March 10 () –
A new technique developed at Oxford University has shown utility in locating critical metal deposits needed to enable the transition to green energy.
The results of the investigation, focused on the potential of underground brines and tested in a Bolivian volcanohave been published in Geophysical Research Letters.
The global shift to a zero-carbon energy system will cause a huge increase in demand for rare earth minerals or limited. These are essential for the manufacture of a wide range of green technologies, such as electric vehicle batteries, wind turbine magnets and copper electrical cables. This raises the urgent need to locate new sustainable sources of these elements.
A potentially rich source of these metals could be underground brines: highly concentrated salt solutions that can accumulate in the earth’s crust. However, their location can be difficult, since they tend to accumulate kilometers deep. Accurately determining the position of these deposits is important to reduce the risks and environmental impact associated with drilling to extract these metal-rich brines.
In this new study, led by Oxford University’s Department of Earth Sciences, researchers developed a novel method that proved capable of mapping both the location and composition of subsurface fluids. For the first time, Two different geological measurements were combined: seismic attenuation tomography and seismic anisotropy.
Lead researcher Dr Thomas Hudson, from Oxford University’s Department of Earth Sciences, explained it’s a statement: “Seismic attenuation measures the loss of energy of a seismic wave as it propagates through a medium. For its part, seismic anisotropy measures how the speed of seismic waves varies depending on the direction in which they propagate. Attenuation tomography shows where the fluids are (sort of like a CT scan in a hospital) and whether the rock is partially saturated (contains gas) or fully saturated (no gas). It tells us how fluids move and accumulate along fault lines.”
INACTIVE VOLCANO IN BOLIVIA
The researchers tested this combined method on the Uturuncua dormant volcano in the Bolivian Andes that last erupted 250,000 years ago.
Dr. Hudson stated: “Uturuncu was an ideal system to test our method of mapping liquids and gases, since it settles on the Altiplano-Puna magmatic body, the largest active magmatic body on Earth. It drives a source of hot, metal-rich fluids that rise from the depths of Uturuncu to the surface. Uturuncu is on the edge of the Atacama Desert, so the surrounding crust is especially dry, which improves imaging of any fluid-rich crust.”
Seismic attenuation and anisotropy measurements were taken from a data catalog of 1,356 earthquakes, which had been captured between April 2010 and October 2012 by a network of 33 seismometers in the vicinity of Uturuncu. Together, the two techniques produced a rough map indicating whether the underlying crust was partially or fully saturated with fluids, with a resolution of approximately one kilometer.
In the words of Dr. Hudson: “The combination of these techniques produced a high-resolution map that identifies which fluids can be found and where in this system. Specifically, we can pinpoint where brines – concentrated salt solutions – are found and whether they contain carbon dioxide (i.e., “foamy”) or not (i.e., “still”). If carbon dioxide is bubbling through them, this tells us that the system is still active, and presumably it is still accumulating metals , whereas if the brines are quiescent, then the system can be treated as stable, that is, that it does not continue to actively accumulate minerals.
The results are very interesting because these brines are rich in essential metals for the transition to green energy. It is hoped that our new method lays the foundation for reducing the risk of the mineral exploration process, which could lead to brine extraction becoming commercially viable.”
