How diking affects the tectonomagmatic evolution of slow spreading plate boundaries: Overview and model

Abstract

Recent diking episodes along slow spreading boundaries included the generation of normal faults, showing that extension is accommodated, on a scale of a few years or less, by both magma intrusion and fault movement. Here we aim to define how diking may affect the overall rift structure on the longer term (=100 yr). We first summarize the main features of the transient diking episodes as obtained from geological, geophysical, geodetic, and modeling studies. We then put these episodes into a broader context, considering the overall longer term shallow and deep structure of the plate boundaries. The synthesis of the data shows that in Iceland crustal extension at depth largely occurs by means of dikes, with negligible normal faulting; faults focus toward the surface (<1 km depth), forming dike-induced grabens commonly propagating downward; along-rift diking episodes (1 in ~200 yr) may induce all the observed surface deformation. The close similarities with transitional (Afar Rift) and magmatic continental rifts (East African Rift System) suggest that repeated diking induces most of the surface deformation along slowly spreading (≤2 cm/yr) magmatic plate boundaries. The frequency of diking and the induced strain may not allow extension to be accommodated amagmatically, through creep or seismic or aseismic faulting. This implies that a diking episode locks any amagmatic faulting until the strain is released (centuries), when the subsequent diking episode occurs, with the cumulative result of controlling and shaping the evolution of slow spreading magmatic plate boundaries. This process appears independent of the stage of magmatic rifting

The Effect of Obliquity of Slip in Normal Faults on Distribution of Open Fractures

“…This can result in fissure eruptions and lava flows filling the MDF (B). (Acocella and Trippanera, 2016). These may represent areas where the connection between the feeder dike and fracture has not yet been established, or where rifting was fast enough that a new dike formed before fracture and dike connected.…”

The Relationship Between Lava Fountaining and Vent Morphology for the 2014–2015 Holuhraun Eruption, Iceland, Analyzed by Video Monitoring and Topographic Mapping

“…Two characteristic transform fault zones are developed, defining the Eastern and the Northern Volcanic Zones, which are associated with several central volcanoes and attached fissure swarms (Thordarson and Larsen, 2007). During rifting events, the fissure swarms are fed by dikes that drive magma laterally away from the central volcanoes (e.g., Acocella and Trippanera, 2016;Medynski et al, 2016). These dikes generate large deformation and normal faulting, such as during the 2014-2015 Holuhraun eruption (Sigmundsson et al, 2015;Ruch et al, 2016).…”

Tectonic Geomorphology and Volcano-Tectonic Interaction in the Eastern Boundary of the Southern Cascades (Hat Creek Graben Region), California, USA

“…At these spreading plate boundaries, extension at depth seems to be accommodated mostly by diking, with normal faulting playing a negligible role. In shallower layers, normal faults and extensional tectonic structures accommodate the deformation, alongside a few feeder dikes (Acocella and Trippanera, 2016, and references therein).…”

“…Volcano morphology is a result of recurring volcanic activity within this diverse tectonic setting, from more than 500 vents over the past 7 Ma (Muffler et al, 1994), making it an important place to study the long-term interrelationship between tectonics, geomorphology, and volcanic activity. Many studies have recently explored the importance of magma in shaping divergent plate boundaries (Wright et al, 2006;Ebinger et al, 2010;Sigmundsson et al, 2015;Acocella and Trippanera, 2016), and here we seek to discern whether some of these ideas also apply to intraplate magmatic provinces experiencing extension, such as the Hat Creek Graben region.…”