The data report new F, Cl, and Br fluid/melt partition coefficients for intermediate to silicic melts, for which F and Br data are particularly lacking; and for varying CO2-H2O contents. The data was collected from basaltic andesite and dacite rock experiments from the Kelud volcano in Indonesia and Quizapu volcano in Chile Over the period of two years, 2020 – 2022. The experiments were conducted at pressures 50–120 MPa, temperatures 800–1100 °C, and volatile compositions [molar XH2O = H2O/(H2O +CO2)] of 0.55 to 1, with redox conditions around the Nickel-Nickel Oxygen buffer (ƒO2 ≈ NNO). Experiments were not doped with Cl, Br, or F and were conducted on natural crystal-bearing volcanic products at conditions close to their respective pre-eruptive state. The data was collected to assess the effects of changing fluid composition (XH2O) on Br fluid/melt partitioning for the first time. Three tables of data are provided; Table 1.xlsx Table 1 Experimental conditions, which were conducted under NNO oxygen buffer. Table 3.xlsx Table 3: Major element and Br, Cl and F contents of experiments, modelled water and CO2 values and Fluid/melt partitioning. The standard deviation (1 sigma) of the multiple analyses for each experiment (n=11-24) Table S2 SIMS and EMPA Secondary standards.xlsx SIMS and EMPA secondary standards Associated paper; Mike Cassidy, Alexander A. Iveson, Madeleine C.S. Humphreys, Tamsin A. Mather, Christoph Helo, Jonathan M. Castro, Philipp Ruprecht, David M. Pyle, EIMF; Experimentally derived F, Cl, and Br fluid/melt partitioning of intermediate to silicic melts in shallow magmatic systems. American Mineralogist 2022;; 107 (10): 1825–1839. doi: https://doi.org/10.2138/am-2022-8109

Halogen (Cl, Br, I) contents measured in (a) basalt glass chips collected from subglacial eruptions in Iceland's neovolcanic zones, and (b) basalt glass chips recovered from the Reykjanes Ridge.