Time evolution of negative buoyancy of an oceanic slab subducting with varying velocity

Slab detachment and mantle plume upwelling in subduction zones: An example from the Italian South-Eastern Alps

“…The model is an adaptation of that presented in Ranalli et al (2000) and Mahatsente and Ranalli (2004), where subduction of an oceanic slab is modelled ab initio. Mass, momentum, and energy conservation equations are solved for a slab and surrounding mantle subject to kinematic boundary conditions (time-dependent subduction rate, subduction dip angle and initial temperature distribution of subducting slab).…”

“…The time-dependent density anomalies within the slab are computed from the temperature distribution at each time step, taking into account phase transitions and their estimated displacement within the slab. The total buoyancy is obtained from the density anomalies by integration (for details see Mahatsente and Ranalli, 2004). This model has been extended to subduction of continental lithosphere (Ranalli et al, 2005), assuming that continental material arrives at the subduction zone at a specified time after the beginning of subduction.…”

“…However, the width of the plume is not an important factor in the present first-order model, as the total strength of the slab is estimated along 1-D profiles across the slab above the plume head. The temperature distribution within the slab at the beginning of slab-plume interaction is obtained from the thermal models of Mahatsente and Ranalli (2004) and Ranalli et al (2005). The plume head is assumed to be at T = 1900 K, that is, approximately 300 K hotter than the surrounding mantle.…”

Continental subduction and exhumation: an example from the Ulten Unit, Tonale Nappe, Eastern Austroalpine

“…Table 1 shows the densities, their P,T-derivatives, thermal conductivities, specific heats, and the initial elastic parameters in the slab and surrounding mantle. Viscous deformation is modelled with the theology of olivine, garnet, and perovskite in the upper mantle, transition zone, and lower mantle, respectively (for parameters and further discussion, see Ranalli et al 2000;Mahatsente & Ranalli 2004). The equations are solved with the explicit finite element code ABAQUS 6.3 (Hibbitt et al 2001).…”

“…The negative buoyancy as a function of time is estimated from the thermal structure and composition of the slab, by integrating the density anomalies within the slab. A full account of the procedure can be found in the work of Mahatsente & Ranalli (2004). Figures 7 and 8 show the evolution of negative buoyancy since the initiation of subduction.…”