41 OCTOBER 2022 WorldWide Drilling Resource® Scientists Propose Mining Volcanoes for Essential Metals Adapted from Information by the University of Oxford In a paper published in Open Science, Oxford scientists, based at the Department of Earth Sciences, revealed how trapped, subterranean brine is a potential “liquid ore” containing a slew of valuable metals, including gold, copper, and lithium, which could be exploited by bringing the fluids to the surface via deep wells. Their models show the brines potentially contain several million tons of copper, a key metal due to its importance in electricity generation and transmission, and electric vehicles. Professor Jon Blundy, based at the Department of Earth Sciences and lead author said, “We need to be thinking of low-energy, sustainable ways to extract metals from the ground. Volcanoes are an obvious and ubiquitous target.” The paper also shows how geothermal power will be a significant by-product of this mining approach, meaning operations at the wellhead will be carbonneutral. The research is part of an international effort using volcanology, hydrodynamic modeling, geochemistry, geophysics, and high-temperature experiments. The team has worked on drill cores from a number of deep geothermal systems in Japan, Italy, Montserrat, Indonesia, and Mexico to confirm their predictions of metal-rich brines. According to the scientists, geophysical surveys of volcanoes show almost every active and dormant volcano hosts a potentially exploitable amount of metal-rich brine. Since volcanoes can be found around the world, metal exploration may not be limited to relatively few countries currently (Chile, U.S., Peru, China, etc.). Principal risks are technological. The process involves drilling into rock more than 6500 feet deep at temperatures over 842°F (450°C). The extracted fluids are corrosive, which places limits on the types of drilling materials. These fluids also tend to dump their metal load in the borehole, a problem known as “scaling” (a bit like limescale in a kettle). Preventing scale formation will require complex consideration of the dynamics of fluid flow and pressure-temperature control in the borehole. Corrosion prevention will require scientific developments to create resistive coatings. The Oxford team said many of these challenges are already being addressed through deep, hot geothermal drilling projects. In some cases, these projects have reached temperatures over 932°F (500°C); occasionally, they have tapped into small pockets of molten rock in Iceland and Hawaii. Ensuring the fluids continue to flow into the well once drilled is a complex issue, and the permeability and porosity of hot, ductile rock is a challenging field. The researchers have already patented an idea for fluid extraction. Risks of triggering volcanic eruptions are very small, but must be assessed. Scientists are not planning to drill into magma itself, but into hot rocks above the magma chamber, which greatly reduces the risk of encountering magma. They have spent the last five years mitigating associated risks, and are ready to drill an exploratory well at a dormant volcano. This will clarify many risks and challenges described, and will be a significant advance in understanding volcanoes, along with their immense bounty of energy and metals. “Continuing the derisking work, which we are pursuing on many fronts through an international collaboration, is important. Likewise, we need to identify the best test-case volcano to drill an exploration well,” added Blundy. If the current plan is successful and challenges can be properly addressed, a working “brine mine” could be 5-15 years away. Mount Kilimanjaro in Tanzania, is the highest peak on the African continent. It is comprised of two extinct volcanoes and one dormant volcano. MIN
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