Project Details
Projekt
Role of serpentinite deformation on OCC tectonics– follow-up investigations to IODP Expedition 399
Applicant
Dr. Rebecca Kühn
Subject Area
Geology
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 546935067
At slow-spreading mid-ocean ridges melt supply can be insufficient to counterbalance the spreading rate. In that case, spreading is tectonically compensated by detachment faulting, forming oceanic core complexes at inside corners adjacent to transform faults. At the ‘Atlantis Massif’, mid-Atlantic Ridge (30°N) the detachment exhumes an extensively serpentinized footwall to the seafloor and rotates it. IODP Expedition 399 drilled the longest oceanic mantle section worldwide into this footwall, the 1.2 km deep hole of U1601C. Besides gabbros, the exposed rocks are mostly serpentinites, formed by hydration of mantle peridotites. Despite the tectonic situation and the rheological weakness of serpentinite, macroscopically observed deformation features are preferentially localized in the deformed gabbros. First light-microscopy observations, however, show dissolution-precipitation creep in the serpentinites. The project RoSe will explore the deformation in the footwall of the Atlantis Massif core complex on multiple scales. Starting from microstructural analysis and identification of deformation mechanisms in the serpentinites using various electron microscopy and other techniques, these results will be upscaled to the entire drill core and the footwall of the detachment fault. To assess overprinting by the adjacent transform fault, we will investigate a second sample set from ODP Leg 209 with multiple drill sites on both sides of the transform fault. From that we will establish a model for the footwall deformation. By implementing the available geophysical data, a 3D geo-tectonic model of the Atlantis Massif core complex formation will be set up. Based on this model as well as the detailed microstructural work we will be able to constrain the role of serpentinite deformation for the tectonic evolution of slow spreading mid-ocean ridges. The results of project RoSe on serpentinite deformation will also be of further importance for other plate tectonic settings of the oceanic lithosphere.
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