The Geology of the Pennines: Northern Lithium

Northern Lithium Taps Ancient Brines in the Pennines

17th March 2022

 

 

Most of the world's lithium is imported across international borders, however more and more nations are trying to secure their own sources of lithium to fuel the rise of electric vehicles and other sustainable technologies. Lithium demand is only expected to increase globally, as it is used as a component in rechargeable batteries for electronic devices and vehicles. Other applications include glass and ceramics production, which “reduces the melting point of compounds and thereby reduces the energy requirements of these processes” (Brown et al., 2016). Additionally, air conditioning and industrial drying systems and magnesium-lithium alloy for armour plating all use this metal. Aluminium lithium alloys are used in aircraft, bike frames and high-speed trains (Lithium - Element information, properties and uses | Periodic Table, 2022).

Lithium is a silvery-white to grey alkali metal. However, because of its reactivity, it does not occur naturally in a solid state. It occurs instead in lithium-bearing minerals that can be found in economic quantities in some locations. Some of the most common lithium-bearing minerals are spodumene, lepidolite and petalite. Spodumene occurs as a long thin prismatic shaped mineral within granites and pegmatites. Lepidolite is especially important as it can contain potassium, rubidium and caesium, and these are all important minerals to many industries. Another way lithium can be extracted is through brines. Brines are “any fluid containing a high level of dissolved solids” (Brown et al., 2016), including elements like sodium, chloride, calcium, potassium and magnesium (Rodina Minerals, 2009).

The Pennines of the UK started out when the island was part of the microcontinent of eastern Avalonia during the Ordovician era. Avalonia was drifting away from the continent of Gondwana, northwards across the Iapetus ocean, towards Laurentia. During this time period, the local sandstones and mudstones of the Ingleton group, formed from sediments deposited off the coast of western Avalonia in turbidity currents, were intruded by a large body of magma now called the Northern Pennine Batholith.

The closure of the Iapetus Ocean in Devonian times brought about many geological changes in this region, causing immense uplift and erosion of the sandstones and mudstones. This period of erosion created an unconformity, a gap in geological time, beneath the younger overlying conglomerates. The final closure of the Iapetus ocean took place in the late Silurian (stages can be seen in Figure 1).

Figure 1: Stages in the closure of the Iapetus Ocean
Earthwise, 2022

The Carboniferous period in the region is represented by basal conglomerates, then dominated by limestone, with thin layers of mudstone and sandstone. Next, in the upper Carboniferous, are regularly repeated units of limestone, marine shales, siltstones, sandstones and locally thin coals. The late Carboniferous produced the coal measures that later formed the north Pennines coal fields. The biggest event in the North Pennines was the intrusion of large granitic batholiths and north-south extension over the Laurentia-Avalonia Convergence Zone, which led to faulting and fracturing in the base Carboniferous rocks. The size of this granite complex can be seen in Figure 2. These granite bodies were hot with hydrothermal fluids that would exploit the fractures caused by the convergence zone and precipitate various minerals in these fractures to form veins. These were later mined by humans for hundreds of years, including all through the British industrial revolution, for minerals like lead, zinc and many others.

Figure 2: The thick solid line indicates the extent of the Weardale granite at about 9 km depth. The thinner solid lines denote the extent of roof regions of the five cupolas (Rookhope, Tynehead, Scordale, Cornsay and Rowlands Gill) underlying the basal Carboniferous unconformity, each denoted by its initial letter. 
Bott and Smith, 2017

The Weardale granite is of special interest for its geothermal potential based on its comparatively high concentrations of uranium, thorium and potassium. Various boreholes drilled in the 1980s showed high geothermal gradients of up to 30 °C km. At Eastgate geothermal borehole, the bottom-hole temperature at 995 m was 46.2 8C, yielding a mean geothermal gradient estimate for this borehole of 38 °C km: much higher than the UK average of 21° C km. If boreholes were to reach around 1800m, the bottom hole temperature would be expected to be in the range of 75-80°C. These are great numbers for geothermal energy wells.

