Researchers from the CNR-IGG and the INGV participated in the study led by the University of Geneva that identified magma reservoirs covering thousands of km³ in Tuscany. The research, published in Communications Earth & Environment, opens new perspectives for the energy transition thanks to to the possibilities of using geothermal heat and the availability of critical metals
A research team from theUniversity of Geneva in collaboration with theInstitute of Geosciences and Earth Resources of the National Research Council, Florence office (CNR-IGG) el 'National Institute of Geophysics and Volcanology (INGV) has identified in Tuscany, in the subsoil of the geothermal areas of Larderello and Monte Amiata, volumes of thousands of cubic kilometers rich in magmatic fluids at depths between 8 and 15 kilometers in the continental crust.
The research, published on Communications Earth & Environment, made use of the environmental seismic noise tomography technique (Ambient Noise Tomography), an innovative prospecting method that uses the Earth's continuous vibrations and therefore has zero environmental impact.
In geological terms, magma bodies of this size are comparable to those that fuel so-called "supervolcanoes" like Yellowstone National Park in the United States, Lake Toba in Indonesia, or Taupo Volcano in New Zealand, which house immense magma reservoirs beneath the surface, measuring several thousand cubic kilometers. Their presence is typically revealed by surface traces such as eruptive deposits, craters, ground deformations, and gas emissions.
However, in the absence of such signals, large volumes of magma can remain hidden and unsuspected deep in the Earth's crust, as in the case of Tuscany where for millions of years magmatic activity has been predominantly plutonic. "We knew that this region, which extends from north to south across Tuscany, is geothermally active, but such large magma reservoirs were difficult to imagine. This discovery is extraordinary.", explains Matteo Lupi, associate professor at the Department of Earth Sciences of the Faculty of Science of the University of Geneva who led the study.
An X-ray of the deep subsoil
Ambient noise tomography, which has allowed the identification of molten rock at depth, is a subsurface exploration technique widely used in seismology: "It's a method that allows us to 'x-ray' the Earth's crust by exploiting the vibrations that are continuously generated by ocean waves, wind, or human activity.", he adds Domenico Montanari coordinator of activities for the Cnr-Igg. The propagation of these signals is captured by high-resolution seismic sensors installed on the surface – about 60 of them were used in this study. When seismic waves propagate at unusually low speeds, this may indicate accumulation zones of partially molten rock, associated with a magma reservoir..
The joint analysis of the recordings allowed us to reconstruct a three-dimensional image of the internal structure of the investigated area. "These results are important both for fundamental research, and for practical applications, primarily to quantify a region's geothermal potential. Beyond their great scientific interest, these studies show that environmental seismic noise tomography, by exploring the subsurface quickly, at low cost, and with no environmental impact, can be a key tool for the energy transition.he concludes Gilberto Saccorotti (INGV).
Finally, the discovery opens the way to faster and cheaper exploration methods for detecting lithium and rare earth elements, whose formation is closely linked to deep magmatic systems.
Useful links:
National Institute of Geophysics and Volcanology (INGV)
Institute of Geosciences and Earth Resources of the National Research Council (CNR-IGG)
Figure: Conceptual model of the Larderello, Travale, and Mount Amiata geothermal systems. The red areas outlined by dashed lines correspond to shear wave velocity anomalies of at least 20%. These volumes are interpreted as accumulation zones of partially molten rock, with dimensions of approximately 6000 km³ and 2000 km³ for the Larderello-Travale and Mount Amiata systems, respectively. The blue arrows indicate the ascent of magmatic fluids toward the uppermost portions of the Earth's crust.
