Geodetic and Geophysical Evidence for Magma Movement and Dyke Injection During the Krafla Rifting Episode in North Iceland
- John M. Sinton
Published Online: 19 MAR 2013
Copyright 1989 by the American Geophysical Union
Evolution of Mid Ocean Ridges
How to Cite
Jocoby, W. R., Zdarsky, H. and Altmann, U. (1989) Geodetic and Geophysical Evidence for Magma Movement and Dyke Injection During the Krafla Rifting Episode in North Iceland, in Evolution of Mid Ocean Ridges (ed J. M. Sinton), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM057p0065
- Published Online: 19 MAR 2013
- Published Print: 1 JAN 1989
Print ISBN: 9780875904580
Online ISBN: 9781118666449
- Sea—floor spreading—Congresses;
- Mid-ocean ridges—Congresses
An accretionary episode occurred along about 100 km of Mid-Atlantic Ridge axis in N-Iceland since 1975. Repeated observations of point positions, elevations and gravity in the region (by various Icelandic and German groups) have provided ample data on local and regional deformation and gravity change (observed Δg. Free Air anomaly ΔFA, and Bouguer anomaly ΔBA). From these data it is possible to model, at least in part, the source geometry of deep (upper mantle) magma transport, of magma chambers below the Krafla volcanic complex, and of dyke injections into the accretionary fissure swarm. The three data sets of horizontal and vertical displacements and of gravity can, however, not be fitted exclusively by the source characteristics as geometry, pressure, dislocations, and mass or density, but they constrain also the lateral and vertical elasticity structure of the confining medium; an elastic half space is too simple a model.
We have applied analytical and numerical modeling and leastsquares optimization; in spite of the model simplicity the results are quite satisfactory. The increments of dyke injection agree well with the seismicity in space and time characterizing the individual injection events. The short-wavelength BA correlates with fissure swarms belonging to presently inactive volcanic systems. The long-wavelength BA indicates that hot, low-density magma moved into the region along the axis of the neovolcanic zone at crust-mantle transition depths. This transition must be modeled as a region of magma accumulation. Seismicity suggests rather long-distance hydraulic connections in the axial rift zone which is interpreted to represent the “deep” expression of the plate boundary.