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Welcome to the InterRidge Working Group on Oceanic Transform Faults.

Transform faults cover a significant portion of the active part of the Mid Ocean Ridge system. They generally consist of a single narrow strike-slip zone offsetting two mid-ocean ridge segments. This oversimplified view is challenged by growing evidences of the tectonic complexity of the transform boundaries and their significant interaction with the magmatic, hydrothermal and thermal setting of the ridges.

Transform faults react rapidly and deform under the influence of far field stresses, as changes in plate motion. However, not all transforms react equally to equivalent stress changes, suggesting the influence of local parameters such as offset length, spreading rate, temperature and composition of the mantle. Numerical models and observational studies reveal the role of transform faults in shaping the geometry of mantle flow and active processes at mid-oceanic ridge axes. These processes are most evident at the extreme limits of spreading rate and transform offset size. At slow and ultra-slow spreading ridges the lateral offset may integrate significant obliquity of the axis. These ridges are also characterised by ultra large offset transforms, defined mega-transforms, such as the Romanche and Andrew Bain FZ (MAR and SWIR respectively). Their morphologies reveal a broad tectonized domain recalling the continental strike-slip systems.

Transform systems act as pathways for deep seawater circulation and allow extensive fluid-rock interactions sustaining chemical and biogeochemical exchanges. The progressive serpentinization and carbonation of the oceanic mantle and crust is a major controller of the global water, carbon and nutrient cycle and represents a powerful mechanism for hydrogen and methane abiotic formation sustaining deep life communities.

Fracture zones represent also an ideal locus to study the temporal evolution of the magmatic cycles at MORs and the response of the melting process to varying physical conditions.

Our understanding of the complexity of these plate boundaries and their role in the evolution of the oceanic lithosphere significantly advanced in the last years. However, several questions need to be addressed calling for a joint effort of different disciplines and communities such as geochemists, petrologists, geophysicists, microbiologists, fluid and numerical modelling specialists. This working group propose to focus on five main questions that are likely of large interest to the Earth sciences community:

  • How do transform domains react to both far- and near-field stress changes?
  • How do transforms interact with the underlying mantle. What are the effects of temperature, rheology and composition?
  • What is the interplay between transform dynamics and magmatism?
  • Which relationship exists between oceanic transform faults and their counterparts on continental margins?
  • Are oceanic transform faults sites of intense fluid-rock interaction and biogeochemical exchange?

Download the text of the working group proposal

IRWG_oceanic_transforms_october17

 

The group was created in June 2017 after approval of the IR Steering Committee and is coordinated by Marcia Maia (CNRS-IUEM, Brest, France), Daniele Brunelli (University of Modena-CNR, Italy) and Barry Hanan (University of California at San Diego, USA).