Halogen variations in alkaline rocks from the Upper Rhine Graben (SW Germany): Insights into F, Cl and Br behavior during magmatic processes

Bromine and chlorine emissions from Plinian eruptions along the Central American Volcanic Arc: From source to atmosphere

“…Therefore, if any halogen removal by means of fractional crystallization occurred, Cl would become more depleted than Br during magma evolution. c) Assimilation of lithologies comprising hydrous minerals could in principle change the halogen contents of the magmas, but would again have little effect on Br due to the low absolute contents in the assimilated minerals and rocks (Teiber et al, 2015;Wang et al, 2014). Furthermore, geochemical and isotopic studies of CAVA magmatic rocks did not find evidence for any significant crustal assimilation (e.g.…”

“…In summary, while fractional crystallization of apatite, amphibole, and biotite may have influenced the concentration of Cl, its potential to remove Br from the melt is quantitatively insignificant due to the limited Br-contents in these minerals (e.g. Teiber et al, 2015;Wang et al, 2014). Therefore, if any halogen removal by means of fractional crystallization occurred, Cl would become more depleted than Br during magma evolution.…”

Chlorine isotope and Cl–Br fractionation in fluids of Poás volcano (Costa Rica): Insight into an active volcanic–hydrothermal system

“…Because of its much smaller ionic radius (F − = 133 pm), F is capable of substituting OH − groups into major rock forming minerals (Luth, 2003) and therefore is much less efficiently extracted from magmas during degassing processes, compared to Cl and Br Balcone-Boissard et al, 2010). As a result, ratios of F over other halogens in magmatic gases are relatively low and variable, and the F/Cl ratios of a melt tend to increase with halogen degassing Wang et al, 2014). Since chlorine and bromine are extracted with similar efficiency, they do not show a significant fractionation from melts at high pressures by H 2 O-rich fluids exsolved from magmas or during slow effusive magma degassing (Balcone-Boissard et al, 2010).…”

Halogen Contents of Mineralized Versus Unmineralized Potassic Igneous Rocks

“…Although, under mantle conditions, F tends to remain in the solid phases rather than partitioning into the first melt increments during partial melting (Vukadinovic and Edgar 1993), alkaline rocks derived in within-plate settings such as OIB are defined by relatively high F concentrations of 900-1100 ppm (cf. Wang et al 2014). During crystallization, F is partitioned into the hydrous phenocrysts rather than remaining in the melt (Edgar et al 1994).…”

“…Due to the similar ionic radii of F − (1.33 Å; Shannon 1976) and OH − (1.32-1.37 Å), F − is much easily incorporated into OH-bearing minerals than the larger Cl − (1.81 Å). Hence, at the magmatic-hydrothermal transition, F is largely retained in the melt whereas Cl preferentially partitions into the fluid phase (Webster et al 2009;Wang et al 2014;Teiber et al 2015). The potential use of high Cl concentrations in mica phenocrysts as a prospecting tool to define mineralized volcanic and subvolcanic rocks was first suggested by Stollery et al (1971).…”