Numerical Modeling of Supercritical ‘Out-Salting’ in the “Atlantis II Deep” (Red Sea) Hydrothermal System

Abstract

Supercritical water behaves close to that of a non-polar fluid and its ability to dissolve salt ions is very low. In rifting locations world-wide, where hot vents occur, it has been shown that seawater attains supercritical conditions. We therefore anticipate that circulation of seawater in hydrothermal systems passing through regions of the supercritical domain results in spontaneous precipitation of salt particles. Thus, the hot 'geysers' of saturated brines observed in the 'Atlantis II Deep' of the Red Sea could result from re-dissolution of salts accumulated in underground fracture systems. Here we report on an advanced numerical modeling study which demonstrates, for the first time, that there is a forced convection cell where salts precipitate and accumulate. These combined numerical thermodynamic simulations and basin modelling results also demonstrate that hot brines reflux back to surface immediately above the magma chamber located beneath the axis of the rift. Based on this study, we predict that hydrothermal 'out-salting' is the main cause of dense, warm brines accumulating in the central portion of the Red Sea. Furthermore, the results are relevant for understanding how large volumes of evaporites (salts) accumulate along rifted plate margins.

Relationship of the Warming of Red Sea Surface Water over 140 Years with External Heat Elements

“…In addition, the Red Sea is characterized by the presence of 25 brine pools, which are large bodies of bottom water of the sea [35]. In the pools, volcanic intrusions generate upwelling of hot brine constantly, evidently resulting in high-temperature deep water in the sea [36]. In the largest brine pool, Atlantis II, the temperature significantly increased over 44 years [37], suggesting that the heat input from the seafloor has been increasing.…”