Deep Electrical Resistivity Tomography (DERT): a versatile method to investigate fluid migration systems and to identify ore deposits

Deep Electrical Resistivity Tomography (DERT) has proven to be a versatile geophysical method to investigate fluid migration systems and to explore metalliferous deposits. We present the survey conducted at Calamita iron skarn deposit, located in Tuscany, Italy. The site, though no longer actively exploited, presents unique opportunities to evaluate the application of DERT in mineral exploration. The goal is to detect causative magmatic intrusions and map the associated mineralized structures at depth.

The DERT survey conducted at Calamita allowed us identifying several features that are part of a complex paleo-geothermal system. The anomaly beneath the Vallone skarn at a depth of -150 m.a.s.l is interpreted as either an altered granitic body or a pathway for the migration of magmatic fluids that are linked to mineralized surface zones. The resistivity model also highlights the presence of extension faults and a southward dip of the deposits which is consistent with the hypothesized location of the magmatic intrusion. Induced Polarization (IP) measurements further indicate widespread pyritization of schists, following their epidotization, at depths ranging from -50 to -200 m.a.s.l.

 

Integrated resistivity and chargeability data illustrate the potential of DERT to investigate skarn deposits and support decision-making in mineral exploration. This approach is particularly effective to define hidden ore bodies and to understand the tectonic control on mineralization and could significantly reduce the uncertainty associated with drilling programs.