Halogens (F, Cl, Br, I) in Thirteen USGS, GSJ and NIST International Rock and Glass Reference Materials

Fluorine, Cl, Br and I measurements are reported for eight international rock reference materials (BHVO-2, BCR-2, BIR-1a, RGM-2, AGV-2, GSP-2, JB-2 and JR-1), and new F data are reported for five silicate glass reference materials (NIST SRM 610 and 612, BHVO-2G, BCR-2G and BIR-1G). Fluorine was measured by SHRIMP in the silicate glasses and in Li-borate flux glasses prepared from the rock powders. Chlorine, Br and I were measured in vacuum-encapsulated rock powders by the noble gas method (extended ⁴⁰Ar/³⁹Ar methodology). The methods yield reliable results: Fluorine has a repeatability of 1–16% in the flux glasses compared with 2–4% in the silicate glasses, which suggests incomplete homogenisation during flux melting, but F was not lost during fusion of flux glasses at 1080 °C. The noble gas method gave repeatability of 1–2% for samples included in a single irradiation and intermediate precision of 2% for Cl, 2–3% for Br and 3–10% for I in samples included in two irradiations. The accuracy of the measurements varies from 5% to 10%, based on the repeatability of our results, the agreement of different calibration procedures and uncertainty in experimentally determined neutron capture cross sections. Our results significantly improve upon the precision with which some of the halogens have been characterised in the selected reference materials previously.