Diffuse CO sub(2) degassing and volcanic activity at Cape Verde islands, West Africa

Diffuse CO sub(2) emission surveys were carried out at Sao Vicente, Brava, and Fogo islands, Cape Verde, archipelago to investigate the relationship between diffuse CO sub(2) degassing and volcanic activity. Total amounts of diffuse CO sub(2) discharged through the surface environment of the islands of Sao Vicente, Brava, and Fogo were estimated in 226, 50, and 828 t d super(-1), respectively. The highest CO sub(2) efflux values of the three volcanic islands systems were observed at the summit crater of Pico do Fogo (up to 15.7 kg m super(-2) d super(-1)). Statistical graphical analysis of the data suggests two geochemical populations for the diffuse CO sub(2) emission surveys. The geometric mean of the peak population, expressed as a multiple of the geometric mean of the background population, seems to be the best diffuse CO sub(2) emission geochemical parameter to correlate with the volcanic activity (age of the volcanism) for these three island volcanic systems at Cape Verde. This observation is also supported by helium isotopic signature observed in the Cape Verde's fluids, fumaroles, and ground waters. This study provides useful information about the relationship between diffuse CO sub(2) degassing and volcanic activity at Cape Verde enhancing the use of diffuse CO sub(2) emission as a good geochemical tool, for volcanic monitoring at Cape Verde as well as other similar volcanic systems.