Mineral system analysis of Tethyan oceanic rocks in the Alps

Mineral system analysis of Tethyan oceanic rocks in the Alps

 PI: Dr Taija Torvela (Leeds)

Co-Is: Dr Jason Harvey (Leeds), Prof Rob Butler (Aberdeen), Liam Hardy (European Copper)

Highlights

• Gain in-depth understanding of globally significant ore deposit types
• Learn to compile multiple datasets into a holistic mineral system model
• Field work in the Alps
• Access to high-end analytical and computing facilities and professional training

IMPORTANT: when applying via Leeds University online system you MUST select ‘NERC YES DTN Yorkshire Environmental Sciences’ as the Planned Course of Study. Failure to do this may result in your application not being considered for this programme.

Summary

This exciting project aims at investigating the known ore deposits found in the Tethyan oceanic floor rocks preserved in the European Alps. There are multiple historic mining sites in Tethyan rocks across the area (Italy, Switzerland, Austria) but there is little modern research into these deposits. As a result, there is at present no holistic understanding of the distribution and characteristics of the deposits. Many of them have been described as Volcanogenic Massive Sulphide (VMS) or Sedimentary Exhalative (SEDEX) deposits, assumed to have formed by the Tethyan rifting and related processes. These interpretations are typically based on basic observations on host rock, overall mineralogy and metal associations, rather than analytical data and robust deposit studies. Your task is to gather detailed field and laboratory data from selected deposits to i) investigate characteristics confirming or ruling out VMS/SEDEX models; and ii) assess whether the Tethyan rocks in the Alps in general may form a discrete mineral system suitable for exploration targeting.

 

Rationale

Sustainable development and the transition to a clean-energy economy are driving an unprecedented demand for metals, far surpassing historical rates of production (e.g. Hoggard et al. 2020). Despite efforts to enhance recycling of scrap metal, over the next ~25 years this surge in demand will exceed the present primary production of most critical and base metals needed in the energy transition (i.e. the “energy transition metals”) such as copper (Cu), lead (Pb), nickel (Ni), zinc (Zn) and cobalt (Co) (Ali et al., 2017; Schodde 2017). Many metals such as cobalt and nickel are produced or refined in countries like Russia, China or Democratic Republic of Congo, which causes concerns for the UK and the EU regarding the security of supply, sustainability, and environmental and health and safety standards of the production. Moreover, many critical metals and elements (e.g. indium and gallium) are sourced entirely or almost entirely as by-products of base metal (e.g. Cu, Pb, Zn) mining, which adds to the security of supply concerns (Nassar et al., 2015; Sovacool et al., 2020).

Our project aims at investigating the potential of the European Alps to host energy transition metal deposits (Fig. 1). We focus on a specific geological system and deposit type: the Tethyan oceanic lithosphere and associated structures, and the Cu-Pb-Zn-Ni-Co-bearing ore deposits situated in these Tethyan rocks. The Tethys Ocean, which existed before the formation of the mountain belt, has been assumed to have hosted hydrothermal ore-forming systems (VMS and SEDEX types; e.g. Robertson & Boyle, 1983). These oceanic rocks and their ore deposits are thought to have been incorporated in the lithospheric plate collision that formed the Alps, evidenced by the numerous historic mines in the region that targeted deposits within the Tethyan oceanic rocks.

However, the paucity of modern research into the deposits means that the true nature and timing of these deposit remains unknown. As such, it is unclear whether the Tethyan rocks truly form a distinct hydrothermal, pre-Alpine mineral system or if they are (partly) a result of later, Alpine mineralisation. Later, Alpine ore deposits do exist in the area (e.g. Bertauts et al., 2022) and it is unclear to what degree Alpine mineralisation extends to the Tethyan rocks as well.

 

Fig. 1. Simplified geological map of the Alps. The lithologies with Tethyan oceanic affinity are in dark blue, and some of the historic mine sites are indicated with stars. Modified from Dal Piaz et al, 2003.

 

Methodology

This project is the first to use the Mineral System Analysis (MSA) approach to understand the regional prospectivity for critical minerals in the Alps. Understanding the mineral system, i.e. the geological framework controlling deposits in a certain area feeds into sustainable exploration: as part of minimising the footprint of a mine cycle, exploration for new targets needs to be done efficiently. MSA is a relatively new concept, similar to the “play analysis” of the petroleum industry, and it is proving very effective in targeting specific deposit types (McCuaig et al. 2010).

The MSA is performed by integrating multiple existing datasets available from public resources and via our industry collaborator Liam Hardy, with new data collected by the project researchers. A GIS statistical and spatial analysis of the relationships and available structural and lithological data from the historic mine sites forms the basis of the MSA analysis and underpins more detailed case-studies. These case studies target know deposits in northern Italy (the Aosta Valley, NW Italy; Prettau area, NE Italy). You will collect field structural and lithological data and samples from these sites, followed by i) mineralogical and paragenetic characterisation with a Scanning Electron Microscope (SEM; Webb et al., 2023); ii) stable isotope analysis of base metal sulphides to characterise the ore-forming fluids; and iii) Re-Os geochronology on pyrite to date the deposits. The results with be fed back to the GIS analysis to assess the potential of the Tethyan rocks to host a regional mineral system in the Alps.

 

Training, support, and employability

You will work with researchers of the Ores and Mineralisation group OMG at Leeds. 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-funded 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 YES.DTN and any other relevant doctoral training networks that accept other NERC students, such as the CDT in mineral resources (TARGET http://target.leicester.ac.uk). Last but not least, you will benefit from collaboration and support from existing PhD students at OMG working on various ore deposits, and in the School of Earth and Environment more widely. You will also benefit from research meetings and events within the School that provide a forum to present and discuss your work in a supportive environment.

The project provides specialist training in: i) mineral system analysis focusing on VMS and SEDEX deposit types; ii) state-of-the-art microanalytical and geochemical techniques; 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 with the industry partner, data sourcing and collation, multi-method analyses, and relevant conferences and other interactions provides non-academic vocational experience. We anticipate that you will have the opportunity 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 the Society of Economic Geology (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 rifts and 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

Ali et al., 2017. Mineral supply for sustainable development requires resource governance. Nature, 543, 367–372.

Bertauts et a., 2022. A New Alpine Metallogenic Model for the Pb-Ag Orogenic Deposits of Macôt-la Plagne and Peisey-Nancroix (Western Alps, France).  Geosciences 12, https://doi.org/10.3390/geosciences12090331

Hoggard et al., 2020. Global distribution of sediment-hosted metals controlled by craton edge stability. Nat. Geosci., 13, 504–510.

Nassar et al., 2015. By-product metals are technologically essential but have problematic supply. Sci. Adv., 1, 10.1126/sciadv.1400180.

Robertson & Boyle, 1983. Tectonic setting and origin of metalliferous sediments in the Mesozoic Tethyan Ocean. In: Hydrothermal Processes at Seafloor Spreading Centres, Springer Publishing.

Schodde, 2017. Long term trends in global exploration–Are we finding enough metals? Fennoscandian Exploration and Mining Conference, Levi, Finland.

Sovacool et al., 2020. Sustainable minerals and metals for a low-carbon future. Science 367, 30–33.

Webb S, Torvela T, Chapman R, Savastano L, 2023. Textural mapping and building a paragenetic interpretation of hydrothermal veins. In: Butler RWH, Williams L, Torvela T  (Eds.) Geological mapping of our world and others. Geol. Soc. London, Special Publication 541, doi.org/10.1144/SP541-2023-17