AbstractsAstronomy & Space Science

For the first time, noble gases dissolved in groundwater were applied in Jordan on a larger scale. Two studies are presented where noble gases, especially the 3He/4He ratio, are used in very different contexts. The first project sheds light on the complex groundwater mixing in the Azraq Oasis, where groundwater reserves are heavily exploited and where the creeping salinization of some wells is explained. It is found that the mentioned wells also contain a considerable amount of mantle derived helium, which is interpreted as an upward leakage of deep groundwater into the shallow aquifer. The observed drawdown in the area lead to enhanced abstraction of water from deeper parts of the this aquifer, which is both saline and contains mantle gases according to the presented mixing scheme. The second study examines the mantle helium component in thermal springs and wells along both the Jordan and the Israeli part of the central Dead Sea Transform, which constitutes the tectonic boundary between the African and the Arabian plates. The collected samples range from almost crustal to clear mantle signature with 3He/4He ratios up to 5RA. The presented data set contradicts the model published by Torfstein et al. [2013], who interpreted their observed increase of mantle influence in Israeli thermal localities to be caused by a progressive decrease of crust thickness. Covering also Jordanian sites, the new data suggest a much more local control by single conductive fractures permitting an ascent of mantle volatiles into shallow groundwaters.