Fluid circulation at midocean ridge flank areas where the igneous crust is young and still hot and sediment cover is usually thin actually produces a major chemical exchange between the ocean and the crust, although temperatures and rates of fluid flow are low (Mottl and Wheat, 1994, doi:10.1016/0016-7037(94)90007-8). The primary objectives of Ocean Drilling Program Leg 168 were to elucidate the mechanism driving flow through the crust and seafloor, the magnitude of elemental chemical exchange between the crust and ocean, and the factors controlling the chemistry of fluids circulating in ridge flanks covered by sediments (Shipboard Scientific Party, 1997, doi:10.2973/odp.proc.ir.168.101.1997). To this purpose, Leg 168 drilled a series of holes in the eastern flank of the Juan de Fuca Ridge along a transect from Site 1023, a transition site from crust without sediment cover, to Site 1027, a site with sediment cover that is about 100 km east of the ridge axis. My research objective on the cruise was to understand the role of sediments in controlling the chemistry of circulating fluid.In this report, all of the data obtained in a shorebased laboratory study involving the total cation exchange capacity (CEC) and equivalent fractions of adsorbed cations on Leg 168 sediments is compiled. Some data on the exchangeable cation composition of clay-rich marine sediments have been reported (Russell, 1970, doi:10.1016/0016-7037(70)90127-4; Manheim and Sayles, 1974; Bischoff et al., 1975, doi:10.1016/0016-7037(75)90002-2; Sayles and Mangelsdorf, 1977, doi:10.1016/0016-7037(77)90154-5), but variation of the composition is poorly understood as functions of temperature with burial depth and of distance from ridge axis because hydrological and geological situations of ridge-flank areas are generally complex and their sediment covers are highly variable in composition and geological history. The present study characterizes the two-dimensional distribution of exchangeable cation compositions in organic-poor terrigenous sediments on the ridge flank as functions of distance from the ridge axis and burial depth.

Sediment depth is given in mbsf. Cation exchange capacity was originally given in meq/100g and was recalculated to mol/kg by dividing by 100. Note that other exchangeable cations were not analyzed, but it was estimated that the contributions to the total CEC are generally negligible in the sediments studied. See also Inoue (2000a) dataset: doi:10.1594/PANGAEA.745240.

Supplement to: Inoue, Atsuyuki (2000): Data Report: Exchangeable cation composition of terrigeneous hemipelagic sediments in the eastern flank of the Juan de Fuca Ridge. In: Fisher, A; Davis, EE; Escutia, C (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 168, 1-8