The geochemical characteristics of boron, which include high solubility in aqueous fluids and high magmatic incompatibility, make B a useful tracer of deep earth fluids and the recycling of subducted materials (You et al., 1995b). In subduction zones, B is an important element for evaluating the origin of fluids that are derived from accretionary prisms and subducted rocks (e.g., Bebout et al., 1993; You et al., 1995a; Deyhle et al., 2001). High B contents in volcanic rocks from island arcs suggest that the fluids may be recycled to the arc crust (e.g., Morris et al., 1990; Ryan et al., 1995; Sano et al., 2001).
Because, compared to other Earth materials, B is strongly concentrated in oceanic sediments, it is important to know their B contents (e.g., Spivack et al., 1987; Vengosh et al., 1991; Ishikawa and Nakamura, 1993). However, little is known about depth profiles of B concentrations within sedimentary sections, and average B contents of oceanic sediments are still unknown (Plank and Langmuir, 1998).
During Ocean Drilling Program Leg 192, thick sedimentary sequences were cored at two sites, Site 1183 and Site 1186 (Mahoney, Fitton, Wallace, et al., 2001). We measured the B contents of sediment samples from these sites.