Motions of the Kerguelen hotspot constrained by high-precision 40Ar/39Ar ages of the Ninetyeast Ridge

Hotspots create linear volcanic features on Earth’s crust as tectonic plates migrate over and thus are often used to trace absolute plate motion. The effectiveness of a hotspot reference frame depends on the hotspot’s fixity or constraints on its motion history. Studies of Pacific hotspots revealed distinct hotspot motions that were variously attributed to shallow and/or deep mantle convection processes, but knowledge of hotspot movements elsewhere remains limited. Here we report robust and high-precision ⁴⁰Ar/³⁹Ar ages for the Ninetyeast Ridge, a >5000-km long linear volcanic ridge generated by the Kerguelen hotspot during the Indian Plate’s northward drift towards Eurasia. New ages suggest changing volcanic progression rates along the ridge, in contrast to a constant rate as previously documented. Combined with independent constraints on the Indian Plate motion and seafloor spreading, we reveal two periods of northward hotspot migration together with the Indian-Antarctic spreading ridge, and two periods of rapid southward motion of the hotspot when it was disconnected from and re-captured by separate spreading ridge segments. These rapidly changing motion histories affected by spreading ridges suggest that mantle plume lateral flows are susceptible to changes in shallow mantle convection processes due to the existence of horizontal ponding zones and vertical conduits as revealed by recent seismic tomography images of mantle plumes.