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Title: Critical metals in porphyry copper deposits
Author: McFall, Katie Anne
ISNI:       0000 0004 6347 4852
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2016
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Critical metals are elements essential to high-tech industry and green technology which are associated with a significant supply risk. Diversifying supplies of these elements is therefore a high priority. Porphyry copper deposits contain potentially economic enrichments of some of these elements, namely rhenium, platinum group elements (PGEs), bismuth and tellurium. This thesis investigates the source, transport mechanism and distribution of these critical elements in two post-collisional Tethyan porphyry deposits. The Muratdere Cu-Mo (Au-Re) porphyry deposit, Turkey, described here for the first time, contains two generations of molybdenite with contrasting Re concentrations. The early, Re-poor molybdenites have magmatic δ34SCDT values, while the late, vein hosted Re-rich molybdenite has δ34SCDT values matching those of the surrounding country rock suggesting that the additional Re has been sourced from hydrothermal fluid-country rock interaction. The Skouries Cu-Au porphyry deposit, Greece, is PGE, Te and Bi enriched. In contrast to Muratdere, Skouries is shown to be an orthomagmatic system hosted by a series of overprinting dykes, with the metal enrichment hypothesised to have been provided by periodic mafic recharge of a deeper source magma chamber. The mineralising fluids in Skouries are shown to have been highly oxidised and hypersaline with complex cation chemistry (Na, K, Fe, Mn and Ca), and with the overall fluid evolution progressing from an early CO2 rich fluid to a later brine. The PGEs in the deposit are located in the main hypogene mineralising veinsets, associated with potassic alteration, and are found to be hosted in bismuth and tellurium complexes. A variety of platinum group minerals are identified, including sopcheite (Ag4Pd3Te4) and sobolevskite (PdBi). LA-ICP-MS of fluid inclusions, combined with microthermometry, has shown gold, bismuth and palladium to be hydrothermally transported by high temperature ( > 500°C), high salinity ( > 65 wt% NaCl+KCl) and highly oxidised fluids, and a bismuth-tellurium collector model is proposed to allow concentration of palladium from under-saturated fluids into platinum group minerals. High semi-metal (Te and Bi) contents in porphyries are therefore proposed to be an indicator of PGE enrichment.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available