Abstract
Ocean plates conductively cool and subside with seafloor age. Plate thickening with age is also predicted, and hot spots may cause thinning. However, both are debated and depend on the way the plate is defined. Determining the thickness of the plates along with the process that governs it has proven challenging. We use S‐to‐P (Sp) receiver functions to image a strong, persistent LAB beneath Iceland where the mid‐Atlantic Ridge interacts with a plume with hypothesized pulsating thermal anomaly. The plate is thickest, up to 84 ± 6 km, beneath lithosphere formed during times of hypothesized hotter plume temperatures and as thin as 61 ± 6 km beneath regions formed during colder intervals. We performed geodynamic modeling to show that these plate thicknesses are inconsistent with a thermal lithosphere. Instead, periods of increased plume temperatures likely increased the melting depth, causing deeper depletion and dehydration, and creating a thicker plate. This suggests plate thickness is dictated by the conditions of plate formation.
Highlights
The lithosphere-asthenosphere boundary (LAB) represents the base of the tectonic plate, a fundamental boundary in plate tectonics
Since it is well established that temperature plays a large role in the strength of materials, the LAB is typically assumed to follow an isotherm (Parsons & Sclater, 1977), with ocean plates progressively thickening as they cool and age (Parsons & Sclater, 1977) and thinning in the presence of hot spots (Detrick & Crough, 1978)
The phase may be associated with the lithosphere-asthenosphere boundary, which will be assessed in subsequent sections
Summary
The lithosphere-asthenosphere boundary (LAB) represents the base of the tectonic plate, a fundamental boundary in plate tectonics. Since it is well established that temperature plays a large role in the strength of materials, the LAB is typically assumed to follow an isotherm (Parsons & Sclater, 1977), with ocean plates progressively thickening as they cool and age (Parsons & Sclater, 1977) and thinning in the presence of hot spots (Detrick & Crough, 1978) In this model, seismic velocities are predicted to gradually decrease from the lithosphere to the asthenosphere (Jackson & Faul, 2010; Rychert et al, 2010; Tharimena et al, 2017; Rychert & Harmon, 2018). The exact relationship between composition and/or melt variations and plate thickness has yet to be established
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