First multidisciplinary evidence of hydrothermal activity at Enmedio deep submarine volcano (Canary Islands)

Abstract The deep submarine volcano Enmedio is located between Tenerife and Gran Canaria, the two most populated islands of the Canary archipelago. This study integrates multidisciplinary data gathered from 2015 to 2024, enabling a comprehensive analysis of the geomorphological, petrological, geochemical, and oceanographic features of this volcano. The combined findings from these disciplines confirm hydrothermal activity at the submarine volcano. The main volcanic cone is characterized by a fracture zone, which crosses it from NNW to SSE and passes over the summit, and a half-moon-shaped depression in the south-western flank, likely caused by a collapse event. In the surrounding area, at least 20 smaller volcanic reliefs have been identified, five of which present crater-like depressions. Backscatter data and seismic profiles suggest significant rock alteration at the fracture zone of Enmedio volcano. This alteration is corroborated by rock samples exhibiting surface modifications characterized by Fe-oxyhydroxide deposits, alongside microscopic filamentous textures typical of biogenic Fe-rich formations. These features suggest a strong association with hydrothermal environments. Additionally, geochemical analyses point to magmatic differentiation processes. The physical, chemical, and biological oceanographic parameters in the seawater show temperature anomalies, water column instabilities, enhanced turbidity, enrichment in inorganic nutrient concentrations, and an overall increase in prokaryotic abundance. These anomalies were found linked to some relevant geomorphological features, such as the summit fracture zone, the half-moon depression, and the two closest smaller volcanic cones. This integrated perspective highlights Enmedio as a focal point of hydrothermal and volcanic activity, shedding light on the dynamic relationship between geological and oceanographic processes in the Canary archipelago.