Data report: ultramafic reference material from core 147-895d-10w

Abstract

Ocean Drilling Program (ODP) Washcore 147-895D-10W is the last core taken in Hole 895D. It represents accidental recovery of drilling rubble during hole reaming, and therefore represents a mix of lithologies that could have been derived from 0 to 93.7 meters below seafloor (mbsf). It consists of 15 distinct pieces of serpentinized ultramafic and gabbroic rocks, with numerous gravel-sized pieces of mixed ultramafic material with small amounts of clay occurring at the bottom of the core. More uncurated rubble was sampled when trying to ream the hole. This uncurated rubble is not described in the Initial Reports volume, but was collected by one of the authors (H.P.). Petrographic inspection of the uncurated rubble showed it to be serpentinized olivine with margins of chrysotile asbestos, small amounts of spinels and gabbroic fragments. It was expected that the rubble composition represents well peridotites of the marine mantle, especially in relation to platinum group elements (PGE) (Prichard et al., this volume). It was decided by the shipboard party to use this uncurated material as a reference for post-cruise geochemical analysis. On board, approximately 4 kg of the uncurated material (Sample 147-895D-10WReference 1) was washed clay-free with demineralized water, dried at 110°C, and then ground in a motor-driven agate mortar. Because the grain size was not yet suitable after this procedure for preparing powder pellets aboard ship for X-ray fluorescence (XRF) trace-element analysis, three small splits were ground in tungsten carbide containers in a shatter box. The results of shipboard XRF-analysis with an Applied Research Laboratories (ARL) machine gave preliminary trace elements only. The data are given in Table 1. At the end of the cruise, small samples of approximately 200 g of 147-895D-10W-Reference 1 were distributed to interested cruise participants. H. Puchelt received additionally about 6 kg of uncurated rubble (Sample 147-895D-10W-Reference 2) for grinding and analysis at Karlsruhe. This material was carefully ground in portions of about 50 g in a shatter box with agate containers and was homogenized.