general conditions for “single current” in situ determination of major elements, F and Cl in hornblende. Results show optimal F counting stability on TAP/LDE1 crystals at 0–5 μm beam sizes. Long dwell times with high currents reduce DLs to 11 μg g ‐1 (F) and 2 μg g ‐1 (Cl), with BG ± 10 mm yielding lower DLs than ±5 mm. However, currents beyond 100 nA cause loss of major components (notably SiO 2 ), so moderate currents are safer. For hornblende F determination, accuracy prioritises PHA setting > BG correction > probe current > counting time > reference material selection > beam size, whereas Cl is less parameter‐sensitive. A general parameter set for simultaneous in situ major element, F and Cl determination in hornblende is established, with results consistent with literature values for the Kakanui and Arenal hornblende reference materials. This method can be applied to research on magmatic‐hydrothermal evolution, metamorphism and subduction‐zone cycling.