Gladys V. Melián1,2, Nemesio M. Pérez1,2, Eleazar Padrón1,2, María Asensio-Ramos1, Pedro A. Hernández1,2, Germán D. Padilla1,2, Alba Martín-Lorenzo1,3,Sttefany Cartaya-Arteaga1,2, Perdomo-Sosa 1,2 and Eduardo Lodoso1,2
¹Instituto Volcanológico de Canarias (INVOLCAN), 38400 Puerto de la Cruz, Tenerife,
Canary Islands, Spain
2Instituto Tecnológico y de Energías Renovables (ITER), 38600 Granadilla de Abona, Tenerife, Canary Islands, Spain
3 STEAM Srl., 56124 Pisa, Toscana, Italia.
Geochemical exploration of geothermal systems commonly relies on the study of thermal waters and gases discharged at the surface. However, this approach can be challenging in volcanic areas where surface manifestations are limited or where the extension of the hydrothermal system is still poorly constrained. In such contexts, soil geochemistry can provide important information on the presence and distribution of deep hydrothermal processes. Boron (B), ammonium (NH4+) and mercury (Hg) are commonly used as geothermal pathfinder elements because of their volatility and their ability to migrate through the shallow environment. This study presents high-resolution soil B, NH₄⁺ and Hg surveys carried out in three volcanic areas of Tenerife (Canary Islands): (1) Madre del Agua (0.7 km2) and Fuente del Valle (0.6 km2) located within the Tenerife South Rift Zone (TFSRZ), and (2) Abeque (0.8 km2), within the Tenerife Northwest Rift Zone (TFNWRZ). A dense sampling strategy was applied, with 450–550 sampling points/km², allowing the identification of small-scale geochemical anomalies potentially related to active hydrothermal pathways. Statistical analysis was performed to distinguish background and anomalous populations, while sequential Gaussian simulations (sGs) were applied to evaluate the spatial distribution of the main geochemical anomalies. The results show two main geochemical populations for each pathfinder element across the three study areas, representing background conditions and anomalous values. Background concentrations were generally higher at Madre del Agua and Fuente del Valle, suggesting stronger baseline hydrothermal influence or differences in geological and soil conditions between the two rift zones. The anomalous populations showed significant enrichments in all three pathfinder elements, with the highest values observed at Abeque, where B and Hg reached maximum concentrations of 1,798.0 and 1,474.9 μg/kg, respectively. These anomalies indicate enhanced permeability zones and efficient transport of volatile geothermal components towards the surface. Conversely, NH₄⁺ anomalies were more pronounced at Madre del Agua and Fuente del Valle, suggesting differences in reservoir conditions, boiling processes, or interactions between rising geothermal gases and organic-rich soil horizons. Overall, the combined distribution of B, NH₄⁺ and Hg provides valuable information on the location of concealed hydrothermal structures and demonstrates the potential of soil geochemistry as an effective exploration tool in volcanic geothermal systems.
Keywords: Soil geochemistry; Boron; Mercury; Ammonium; Tenerife; Canary Islands
Author Profile (first or corresponding author):
Nemesio M. Pérez, INVOLCAN’s Scientist-in-charge, mainly engaged in geochemical research applied to volcano monitoring, surface geothermal exploration, groundwater studies and environmental issues, etc.
E-mail: nperez@iter.es
