Abstract:
Biotite is a key hydrous silicate mineral in evolved magmatic systems, but its control on the behaviour of minor- and trace-elements, in particular the REE, Nb, Li, and F is not well understood. Here, we quantify that control in sodic (per)alkaline H2O-saturated magmas with variable F-content through crystallisation experiments at 650--800ºC and 200 MPa total pressure, at log fO2 ~FMQ +1. Biotite-glass pairs from tephriphonolite to phonolite fall deposits from Tenerife, Canary Islands, complement our experimental data set. The biotite-melt Kd F/OH exchange coefficients are 2.9–47.0, typically 6.5–12.5, with minima for Al-rich, Mg-poor biotite. Lithium partition coefficients are 0.24–32.8 with minima in Si-poor biotite formed at high temperatures. D values for the large alkali metal ions Na–Cs define Onuma parabole consistent with their incorporation on the biotite XII A-site. Niobium partition coefficients are 0.1–1.2, and highest in Ti-rich biotite. The REE and actinides have D values less than 0.01 as their ionic radii fall between the size of the XII A-site and VI M-sites of biotite. Our data, alongside a literature compilation constrain empirical models that: (1) describe the exchange of F and OH between the silicate melt and the biotite W-site; (2) predict the partitioning of 1+ cations Li–Cs between silicate melt and the biotite A- and M-sites; (3) predict D Nb values. The models use the major-element composition of biotite and melt, pressure and temperature as input. Models are calibrated for use over a wide range of $P$-$T$-$X$ and can be used to interrogate biotite from natural systems to determine the composition of their source melt, or to forward model the trace-element evolution of mafic to evolved igneous systems at upper-mantle to crustal pressures.
How to cite this dataset:
Beard, C. D., van Hinsberg, V. J., Stix, J., Humphreys, M. C., Weller, O. M., 2025. Experimental data on biotite-melt trace-element partitioning, Version 1.0. Interdisciplinary Earth Data Alliance (IEDA).
https://doi.org/10.60520/IEDA/113921. Accessed 2025-08-14.
User Contributed Keyword(s):
Experimental petrology; Halogens; Mica group; Partition coefficient; Pegmatite