Variability of basin-related mineralisation in Northern England and Southern Scotland

Variability of basin-related base metal mineralisation in Northern England and Southern Scotland

Supervisors: Phillip Murphy, Taija Torvela, Dan Morgan, Richard Walshaw (Leeds); Steve Hollis (Edinburgh)

• Develop an understanding of the processes resulting in the formation of a key ore deposit type for the energy transition
• Learn to use a holistic minerals-system approach integrating multiple methods and regional datasets
• Contribute to the general understanding of the metallogeny of an economically important rift system via an analysis of the tempo-spatial evolution of mineralization
• Field work in Northern England and Southern Scotland
• Opportunity to publish high-impact papers or focus on applied, industry-style approaches according to your career trajectory

Background

Sedimentary basins host many metals that are key in the energy transition. Lead, zinc, copper, cobalt and silver are all needed in both the energy production (e.g. wind turbines and solar panels) and in lower-carbon technologies (e.g. electric vehicles). The bulk of these metals globally are mined from ore deposits formed in sedimentary basin settings. The Carboniferous basins of Ireland and the UK host a number of known Pb-Zn-(Cu-Co-Ag) deposits, some of which have been, or are being, mined. Ireland in particular has been an important producer for these metals and currently hosts Europe’s largest active lead-zinc mine (the Boliden Tara Mines in Navan).

In Ireland, most of the base metal deposits are related to the early phases of the Carboniferous rifting (e.g. Ashton et al., 2015; Torremans et al., 2018). The Early Carboniferous lead–zinc system in Ireland is well known with its > 25 economic and sub-economic deposits and has been extensively studied. The Irish mineralisation occurs as stratabound replacement ore within the Lower Carboniferous pre- to syn-rift carbonate sequences and is closely associated with major normal faults that acted as main fluid conduits. The mineralisation within the continuation of the basin system to Northern England and Southern Scotland, on the other hand, has been comparatively poorly studied despite the occurrence of many metalliferous vein systems, some of which have been historically mined. How and if the know occurrences relate to the Early Carboniferous rifting, similarly to the Irish deposits, is still unclear. At least some of the mineralisation has been dated to be Permian in age (Kimbell et al., 2010) but some strata-bound mineralisation occurs within the Lower Carboniferous rocks as well (e.g. Smith et al., 1996). The basin system in Northern England and Southern Scotland was active at the same time as the Irish basins, offering a suitable tectonic and structural framework for Irish-type mineralisation to form (Jenkins and Torvela, 2020) but the extent of this mineralisation type remains unknown. In order to understand the mineralisation styles and the potential for Irish-type mineralisation in the area, the current understanding needs to be supplemented, starting with a regional analysis of the variability and styles of mineralisation.

Main aims and objectives

The main aim of the project is to investigate the variability of the known metalliferous vein systems in Northern England and Southern Scotland, in order to determine areas where mineralisation is likely to relate to Early Carboniferous rifting, versus areas where mineralisation is likely to be a younger event. Your main tools will be the Scanning Electron Microscope (SEM) for textural, mineralogical and paragenetic investigation of the vein samples; Electron Microprobe analyses (EPMA) and Laser Ablation Inductively Couples Mass Spectrometry (LA-ICP-MS) to determine more detailed elemental variations within the sulphides; and stable isotope analyses of the sulphides to investigate the potential fluid sources for the mineralisation in different areas. For example, lead and sulphur isotopes are widely used to understand the characteristics and sources of metal-bearing fluids and their regional variability (e.g. Stacey and Kramers, 1975; Standish et al., 2014). Additional information of the vein systems and their variability may be gained by trace element analyses that can inform of the local precipitation conditions, and there may also be an opportunity for direct age determination of some of the veins with e.g. Re-Os geochronology. A large sample suite is already available at the University of Leeds but you will have the opportunity to complement the sampling during the field visits. All analyses will be underpinned by a detailed understanding of the geological and structural framework for each vein system via field visits and collating information from available sources (geological maps, literature, core data, seismic data, etc). Specifically, you will use ArcGIS to collate and analyse the regional geospatial data of the vein-structural-lithological relationships.

