Dr Frances Jenner

There are many Miocene collision-and subduction-related porphyry cu deposits in the Eastern Tethyan orogenic belt. Our previous results indicate that the ore-bearing rocks may be related to ore-enriched sources(sulfide-rich cumulate) at the lower crust. However, it is unclear what the geological processes leading to the selective precursor concentration of the economically important metals Cu, Au and what the mechanism control the subsequent release of those metal from sulfide-cumulate. My proposed study is to understand the partitioning behavior of chalcophile and siderophile elements, in order to understand the pre-enrichment step in the formation of porphyry Cu deposits. Then I will compare the magmatic state of the ore-bearing porphyries, coeval ore-barren rocks, and the pre-mineralization one-barren rocks in Iran, as attempts to reveal if the magmatic oxidation state is the key point to strip Cu and Au from melt during the pre-mineralization period and to liberate those metals during the ore-forming period. The proposed research will also have it's significant implication on continent formation.

The rise of electric vehicles is driving demand for critical elements (http://tinyurl.com/z77y4v7), including Li, Nb, Ta, and Be. These elements are currently produced in relatively few countries, raising the spectre of disruption to their supply. They are commonly hosted in Sn-W bearing granites and pegmatites, but little is known about which minerals carry and concentrate these elements from the crustal protolith, via metamorphism and partial melting (anatexis), to the granitic magma. This project will track these trace elements from their original source to the host granite. A recent study(1) proposes a critical role for both the composition of the starting materials and the melting conditions in determining whether granites are enriched in critical elements or not. Unmineralised Himalayan leucogranites represent a rare example of granites formed from a known, accessible single source: pelitic metasediments (e.g. 2). This situation offers an opportunity to investigate the partitioning of critical elements by key mineral phases (e.g. feldspar, micas, tourmaline, titanite, magnetite, rutile) through metamorphism and low temperature (750°C)1,3. This project will exploit recent advances in laser ablation in situ analytical methods4 to determine element concentrations in minerals from mineralised and unmineralised granites and their corresponding source rocks. Existing samples of granites and source rocks from the Himalaya (OU) and Africa (BGS) will be supplemented by field sampling in Europe. The elemental data will constrain the budgets of critical elements at the mineral species level and investigate potential enrichment processes from protolith to melt formation. The results will test a recent model1 that links Sn-W granite mineralisation to high-temperature anatexis of an intensely weathered protolith. We can test the hypothesis by 1) modeling element concentrations in high-T (>750°C) melts that would theoretically be formed by biotite breakdown in Himalayan samples; 2) comparing these model results with Variscan metalliferous high-T melts to assess the role of temperature in causing mineralisation of economic proportions during granite formation. (1) Romer & Kroner, 2016, Gondwana Res. 31: 60–95

Society is dependent on a reliable supply of metals and minerals for economic growth, improved standards of living, and development of infrastructure. Population growth means that even with increased recycling and resource efficiency, new mineral deposits still need to be discovered. The efficient exploration for, and discovery of, new resources requires new concepts and new tools. The Mineral Systems approach to exploration considers ore deposits on a lithospheric scale, in terms of the "ingredients", processes and environments that favour their formation. This approach amounts to a "source-pathway-trap" model, with an increased emphasis on predictive capacity, rather than just feature recognition. Historically, much research has focused on the trap, and characterisation of the ore deposits themselves; here we aim to focus deeper in the system by integrating ore deposit formation with concepts of magmatism that arise from igneous petrology and volcanology. Therein lies a challenge because extant models for porphyry systems are increasingly at odds with magmatic models for crustal construction and arc volcanism. Rather than seeing magmatic systems in terms of large, liquid-rich magma chambers, emerging petrological models for crustal magmatism are turning instead to crystal-dominated, volatile-bearing "mushy" systems that traverse most or all of the crust. The dynamics of such systems have important consequences not just for arc magmatism, but also for the chemistry of the volatiles that are exsolved. These same volatiles fuel mineralisation and this is the synergy that we aim to exploit by assembling a multidisciplinary team of researchers from economic geology, igneous and metamorphic petrology, volcanology, geochemistry, numerical modelling and fluid dynamics. Our team embraces almost everyone currently engaged in porphyry mineralisation research in the UK and capitalises on strong existing links between UK ROs and the mining industry, many of who are Project Partners. The research will involve analysis of minerals from a wide variety of mineralised and barren settings using a wealth of modern analytical tools that enable determination of an extensive suite of trace elements and isotope tracers. As each trace element responds to magmatic processes in subtly different ways due to the affinity of different elements for different phases (minerals, melts and fluids), so the multi-element approach affords many advantages over conventional proxies in which the full potential of the Periodic Table is not exploited. The analysis of natural systems will be underpinned by high pressure and temperature experiments to establish the phase relationships of ascending arc magmas and the partition coefficients that capture the affinities of elements for certain phases. As fluid accumulation and migration is an essential, but poorly understood, final step in ore deposit formation, we will develop, in tandem with the geochemistry, numerical models for fluid-bearing mushy systems. Finally, consideration will be given to critical metals that are passengers through the main ore-forming processes, but constitute important, often under-explored, by-products of porphyry mineralisation. The research proposed has a strong element of blue skies investigation, but a particular focus on outcomes that will benefit industry through improved exploration tools. Thus the project bridges the divide between academic and applied research in a way that is not normally possible through industry-funded projects. This bridging activity lies at the heart of the Highlight Topic call, specifically through the integration of new advances in the study of mineral systems, igneous petrology and geochemistry, with a view to identifying conditions that can act as pathfinders for new targets. A key outcome will be a range of trace element proxies that will enable the mining industry to establish the potential fertility of a magmatic arc on local to regional scales.

This project is Funded studentship tied to the large NERC consortium grant titled Mantle Volatiles: Contemporary Processes, Reservoirs and Fluxes. Ginevra Chelli is studying “The role of degassing on the distribution of >60 elements during crustal processes and eruption of basaltic melts”

This project seeks to significantly advance our understanding of how the terrestrial mantle acts as both a source and sink for the major exosphere (Ocean and Atmosphere) volatiles water, carbon, sulphur and halogens; volatiles which over Earth history have had a profound effect on the ability of the planet’s surface to support life. The OU contribution is in two work packages on the sulfur cycle and noble gases where we are project partners