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Ildefonse, B, Blackman DK, John BE, Ohara Y, Miller DJ, MacLeod CJ, Abe N, Abratis M, Andal ES, Andreani M, Awaji S, Beard JS, Brunelli D, Charney AB, Christie DM, Delacour AG, Delius H, Drouin M, Einaudi F, Escartin J, Frost BR, Fryer PB, Gee JS, Godard M, Grimes CB, Halfpenny A, Hansen HE, Harris AC, Hayman NW, Hellebrand E, Hirose T, Hirth JG, Ishimaru S, Johnson KTM, Karner GD, Linek M, Maeda J, Mason OU, McCaig AM, Michibayashi K, Morris A, Nakagawa T, Nozaka T, Rosner M, Searle RC, Suhr G, Tamura A, Tominaga M, von der Handt A, Yamasaki T, Zhao X, Integrated Ocean Drilling Program, Expedition 305 SSP.  2007.  Oceanic core complexes and crustal accretion at slow-spreading ridges. Geology. 35:623-626.   10.1130/G23531A.1   Abstract

Oceanic core complexes expose gabbroic rocks on the sealloor via detachment faulting, often associated with serpentinized peridotite. The thickness of these serpentinite units is unknown. Assuming that the steep slopes that typically surround these core complexes provide a cross section through the structure, it has been inferred that serpentinites compose much of the section to depths of at least several hundred meters. However, deep drilling at oceanic core complexes has recovered gabbroic sequences with virtually no serpentinized peridotite. We propose a revised model for oceanic core complex development based on consideration of the rheological differences between gabbro and serpentinized peridotite: emplacement of a large intrusive gabbro body into a predominantly peridotite host is followed by localization of strain around the margins of the pluton, eventually resulting in an uplifted gabbroic core surrounded by deformed serpentinite. Oceanic core complexes may therefore reflect processes associated with relatively enhanced periods of mafic intrusion within overall magma-poor regions of slow- and ultra-slow-spreading ridges.

Kelley, DS, Karson JA, Blackman DK, Fruh-Green GL, Butterfield DA, Lilley MD, Olson EJ, Schrenk MO, Roe KK, Lebon GT, Rivizzigno P, * SPAT, Gee JS *.  2001.  An off-axis hydrothermal vent field near the Mid-Atlantic Ridge at 30 degrees N. Nature. 412:145-149.   10.1038/35084000   AbstractWebsite

Evidence is growing that hydrothermal venting occurs not only along mid-ocean ridges but also on old regions of the oceanic crust away from spreading centres. Here we report the discovery of an extensive hydrothermal field at 30 degrees N near the eastern intersection of the Mid-Atlantic Ridge and the Atlantis fracture zone. The vent field-named 'Lost City'-is distinctly different from all other known sea-floor hydrothermal fields in that it is located on 1.5-Myr-old crust, nearly 15 km from the spreading axis, and may be driven by the heat of exothermic serpentinization reactions between sea water and mantle rocks. It is located on a dome-like massif and is dominated by steep-sided carbonate chimneys, rather than the sulphide structures typical of 'black smoker' hydrothermal fields. We found that vent fluids are relatively cool (40-75 degrees C) and alkaline (pH 9.0-9.8), supporting dense microbial communities that include anaerobic thermophiles. Because the geological characteristics of the Atlantis massif are similar to numerous areas of old crust along the Mid-Atlantic, Indian and Arctic ridges, these results indicate that a much larger portion of the oceanic crust may support hydrothermal activity and microbial life than previously thought.

Klootwijk, CT, Gee JS, Peirce JW, Smith GM.  1992.  The origin of Ninetyeast Ridge: palaeomagnetic constraints from ODP Leg 121. Journal of Southeast Asian Earth Sciences. 7:247-252.   10.1016/0743-9547(92)90004-u   AbstractWebsite

Palaeomagnetic results from a lower Turonian to Middle Eocene ash-rich sedimentary sequence on Broken Ridge (ODP Sites 752–755) and ash and basalt sequences on Ninetyeast Ridge (90ER) (Sites 756–758) (1) support a Kerguelen hotspot origin for the 90ER volcanic pile; (2) are consistent with models for a large-scale southward jump of the Southeast Indian Ridge (SEIR) west of the 90ER at about 58 Ma; and (3) suggest a possible Amsterdam-St Paul hotspot origin for magnetic overprints on the 90ER.