Combustion Metamorphism in Mud Volcanic Events: A Case Study of the 6 May 2000 Fire Eruption of Karabetova Gora Mud Volcano

The violent eruption of Karabetova Gora mud volcano on 6 May 2000 (Taman Peninsula, 45 degrees 12 ' 16 '' N; 36 degrees 47 ' 05 '' E) triggered gas ignition as a giant straight-flow vertical gas flare. The 400 m high, short-lived (similar to 15 min) gas flare left no thermal halo on the ground surface, but the thermal shock caused melting or annealing of mud masses which became dispersed in <= 2 m(3) blocks to distances within 30 m around the volcano conduit. The flare reached the maximum temperatures (similar to 1400-1540 degrees C) at heights from 75 to 250 m, as estimated by a numerical simulation in SigmaFlow. Bulk melting of dehydrated mud masses was mostly limited to <1.5 cm near the surface of the blocks. Porous paralavas at the site consisted of low- and high-silica K-Al glasses (70%-80%) with residual unmolten grains of detrital quartz and fine (<30 mu m) new phases: main intermediate members of the magnetite-ulvospinel solid solutions and plagioclase (An(45-61)Ab(37-44)Or(2-11) to An(73-90)Ab(10-27)Or(0.5-1)), minor cordierite (X-Fe = 26%-46%), pigeonite (X-Fe = 42%-60%), tridymite, cristobalite, and rare mullite. The metapelitic rocks affected by combustion metamorphism were heterogeneous in terms of phase composition and texture. They failed to attain homogeneity due to the high viscosity of anhydrous silicate melts and brevity of the thermal impact. The revealed features of rocks altered by a giant gas fire may serve as a proxy for phase transformation patterns in highly disequilibrium conditions of a thermal shock, far from the formation conditions of ordinary metamorphic rocks.

Automated summary

The violent eruption of Karabetova Gora mud volcano on 6 May 2000 triggered a giant vertical gas flare, reaching maximum temperatures of approximately 1400-1540°C. The short-lived gas flare lasted for about 15 minutes and caused thermal shock, resulting in the melting or annealing of mud masses. The dispersed blocks of melted mud covered distances within 30 meters around the volcano conduit.