Reykjanes Ridge evolution: Effects of plate kinematics, small-scale upper mantle convection and a regional mantle gradient

Abstract The Reykjanes Ridge is a key setting to study plate boundary processes overlaid on a regional mantle melting anomaly. The ridge originated as one arm of a ridge-ridge-ridge triple junction that separated Greenland, Eurasia, and North America. It initially formed a linear axis, spreading orthogonally at slow rates without transform faults or orthogonal crustal segmentation. Stable spreading continued in this configuration for ~18 Myr until Labrador Sea spreading ceased, terminating the triple junction by joining Greenland to North America and causing a rapid ~30° change in opening direction across the ridge. The ridge abruptly became segmented and offset by a series of transform faults that appear to decrease in length and spacing toward Iceland. Without further changes in opening direction, the ridge promptly began to reassemble its original linear configuration systematically and diachronously from north to south, even though this required the ridge to spread obliquely as it became linear again. Prominent V-shaped crustal ridges spread outward from the axis as the ridge became linear. This reconfiguration is presently nearly complete from Iceland to the Bight transform fault, a distance of nearly 1000 km. Both mantle plume and plate boundary processes have been proposed to control the tectonic reconfigurations and crustal accretion characteristics of the Reykjanes Ridge. Here we review the ridge characteristics and tectonic evolution and the models proposed to influence them.