Slow-spreading ridge magmatic activity is considered to be focused at segment centers. the Mid-Atlantic Ridge between 14° and 16°N is supposed to be a region of weak magmatic production, where mafic crust is locally absent and peridotites outcrops are common. ODP Leg 209 obejctive was to drill a seris of sites to study the along-axis variability of structure, mantle composition, alteration, ...
We drilled 1187 m of serpentinized peridotite, troctolite, gabbro, and diabase (recovery 30%), showing little along-axis variability. 15°N peridotites are among the most depleted abyssal peridotites ; they are weakly deformed. Deformation associated to mantle uplift/denudation is highly localized, along ductile shear zones, evolving as brittle faults at shallow depth. Very strong hydrothermal alteration affects 60% to 100% of recovered peridotites, and results of varying processes. The large amount of recovered gabbro indicates that these segment ends are not magma-starved. They confirm the heterogeneous nature of slow spreading ocean crust, composed of serpentinized peridotites and gabbros in poorly known proportions.
References : 
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