Elastic flexure controls magma trajectories and explains the offset of primary volcanic activity upstream of mantle plume axis at la Réunion and Hawaii hotspot islands

摘要: Abstract Surface volcanism at la Reunion and Hawaii occurs with an offset of 150–180 km upstream to the plume axis respect plate motion. This striking observation raises questions about forcing plume-lithosphere thermo-mechanical interactions on melt trajectories beneath these islands. Based visco-elasto-plastic numerical models handled kilometric resolution, we propose explain this by development compressional stresses base lithosphere, that result from elastic bending above upward load exerted head. horizontal compression adopts a disc shape centered around axis: (i) it is 20 thick, (ii) has 150 radius, (iii) lays part i.e., ∼50–70 depth where temperature varies ∼600 °C ∼750 °C, (iv) lasts for 5 10 My in oceanic age greater than 70 My, (vi) controlled visco-elastic relaxation time depth. period exceeds during which both Somalian/East-African Pacific plates drift over plumes, respectively. indicates basal actually persistent feature. It inferred buoyant melts percolating head pond below zone eventually spread laterally until most compressive principal reverse vertical, ∼150 away There, propagate through dikes upwards ∼35 depth, curvature reverses ambient diminishes. 30–35 may thus host magmatic reservoir transported dykes pond. Only after further differentiation can resume their ascension up surface begin forming volcanic edifice. As volcano grows because accumulation top plate, lithosphere flexed downwards, inducing extra tensile stress ∼15 (induced edifice load). implies now form another lying just underneath crust. These processes ponding primary (shield) depths as recorded La Reunion, Mauritius or volcanoes, all shifted axis.