DIFFERENCES IN GAS VENTING FROM ULTRAMAFIC-HOSTED WARM SPRINGS: THE EXAMPLE OF OMAN AND VOLTRI OPHIOLITES

摘要: Serpentinisation of mantle rocks, leading to natural venting hydrogen and methane, has been reported occur at the global scale, wherever fluids percolate in ultramafic formations. Here we compare gas composition from two on-land, low-temperature, hyper-alkaline springs hosted on rocks ophiolite massifs Sultanate Oman Ligurian Alps (Voltri Group, Genoa region, Northern Italy). These settings exhibit similar chemical mineralogical features but show diverse styles venting. Commonly all springs, gases are characterised by relatively high N 2 , very low O CO concentrations, a strong enrichment H CH 4 . The comparison between Liguria highlights variability /CH ratios whereby phase Ophiolite is enriched whereas being Voltri Ophiolite. results combined with literature data define three groups that may reflect different stages serpentinisation producing hydrogen-dominated methane-dominated. origin these distinct might lie difference within which circulate, degree alteration finally geological/metamorphic history ophiolite.