Partitioning of indium between ferromagnesian minerals and a silicate melt

Abstract Indium demand has increased with the development of new 21st century technologies. The association of indium deposits with felsic igneous rocks suggests a need for increased research on the behavior of indium in magmatic-hydrothermal systems. In order to better understand the relationship between igneous processes and the formation of indium-bearing deposits, experiments have been conducted at 750 and 800 °C and 100 MPa to constrain the partitioning of indium between ferromagnesian (biotite and amphibole) minerals and felsic melts. The partition coefficient D In Bt / Melt ranges from 0.6 ± 0.1 (1 σ m (standard deviation of the mean)) to 16 ± 3 (1 σ m ). The variation in D In Bt / Melt is a function of X Annite Bt (the proportion of Fe 2+ in the octahedral site), tetrahedral aluminum, and titanium, such that D In Bt / Melt decreases with increasing X Annite Bt , tetrahedral aluminum, and titanium. D In Amp / Melt has a mean of 36 ± 4 (1 σ m ) and composition has only a minor effect on the magnitude of D In Amp / Melt . Additionally, an aqueous volatile phase was recovered from select experiments, which provides an initial constraint on D In Vapor / Melt . D In Vapor / Melt can be influenced by the chlorine content of both the vapor and melt, and is estimated to be ~17 ± 5 (1 σ m ). Theoretical considerations suggest that D In Bt / Melt can be affected above and beyond the effect of X Annite Bt by water fugacity and the activity of the sanidine component in the system. Theoretical considerations suggest that D In Amp / Melt can be affected by the activities of diopside, anorthite, and enstatite in the system and the fugacity of water. These results suggest that the amount of magmatically-derived indium available for ore formation is a function of the proportion of ferromagnesian minerals in the crystallization products of the magma.