The W-Sn-Cu-As-Zn-Pb ore field, centred upon the Early Permian Cornubian Batholith, is a global exemplar of magmatic-hydrothermal mineralisation associated with peraluminous granites and mineral zonation, where there is often a progressive change in dominant mineral assemblage with distance from the granite (W-Sn ± As proximal and Cu, Zn and Pb distal). Changes in source melting and differentiation control the broad distribution of granite types and metal prospectivity (Simons et al., 2017). But the heterogeneous distribution of metals and mineralisation styles around “emanative centres”, including the anomalous occurrence of substantial Cu with peraluminous granite, indicates a complex relationship between magmatism, separation of magmatic volatile phases, faulting and fluid mixing.
The purpose of this project is to: (1) provide a state-of-the-art characterisation of the principal mineral parageneses and associated fluid types, and (2) evaluate the role of structurally controlled fluid migration and mixing on the distribution of these mineral assemblages and metals. The project is in collaboration with four CASE partners: Cornish Lithium, Cornwall Resources, Cornish Metals and Osprey Mining.
Project Aims and Methods:
The project is focussed upon the systematic analysis of melt and fluid inclusions in different granite types and mineralisation styles from across the SW England orefield. These will be used to determine: (1) the compositional variability of primary exsolved magmatic-hydrothermal fluids and their control by evolving melt compositions, and (2) the parameters controlling precipitation of ore metals from these solutions (e.g. cooling, phase separation, wall-rock reaction). Careful sample mineralogy and petrography, including SEM, QEMSCAN and cathodoluminescence techniques, will underpin the fluid inclusion microanalysis using microthermometry and laser ablation ICP-MS. Isotopic analysis of minerals will be used to evaluate alternative models for the source and evolution of fluids.
These data will be combined with the distribution of syn-magmatic fault systems and historical metal production, to provide a re-evaluation of the controls on mineralisation, mineral zonation and the origin of “emanative centres”. The project will utilise material from CASE partner drillcore and archive collections but will also include fieldwork in SW England.
We are looking for a well-qualified and highly motivated Earth Sciences/Geology graduate who wishes to carry out a PhD in mineralogy/petrology and economic geology. Excellence in geochemistry and mineralogy are essential; experience of microanalytical techniques and statistical data evaluation are desirable.
The four CASE partners are actively involved in mineral exploration and development across Cornwall. They will provide the student with an unparalleled insight into contemporary mineral exploration and access to diamond drill cores for sampling and relevant assay and historical production data showing distribution of metals within fault-controlled vein systems (lodes).
The student will spend 80% of their time at the University of Exeter (UoE) where they will be based for their fieldwork and receive training in GIS / sample collection / preparation, transmitted / reflected microscopy, SEM / QEMSCAN (automated SEM), cathodluminescence, electron probe microanalysis and preliminary microthermometric evaluation of inclusion fluids. The student will spend 10% of their time at the NHM where they will receive training in laser ablation ICP-MS analysis of granite melt inclusions and inclusion fluids in granite-hosted magmatic quartz and inclusion fluids in representative hydrothermal vein parageneses.
For information relating to the research project please contact the lead Supervisor via firstname.lastname@example.org http://emps.exeter.ac.uk/csm/staff/rshail
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