Geochemical evidences of seismo-volcanic unrests at the NW rift zone of Tenerife, Canary Islands, inferred from diffuse CO2 emission

Abstract

We report the results of 49 soil CO2 efflux surveys by the accumulation chamber method at the North West Rift (NWR) Zone of Tenerife Island, Canary Islands. The surveys were carried out from 2000 to 2016 to evaluate the temporal and spatial variations of CO2 efflux and their relationships with the volcanic and seismic activity at Tenerife. Soil CO2 efflux values ranged from non-detectable (<0.5 g m−2 day−1) up to 141 g m−2 day−1, with the highest values measured in May 2005, whereas total CO2 emission rates ranged between 52 and 867 t day−1 (metric tons per day). Isotopic analyses of soil gas in carbon dioxide (δ13C–CO2) suggest a mixing between organic and atmospheric CO2 with a small contribution of deep-seated CO2. The main temporal variation in the total CO2 output does not seem to be driven by external factors; it shows a clear temporal correlation with the onsets of seismic activity. Subsurface magma degassing affecting the central part of the island is proposed as a cause for the observed changes in the total output of diffuse CO2 emission, as well as for the spatial distribution of soil CO2 efflux.