Formation of the Igneous Logi Ridge, NE Atlantic

Abstract

The igneous Logi Ridge is located in the NE Atlantic north of the West Jan Mayen Fracture Zone on oceanic crust. The origin of the ridge may relate to the increased influence of the Iceland plume in the Oligocene though the exact mechanism is uncertain. We estimate the igneous volume and magma production rate of the ridge from 10 transects, comprising a refraction profile, six reflection profiles, and three bathymetric profiles. The refraction profile shows up to 12 km crustal thickness of the ridge, and the forward gravity modeling and/or isostatic balancing shows that this is characteristic for most of the ridges. A 3D volume model was created by interpolating between profiles and subtracted the similarly made regional crustal thickness (5–7 km), which gives an excess magma volume of (1.7 ± 0.6) × 1013 m3. The admittance function between bathymetry and gravity indicates an elastic plate thickness of 3–5 km during the main ridge formation. This is consistent with the ridge being built on oceanic crust from Oligocene to earliest Miocene, indicating a main magmatic phase of ∼5 Ma duration, which gives a magma production rate of 0.07–0.15 m3/s, comparable to the Louisville Seamount Chain (LSC). However, the lower crustal velocities of the refraction profile differ from that of the Louisville Guyot in the LSC, suggesting that the melting event was not mainly caused by high mantle temperature, instead it may have been caused in part by the enriched mantle presently seen at the northern end of the Kolbeinsey Ridge to the south.