Geochemical history of sediments in the northwestern Pacific Ocean

Abstract

NW Pacific surface sediments are dominantly detrital with lesser amounts of biosiliceous and hydrogenous material. The detrital components change regularly from trench sediments dominated by island-arc volcanoclastic debris to open-ocean sediments with higher REE, Th, Rb, Cs, La/YbNt La/Sc and Th/Hf but lower Eu/Eu, Co/Th, K/Rb and Rb/Cs. The open-ocean sediments are dominated by upper continental crustal debris. Buried sediments from DSDP holes pass through a three-stage evolution: ocean-ridge basaltic debris and hydrothermal precipitates, abyssal plain sediments characterised by hydrogenous material and upper continental crustal debris, and near-shore island-arc detritus with intermittent air-fall ash. Biogenic and within-plate basaltic/hydrothermal components cause important local deviations from this evolution. © 1993, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.