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Abstract

Oceanic core complexes are generally recognized at ultraslow, slow, and intermediate rate spreading centers at mid-ocean ridges and back arc basins by their domal morphology and/or corrugated surfaces. Oceanic core complexes may comprise more than 50-60% or more of some spreading centers. Although oceanic core complexes are less accessible for direct observations of detachment faults when compared to continental core complexes, there are several advantages for understanding the origin and evolution of core complexes. They represent new mafic oceanic crust and mantle lithospheric components that result from upwelling asthenosphere, they have no complicating preexisting structural history, the detachment faults and domal structures of the core complex are subject to little erosion and masking by sedimentary deposition post formation (which could obscure the structure of the basement detachment surface), and they can be placed in the context of the ridge morphology and depth, basement surface samples collected, and magma supply associated with the particular spreading center.

An attempt is made to bridge the gap between continental core complexes and oceanic core complexes in a way that may have significance in our understanding of ocean-continent transitions that may contain mixtures of oceanic crustal, serpentinized mantle, and continental basement types. These basement types could commonly be obscured by thick sedimentary prisms and acoustic and density uncertainties. Considered are: the range of expression of spreading center core complexes, variations in the nature and composition of footwalls and hanging walls associated with core complexes, the extent of rotation of oceanic detachment faults documented, the role of magmatism in core complex development, fluid rock interaction during development, the role of serpentinization in obscuring the definition of mafic oceanic crust and MOHO, the extent of strain localization, variation in the scale of spreading-center-parallel lateral extent of core complexes, the lateral and slip-parallel extent of mantle exhumation on various detachment faults, lateral variation of slip along single detachments, variations in slip amounts among oceanic detachments worldwide, the obscuring effects of rafted or rider blocks in delineating the full extent of detachments, the mechanisms of initiation and termination of core complexes, and the correlations of core complex development with ridge depth and overall magma supply. Finally, modeling results based on mantle composition and magma supply controls on core complex development are assessed.

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