Hydrothermal activity along the young, ultra-slow spreading Red Sea Rift – an update from recent discoveries

Hydrothermal activity has been intensively studied at mature mid-ocean ridges and is crucial for the formation of mineral resources, as habitats for chemosynthetic communities, and for the cooling of the newly formed oceanic lithosphere¹. However, the role of hydrothermal circulation in the early history of a young emerging ocean basin shortly after continental breakup and the geological expression of its hydrothermal vents, their geochemical characteristics, and their associated ecosystems can only be studied at a few locations. The Red Sea Rift is one of Earth’s youngest ocean basins, but despite ample indications for hydrothermal activity based on rock chemistry, the presence of extinct chimney fields, metalliferous sediments, and high-temperature brine pools^{see overview in 2}, the first direct observation of active hydrothermal vents was only reported in 2022³. These vents at the axial volcano, Hatiba Mons, constitute one of the largest active hydrothermal areas worldwide, hosting 43 individual fields. In contrast to many mature locations, no high-temperature vent nor specialized macro-fauna was observed. Instead, the vents were characterized by low-temperature fluids, numerous Fe-Mn-oxyhydroxide mounds, and thriving microbial mats³. As this was the first active hydrothermal area observed in the Red Sea, the question remains if this is typical for the Red Sea and potentially for young mid-ocean ridges.

Here we present the outcomes of two expeditions in 2023 with the R/V Aegaeo (KRSE5-1) and R/V Meteor (M194)⁴, which resulted in the discovery of five more hydrothermally active areas distributed along the Red Sea Rift between 17°N and 25°N at water depths between 400-1,800 m. All hydrothermal areas consist of multiple smaller vent fields with similar low-temperature venting as reported from Hatiba Mons. The locations of the vents in their geological context and the expressions of hydrothermal occurrences show some variations ranging from small chimneys along fault lines to larger mounds covering wider areas.  We compare the six hydrothermal fields in terms of their geology, geomorphological expression, precipitate chemistry, and fluid characteristics to evaluate their regional differences and similarities to further understand the nature of hydrothermal venting in a young oceanic basin.

 

¹Hannington et al. (2005) In: Economic Geology 100th Anniversary Volume, 111-141

²F. M. van der Zwan et al. (2019) In: Geological Setting, Palaeoenvironment and Archaeology of the Red Sea. Springer, 221-232

³F. M. Van der Zwan et al. (2023) Communications Earth & Environment 4 (1), 496

⁴N. Augustin (2023) METEOR Short Cruise report, M194. GEOMAR Helmholtz Centre for Ocean Research https://oceanrep.geomar.de/id/eprint/59591