Abstract
The objective of the Manaute cruise of the R.V. L'Atalante with the submersible Nautile was the in situ study of accretion processes, magmatic activity and hydrothermalism in the Manus Basin. Twelve dives and 18 dredges, focusing on the eastern and western tips of the basin, allowed us to demonstrate that in the eastern part of the basin the oceanic accretion is reduced to two axes propagating between Djaul and Weitin FZ. However the magmatic and hydrothermal activity is widely spread along the axes but also on volcanoes and ridges aligned on a N110 oblique direction. In the western part of Manus basin the oceanic accretion is located along two axes propagating rapidly to the southwest. The magmatic and hydrothermal activities are variable and diffuse over the whole area. The effect of the subduction of the Australian Plate in the New Britain Trench is evident throughout the basin.