Volcanism and hydrothermalism on a hotspot–influenced ridge: Comparing Reykjanes Peninsula and Reykjanes Ridge, Iceland

• Published in: Journal of Volcanology and Geothermal Research
• Main Authors: Palgan, Dominik, Devey, Colin W., Yeo, Isobel A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2017
• Subjects: Reykjanes; Iceland
• Online Access: https://oceanrep.geomar.de/id/eprint/40027/; https://oceanrep.geomar.de/id/eprint/40027/1/1-s2.0-S0377027317300616-main.pdf; https://oceanrep.geomar.de/id/eprint/40027/7/Palgan.pdf; https://doi.org/10.1016/j.jvolgeores.2017.10.017

Highlights • Formation of Axial Volcanic Ridges is more complex than previous models suggest. • Faults on the Reykjanes Ridge strike orthogonal to spreading direction. • Seamounts and fault densities reflect volcanic robustness of Axial Volcanic Ridges. • Steinahóll Vent Field occupies shallow eruptive fissure located between two faults. Abstract Current estimates indicate that the number of high-temperature vents (one of the primary pathways for the heat extraction from the Earth's mantle) – at least 1 per 100 km of axial length – scales with spreading rate and should scale with crustal thickness. But up to present, shallow ridge axes underlain by thick crust show anomalously low incidences of high-temperature activity. Here we compare the Reykjanes Ridge, an abnormally shallow ridge with thick crust and only one high-temperature vent known over 900 km axial length, to the adjacent subaerial Reykjanes Peninsula (RP), which is characterized by high-temperature geothermal sites confined to four volcanic systems transected by fissure swarms with young (Holocene) volcanic activity, multiple faults, cracks and fissures, and continuous seismic activity. New high-resolution bathymetry (gridded at 60 m) of the Reykjanes Ridge between 62°30′N and 63°30′N shows seven Axial Volcanic Ridges (AVR) that, based on their morphology, geometry and tectonic regime, are analogues for the volcanic systems and fissure swarms on land. We investigate in detail the volcano-tectonic features of all mapped AVRs and show that they do not fit with the previously suggested 4-stage evolution model for AVR construction. Instead, we suggest that AVR morphology reflects the robust or weak melt supply to the system and two (or more) eruption mechanisms may co-exist on one AVR (in contrast to 4-stage evolution model). Our interpretations indicate that, unlike on the Reykjanes Peninsula, faults on and around AVRs do not cluster in orientation domains but all are subparallel to the overall strike of AVRs (orthogonal to spreading direction). High ...