The transition towards renewable energy, net zero emissions and the digital economy depends on the supply of metals such as lithium, copper, arsenic, tungsten and tin. Magmatic and hydrothermal fluid systems transport and concentrate economically important quantities of trace metals from the Earth’s interior into mineralized veins around igneous intrusions. It is therefore critical to understand how trace and rare metals are distributed and cycled through the Earth’s heterogeneous mantle and transported to the surface by melts and fluids.
This project will investigate the magma and fluid geochemistry of lamprophyres associated with the Caledonian (~430-400 Ma) ‘Newer Granites’ of northern Britain. The Newer Granite intrusions were historically important sources of porphyry-style Cu-Mo-Au-As mineral enrichments, as well as more unusual enrichments in W, Sn and Mo. The associated lamprophyres represent small-fraction melts of metasomatized sub-continental lithospheric mantle (SCLM), and were intruded in dykes on either side of the Great Glen Fault, a major tectonic structure of Caledonian age with ~1000 km strike-slip displacement. Isotopic studies reveal that the lamprophyres sampled two geochemically distinctive SCLM sources, one on either side of the Great Glen Fault. However, we do not yet understand the distinctive trace metal and volatile element signatures of these heterogeneous SCLM domains; nor do we understand the role that small-fraction lamprophyric melts and their associated magmatic fluids played in transporting and concentrating trace metals from the mantle into economically important mineral resources. What was the trace metal chemistry of the lamprophyric magmas and their SCLM sources? How quickly, and by what mechanisms, did the buoyant volatile-rich lamprophyres ascend through the crust? What were the compositions of the magmatic fluids associated with these small-fraction melts, and to what extent did metal-carrying fluids percolate along and/or across the Great Glen Fault? What can we learn about the mechanisms of trace metal enrichment in the SCLM, and could similar tectonic settings be potentially fruitful areas for future mineral resource exploration?
This project will involve a range of analytical techniques to reconstruct the magmatic origins and mineralization potential of these Caledonian lamprophyres. We will begin with detailed petrographic and geochemical characterization of lamprophyres from the southern side of Great Glen Fault. There will be opportunities for fieldwork to collect additional samples and explore the field relationships between lamprophyric dykes, larger granitoid intrusions, and mineralized veins. Major element and trace metal compositions of silicate and non-silicate minerals in the lamprophyres will be used to reconstruct the compositions of primary magmas and their SCLM sources; the compositions of magmatic and secondary fluids will be measured by fluid inclusion microthermometry and micro-Raman spectroscopy. The student will develop geochemical and numerical models to explore metasomatic volatile and trace metal heterogeneities in the SCLM, and the metal-carrying capacity of small-fraction lamprophyric magmas. The project could also explore magma storage depths, ascent rates, and/or mechanisms of deep crustal hydrofracturing by buoyant volatile-rich melts. The overall aim is to evaluate the economic potential of metal-bearing mineralization across an ancient tectonic structure and of equivalent modern-day tectonic settings.
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Please search and select PhD Earth Science (academic programme) and PhD Earth Science (academic plan)
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