Figure 3: The Rookhope borehole showing geological column and temperature measurements.
Redrawn from Bott et al. (1972, fig. 3) (Bott and Smith, 2017)

Previous studies of the groundwater within the Weardale Granite have identified that lithium is present at sufficiently high concentrations to consider the potential for commercial production. This was confirmed by the testing of groundwaters extracted from a nearby geothermal project, where the presence of a deep aquifer with the potential for use as a geothermal source of renewable energy was established by drilling and testing carried out in 2004-2006. The chemical analysis of samples obtained from both a nearby fluorspar mine and the geothermal project indicate lithium concentrations at an economically viable grade.

Northern Lithium started out in 2017 as Whitman Acquisitions Limited, with Richard Henry Whitman Morecombe heading the company since its inception. 3 years later, in December 2020, Whitman Acquisitions Limited changed to Northern Lithium. Northern Lithium has secured the rights to explore for and extract lithium from hot saline brines within the Weardale Granite covering an area of approximately 185 sq km. This could potentially be a large boost to the UK’s electric vehicle and components industry, while stabilising the UK’s supply chain and lessening the dependency on overseas sources.

 

References:

Northern Lithium secures rights to explore for and extract lithium from hot saline brines within the Weardale Granite of County Durham, 2022 [ebook] Northern Lithium: Northern Lithium. Available at: <http://www.northernlithium.uk/wp-content/uploads/2021/02/NORTHERN-LITHIUM-PRESS-RELEASE-11th-FEB-2021.pdf> [Accessed 2 March 2022].

Bott, M. and Smith, F., 2017. The role of the Devonian Weardale Granite in the emplacement of the North Pennine mineralization. Proceedings of the Yorkshire Geological Society, 62(1), pp.1-15.

Brown, T., Walters, A., Idoine, N., Gunn, G., Shaw, R. and Rayner, D., 2016. Lithium. [online] www.MineralsUK.com. Available at: <https://www2.bgs.ac.uk/mineralsuk/download/mineralProfiles/lithium_profile.pdf> [Accessed 2 March 2022].

Earthwise.bgs.ac.uk. 2022. Early Palaeozoic Iapetus Ocean, South of Scotland - Earthwise. [online] Available at: <http://earthwise.bgs.ac.uk/index.php/Early_Palaeozoic_Iapetus_Ocean,_South_of_Scotland> [Accessed 6 March 2022].

Manning, D., Younger, P., Smith, F., Jones, J., Dufton, D. and Diskin, S., 2007. A deep geothermal exploration well at Eastgate, Weardale, UK: a novel exploration concept for low-enthalpy resources. Journal of the Geological Society, 164(2), pp.371-382.

Rodina Minerals Inc. 2009. Technical report on the clayton Valley Lithium Property , Esmerelda County, Nevada. Prepared By coast Mopuntain Geological Ltd, 12 March 2009

Rsc.org. 2022. Lithium - Element information, properties and uses | Periodic Table. [online] Available at: <https://www.rsc.org/periodic-table/element/3/lithium#:~:text=It%20has%20the%20lowest%20density,It%20reacts%20vigorously%20with%20water.&text=The%20most%20important%20use%20of,heart%20pacemakers%2C%20toys%20and%20clocks.> [Accessed 2 March 2022].

Young, B., 2016. A GEOLOGICAL OUTLINE OF THE NORTHERN PENNINES. e North Pennine AONB OREsome Project, [online] (2), pp.4-6. Available at: <https://www.northpennines.org.uk/wp-content/uploads/2019/11/A-Geological-Outline-of-the-Northern-Pennines.pdf> [Accessed 6 March 2022].

 

 

 

 

 

 

 

Jane Lockwood

View posts by Jane Lockwood
Jane Lockwood is an Australian geoscientist living and working in Germany. She holds a Master's of Earth Science (Advanced) from the Australian National University and has spent several years reporting on the junior mining industry for Spotlight Mining, as well as conducting social media management for junior mining companies.