Global attention has been drawn to the source, extraction, and supply of lithium from igneous micas and lacustrine brines. Lithium is an essential component in batteries for low-carbon transport and energy storage solutions, however UK lithium potential has only recently been researched (British Geological Survey, 2020). Rising demand, the post-Brexit trading environment, and concerns over the environmental cost of global trade, mean it is timely to research the origins and potential for local extraction of critical raw materials, including lithium.
Lithium-bearing minerals, such as zinnwaldite, spodumene, lepidolite and tourmaline, are related to granitoid magmas derived from melting of, or interaction with, Al-rich sedimentary rocks. Occurrences are associated with a range of other minerals including valuable high field strength elements such as tungsten (British Geological Survey, 2020). In Cornwall, such “S-type” granites may soon be exploited via the extraction of lithium from geothermal brines as an offshoot from the production of geothermal energy (https://www.iom3.org/resource/cornish-lithium-grades—compelling-resource.html). The other principal location of interest is the NE Grampian Highlands of Scotland. Magmatism there is principally associated with the duration and aftermath of the Caledonian Orogeny from ~475-390 Ma. Unlike the bulk of mantle- and meta-igneous crust-derived Caledonian (I-type) granitoids elsewhere, many NE Grampian granitoids have S-type characteristics related to melting of Dalradian meta-sediments. Different Li-bearing minerals are reported from scattered localities over ~600 km2. These include Caledonian pegmatites found in float near Ballater at up to 1.7% Li (British Geological Survey, 2020), the historic Mn mine near the Lecht ski centre, and most extensively, a body of granite at Glen Gairn near Banchory (Hall and Walsh, 1972), where 5-20% of the Coilacreich facies of this granite comprises Li-bearing zinnwaldite (Smith et al. 2002) (Figure 1).
This study will address the currently incomplete picture of the timing and distribution of lithium resources and their genetic relationship to Caledonian magmatism in NE Scotland. It will take both a field and laboratory approach, building on evidence that a clear understanding of the timing and petrogenesis of granitoid magmatism is integral to tackling the broad relationship between granite petrogenesis and lithium metallogenesis (e.g., the Cornubian example of Simons et al. 2017). The two key components and five research objectives of this project are:
1) Granitoid petrogenesis:
i) geochemical characteristics of Li- rich and Li-poor granitoids, comparing S-and I-type examples.
ii) granitoid petrogenesis, including nature of source and assimilation processes.
iii) timescales of Caledonian magma residency and emplacement, relationship to regional geodynamics, deep crustal hot zone development, and ore mineralisation.
2) Metal distribution during the magmatic cycle:
i) timing of metal enrichment in the life history of each NE Grampian granitoid, addressing the relationship of mineralization event(s) to stages of magmatic history from melting, magmatic evolution, to later hydrothermal activity
ii) tracing mobility of Li and co-genetic transition metals though the magmatic cycle via mineral phase compositions, principally zircon.
iii) spatial and genetic relationship of Li mineralisation to Caledonian plutons and an assessment of future exploration possibilities.