Buttitta Dario, Capasso Giorgio, Paternoster Michele, Barberio Marino Domenico, Gori Francesca, Petitta Marco, Picozzi Matteo, Caracausi Antonio
Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Palermo, 90146, Italy; University of Basilicata, Department of Sciences, Potenza, 85100, Italy.
Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Palermo, 90146, Italy.
Sci Total Environ. 2023 Nov 1;897:165367. doi: 10.1016/j.scitotenv.2023.165367. Epub 2023 Jul 9.
This study is focused on fluids characterization and circulations through the crust of the Irpinia region, an active seismic zone in Southern Italy, that has experienced several high-magnitude earthquakes, including a catastrophic one in 1980 (M = 6.9 Ms). Using isotopic geochemistry and the carbon‑helium system in free and dissolved volatiles in water, this study aims to explore the processes at depth that can alter pristine chemistry of these natural fluids. Gas-rock-water interactions and their impact on CO emissions and isotopic composition are evaluated using a multidisciplinary model that integrates geochemistry and regional geological data. By analyzing the He isotopic signature in the natural fluids, the release of mantle-derived He on a regional scale in Southern Italy is verified, along with significant emissions of deep-sourced CO. The proposed model, supported by geological and geophysical constraints, is based on the interactions between gas, rock, and water within the crust and the degassing of deep-sourced CO. Furthermore, this study reveals that the Total Dissolved Inorganic Carbon (TDIC) in cold waters results from mixing between a shallow and a deeper carbon endmember that is equilibrated with carbonate lithology. In addition, the geochemical signature of TDIC in thermal carbon-rich water is explained by supplementary secondary processes, including equilibrium fractionation between solid, gas, and aqueous phases, as well as sinks such as mineral precipitation and CO degassing. These findings have important implications for developing effective monitoring strategies for crustal fluids in different geological contexts and highlight the critical need to understand gas-water-rock interaction processes that control fluid chemistry at depths that can affect the assessment of the CO flux in atmosphere. Finally, this study highlights that the emissions of natural CO from the seismically active Irpinia area are up to 4.08·10 mol·y, which amounts is in the range of worldwide volcanic systems.
本研究聚焦于意大利南部活跃地震带伊尔平尼亚地区地壳中的流体特征与循环，该地区经历了多次高强度地震，包括1980年的一次灾难性地震（震级M = 6.9 Ms）。本研究利用同位素地球化学以及水中游离和溶解挥发物中的碳 - 氦系统，旨在探索能够改变这些天然流体原始化学性质的深部过程。使用整合了地球化学和区域地质数据的多学科模型，评估气 - 岩 - 水相互作用及其对CO排放和同位素组成的影响。通过分析天然流体中的氦同位素特征，证实了意大利南部地区地幔源氦的区域性释放，以及深部来源CO的大量排放。该模型得到了地质和地球物理约束的支持，基于地壳内气体、岩石和水之间的相互作用以及深部来源CO的脱气过程。此外，本研究表明，冷水总溶解无机碳（TDIC）源于浅层和深层碳端元之间的混合，深层碳端元与碳酸盐岩性达到平衡。此外，热的富碳水中TDIC的地球化学特征可通过补充的次生过程来解释，包括固、气、水相之间的平衡分馏，以及矿物沉淀和CO脱气等汇。这些发现对于制定不同地质背景下地壳流体的有效监测策略具有重要意义，并突出了理解控制深部流体化学性质的气 - 水 - 岩相互作用过程的迫切需求，这些过程会影响大气中CO通量的评估。最后，本研究强调，地震活跃的伊尔平尼亚地区天然CO的排放量高达4.08·$10^{5}$ mol·$y^{-1}$，这一数量处于全球火山系统的范围内。
