HotStuff - Lateral dikes during the 1975–1984 Krafla rifting episode in Iceland: Re-examination of the role of tectonic stress and topography: Yilin Yang

The spatial pattern of repeated lateral dike intrusions in a rift zone depends on pressure build-up and conditions where magma accumulates prior to dike events, along with external factors including tectonic stress and topography. We reexamine the effects of these factors on the spatial distribution of dike openings during the 1975–1984 Krafla rifting episode in north Iceland, when about 20 dikes were injected in sub-sequences, to the north or south of the Krafla caldera. A simplified elastic model of rifting by Buck et al. (2006) is revised such that topographic gradients and tectonic stress supply driving pressure for lateral dike propagation, but dike opening is limited by tectonic stress. In the model, dikes propagate while driving pressure increases and stop expansion when it decreases to zero. The observed dike pattern is consistent with magma flowing laterally from an inlet under the northern part of the Krafla caldera where the elevation is highest. A plausible set of model parameters predicts (i) a relatively low magma overpressure of 0–10 MPa at the inlet prior to the first and largest dike of the sequence, compared to >20 MPa of driving pressure contributed by tectonic stress and topographic effects, (ii) flow into later dikes when magma pressure at the inlet is less than the lithostatic, (iii) higher breakout pressure for the first dike than the later dikes by a factor of 2. The model is also applied to the three rifting events 2023-2024 at Sundhnúkur crater row, SW Iceland.