Lithogeochemistry of the Nesjavellir Geothermal Field, Sw Iceland - Implications for Elemental Mass Movement in Active Geothermal Systems

The lithogeochemistry of altered basalts was investigated to assess elemental mass changes in the active meteoric water dominated geothermal system at Nesjavellir, SW Iceland. The study revealed that elemental mass changes upon hydrothermal alteration is rather limited and the extent of metasomatism is controlled by the type of alteration minerals. Large mass movement was detected in volatiles (C and S), likely derived from magma degassing. The geothermal system at Nesjavellir may thus provide an ideal locality to investigate the natural sequestration of deep-sourced volatiles and deliver insights in quantifying the input of mantle degassing on the budget of geothermal systems.