Melt Production and Ridge Geometry Over the Past 10 Myr on the Southern Kolbeinsey Ridge, Iceland

Abstract

Excess melt production due to the interaction between the northern Mid-Atlantic Ridge and the Iceland mantle plume generates anomalously thick oceanic crust. Observed V-shaped gravity anomalies on the Reykjanes Ridge south of Iceland are inferred to reflect changes in melting with a periodicity of 5-6 Ma. A 2-D tomographic inversion of travel times recorded on a seismic refraction line on the Kolbeinsey Ridge north of Iceland constrains crustal velocity and Moho depth. I do not find increased melt production on a 5-6 Ma period, but with a period of ~8-9 Ma, with Moho depth varying from 7.8 - 12.5 ± 0.5 km. Unlike the Reykjanes Ridge, the thickest crust does not correspond with a high gravity anomaly. However, it is a region of slow p-wave velocities and significant decay of magnetic signal. I interpret the V-shaped anomaly in this region to record the northward migration of a ridge segment offset.