Carbon dioxide release from cooling magmatic underplate: Implications for the origin of CO2 emanations in the Cheb Basin, Western Ohře (Eger) Rift area, Bohemian Massif

Geodynamic activity in the western Ohře (Eger) Rift area, Bohemian Massif, comprises seismic swarms, CO2 emanations, and Cenozoic volcanic activity, with relationships between individual phenomena remaining debated and largely unknown. Above that, seismic studies and petrological observations of mantle xenoliths in the area suggest a possibility of (sub)recent magma underplating and ponding at crust/mantle boundary. In this contribution, we integrate new and existing lithospheric thermal models with phase equilibria calculations and CO2 solubility models. By this approach, we determine the release dynamics of CO2 from crystallizing magmatic underplate, to shed light on a possible connection between CO2 emanations and underplating in the area. We show that CO2 flow rates estimated in the western Ohře Rift (order of 100 t/day) may be related to the underplate body, providing it is being actively filled with a new magma (ca. 0.001 km3/year), or the underplate is relatively recently emplaced (ca. <1 My). Long-term activity of CO2 degassing, as evidenced by local travertine occurrences, may thus be of magmatic origin providing it is episodic, in response to fluctuating magma generation or emplacement rates.