Halogens (F, Cl) in Natural Diamond: SIMS Study

Abstract Halogens play an essential role in mantle petrology, but no data on halogen content in diamonds are available to date. Concentrations of fluorine and chlorine in diamond were determined quantitative for the first time, using quantitative SIMS analysis based on external standards prepared by the ion-implantation of halogens. Fluorine concentrations in diamond vary from 0.018 to 0.036 at ppm (3.2‒6.3 × 10 15 at/cm 3 ); chlorine concentrations are similar, from 0.014 to 0.034 at ppm (2.4‒4.5 × 10 15 at/cm 3 ). Most likely, F and Cl are related to microinclusions in diamonds, although one cannot exclude their position in the diamond lattice. The source of halogens in the studied diamonds is complex. A part of F and Cl is juvenile, remained from their primary concentrations. Another part, forming the halogen repository in the deep Earth, comes to the mantle via subduction. Fluorine may form the fluorine–vacancy (F–V) complex in the diamond structure, F and Cl may be compositional parts of microinclusions in diamonds as well. The F/Cl ratio in the studied diamonds (1.00–1.82) is similar to F/Cl ratios in kimberlites (0.38‒1.68). It differs from the estimates for the Earth’s mantle (0.62–0.68) but is close to enstatite chondrite values (1.16–2.77).