The contribution of ascending nephelinitic magmas to the CO2 fluxes in the Eger rift system – a case study from Bazina Maar (Czech Republic)

• Applicants: Professor Roman Botcharnikov, Ph.D.; Professor Dr. Francois Holtz; Professorin Dr. Agnes Kontny
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 578916298

The Cenozoic volcanic and geodynamic activity in the Czech Republic is mainly located in the Eger Rift. The latest magmatic activity, centered in the Cheb basin, is associated with widespread diffuse degassing of mantle-derived CO2. Current models assume that this CO2 is transported in CO2-rich melts generated from partial melting of the mantle. These melts ascended in crustal reservoirs, where they crystallize at depth and release CO2. The nephelinites in the Cheb basin are representative of such magmas and are ideal volcanic rocks to constraining CO2 fluxes linked to magmatic activity and magma ascent. In this study, we plan to perform geochemical analyses of the mineral phases (olivine and Cr-spinels) in nephelinites from the Bazina maar (samples obtained from ICDP drilling), as well as high pressure experimental studies to constrain the CO2 concentrations in the primary nephelinitic magmas, pre-eruptive conditions, magma ascent rates and the processes of CO2 release during ascent. Thermobarometry using olivine and Cr-spinels, the analysis of melt inclusions in olivine and experimentally determined phase relationships will be applied to characterize the conditions of magma reservoirs and CO2 concentrations in magmas at depth. Concentration profiles in olivine related to diffusion processes will be used to derive magma ascent rates. Possible hypotheses explaining the formation of carbonatites, observed in the Bazina nephelinites, will be tested with experimental simulations. The analytical and experimental results will be integrated with petrophysical and geophysical data from research partners to develop a consistent model for magmatic processes and related CO2 fluxes in the Cheb basin.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1006: Infrastructure area - International Continental Scientific Drilling Program (ICDP)
• Co-Investigators: Renat Almeev, Ph.D.; Dr. Martin Oeser-Rabe