Sediments from Hess Deep, Ocean Drilling Program Leg 147 Site 894, and from the deepest point of Hess Deep (recovered during cruise Sonne 60, core 95) were examined. Different lithologies within these sediments have different geochemical signatures. It is possible to distinguish the source rocks of the different sediment types and to reconstruct the processes affecting the genesis of the sediments. Foraminiferal ooze from Site 894 has high Sr concentrations and elevated but not constant Ba values. Sediments from lithic breccia sequences have nearly the same element concentrations and rare earth element (REE) patterns as underlying gabbroic rocks. The lithic breccias are a pure physical weathering product, exhibiting no alteration. Hydrothermal sediments from core 95 have varying concentrations of Mn, As, and other elements precipitated by hydrothermal activity. A serpentine sequence in the middle of the sediment-core is of turbiditic origin, inferred from high Mg, Ni, and Cr concentrations. Platinum group elements (PGE) in the serpentinitic sediments were fractionated during the alteration of peridotite. In the hydrothermal sediments PGE are partially enriched.

Date of initial receipt: 8 August 1994
Date of acceptance: 27 April 1995:

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