Training, support, and employability

You will work within researchers of the Ores and Mineralisation Research Group OMG at Leeds (Facebook and Twitter: @OMGLeeds). The OMG draws upon a raft of expertise covering all necessary techniques. In addition to the in-house microanalytical facilities and stable isotope laboratories, as a NERC DTP student you will have access to NERC facilities such as the isotope laboratories at SUERC in Glasgow. You will also have access to the training within both Panorama DTP and any other relevant DTPs/CDTs that accept other NERC students, such as the new CDT in Mineral Resources. Last but not least, you will benefit from collaboration and support from existing PhD students at OMG working on various sulphide and gold deposits. You will also benefit from participation in the OMG research meetings and events that provide a forum to present and discuss your work in a supportive environment.

The project provides specialist training in: (i) state-of-the-art microanalytical and geochemical techniques; (ii) textural-structural and mineralogical analysis and field work; and (iii) industry-standard exploration and software skills. The PhD study is equally suited to career pathways in academia or industry. The expected outputs of the project have global significance for producing a rare regional study of an entire minerals system and as such there is excellent potential for high-impact publications. At the same time, exposure to industry-relevant skills in exploration and ore geology through field work, data sourcing and collation, multi-method analyses, and relevant conferences and other interactions provides non-academic vocational experience. We anticipate that you will be able to publish up to three research papers, and attend both national conferences (e.g. MDSG) and international academic/ industry facing conferences (e.g. SGA, EGU, GSA, AGU, SEG, AMEBC Roundup) according to your career trajectory. You would also be expected to contribute to the activities of the Leeds Chapter of SEG, with all the associated benefits of networking across industry and academia.

Student profile

The successful candidate will have at least a BSc with a high 2:1 or a 1st from a Geological Sciences or similar programme; an MSc/MGeol qualification or relevant industry experience is advantageous, as is experience of publication or other relevant extra-curricular research activities. Excellent time management, critical thinking and analytical skills, ability to collate, analyse and interpret multiple different datasets, and the ability to clearly communicate results are essential. Required existing subject-specific and technical skills can vary but you will benefit from being able to demonstrate experience in one or more of the following: base metal sulphide geochemistry, particularly stable isotopes; structural evolution of sedimentary basins; mineralogical and paragenetic analyses using SEM; EPMA or LA-ICP-MS analyses; ArcGIS for geospatial data analysis; and/or other techniques directly relevant to the project. Training will be provided to develop and enhance all skills and knowledge.

 

References

Ashton, J.H., Blakeman, R.J., Geraghty, J.F., Beach, A., Coller, D., Philcox, M.E., Boyce, A.J., Wilkinson, J.J., 2015. The giant Navan carbonate-hosted Zn-Pb deposit : a review. In: Archibald, S.M., Piercey, S.J. (Eds.), Current Perspectives on Zinc Deposits. Irish Association for Economic Geology, Dublin, pp. 85–122.

Jenkins AP, Torvela T, 2020. Basin analysis using seismic interpretation as a tool to examine the extent of a basin ore ‘play.’ Ore Geology Reviews 125:103968.

Kimbell, G.S., Young, B., Millward, D., Crowley, Q.G., 2010. The North Pennine Batholith (Weardale Granite) of northern England: new data on its age and form. Proceedings of the Yorkshire Geological Society 58, 107–128.

Smith, R.T., Walker, A.S.D., Bland, D.J., 1996. Mineral investigations in the Northumberland Trough: Part 1, Arnton Fell area, Borders, Scotland. British Geological Survey Mineral Reconnaissance Programme report 18, 49 p.

Stacey, J.T. and Kramers, J.D. 1975. Approximation of terrestrial lead isotope evolution by a two-stage model. Earth and Planetary Science Letters. 26(2), pp.207-221.

Standish, C.D., Dhuime, B., Chapman, R.J., Hawkesworth, C.J. and Pike, A.W.G. 2014. The genesis of gold mineralisation hosted by orogenic belts: A lead isotope investigation of Irish gold deposits. Chemical Geology. 378, pp.40-51.

Torremans, K., Kyne, R., Doyle, R., Güven, J.F., Walsh, J., 2018. Controls on metal distributions at the Lisheen and Silvermines deposits: insights into fluid flow pathways in Irish-type Zn-Pb deposits. Economic Geology 113, 1455–1477.