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doi:10.2204/iodp.proc.304305.202.2009 BackgroundIntegrated Ocean Drilling Program (IODP) Expedition 304/305 was conceived to investigate the formation and evolution of oceanic core complexes exposing lithologies from the lower oceanic crust and upper mantle via long-lived detachment faulting. This expedition was the fourth location where drilling penetrated an inside corner high and/or a corrugated dome associated with a transform fault along a slow-spreading oceanic ridge. Atlantis Massif is located along the Mid-Atlantic Ridge at 30°N (Fig. F1). Submersible surveys prior to this expedition suggested significant outcrops of serpentinized peridotite were a characteristic feature of Atlantis Massif. Particularly intriguing was gravity and seismic modeling, which suggested high velocity, dense rock, and potentially fresh mantle material at a depth within the dome that could be attained via ocean drilling. With a penetration of more than 1400 m into oceanic basement and in excess of 80% recovery, Expedition 304/305 represents one of the hallmark achievements of scientific ocean drilling. To the delight of many and the dismay of some, the core was essentially entirely mafic; only rare thin screens of moderately to pervasive altered ultramafic rock were recovered. The primary lithologies represented in the Expedition 304/305 sample suite are, in decreasing abundance, gabbro, olivine gabbro, troctolite, oxide-bearing gabbro, oxide gabbro, gabbronorite, and oxide- and olivine-bearing gabbro and gabbronorite. As a resource for researchers interested in compositional variability in ocean crust materials, several disciplinary groups from Expedition 304/305 expressed an interest in compiling data sets for publication in the IODP Proceedings volume. This volume presents an ideal venue for these data compilations, making vast amounts of data available to not only other members of the shipboard science party but also to the earth sciences community. |