Diffused flow of molecular hydrogen through the Western Hajar mountains, Northern Oman
Résumé
We report the discovery of a general, diffused flow of molecular hydrogen (H2) through the Western Hajar mountains of Northern Oman. H2 was detected across a fracture system in the peridotites of the Semail ophiolite massif, and no traces of this gas were found in unfractured peridotites. H2 seeps in these rocks have been classically interpreted to be the result of reduction of groundwater during the process of peridotite serpentinization. However, there is evidence of hydrogen seepage in other geological units of Northern Oman, particularly in the Precambrian to Early Permian metamorphic sequences of the Jebel Akhdar massif, and to a lesser extent in the Hawasina sequence underthrust beneath the ophiolitic units. As a consequence, hydrogen flows are also being detected from geological formations structurally located below the ophiolites. Our sampling shows that increased flow is not observed in the peridotites, but in the deeper stratigraphic and structural units (Upper Proterozoic). These observations suggest a source of H2 existing below the ophiolites. Minimum estimated H2 flows using various methods range from 70 to 150 m3/km2 per day from peridotites and up to 1300 m3/km2 per day from the Upper Proterozoic.