Surface sediments from Holes 894D, 894E, and 895A of ODP Leg 147 were examined for chromian spinel and other detrital minerals in order to determine the source rocks of the Hess Deep sediments. The detrital chromian spinel, except for that in basalt particles, has an intermediate Cr# (= Cr/[Cr + Al] atomic ratio), similar to spinel in ultramafic-mafic plutonic rocks drilled at Site 895. Chromian spinel derived from peridotites and related mafic plutonic rocks was not found in sediments from Site 894. Detrital spinel from Site 895 is generally low in Ti, which indicates a derivation mainly from harzburgite or peridotite intermediate between harzburgite and dunite, that is, a slightly melt-impregnated harzburgite. The peridotites that supplied the clastic particles represent less melt-impregnated rocks than the peridotites cored at Site 895. Lherzolitic peridotites, which have chromian spinel with Cr# <0.4 and are predominant in the Atlantic fracture zones, are absent in Hess Deep.

Date of initial receipt: 2 August 1994
Date of acceptance: 29 November 1994

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