Fault kinematics and stress control on monogenetic volcanism in compressional setting: the Lesser Caucasus key example (Georgia, Armenia, Azerbaijan)

We propose a detailed approach to studying the volcanotectonics of the Lesser Caucasus compressive belt, analysing 744 Quaternary monogenetic volcanoes with respect to field structural and geophysical data. For 394 volcanoes lying on a horizontal substrate, we identified the underlying magma-feeding fracture based on morphometric parameters of the cone, relating its azimuth with the geometry and kinematics of the main regional Quaternary faults, GPS data and shallow earthquake focal mechanisms. We calculated the density areas of all Quaternary monogenetic volcanoes and the distance of each cone from the nearest main Quaternary fault, using subsets based on fault kinematics. Volcanic clusters developed mostly in areas of strike-slip faulting, and less commonly in areas of reverse and normal faulting. Shallow magma pathways have a greater range of orientations compared to volcanic clusters. Most cones are at a distance > 1 km from the nearest main fault, implying that the regional Quaternary faults do not represent the preferential magma path at shallow levels in the study area. Magma could have followed minor structures with a different geometry inside major tectonic blocks, originated from tectonic stresses, or self-generated hydrofractures. Our data also indicate that shallow magma paths are not necessarily perpendicular to the regional σ 3 , claiming caution to the use of volcano alignment/elongation to extrapolate stress orientations.