Linking Long-Term Rock Uplift and Shear-Wave Anomalies to trace Magma Emplacement

Le résumé fourni par la source

Subsurface magma emplacement in the middle/shallow crust triggers rock-/surface-uplift, rock deformation and crustal heating. Understanding dimensions, depths and the short- to long-term evolution of such intrusions might be crucial for geothermal explorations or surveillances and monitoring of un-resting volcanic settings. Several approaches are currently applied for exploring both active and inactive blind subsurface intrusions, but commonly based on invasive, costly, and time-demanding methods which in most cases only provide a current snapshot. To overcome these limits, we test a novel linear river inversion scheme in the active geothermal field of Larderello-Travale-Magmatic-System (LTMS) in the Northern Apennines of Italy, through which we extract spatially explicit maps of rock-uplift rates from topographic and geological data. After combining our pattern of rock-uplift rates with available low shear-wave velocity anomaly (SW), imaging the current magma body beneath LTMS, we document a strong correlation in space and wavelength between surface topographic responses to subsurface magmatic processes. This exercise allows us to infer the location and depth of the magmatic system, the associated surface deformation caused by the emplacement of magma, a minimum estimate for the active volume of partial melt characterizing the geothermal system, and a preliminary estimate for the magma overpressure. Our approach, for the first time, offers the opportunity to bridge different time scales of observations together with supporting the interpretation of geophysical analyses such as the ambient noise tomography. Eventually, with this work we demonstrate that early-stage exploration or monitoring of crustal magmatic intrusions is possible by using non-invasive, environmentally sustainable and extremely low-cost river network inversions, representing significant advantages over previous methods.

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