Program > Browse abstracts by speaker > Gao Yajie

For apatite to be a useful monitor of volatiles in magmas we must first determine the partitioning of volatiles between apatite and melts. Here, we investigated hydroxyl, fluoride, chloride and sulfur partitioning between apatite and synthetic rhyolite/andesite melts at 1 to 3 kbar and 800 to 900 °C, using piston-cylinder or cold-seal apparatus. Volatile concentrations in the experimental charges were measured by ion probe and electron probe microanalysis. Our results show that melt composition influences the crystallization behavior of apatite, with rhyolite melts containing smaller crystals than those in andesite, regardless of run duration. The presence of fluorine in the system favors partitioning of chlorine into the melt phase. An increase in iron content in the rhyolitic melt leads to larger apatite crystals and alters the fluorine partition coefficient, such that melts containing 1.63 wt% Fe partition fluorine into apatite while melts with higher iron (3 wt.%) contents retain less fluorine in the apatite. These experiments will provide insights into apatite crystallization behavior and contribute to accurate modeling of apatite-melt volatile partitioning in igneous systems.