Abstract:

Particulate samples(>0.45 μm) from a hydrothermal plume in Lau basin are collected by filtering on deck and analyzed by scanning electron microscope(SEM) and X-ray energy dispersive spectroscopy(EDS). Four types of particles have been morphologically characterized. i)Biogenic detritus mainly device from background water. ii)Microbial particles include filamentous and clustered configuration; and these specific morphology suggest specific microorganism community. iii)Amorphous particles are divided into S-Zn-Ba-Ca phase, Fe-oxide phase containing trace of Ba-Zn-Ca, Fe-Mn-Ca-Ba phase containing trace of Zn, sulfide particles and polymetallic particles, and the amorphous forms should originate from precipitation in the external part of sulfide chimney or the fragmentation of chimney rocks. iv) Automorphic particles are probably formed in an area where the chemical conditions are homogeneous, i.e. the internal part of sulfide chimney. So many particles related to hydrothermal activity and the distributions of amorphous particles in different water layers indicate  that our study station locats at the incipient stage of formation of hydrothermal plumes, and during the several hundreds meters there may exist an active hydrothermal vent area.

Key words: hydrothermal plumes, buoyant particles, vents, micro-analyzed, Lau basin