Deep-sea electric and magnetic data: the winning combination for hydrothermal exploration

Abstract:

Under the framework of the European Blue Mining Project, a research team from GEOMAR (Kiel, Germany) has developed a passive electric field acquisition system designed for Autonomous Underwater Vehicles (AUVs) to optimize exploration campaigns for seafloor massive sulfides. This sensor has been successfully tested at sea during a cruise in the Atlantic and has underlined the complementarity between deep-sea electric and magnetic data for the search for active and inactive hydrothermal vent fields. With these combined datasets, we now aim to directly determine the geological nature of targets defined by high-resolution magnetic data without involving additional and costly underwater tools to collect samples for verification. Nevertheless, data processing and analysis has also revealed that variations of the AUV attitude induce a distortion of the signal that prevails for dives at altitudes of 80 m or higher above the seafloor. We use this knowledge to discuss engineering adjustments that could be envisioned in collaboration with AUV teams to improve the performances of the acquisition system and overcome these constraints. These adjustments may consist of masts at the stern of the AUVs to tow rigid and neutrally buoyant damping arrays of electrodes. By conducting deployments in such configurations, we believe that deep-sea passive electric measurements in combination with high-resolution magnetic measurements can become a highly reliable and efficient exploration tool, including for inactive sulfide deposits.