Finely laminated and undisturbed except in the area of the southwest basin; in this part, bedding, resedimentation, and brecciation are common. In addition, some sediment cores contain vein minerals precipitated in open fissures which crosscut unlithified metalliferous sediments. These veins are the conduits by which new hot brine vents into the Deep. Vein mineralogy is dominated by anhydrite, talc, smectite, pyrite, sphalerite, and chalcopyrite. Vertical zonation due to cooling and reaction of the incoming brine as it rises through the metalliferous sediment. Near the Southwest Basin- west basin transition, metalliferous sediment has been locally recrystallized to a hematite-magnetite-pyroxene assemblage, probably due to the intrusion of basalt into the metalliferous sediments.--Modified journal abstract.