INVESTIGATION OF THE EFFECT OF SILICATE MELT COMPOSITION ON THE METAL-SILICATE PARTITIONING BEHAVIOUR OF THE MODERATELY SIDEROPHILE AND REFRACTORY ELEMENT MOLYBDENUM

Abstract

Metal-silicate partitioning is crucial in understanding the early differentiation histories of terrestrial planets, asteroids, and parent bodies for meteorites such as Angrites. However, there is a lack of systematic studies on the impact of critical factors like temperature and melt composition on partitioning for many key elements that are sensitive to metal-silicate segregation processes in planetary bodies. The refractory nature of the moderately siderophile element Molybdenum (Mo), in particular, makes it a valuable element in understanding the metal-silicate equilibration conditions present during planetary differentiation process in terrestrial planetary bodies. However, there are only limited published for experimental metal silicate partitioning data for Mo, particularly focussing on isolating the effects of the different factors that control its fractionation between molten metal and molten silicate phases. To fill this knowledge gap, a series of experiments were conducted to investigate the partitioning of Mo between Fe-rich metallic liquid, and silicate melts with varying compositions from basaltic to peridotitic compositions (in terms of NbO/T), under constant conditions of temperature (T=1800o C) and pressure (P=1 atm), using the newly installed high temperature experimental furnace in the Geochemistry laboratory, Department of Earth Siences, IIT Roorkee. Changing the silicate melt composition under constant P-T conditions, allowed to isolate the effect of the silicate melt on the metal-silicate partitioning behaviour of Mo. Results show that metal-silicate partition coefficient for Mo can vary by a factor of ~7 depending upon whether the equilibrating silicate melt is a basalt or a peridotite, with identical metallic liquids and P-T conditions. The results of these experiments demonstrate the strong effect of silicate melt composition on the partitioning behaviour of Mo, and also provide essential insights into the early evolution of planets and asteroids, as well as their differentiation processes. By understanding how elements partition between metal and silicate phases, we can better understand the formation and evolution of planetary bodies. Additionally, the data obtained from these experiments can contribute to refining existing geochemical models and can aid in identifying potential mineral resources. Overall, these experiments represent a crucial step in advancing our understanding of metal-silicate partitioning and its role in planetary evolution.