By contrast, the eastern Manus Basin is dominated by arc-type volcanism. The southeast-trending Djaul transform is conspicuous. The northeast trending deep on the western side is a failed spreading segment. Seafloor geology of the eastern Manus Basin. Edifices of the Eastern Manus volcanic zone, which extends between the active ends of the Djaul and Weitin transform faults, range from picritic basalt to rhyodacite in composition.
Gray lines indicate extensional fault scarps.
Active hydrothermal areas containing sulfide chimneys are identified. Proposed Site PCM-4A lies at the foot of the southeastern flank of Pual Ridge. Zones of progressively higher temperature alteration are expected to be telescoped under the focused vent site with massive sulfide chimneys relative to the situation under the diffuse venting zone at Snowcap. Leg 193 is not expected to intersect the main intrusive body but might cut some smaller apophyses. A fault is interpreted under Site PCM-4A, where 150 m of basaltic andesite is interpreted to overlie earlier Tertiary basement in the hanging wall.