Continental Hotspots Tracks From an Analysis of GOCE Gravity Gradients Data

Abstract

AbstractThis study aims to detect residual thermal anomalies along the path of a hotspot beneath the continental lithosphere using gradiometry data. We calculate perturbations in gravity vectors and gradients by employing a simple thermal anomaly model. The results highlight that the horizontal components of Bouguer gravity gradients, sensitive to source structure and elongation, exhibit substantial magnitudes, exceeding current detection levels. To improve signals from sources of different sizes and orientations, we apply a filtering approach involving wavelet transforms and rotated local frames. We also assess the impact of lateral crustal variations on the gravity field by introducing random density anomalies and a seismic crustal model, testing the method's ability to distinguish between these anomalies and thermal sources. Using Gravity field and steady‐state Ocean Circulation Explorer satellite data, we generated scale‐orientation diagrams aiming to identify signals aligned with the direction of plate movement and with a spatial scale of a few hundred kilometers (scale of the plumes). Maps of filtered Bouguer gravity gradients aligned with hotspot trajectories are generated for all continental hot plumes, with the position and the age of the intraplate volcanism to support the interpretation. While we do not show a clear signal in regions that are too tectonically complex or with lateral variations in the crust or at the lithospheric boundary correlated with the hotspot trace, we found observed signals with expected sign and amplitude over Hoggar, Tibesti, Darfour and Cameroon tracks in Africa and over Iceland and Jan Mayen in Greenland. However, determining corresponding mass source depths remains a complex task.