Leg 158, Hole 957C, Core 11N, Section 1, 70-110 cm
This core, collected from a hydrothermal mound near the Mid-Atlantic Ridge in 1994, showed for the first time that hydrothermal ores are deposited both above and below older sediments. Before Leg 158, scientists thought that these brecciated (coarse grained with angular rock fragments) ore deposits formed by tectonic deformation; however, study of this core showed that this brecciation is not caused by tectonic forces but occurs in place, greatly increasing our understanding of these important ore deposits.
Download a photo of the core. (JPG, 550 KB)
See http://www-odp.tamu.edu/publications/leg_ndx/158bndex.htm for more detailed information about Leg 158.