Title: The distribution of precious and energy critical elements at the scale of a Zn and Cu mineral deposit
Researchers: Maurice Brodbeck, Prof. Balz Kamber, Dr Sean McClenaghan
This project aims to systematically survey, document and categorise Cu deposits for the distribution, concentration and mineralogy of precious metals and energy critical elements (ECE's). Porphyry Cu systems are the main focus of research, as these represent the major repositories of the world's Cu ore.
For porphyry Cu systems with large metal endowments, major commodities such as Cu, Mo, Au, Ag are well constrained, however the distribution of ECE’s are poorly understood. These can potentially be recovered as by-products and thus add value to the primary commodities. Approximately 90% of the total Te currently produced worldwide, for example, is recovered from anode slimes during the Cu refining process (USGS Mineral Commodity Summaries 2016). However, the mineralogy and substitution mechanisms responsible for the deportation of trace ECE’s in Cu ores is not fully understood and may limit their effective recovery. Furthermore, there is insufficient knowledge on the mineral scale distribution of deleterious elements (e.g. Se, As, Cd) that may result in refining penalties and represent an environmental hazard. For best recovery, ore that is extracted from a part of a deposit yielding high trace metal potential should not accidentally be diluted with ore of a lesser content. Characterisation of sulphide phases in terms of trace metal signatures (penalty vs. credit) may add value to ore resources, improve recovery and help mitigate environmental effects of metal dispersion in the environment.
Although genetic processes were generally similar, porphyry Cu systems formed under a variety of geochemical conditions and different temporal relations relative to geotectonic events. It is expected that the ECE and precious metal potential of a deposit is linked to its unique physiochemical evolution. Therefore, a geochemical comparison between different porphyry systems will contribute to answering the question why some deposits are enriched and some are depleted in ECEs, precious- and deleterious metals.
In close collaboration with Industry Partners Teck Ireland, Boliden Tara Mines, Lundin Mining, SLR (PIPCO), and Trevali Mining Corporation, this project will seek to systematically study ECE and ITN incorporation into copper and zinc ores across the various deposit types. In terms of zinc ores, the study will particularly focus on a comparison of Irish-type deposits with other major Zn resources. i) For a few key deposits of the industry sponsors, a comparison will be conducted between existing exploration lithogeochemistry data for ECE and ITN elements with high precision and accuracy 'academic' rate data, obtained in the TCD laboratories (see e.g. Kamber, 2009; Baldwin et al., 2013). This will establish how well exploration lithogeochemistry data capture the ECE and ITN potential; ii) Samples and existing data from the sponsors will be used to define extreme Cu and Zn deposits in terms of ECE and ITN potential. The 'type' samples will then be studied with LA-ICP-OES (link with project 1.3PD1) in order to establish how these elements partition into the primary ores (e.g. Ulrich et al., 2011) and whether a chemical fingerprint can also be established from gangue minerals. iii) As an on-going exercise, this project will continuously build a database (using both existing and newly acquired data) for ECE and ITN element systematics of globally distributed Zn and Cu deposits. This will include building on historic mine, museum, personal and teaching collection specimens. iii) The final thread to this project will relate to exploration. With the compiled databases, it will be possible to establish for particular types of deposits, whether the association and relative abundance of the accessory elements relate to the tonnage of the primary Cu and Zn ores and could therefore serve as an early stage exploration guide to the potential of a prospect.