Two ODP expeditions were sailed prior to Leg 209 with the objective of sampling exposures of Earth's mantle from fast- and slow-spreading ridges. Leg 147 to Hess Deep (Shipboard Scientific Party, 1993) cored six holes from 10 to 94 meters below seafloor (mbsf). Four of these holes are separated by <20 m; the other two are located ~250 and ~400 m away from the four-hole location. Only two of the holes penetrated deeper than 40 mbsf, and total recovery from all six holes was ~65 m. From this suite of samples, Puchelt et al. (1996) determined that the sulfide mineralogy was dominated by Ni-bearing phases and that the presence of native metals and Ni-Fe alloys indicated mobilization of sulfur under strongly reducing conditions. They also estimated the primary sulfur content of the mantle section represented by the samples to be ~300 ppm. Prichard et al. (1996) demonstrated that the partially serpentinized rocks retain platinum-group elements.
During Leg 153 to the Kane Fracture Zone area on the Mid-Atlantic Ridge (MARK), two holes were cored (to 126 and 200 mbsf) within meters of each other but with nearly 150 m of recovery (Shipboard Scientific Party, 1995). Gaggero et al. (1997) report a primary sulfide mineral assemblage from the MARK samples of pentlandite, chalcopyrite, and pyrrhotite, with a secondary sulfide mineral assemblage of violarite and mackinawite.