Fossil evidence for serpentinization fluids fueling chemosynthetic assemblages

Franck Lartaud (1) , Crispin T.S. Little (2) , Marc de Rafelis , Germain Bayon (3) , Jerome Dyment (4) , Benoit Ildefonse (5) , Vincent Gressier (6) , Yves Fouquet (3) , Françoise Gaill (7) , Nadine Le Bris (1, 8)

1 LECOB - Laboratoire d'Ecogéochimie des environnements benthiques
2 SEE - School of Earth and Environment [Leeds]
3 GM - Unité Géosciences Marines
4 IPGP - Institut de Physique du Globe de Paris
5 Géosciences Montpellier
6 iSTeP - Institut des Sciences de la Terre de Paris
7 IRD - Institut de Recherche pour le Développement
8 LEP - Laboratoire Environnement Profond

Among the deep-sea hydrothermal vent sites discovered in the past 30 years, Lost City on the Mid-Atlantic Ridge (MAR) is remarkable both for its alkaline fluids derived from mantle rock serpentinization and the spectacular seafloor carbonate chimneys precipitated from these fluids. Despite high concentrations of reduced chemicals in the fluids, this unique example of a serpentinite- hosted hydrothermal system currently lacks chemosynthetic assemblages dominated by large animals typical of high-temperature vent sites. Here we report abundant specimens of chemosymbiotic mussels, associated with gastropods and chemosymbiotic clams, in approximately 100 kyr old Lost City-like carbonates from the MAR close to the Rainbow site (36 °N). Our finding shows that serpentinization-related fluids, unaffected by high-temperature hydrothermal circulation, can occur on-axis and are able to sustain high-biomass communities. The widespread occurrence of seafloor ultramafic rocks linked to likely long-range dispersion of vent species therefore offers considerably more ecospace for chemosynthetic fauna in the oceans than previously supposed

Mots clés: Bathymodiolus; Ghost City; ultramafic-hosted; mid-ocean ridge; ecogeochemistry

Domaines: Planète et Univers [physics]

Franck Lartaud, Crispin T.S. Little, Marc de Rafelis, Germain Bayon, Jerome Dyment, et al.. Fossil evidence for serpentinization fluids fueling chemosynthetic assemblages. Proceedings of the National Academy of Sciences of the United States of America, 2011, 108, pp.7698-7703. ⟨10.1073/pnas.1009383108⟩. ⟨insu-01352929⟩