The effect of fluorine, boron and phosphorus on the viscosity of pegmatite forming melts

Geology and evolution of pegmatite-hosted U-Th ± REE-Y-Nb Mineralization, Kulyk, Eagle, and Karin Lakes region, Wollaston Domain, northern Saskatchewan, Canada: examples of the dual role of extreme fractionation and hybridization processes

“…Network-forming cations (Al and Si) and U, Th, REE and other HFSE would diffuse during viscous stress relaxation in melts, which typically occurs with the addition of volatiles (e.g., Bagdassarov et al 1993;Mungall 2002). Experimental studies of volatile-rich pegmatite melts (Bartels et al 2011(Bartels et al , 2012 have also shown the effectiveness of the of U, Th, and REE diffusion related to the changes in residual melt composition, either as a result of fractionation or volatiles loss. We have proposed that the separation of a SCF and infiltration of a volatile phase through crystallized portions of the pegmatite (and eventually the host rocks) would facilitate metasomatic transfer, i.e., assist in the diffusion and advection of elements, such as rare alkalis and HFSE from the melt.…”

The effect of lithium on the viscosity of pegmatite forming liquids

“…Bartels et al (2011) note that the viscosity of a hydrous synthetic melt, containing F, B, P and Li, can be more than four log units lower than that of a rhyolitic melt containing similar amounts of water. Additionally, Bartels et al (2013) investigated the individual influences of H 2 O, F, B and P on the viscosity of pegmatite forming liquids. They conclude that beside water, fluorine is the main element influencing melt viscosity and that P and B do not play a major role on viscous flow in waterrich pegmatitic systems.…”

The missing link between granites and granitic pegmatites

“…Generally, the influence of P on the viscosity and water solubility is significantly lower than that of H 2 O, F, B, and alkalis (Johannes and Holtz 1996;Sowerby and Keppler 2002;Bartels et al 2011Bartels et al , 2013 and by itself cannot reduce the viscosity down to values of c. 10 2 Pa.s at 700 °C which are considered to be the threshold values for the separation of residual melt (McKenzie 1985) except at very high concentrations. Although P is often significantly enriched in intergranular melts, and has been considered a possible fluxing element, it appears to be of less importance than F or B. water-and boron-rich melt systems moving in part as supercritical fluid through the parental granite ).…”

“…Thus, primary melt and fluid inclusions trapped in magmatic minerals during magma crystallization provide almost the only method of estimating true original melt volatile concentrations. Melt and fluid studies are not without their difficulties, as is the interpretation of their results (for example see Roedder 1984;Lowenstern 1995), but these techniques are very rarely taken into account by the experimental petrologists (e.g., Johannes and Holtz 1996;London 2008;Bartels et al 2011Bartels et al , 2013.…”

“…There are several models for the estimation of felsic melt viscosity, starting with the empirical approach based on compilations of experimental results presented by Shaw (1972) and the improved model by Giordano et al (2008). Recently Bartels et al (2013) studied the effect of fluorine, boron and phosphorus on the viscosity of pegmatite-forming melts. However, in this work the known facts obtained from new experiments (e.g., Audétat and Keppler 2004), and especially the data and facts obtained from the study of melt inclusions, are completely ignored.…”