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This project is eligible for support from Cardiff Universtiy through the School of Earth & Ocean Sciences.

To apply, please visit the Cardiff University Postgraduate Research portal: http://www.cardiff.ac.uk/for/prospective/postgraduate/applying.html

Description

The aim of this project is to locate gold in different parts of the hydrothermal system in the Troodos ophiolite, Cyprus and so understand the processes that concentrate it into ore. Gold has been known in Cyprus for hundreds of years and was mined in the 1980s; however its distribution, origin and extent are poorly understood. In the light of recent advances in understanding the hydrothermal fluid circulation at mid-ocean ridges and marginal basins, and consequent volcanogenic massive sulphide (VMS) mineralisation, it is timely to re-examine the controls on gold mineralisation in Cyprus.

The Troodos ophiolite is an excellent area to study VMS-related gold mineralisation as the oceanic upper crustal sequence is extremely well preserved and exposed.  We have recently re-examined the upper crustal structure of the ophiolite and its original seafloor topography, faulting pattern and volcanic architecture. On this basis we have a well-constrained context for understanding the tectonic and magmatic controls on the hydrothermal system, from its root zones deep in the crust up to the variably gold enriched sea-surface VMS, ochres, umbers and late silica-rich vein systems.

The proposed research will constrain the location of the gold with respect to the geometry of the upper oceanic crust, the main volcanic centres and the fault systems that formed as the newly formed oceanic crust moved away from the spreading centre. This research will have implications for improving the search for these types of gold deposit in other ophiolite complexes and modern ocean-floor systems.

Fig 1

Fig 1. Gossan in lavas, foreground, with VMS in the distance.

Training

The student will be trained in field mapping and sampling in Cyprus, especially in collection and interpretation of structural data; also in analytical techniques including whole-rock geochemical analysis of gold (by ICP-MS), and mineral analysis using the scanning electron microscope and laser-ablation ICP-MS at Cardiff University. Fine gold will be located using the QEMSCAN® at the University of Exeter, Camborne School of Mines.  With the aid of expertise in sea floor alteration mineralogy at the Natural History Museum the student will use a portable XRD to determine the distribution of high and low temperature clays associated with the gold-bearing veins, giving an indication of the heat capacity of mineralising fluids. At the British Geological Survey the student will measure the temperature and type of fluid inclusions in the quartz associated with the different generations of gold mineralisation. Also they will have access to both their airborne thematic mapper data base and high resolution digital LiDAR elevation model data for the northern lava sequences in Troodos; an excellent proxy for paleobathymetry. All this will assist in the understanding of the distribution of the gold with respect to the different structures within this fossil oceanic crust. The gold will be identified on two scales, both as a map of the occurrence of gold in the upper crust of the Troodos ophiolite, and on a petrological scale with the host mineral associations for the gold. From all this, the student will develop models for the different processes that concentrate the gold in a variety of hosts within in the hydrothermal system in the upper part of the oceanic crust.

Background Reading

Prichard, H.M. & Maliotis, G., 1998, Au mineralisation associated with low temperature, off-axis fluid activity in the Troodos ophiolite, Cyprus. Journal Geological Society London 155, 223-231.

Contact Details

Dr Hazel Prichard – prichard@cardiff.ac.uk