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Dr Paul Davidson is an honorary research associate in melt and fluid inclusion studies based at CODES. He received his BSc from the University of Tasmania in 1999, and in 2004 his PhD, titled A new methodology for the study of the magmatic-hydrothermal transition in felsic magmas: applications to barren and mineralised system (under the supervision of professors Dima Kamenetsky and Tony Crawford). After graduating, Paul continued with UTAS as a researcher to further his melt and fluid inclusion work, beginning with investigating issues that had emerged from his PhD project on the metal and volatile budgets of felsic magmas. This research involved a melt inclusion study of rhyolitic lavas from Okataina in the Taupo Volcanic Zone, in the North Island of New Zealand, and was part of a project on felsic magmas and their roles in formation of a variety of hydrothermal ore deposits. Paul is currently involved in a new project P1B3B Melt-melt immiscibility and the origin of Kiruna-style magnetite-apatite deposits. This project is aimed at providing evidence for the existence of Fe-Ti oxide melts in nature, a still controversial idea. Additionally, he has collaborated with Dr Rainer Thomas from the GFZ Potsdam on a series of papers on the origin and internal evolutions of pegmatites.
Paul has specialised in the study of primary magmatic melt and fluid inclusions, and their potential to constrain magmatic immiscibility processes. In this group of related processes, melts spontaneously divide into two or more mutually immiscible phases under specific TPX conditions, usually in response to saturation in one or more elements. The newly-formed immiscible phases can include one or more melts (e.g. silicate, sulfide, or Fe-Ti-oxide melts) ± aqueous fluid (liquid and/or vapour). Paul's research is focused both on silicate melt/aqueous fluid immiscibility, and Fe-oxide/silicate melt-melt immiscibility. Primary melt and fluid inclusions can constrain the compositions of melts and exsolved aqueous fluids that coexisted in magmas, and improve our understanding of the mechanisms of melt-melt and melt/volatile phase exsolution in nature.
This work has both academic interest and economic significance, since immiscibility can involve a sudden, intense, step-wise change in the composition of a magma. Commonly, the newly-formed immiscible phases have strongly contrasting physical characteristics, primarily density and viscosity, in addition to very different compositions. Given these strong density and viscosity contrasts there is usually a pronounced tendency for the two (or more) immiscible phases to separate, and in the process to preferentially sequester different elements into the diverging phases. In the case of aqueous fluid immiscibility, exsolved magmatic fluids are a major source of metals in orthomagmatic orebodies, and the pathways from metals dissolved in felsic magmas to those concentrated in orebodies, while understood in broad-brush outline, remain in need of a much more detailed understanding. Similarly, melt-melt immiscibility may produce silicate melt and a conjugate metal-rich melt (either sulphides or Fe-Ti oxides), which may form orebodies directly, or might conceivably exsolve magmatic fluids that may in turn produce orebodies (e.g. IOCG deposits).
Authorised by the Head of School, Physical Sciences
2 December, 2014