Hydrothermal Systems at the Mid-Atlantic-Ridge – combined in two cruises M190 (2023) and M210 (2025)
Hydrothermal systems along the Mid-Atlantic Ridge (MAR) are key to understanding fluid–rock interactions, geochemical cycling, and biological activity at slow-spreading oceanic plate boundaries. These systems typically occur where seawater infiltrates fractured oceanic crust, is heated by magmatic or tectonic processes, and re-emerges at the seafloor as hydrothermal fluid rich in metals, volatiles, and reduced chemical species. Unlike fast-spreading ridges, the MAR is characterized by lower magmatic heat flux and pronounced tectonic segmentation, leading to more spatially heterogeneous hydrothermal structures.
A particularly noteworthy example is the Rainbow Hydrothermal System, located at 36°13.8′N – 33°54.15′W. It is situated on a massif composed predominantly of serpentinized peridotites. This ultramafic host-rock acts as a source for distinct geochemical signatures to the vent fluids. Rainbow emits high-temperature (>365 °C), low-pH fluids that are rich in iron, hydrogen, methane, and other reduced species (Koschinsky et al., 2020, Seyfried et al., 2011). These chemical profiles result from extensive serpentinization reactions, which generate heat and facilitate the abiotic synthesis of hydrocarbons—processes of high relevance to studies on the origin of life and deep carbon cycling (McCollom et al., 2007).
Overall, hydrothermal systems along the MAR—including Rainbow, TAG, and Lost City—highlight the diversity of geological settings and biogeochemical processes at slow-spreading ridges. They provide crucial insights into seafloor mineralization, extremophile ecosystems, and the potential for life in analogous extraterrestrial environments.
The marine trace metal geochemistry team of the Constructor University Bremen (led by Andrea Koschinsky) participated in two cruises in the years 2023 (M190) and 2025 (M210) to investigate these fascinating systems, to further understand the influence of environmental parameters including pressure, temperature and host rock on metal mobility and interactions with organic matter alongside researchers from collaborating institutes.
Click below on the logos for more details on the individual cruises:
References:
Koschinsky, A., Schmidt, K. & Garbe-Schönberg, D. Geochemical time series of hydrothermal fluids from the slow-spreading Mid-Atlantic Ridge: Implications of medium-term stability. Chem. Geol. 552, 119760 (2020).
McCollom, T. M. & Seewald, J. S. Abiotic Synthesis of Organic Compounds in Deep-Sea Hydrothermal Environments. Chem. Rev. 107, 382–401 (2007).
Seyfried, W. E., Pester, N. J., Ding, K. & Rough, M. Vent fluid chemistry of the Rainbow hydrothermal system (36°N, MAR): Phase equilibria and in situ pH controls on subseafloor alteration processes. Geochim. Cosmochim. Acta 75, 1574–1593 (2011).