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Mud volcanism is a process that leads to the extrusion of subsurface mud, fragments of country rocks, saline waters and gases. This mechanism is typically linked to hydrocarbon traps, and the extrusion of this material builds up a variety of conical edifices with a similar morphology to those of magmatic volcanoes, though smaller in size. The Differential Interferometry Synthetic Aperture Radar (DInSAR) technique has been used to investigate the ground deformation related to the activity of the mud volcanoes of Azerbaijan. The analysis of a set of wrapped and unwrapped interferograms, selected according to their coherence, allowed the detection of significant superficial deformation related to the activity of four mud volcanoes. The ground displacement patterns observed during the period spanning from October 2003 to November 2005 are dominated by uplift, which reach a cumulative value of up to 20 and 10 cm at the Ayaz–Akhtarma and Khara-Zira Island mud volcanoes, respectively. However, some sectors of the mud volcano edifices are affected by subsidence, which might correspond to deflation zones that coexist with the inflation zones characterized by the dominant uplift. Important deformation events, caused by fluid pressure and volume variations, have been observed both (1) in connection with main eruptive events in the form of pre-eruptive uplift, and (2) in the form of short-lived deformation pulses that interrupt a period of quiescence. Both deformation patterns show important similarities to those identified in some magmatic systems. The pre-eruptive uplift has been observed in many magmatic volcanoes as a consequence of magma intrusion or hydrothermal fluid injection. Moreover, discrete short-duration pulses of deformation are also experienced by magmatic volcanoes and are repeated over time as multiple inflation and deflation events. [ABSTRACT FROM AUTHOR]

Azerbaijan is famous for the impressive phenomenon of mud volcanism that dominates the landscape of the central sector of the country. The gases released are here strongly CH 4 enriched. Conversely, the Lesser Caucasus to the NW host numerous thermo-mineral springs into which CO 2 -rich gas are bubbling. In the Talysh area, located to SE at the border with Iran, CH 4 -, N 2 - and CO 2 -rich gases are discharged. The chemical and isotopic composition of the free-gases from the Lesser Caucasus and Talysh was investigated to define their origin in a particularly complex geodynamical and geological setting. The CO 2 in the Lesser Caucasus was apparently associated with thermometamorphic processes affecting the Jurassic and Cretaceous limestones, at which a minor contribution by a mantle component (helium) was also recognized, likely related to oceanic subduction and/or fluid interactions with the accreted ophiolite complex. The fold zone of Talysh, which represents the northern extension of the Iranian Alborz chain, produced the Early and Middle Eocene to Pleistocene volcanism that was invoked to explain the distinct chemical and isotopic composition of the discharged gases. The CO 2 -rich gases at Buludul showed helium and carbon isotopic ratios that suggested mixing processes between (i) a crustal component produced by hydrolysis of limestones and interaction with volcano-sedimentary complexes rich in organic material, and (ii) tectonically driven mantle-derived fluids. The relatively high R C /R A values (~6) are indeed comparable with those recorded in the active volcanoes of the region, indicating the presence of degassing magmas at depth. Finally, typical hydrothermal gas compounds, e.g. CO and H 2 S, were not detected in both the study areas. Unless secondary processes at shallow depth are occurring, the presence of developed hydrothermal systems at regional scale is unlikely. • CO 2 -rich springs from Lesser Caucasus are related to thermometamorphic processes. • Their low amounts of mantle helium are possibly related to oceanic crust subduction. • CO 2 -dominated gases from Talysh region show high proportions of mantle helium. • Mantle helium at Talysh depends on both tectonic setting and degassing magmas. [ABSTRACT FROM AUTHOR]