Physics – Geophysics
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufmos21c..06k&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #OS21C-06
Physics
Geophysics
3000 Marine Geology And Geophysics, 3017 Hydrothermal Systems (0450, 1034, 3616, 4832, 8135, 8424), 3035 Midocean Ridge Processes, 4832 Hydrothermal Systems (0450, 1034, 3017, 3616, 8135, 8424), 8424 Hydrothermal Systems (0450, 1034, 3017, 3616, 4832, 8135)
Scientific paper
For over two decades volcanically driven black smoker hydrothermal systems have been assumed to typify hot-spring systems on the seafloor. However, the serendipitous discovery of the Lost City hydrothermal field (LCHF) in 2000 may require re-examination of this belief. Sitting on 1-2 my old serpentinite crust, the LCHF hosts numerous active carbonate pinnacles that tower up to 60 m above the surrounding seafloor. Subsurface exothermic mineral-fluid reactions and lithospheric cooling in the underlying mantle host rocks produce >90 ° C, hydrogen- and methane-rich, high-pH fluids, which support novel microbial and macrofaunal communities. These peridotite-hosted biotopes differ significantly from axial, magmatically driven vent systems in which carbon dioxide is a dominant volatile species. The range and complexity of environments hosting peridotites and other ultramafic rocks is vast. Under appropriate conditions, any of these might support hydrothermal systems similar to the LCHF. From ancient komatiitic rocks of the Early Archaean to ophicalcite deposits within the Apennine ophiolites comes evidence that hydrothermal systems have indeed been operative within ultramafic environments for much of Earth's history. Within contemporary oceanic crust, there is a diverse array of submarine environments affected by on-going serpentinization reactions, which include systems such as the Mariana forearc, the Arctic, Antarctic, Southwest Indian and Mid-Atlantic Ridge spreading networks, major transform faults, and highly extended rifted margins. Any of these tectonic settings could host LCHF-type ecosystems. Yet, only recently has the potential importance of these peridotite-hosted environments been recognized with respect to the origin and evolution of life on this planet and perhaps elsewhere. Just as with the initial discovery of black smoker systems, a major driving force for continued exploration of LCHF environments will be the role that peridotite-hosted systems may serve as refugia or stepping-stones for animals hosting symbionts that include chemosynthetic organisms dependant on hydrogen- and methane-rich hydrothermal fluids. In addition, the discovery of seafloor hydrothermal ecosystems such as Lost City that do not require magmatic heat may have important implications in our search for life on other differentiated, tectonically active planets or in systems where ultramafic rocks have been exposed through meteorite impact events. The certainty that water exists, and has existed on Mars where there is good evidence for ultramafic rocks, raises the question of whether systems similar to LCHF may be present (or have once been present) elsewhere in the solar system as well.
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