Multi-stage detachment localization and evolution of the Akapnou Forest Oceanic Core Complex, Troodos Ophiolite, Cyprus

Oceanic core complexes (OCCs) are key features of the oceanic crust, yet their geometry and formation remain poorly constrained as the oceanic crust is largely submerged. While the Troodos Ophiolite is one of the most well-preserved ophiolites in the world, the tectonic origin of the Southern Troodos Fault Zone (STFZ) remains contested, with interpretations suggesting either a leaky transform fault zone or an OCC setting. This study investigates the kinematics and structure of the tectonic contacts surrounding the Akapnou Forest Complex (AFC) in the STFZ by field mapping and drone photogrammetric models. Fieldwork reveals that domed mantle material, interpreted as an OCC, is bounded by a high-angle serpentinite shear zone (HASSZ), interpreted as the segment end of a mid-oceanic ridge, and multiple low-angle serpentinite shear zones (LASSZs), interpreted as detachment faults. The LASSZs have a consistent top-to-WNW movement. Three distinct LASSZs were identified, suggesting the detachment system evolved through multiple stages. Initial detachment localized along the ultramafic cumulates that subsequently isostatically folded, causing the detachment to step up to a shallower rheological horizon through the sheeted dike-gabbro transition. This younger detachment underwent multiple locking events, creating rafted blocks of the hanging wall. Laterally, fault locking may have varied. Lower friction closer to the segment end allowed for continuous slip, facilitating mantle exhumation to the surface. We conclude that the AFC represents a fossil OCC, and the derived conceptual model provides key insights into the multi-stage dynamics of mantle exhumation along sequentially localized detachment zones.