Temporal and spatial cyclicity of accretion at slow-spreading ridges—evidence from the Reykjanes Ridge.

• Published in: Geophysical Journal International
• Main Authors: Peirce, C., Gardiner, A., Sinha, M. C.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Blackwell 2005
• Subjects: Crustal accretion; Crustal structure; Gravity anomalies; Mid-ocean ridges; Oceanic crust; Residual mantle Bouguer anomaly; Mid-Atlantic Ridge; Reykjanes; Iceland
• Online Access: http://dro.dur.ac.uk/2154/; http://dro.dur.ac.uk/2154/1/2154.pdf; https://doi.org/10.1111/j.1365-246X.2005.02738.x

A unifying model of oceanic crustal development at slow spreading rates is presented in which accretion follows a cyclic pattern of magmatic construction and tectonic destruction, controlled by along-axis variation in melt supply and coupled to along-axis variation in spreading rate and across-axis asymmetry in spreading. This study focuses on the Reykjanes Ridge, Mid-Atlantic Ridge south of Iceland, which is divided along its entire length into numerous axial volcanic ridges (AVR). Five adjacent AVRs have been analysed, located between 57°30'N and 58°30'N and south of any strong Iceland hotspot influence. The seabed morphology of each AVR is investigated using sidescan sonar data to determine relative age and eruptive history. Along-axis gravity profiles for each AVR are modelled relative to a seismically derived crustal reference model, to reveal the underlying crustal thickness and density structure. Correlating these models with seabed features, crustal structure, ridge segment morphology and relative ages, a model of cyclic ridge segmentation is developed in which accretion results in adjacent AVRs with a range of crustal features which, when viewed collectively, reveal that second-order segments on the Reykjanes Ridge have an along-axis length of 70 km and comprise several adjacent AVRs which, in turn, reflect the pattern of third-order segmentation. Tectono-magmatic accretion is shown to operate on the scale of individual AVRs, as well as on the scale of the second-order segment as a whole.