Proceedings of the Ocean Drilling Program, 209 Initial Reports

Orogenic, Ophiolitic, and Abyssal Peridotites

“…Such peridotites were notably found along the ultraslowspreading Southwest Indian Ridge (Johnson et al, 1990;Seyler et al, 2003Seyler et al, , 2004 and the slow-spreading Mid-Atlantic Ridge, between 14 N and 16 N (Kelemen et al, 2004;Sobolev et al, 1992). The significance of these peridotites is discussed in the preceding text (Section 3.4.2.3).…”

“…From recent studies stems a growing body of observations indicating that the composition of oceanic peridotites often violates the classic paradigm stating that their degree of depletion and, therefore, their degree of melt extraction is directly correlated to spreading rates, which was interpreted as direct evidence for the dynamics of mantle upwelling (hot and buoyant vs. cold and sluggish -e.g., Boudier and Nicolas, 1985;Langmuir et al, 1992;Niu and Hékinian, 1997b). For instance, harzburgites have been collected at the Southwest Indian Ridge, an ultraslow-spreading ridge (Johnson et al, 1990;Seyler et al, 2003), and extremely refractory harzburgites have been sampled between 14 N and 16 N on the slowspreading Mid-Atlantic Ridge (Kelemen et al, 2004;Sobolev et al, 1992). These peridotites plot at the depleted end-member of the abyssal peridotites in terms of forsterite content in olivine (cationic ratio Mg/(Mg þ Fe) ¼ 0.91-0.92), chromium component in spinel (cationic ratio Cr/(Cr þ Al) ¼ 0.43-0.51), and trace element content in whole rocks and cpx (Godard et al, 2008;Seyler et al, 2007).…”

“…Most abyssal peridotites were collected by dredging or using submersibles (Karson, 1998;Lagabrielle et al, 1998;Tisseau and Tonnerre, 1995). Several peridotite samples were also collected in the frame of the international drilling programs Deep Sea Drilling Project -83) and Ocean Drilling Program (1985) (e.g., Karson et al, 1997;Kelemen et al, 2004;Mevel et al, 1996).…”

Expedition 309/312 summary

“…Drilling at several sites has provided a wealth of new data and understanding of gabbros and peridotites from the lower crust and serpentinized upper mantle (e.g., Hess Deep: Gillis, Mével, Allan, et al, 1993;Kane Fracture Zone area: Cannat, Karson, Miller, et al, 1995;Southwest Indian Ridge: Dick, Natland, Miller, et al, 1999; 14°-16°N MidAtlantic Ridge: Kelemen, Kikawa, Miller, et al, 2004;Atlantis Massif: Expedition 304 Scientists, 2005, Expedition 305 Scientists, 2005. However, serious problems still exist with drilling tectonized rocks with little sediment blanket or without erosional removal of fractured material, and it is also commonly difficult to relate drilled sections to regional geology (e.g., Gillis, Mével, Allan, et al, 1993).…”

Expedition 314 summary

“…F5). A number of previous Ocean Drilling Program (ODP) and IODP expeditions have employed LWD technology (Riedel et al, 2006;Flemings et al, 2006;Tréhu, Bohrmann, Rack, Torres, et al, 2003;Mikada, Becker, Moore, Klaus, et al, 2002;Kelemen, Kikawa, Miller, et al, 2004). We deployed Schlumberger LWD-measurement-while-drilling (MWD) tools including the following:…”