Unravelling the process of subduction initiation: style, mechanism, and timing

Subduction is a key step in the solid Earth cycle that allows tectonic plates to move. During the formation of a new subduction zone, when lithosphere initiates its descent into the upper mantle, a number of tectonic, geochemical, and petrological processes affect the leading edge of the plate above the subduction zone (i.e., forearc). These transformations may provide fundamental insights into the still poorly understood process of subduction initiation.
Fluids released by the subducting plate during subduction initiation hydrate the overlying mantle and create a new mineralogical phase called serpentine. This process, known as “serpentinisation”, drastically reduces the strength of the mantle and enormously increases its magnetisation. The study of the magnetic and physical properties of serpentinised mantle rocks are therefore instrumental to track the location, entity, and timing of mantle hydration and hence of subduction initiation. A recently developed technique to date magnetite grains[1] may be used to constrain the timing of serpentinisation associated to subduction initiation. Subduction initiation also induces tectonic stretching in the forearc region. Extension may eventually result in new magmatism which is responsible for the formation of new oceanic lithosphere called “ophiolite”. Recent studies of ophiolites[2,3] have shown that the initial stages of subduction are frequently characterized by a pervasive stretching of the forearc, which produces lithosphere thinning and tectonic rotations. Reconstructing the kinematics of forearc deformation is key to constrain the style and mechanisms of subduction initiation.
The Oman ophiolite represents the ideal natural laboratory to study the chemical, petrological and tectonic processes associated to subduction initiation. It is the most complete and best-preserved ophiolite and is composed of a 5-7 km thick mantle sequence and a 4-5 km thick crustal sequence. This ophiolite formed in the forearc of a new subduction zone initiated in the Late Cretaceous at 104 Ma[4]. The goal of this project is to investigate the Oman ophiolite using a multidisciplinary approach, which employs palaeomagnetism, rock magnetism, magnetic fabric, geochronology, and petrology, to unravel the complex history of events associated to a past subduction initiation event.
For further info please contact Dr Maffione at [Email Address Removed]
For more info on the scientific activity of the PI Maffione go to www.marcomaffione.com
For further info on where and how to apply go to the CENTA website (http://www.centa.org.uk/training/)