Abstract 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 CH4 enriched. Conversely, the Lesser Caucasus to the NW host numerous thermo-mineral springs into which CO2-rich gas are bubbling. In the Talysh area, located to SE at the border with Iran, CH4-, N2- and CO2-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 CO2 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 CO2-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 RC/RA 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 H2S, 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.

中文翻译：

---

与区域大地构造背景相关的小高加索和塔雷什山脉（阿塞拜疆）气体排放中的地幔与地壳流体源

摘要 阿塞拜疆以令人印象深刻的泥火山现象而闻名，该现象主导了该国中部地区的景观。此处释放的气体富含 CH4。相反，西北部的小高加索拥有许多热矿泉，富含二氧化碳的气体正在冒泡。在位于伊朗边境东南部的 Talysh 地区，排放富含 CH4、N2 和 CO2 的气体。研究了来自小高加索和塔雷什的游离气体的化学和同位素组成，以确定它们在特别复杂的地球动力学和地质环境中的起源。小高加索地区的 CO2 显然与影响侏罗纪和白垩纪石灰岩的热变质过程有关，其中还认识到地幔成分（氦）的微小贡献，可能与海洋俯冲和/或流体与增生蛇绿岩复合体的相互作用有关。Talysh 褶皱带代表了伊朗 Alborz 链的北部延伸，产生了早、中始新世到更新世的火山活动，被用来解释排放气体的独特化学和同位素组成。Buludul 富含 CO2 的气体显示出氦和碳同位素比率，这表明 (i) 石灰岩水解产生的地壳成分以及与富含有机物质的火山沉积复合体相互作用，以及 (ii) 构造驱动的地幔衍生的混合过程流体。相对较高的 RC/RA 值（~6）确实与该地区活火山中记录的值相当，表明深部存在脱气岩浆。最后，在两个研究区均未检测到典型的热液气体化合物，例如 CO 和 H2S。除非发生浅层次生过程，否则不太可能在区域尺度上存在发达的热液系统。