VOLUMETRIC ANALYSIS OF SUBDUCTION HISTORY USING GLOBAL PLATE KINEMATIC MODELS

Subduction of oceanic lithosphere is a main component of Earth’s mantle convection. The convergence rates and volumes of subducted oceanic lithosphere along subduction zones determine the amount of downwelling material entering the mantle and exert a primary control on the mantle-convection-induced surface deflection known as dynamic topography.

Current approaches used to predict dynamic topography rely on either forward kinematic models based on the subduction history, or inverse tomographic approaches to model the mantle structure. Both these approaches require reasonable boundary conditions (i.e. plate kinematic models for forward approaches, reliable tomographic models for the inverse approach) in order to accurately model dynamic topography though time. However, anomalous plate velocities and plate motion directions caused by incorrect plate models or wrongly calculated plate crossovers for example, can lead to significant inconsistencies in kinematic models, leading to large errors.

We present a novel workflow to calculate time integrated subducted volumes from lithospheric thickness and plate velocity arguments. Implicit in this workflow is a way to detect anomalous velocities and plate motion directions. Subducted volumes are time dependent, allowing the history of volumetric subduction to be easily assessed at first order without the need of high performance computing. This relatively simple workflow allows quick quality control on plate kinematic models and allows dynamic topography amplitudes and timescales to be further investigated. We use this workflow to analyze subducted volumes both globally and at key regionally significant subduction zones in the Tethys, the Pacific and along the South American margin.