| Summary: | Author Posting. © American Geophysical Union, 20222. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 127(3), (2022): e2021JB023244, https://doi.org/10.1029/2021jb023244. Spatial variations in mantle melting induced by the Iceland hotspot have strong effects on meso-scale mantle upwelling and crustal production along the slow-spreading Reykjanes Ridge. The ridge-hotspot interaction has been recorded by diachronous V-shaped ridges and troughs extending away from Iceland, as well as by changes in ridge segmentation since 37 Ma. The origins of V-shaped structures are widely debated, while the causes of the gradual erasion of ridge segments bounded by transform faults are rarely investigated. Through 3D time-dependent geodynamic modeling, this study investigates how the hotspot-induced regional mantle melting variations affect ridge segmentation. Periodic temperature perturbations were initially imposed beneath the melting zone to trigger buoyant upwelling cells, which corresponded to the offset ridge segments at the Reykjanes Ridge. Iceland hotspot-induced long-wavelength mantle melting variations were generated by applying a regional linear temperature gradient at the bottom of the model domain. Modeling reveals a two-stage evolution of the buoyant upwelling cells that characterizes the segmentation transition at the Reykjanes Ridge. In Stage 1, the regional mantle melting variations trigger along-axis pressure-driven mantle flow, which alters the segment-scale mantle upwelling and promotes the propagation of segment boundaries away from the region with relatively higher mantle temperature. In Stage 2, buoyant upwelling cells are destroyed progressively as along-axis mantle flow dominants, leaving V-shaped diachronous boundaries between the segmented and unsegmented crust. These results advance our understanding of the effects of long-wavelength mantle melting ...
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