IAP-25-111

A metallogenic model for lithium and rare metal resources in the Glen Gairn granite

Lithium is defined as a critical metal by the EU and UK governments and will be a crucial part of the transition to net zero, needed for electric vehicle batteries within the transport sector. Tin and tungsten are also critical metals, underpinning a variety of applications in electronics and alloys, respectively. This project will examine the fate of rare metals during granite emplacement and alteration, through case studies including the Glen Gairn and Ballater granites, eastern Grampians, Scotland. These intrusions host lithium-bearing minerals such as zinnwaldite, as well as other metals such as tin and tungsten. The granites also have some of the highest heat production values within the UK, raising the possibility of a mixed resource model involving geothermal energy combined with minerals extraction, similar to those currently being developed in Cornwall and in Weardale. Could these resources play a part in helping the UK through the transition to a low-carbon future?

This project will answer this question by tracing the enrichment, distribution and sequestering of metals throughout the lifecycle of magma intrusion, cooling, fluid liberation and weathering/ alteration at Glen Gairn and Ballater. We will do this using a combination of fieldwork, examination of cores, bulk rock geochemistry, petrology. The project will use in situ microanalysis techniques, such as laser ablation ICP-MS and electron beam methods, to determine the major and trace element contents of primary magmatic minerals and their counterparts formed through later hydrothermal circulation. This will allow the timing of retention or release of key metals to be identified. Understanding the petrology and geochemistry of each stage of development is key to creating a metallogenic model for these granites. Key questions include:
– How do lithium and critical metal contents of minerals reflect progressive evolution of the magmas and formation of a separate magmatic volatile phase?
– How do episodes of fluid alteration, such as during greisen formation, sericitization and chlorite formation affect the distribution of critical metals?
– How does metal enrichment at Glen Gairn and Ballater relate to the wider tectonic framework for the region, such as basement structures?
– What key geological features and chemical weathering processes can affect Li and trace metal mobilisation in modern day low enthalpy geothermal fluids in this region?

The project will use methods including:
– Fieldwork to sample the granites and investigate contact relationships and the spatial distribution of pegmatites and greisen structures.
– Examination of core material from Ballater and other regional granites
– XRF, and ICP-MS to quantify bulk rock major- and trace-element analysis of samples
– Scanning Electron Microscopy and optical microscopy for characterisation of magmatic and alteration textures
– Analysis of clays
– Laser Ablation ICP-MS to determine in situ major and trace element compositions of minerals in their spatial context
– Fluid-rock interaction modelling to determine the key processes that control critical metal distribution, and redistribution, during hydrothermal alteration and chemical weathering

The project will draw on the complementary expertise of the supervisory team, including fieldwork, petrology, geothermal lithium, granite alteration, mineralogy, and fluid-rock interaction, as well as development of models for metallogenesis.

Year 1

Literature review. Examination of cores. Fieldwork in Scotland. Sampling and bulk rock geochemistry. Petrographic examination and in situ geochemical analysis of primary igneous textures (SEM). Interpret granite emplacement mechanism and magmatic evolution.

Year 2

In situ geochemistry and characterisation of key alteration assemblages, as well as greisen and pegmatites. Interpret conditions for formation of pegmatites and greisen. Paper 1. Conference attendance, national.

Year 3

Fluid-rock interaction geochemical modelling of alteration processes. Generate overall metallogenic model for the locality. Paper 2. Conference attendance, international.

Year 3.5

Write and submit thesis. Paper 3.

Fieldwork. XRF, solution and laser ablation mass spectrometry. Interpretation of geochemical data. Scanning electron microscopy. Thermodynamics and fluid-rock modelling. Petrographic interpretation of primary and alteration textures. Written communication, literature review and presentation skills. Data management skills.