Zinc-iron sulphide mineralization in tubes of hydrothermal vent worms

Nanocrystalline zinc-iron sulphide minerals were found within tubes of Alvi nella pompejana, collected at 9 degreesN on the East Pacific Rise, in a pre liminary study carried out by conventional analytical transmission electron microscopy. Their structure is consistent with either the sphalerite or wu rtzite polymorphs of ZnS. In contrast with sulphides usually observed in de ep-sea hydrothermal environments, the unique sulphide observed within the e xoskeleton of the pompeii worms has a (Zn0.88Fe0.12)S composition. The zinc -iron sulphide nanocrystals are grouped in submicrometer-sized clusters whi ch form layers, concentrically to the proteinaceous tube axis. This is the first characterization of minerals precipitated within a biological matrix from hydrothermal vents organisms. These minerals represent a new example o f zinc-iron biologically induced mineralization. Such layers of nanocrystal line zinc-iron sulphide minerals could be used as valuable markers of annel id tubes, in the growing field of studies focusing on fossilized paleo-hydr othermal vent systems.