Co2 –driven Hydrothermal Eruptions in Geothermal Systems of Turkey

Substantial CO2 degassing occurs from geothermal waters in Turkey as evident from ongoing deposition of recent terrace travertines and emplacement of significant travertine vein and breccia deposits representing hydrothermal eruption products. Geochemical data indicate rapid ascent of CO2bearing fluids without significant interaction with basement and host rocks. High-precision U-series dates of most travertine veins coincide with times of cold/dry climate events. Late Quaternary climate variability controls the availability and quantity of geothermal waters, with relatively wet climate events (such as today) leading to CO2 discharge and dissipation at surface through deposition of terracemound travertines. We hypothesise that a significant reduction in surface or near surface discharge of CO2 by spring or geothermal waters during dry climate periods evidently promotes oversaturation of CO2 in deep reservoirs. It is concluded that host rock fracturing in response to seismic shaking and fluid overpressure results in rapid exsolution and expansion of the dissolved gas leading to hydrothermal eruptions.