During 2019, Cornish Lithium plan to drill two to three exploration boreholes near United Downs, from the surface down to a depth of approximately 1,000 m (3,300 ft). These boreholes are designed to intercept the geothermal waters which are circulating naturally within geological structures and have the purpose of testing our exploration concept, which you can find out more about here.
Our holes will target structures well below historic mine workings but are much shallower than the nearby holes drilled at GEL’s United Downs Deep Geothermal Power Project. The boreholes will be drilled by a specialist drilling contractor with extensive experience of drilling this type of borehole, and with a proven track record of successfully carrying out similar programmes across the UK and Europe. Our chosen contractor will use a tried and tested, low-impact drilling technique known as diamond core drilling.
During the drilling we plan to sample the deep geothermal waters and then test how much lithium is contained within them. This will help us understand whether it may be possible to extract the lithium in commercial quantities in the future. The results will allow us to refine our exploration programme and to better understand the geology beneath our feet. Several exploration phases are likely to occur over the next few years before any commercial lithium extraction plants are built.
Schematic geological cross-section, illustrating how we envisage the movement of waters and how we plan to sample them from the deep permeable structures.
Exploration boreholes are a common tool employed by mineral exploration companies across the globe. They are the only tool which allow geologists to obtain a sample of rock from depth to validate their models. There are various types of exploration drilling, but Cornish Lithium will use a method known as diamond core drilling. Diamond drilling uses a relatively small rig which is typically track mounted. When the drilling rig arrives on site, Cornish Lithium’s geologists will ensure that the rig is oriented correctly before it starts drilling from surface, down towards the target area. This method of drilling brings a cylinder of rock known as ‘core’ to surface, which allows geologists to understand the geology, structures and mineralisation at specific depths. This data can then be incorporated into the Company’s geological model.
Cornish Lithium are not sampling or extracting the mine waters. Cornish Lithium are targeting geothermal waters which occur at depths deeper than the historic mines, and circulate naturally within the permeable geological structures. The mine water and geothermal water systems are separate, and only interacted in the past when the miners intercepted hot springs underground whilst they were mining for tin and copper.
The United Downs Deep Geothermal Power Project is drilling for renewable energy rather than for mineral exploration. They are using a different and much larger rig, drilling a much larger diameter (609.6 mm at surface and 215.9 mm at the bottom compared to our 122.6 mm at surface and 96 mm at the bottom) and to much greater depths than we are planning (>5,000m instead of our 1,000m). They are aiming to harness the geothermal energy potential stored deep underground in order to generate clean and sustainable electricity and heat.
In contrast, we are exploring at shallower depths to evaluate the potential of lithium within the circulating geothermal fluids. These fluids are at elevated temperatures so there are obvious synergies in how lithium extraction and geothermal energy might be exploited together in the future. We would ultimately like to utilise the geothermal energy of these fluids as well, but currently our focus is purely on generating an economic lithium prospect.
Cornish Lithium’s drilling programme will be conducted in accordance with Cornwall Council and Environment Agency requirements and all drill sites will be fully reinstated, with holes capped to make the site secure once the drill programme is complete.
Each borehole will take approximately 5-6 weeks to drill and our drilling will only occur during 12 hour day shifts. Cornish Lithium will take measures to reduce the noise and visual impact on the local community during the operations.
A photograph of an example drill site layout in Cornwall, from Cornwall Resources’ drilling last summer. This is similar to the type of layout and drill rig which we plan to use during our drilling programme this year (Photo courtesy of Cornwall Resources)
These boreholes are only exploration holes, aiming to prove our exploration concept. It is likely that we will undertake several drilling phases over the next few years across the County, during which time we will identify the best, and most suitable locality, to build a lithium extraction plant.