Post-rifting stress relaxation at the divergent plate boundary in Northeast Iceland

Foulger, G. R.; Jahn, Cord-Hinrich; Seeber, Günter; Einarsson, Páll; Julian, Bruce R.; Heki, Kosuke

doi:10.1038/358488a0

Cited by 111 publications

(78 citation statements)

References 13 publications

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“…When these sites were reoccupied in 1990, they revealed spreading rates across the plate boundary of up to 6 cm yr -1 , around three times higher than the long-term, far-field average 67 . Average rates, at distances of 50 km and more, had in the 1993-2004 period returned to approximately background levels 68 .…”

Section: Readjustment Following Rifting Episodesmentioning

confidence: 99%

“…Average rates, at distances of 50 km and more, had in the 1993-2004 period returned to approximately background levels 68 . The deformation data have been modelled using a variety of simple viscous 67,69 or viscoelastic 70,71 rheologies, with no magma movement. These models suggest that viscous relaxation occurs under an elastic upper layer that is ~10 km thick, and that the viscosity of the layer that relaxes fastest is in the range of 1-3 × 10 18 Pas (refs 70,71).…”

Section: Readjustment Following Rifting Episodesmentioning

confidence: 99%

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Geophysical constraints on the dynamics of spreading centres from rifting episodes on land

et al. 2012

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Most of the Earth's crust is created along 60,000 km of mid-ocean ridge system. Here, tectonic plates spread apart and, in doing so, gradually build up stress. This stress is released during rifting episodes, when bursts of magmatic activity lead to the injection of vertical sheets of magma -termed dykes -into the crust. Only 2% of the global mid-ocean ridge system is above sea level, so making direct observations of the rifting process is difficult. However, geodetic and seismic observations exist from spreading centres in Afar (East Africa) and Iceland that are exposed at the land surface. Rifting episodes are rare, but the few that have been well observed at these sites have operated with remarkably similar mechanisms. Specifically, magma is supplied to the crust in an intermittent manner, and is stored at multiple positions and depths. It then laterally intrudes in dykes within the brittle upper crust. Depending on the availability of magma, multiple magma centres can interact during one rifting episode. If we are to forecast large eruptions at spreading centres, rifting-cycle models will need to fully incorporate realistic crust and mantle properties, as well as the dynamic transport of magma.

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Section: Readjustment Following Rifting Episodesmentioning

confidence: 99%

Section: Readjustment Following Rifting Episodesmentioning

confidence: 99%

Geophysical constraints on the dynamics of spreading centres from rifting episodes on land

et al. 2012

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“…The coincidence between the zone of magma intrusion and the previously mapped Dabbahu rift segment indicates that magmatic processes establish and maintain along-axis segmentation during continental rupture. Ongoing petrological, geochemical, seismic and geodetic studies will allow us to further probe the number and depth of magma sources, the temporal and spatial distribution of strain along and across the length of the Dabbahu magmatic segment, and the viscous relaxation 26,27 of the lower crust and mantle beneath the rift. …”

Section: (Ref 9)mentioning

confidence: 99%

Magma-maintained rift segmentation at continental rupture in the 2005 Afar dyking episode

Wright

Ebinger

Biggs³

et al. 2006

Nature

512

538

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“…The $5 month average time between the major propagating events should limit the amount of viscoelastic stress relaxation between events to several tens of percent of the syndike stress change [e.g., Foulger et al, 1992].…”

Section: Variables and Constraintsmentioning

confidence: 99%

Tectonic stress and magma chamber size as controls on dike propagation: Constraints from the 1975–1984 Krafla rifting episode

2006

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[1] The best-studied dike intrusion events on a divergent plate boundary occurred along the Krafla segment of the northern rift zone in Iceland from [1975][1976][1977][1978][1979][1980][1981][1982][1983][1984]. Seismic and geodetic measurements there showed that a central magma chamber fed dikes that propagated laterally many times the thickness of the lithosphere. The patterns of dike length, dike width, caldera subsidence, and lava extrusion strongly suggest that dike propagation is affected by tectonic stresses that change with each dike intrusion event and that magma pressures are linked to the dike opening. These observations have inspired us to develop a quantitative model for the lateral propagation of basaltic dikes away from a magma chamber. We assume dikes propagate as long as there is sufficient driving pressure, defined as the difference between magma pressure and tectonic stress at the dike tip. The opening dike and the magma chamber are treated as a closed system for a given dike intrusion event. During an event, magma pressure is reduced linearly with the magma volume withdrawn from the chamber. Relative tectonic tension in the lithosphere is reduced linearly as the dike width increases. A dike begins propagation when the driving pressure equals the ''breakout'' pressure needed to force the magma out of the chamber. It stops when the driving pressure reaches a minimum value. Generally, the dike width is proportional to this ''stopping'' pressure, and a reasonable value gives a width of 1 m. Besides the breakout and stopping pressures, the propagation distance depends on the initial distribution of tectonic stress and the thickness of the lithosphere cut by a dike. The intrusion of a dike changes the tectonic stress distribution so that subsequent dikes may propagate different distances and directions than the first dike. After a period of magma chamber refilling, a new dike can initiate if the breakout pressure is reached. For an idealized spreading segment the tectonic stress field evolves to produce a sequence of dikes propagating in one direction followed by a sequence of dikes propagating in the opposite direction. The first dike in each sequence should be the longest followed by successively shorter dikes. When tectonic stresses close to a magma chamber have been largely relieved, then extrusion of magma may start. The model pattern of dike propagation and extrusion is consistent with data from the Krafla episode. Magma chamber size should have a major effect on magmatic systems in other tectonic settings with larger magma chambers producing longer characteristic dikes.Citation: Buck, W. R., P. Einarsson, and B. Brandsdóttir (2006), Tectonic stress and magma chamber size as controls on dike propagation:

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Post-rifting stress relaxation at the divergent plate boundary in Northeast Iceland

Cited by 111 publications

References 13 publications

Geophysical constraints on the dynamics of spreading centres from rifting episodes on land

Geophysical constraints on the dynamics of spreading centres from rifting episodes on land

Magma-maintained rift segmentation at continental rupture in the 2005 Afar dyking episode

Tectonic stress and magma chamber size as controls on dike propagation: Constraints from the 1975–1984 Krafla rifting episode

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