Variability of Sea-Surface Magnetic Anomalies at Ultraslow Spreading Centers: Consequence of Detachment Faulting and Contrasted Magmatism?

F. Zhou (1) , J. Dyment (1)

1 IPGP (UMR_7154) - Institut de Physique du Globe de Paris

The capacity of oceanic crust to record geomagnetic polarity reversals makes sea-surface magnetic anomalies an essential tool to study plate tectonics. The anomalies are usually well-defined at magmatic spreading centers, but are distorted and eventually disappear on magma-poor mid-ocean ridges such as the ultraslow Southwest Indian Ridge (SWIR), making their interpretation difficult. We attribute the variability of the SWIR sea-surface magnetic anomalies to the alternance of magmatic spreading and detachment faulting. A three-layer magnetic model is used to simulate the influence of such an alternance on the sea-surface magnetic anomalies. Conversely, observed magnetic profiles at the SWIR are modeled to unravel their off-axis crustal structure and past mode of spreading. The intruding gabbro bodies on the footwall of detachment faults play a major role in explaining the variability of sea-surface magnetic anomalies at slow and ultraslow spreading ridges.

Mots clés: sea-surface magnetic anomaly; ultraslow spreading centers; degree of magmatism; detachment fault; Southwest Indian Ridge

Domaines: Planète et Univers [physics]; Sciences de la Terre

F. Zhou, J. Dyment. Variability of Sea-Surface Magnetic Anomalies at Ultraslow Spreading Centers: Consequence of Detachment Faulting and Contrasted Magmatism?. Geophysical Research Letters, 2022, 49, ⟨10.1029/2021GL097276⟩. ⟨insu-03643048⟩