Lost City Hydrothermal Field

Lost City Hydrothermal Field
Name	Lost City Hydrothermal Field
Location	Mid-Atlantic Ridge near Atlantis Massif
Coordinates	approx. 30°8′N 42°8′W
Depth	~700–1000 m
Discovered	2000
Discovered by	R/V Atlantis / Alvin
Type	Serpentinization-driven alkaline hydrothermal field

Lost City Hydrothermal Field is an unusual seafloor hydrothermal site located on the flanks of the Atlantis Massif on the Mid-Atlantic Ridge that hosts towering carbonate chimneys, alkaline fluids, and chemosynthetic ecosystems. It contrasts with black smoker systems at locations such as Juan de Fuca Ridge, East Pacific Rise, and TAG Hydrothermal Field in fluid chemistry, thermal regime, and geological processes. The field has become a focal point for research by institutions including Woods Hole Oceanographic Institution, Scripps Institution of Oceanography, National Oceanic and Atmospheric Administration, and international partners like MPI for Marine Microbiology.

Discovery and Location

The field was found during cruises by R/V Atlantis and dives with Alvin in 2000 near the northwestern corner of the Atlantis Massif close to the Mid-Atlantic Ridge transform and fracture zones. Subsequent mapping by NOAA Ship Okeanos Explorer, multibeam surveys from R/V Knorr and autonomous surveys by AUVs and ROVs such as Jason and ROPOS refined site coordinates and extent. The site lies within the same transform-fracture domain that hosts features studied by IODP Expedition 304/305 and later drilling by the International Ocean Discovery Program.

Geological Setting and Formation

The field sits on the periphery of an ultramafic massif formed by detachment faulting akin to features at Atlantis Bank and exposed mantle peridotite studied at Ocean Drilling Program sites. Serpentinization of mantle peridotite drives hydration reactions that generate hydrogen and heat, analogous to processes inferred for ophiolites like Semail Ophiolite and massifs investigated during DSDP and ODP expeditions. Tectonic context includes slow-spreading processes on the Mid-Atlantic Ridge, faulting similar to that documented at the Gakkel Ridge and interaction with fracture zones like the Charlie-Gibbs Fracture Zone.

Hydrothermal Chemistry and Fluid Dynamics

Fluids at the field are highly alkaline (pH ~9–11), rich in hydrogen and methane, and low in dissolved metals compared with black smoker fluids at TAG Hydrothermal Field or Lucky Strike. Geochemical signatures point to abiotic organic synthesis through Fischer–Tropsch–type reactions and serpentinization pathways analogous to processes modeled for Enceladus and Europa. Isotopic studies employing techniques developed by labs such as Lamont–Doherty Earth Observatory and USGS have traced carbon and hydrogen sources, while fluid flow patterns mapped using methods from NOAA and WHOI reveal diffuse, low-temperature venting over a broad area rather than focused high-temperature plumes.

Biological Communities and Ecology

The field supports chemosynthetic communities dominated by microbial mats, archaea like those related to Methanopyrus-type lineages, and bacterial groups including relatives of Hydrogenobacter and Thermotogae-affiliated clades. Macrofauna include protists, amphipods, and specialized sessile organisms whose ecology has been compared to communities from Galápagos Rift and Lō‘ihi Seamount. Studies led by researchers from Max Planck Society, University of Washington, and University of Southampton have used metagenomics, 16S rRNA surveys, and cultivation experiments to link microbial metabolisms to hydrogen and methane fluxes, with implications for models of the origin of life advanced by proponents associated with NASA astrobiology programs and SETI-related hypotheses.

Mineralogy and Chimney Structures

Chimneys are composed primarily of carbonate minerals such as aragonite and calcite with brucite, magnetite, and serpentine-group minerals formed during precipitation from high-pH fluids, paralleling mineral assemblages reported from ophiolite complexes and carbonate vents like Prehistoric Bajada. Chimney morphologies reach tens of meters, with internal porosity and microhabitats studied via petrography from specimens curated at Smithsonian Institution and thin-section analyses conducted by labs at ETH Zurich and University of Edinburgh. Mineral deposits provide insights relevant to marine mineral exploration policies debated in forums like International Seabed Authority.

Exploration, Research, and Methods

Investigation has combined deep-sea expeditions using Alvin, Jason, ROPOS, AUV mapping platforms such as Sentry (AUV), coring by ODP/IODP drillships like JOIDES Resolution, and in situ experiments from platforms operated by NOAA and WHOI. Analytical approaches include high-resolution mass spectrometry developed at Lawrence Livermore National Laboratory, synchrotron analyses at facilities like Diamond Light Source, and molecular methods advanced at institutions including Broad Institute. International collaborations involve universities and agencies such as Dalhousie University, University of Puerto Rico, Institut Français de Recherche pour l'Exploitation de la Mer, and funding from organizations like National Science Foundation.

Significance and Conservation

The field informs theories about serpentinization-driven hydrothermal systems, abiotic organic synthesis, and potential analogues for extraterrestrial habitats at Europa and Enceladus, influencing programs at NASA Jet Propulsion Laboratory and astrobiology initiatives at European Space Agency. Conservation concerns have been raised in contexts involving the International Seabed Authority and environmental assessments modeled after policies for hydrothermal sites like Rainbow (hydrothermal field). The site remains a priority for long-term monitoring by consortia including NOAA, WHOI, and academic partners to balance scientific research with preservation of unique mineralogical and biological resources.

Category:Hydrothermal vents