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Metal sources and transport mechanisms in the deep lithosphere

South East Greenland

This study will provide new knowledge of the character and behaviour of Earth fluids and unravel the complex transport and concentration mechanisms of metals at sub-crustal depths. Despite the significance attributed to mantle-derived fluids as key elements in the transport and concentration of metals within the crust, we lack a robust understanding of the processes through which the mantle evolves and interacts with fluids at the P-T conditions of the lithospheric mantle and asthenosphere. 

This multi-scale integrated study will address this void in our understanding through (1) designing a set of key experiments to evaluate the chemical behaviour of fluid systems at lithospheric mantle-asthenospheric conditions, and (2) testing these experiments through the measurement of rock samples collected from key localities where the deep lithosphere is exposed. This project is designed to (1) provide new knowledge of the character and behaviour of Earth fluids, such as silicate and sulphide melts, brines, vapours, hydrocarbons, supercritical fluids, in mantle rocks at the P-T conditions of the lower lithosphere –and asthenosphere and (2) unravel the complex transport and concentration mechanisms of siderophile-chalcophile elements such as Ni, Cu and PGE in the deep lithosphere.

Despite the significance attributed to mantle-derived fluids as key elements in the transport and concentration of metals within the crust, we lack a robust understanding of the processes through which the mantle evolves and interacts with fluids at sub-crustal depths, in the lithospheric mantle and asthenosphere. The rationale of this multi-scale integrated study is address this void in our understanding through (1) designing a set of key experiments to evaluate the chemical behaviour of fluid systems at lithospheric mantle-asthenospheric conditions, and (2) parameterising and testing these experiments through the measurement of rock samples collected from two key areas: (a) the Ivrea-Verbano Zone in northern Italy and (b) the granulite facies terrains of South Eastern Greenland. As well as representing direct exposure of continental lithospheric mantle rocks, these zones host unusual nickel sulphide deposits that offer rare insight into how metallogenic fluids behave at such depths. Most known world-class nickel sulphide deposits were emplaced far from their primary mantle metal sources, at the surface or in the uppermost levels of the lithosphere. The nickel sulphide systems of the Ivrea-Verbano Zone and in the granulite terrains of Eastern Greenland, however, were formed in the mid-to-lower crust and upper lithospheric mantle. Evaluation of these areas thus offers critical insight into the deeper behaviour of mantle-sourced metallogenic fluids that is not currently incorporated into deposit evolution and exploration models. As a corollary to these two key research streams, the proposed study will also investigate the optimisation and integration of analytical techniques to constrain the behaviour of fluids and melts at relevant P-T conditions. This approach will provide improved insight into the meaning and significance of the geochemical signature of deep mineral systems, with a specific focus on the Nickel Mineral System. Consequently, the experimental results from the proposed study will generate new parameters that can be integrated in the predictive modelling of metal reservoirs, contributing to improved exploration models and opening up new exploration search space for nickel sulphide systems in the deeper portions of the lithosphere.