Beitrag zum Geodynamik Workshop 2000 in Caputh bei Potsdam

On the Interaction of Plumes and Ridge-Transform Fault Systems (Poster)

Daniel-A. Heller und Gabriele Marquart (Inst. for Geophysics, Univ. Frankfurt)

1. Introduction

Iceland, due to the interaction of a mantle plume with the midatlantic ridge, is a very interesting area for geodynamic studies. The presence of a mantle plume under Iceland is well known by geological, geodynamic (Ito et al., 1999) and geochemical (Mertz et al., 1991) investigations. The plume is assumed to have a broad plumehead but despite of recent seismological studies (Wolfe et al., 1997, Bijwaard and Spakman, 1999) the detailed structure of the Iceland Plume is not known. The V-shaped structure of the Reykjanes Ridge is explained either by higher mantle temperatures below or lateral flow of plume material along the ridge axis (Albers and Christensen). An equal mode of plume-ridge interaction is not observed for the Kolbeinsey Ridge north of Iceland, which may be the influence of the Tjörnes Fracture Zone.

2. Modelconfiguration

The models are calculated with the program DECO3D, using a Spectral/Finite-Difference approach, written by G. Marquart. Model definitions and parameters are shown in Table 1. The calculations are performed with depth or temperature-depth dependent viscosity, with a low viscosity zone (h = 1x10**19 Pa s) in a depth of 50 to 200 km. Mantle material can enter the model at the middle part of the lower boundary. Descending material leaves the box at both sides of the lower boundary for the conservation of mass. Influx velocity is vinflux = 1.5 cm/a. The ridge system spreads with a constant velocity of vridge = 1.0 cm/a, the rigid lithosphere is defined thermally by TL

3. Results

The dynamic calculations are able to explain the following characteristics of the plume-ridge-transform fault system:

The distribution of plume material is influenced by the overlying divergent lithosphere plates and by the shape of the ridge-transform fault system. A flow of plume material along the ridge axis could not be observed with this model. The mixture of plume and mantle markers may be used to calculate the geochemistry of erupted magmas at the ridge axis. Further calculations with different ridge-transform geometries are intended for a systematic variationof the parameter space and a better explaination of the plume-ridge interaction.


  1. Albers and Christensen. Plume-Lithosphere Interaction under Mid-ocean Ridges with Temperature Dependant Viscosity. Oral Presentation
  2. Bijwaard and Spakman (1999). Tomographic Evidence for a narrow whole Mantle Plume below Iceland. EPSL, 166, 121-126.
  3. Ito et al. (1999). Mantle Flow, Melting and Dehydration of the Iceland Mantle Plume. EPSL, 165, 81-96.
  4. Mertz et al. (1991). Sr-Nd-Pb Isotope Evidence against Plume-Asthenosphere Mixing North of Iceland. EPSL, 107, 243-255.
  5. Ribe et al. (1995). The Dynamics of Plume-Ridge Interaction, 1: Ridge-centered Plumes. EPSL, 134, 155-168.
  6. Wolfe et al. (1997). Seismic Structure of the Iceland Mantle Plume. Nature, 385, 245-247.