Oceanic Core Complex Development in Modern and Ancient Oceanic Lithosphere: Gabbro?Localized versus Peridotite?Localized Detachment Models

Drilling and submersible studies of the Atlantis Bank (Southwest Indian Ridge) and the Atlantis Massif (Mid-Atlantic Ridge) oceanic core complexes reveal “gabbro-localized” and “peridotite-localized” end-member models of strain localization and deformation during core complex development, in which the gabbroic fault rocks exhibit extensive and rare high-temperature ductile-deformation fabrics, respectively. Both models emphasize a footwall cored by gabbroic intrusions, therefore precluding an amagmatic origin of core complex formation. We test these models by using relict oceanic core complexes preserved in the western Mirdita Ophiolite in Albania. The Puka and Krabbi massifs display traits of the peridotite-localized detachment model, whereby amagmatic tectonic extension is not required for the formation of this category of core complexes.