New Evidence Supporting the Pacific Mantle Outflow: Hints from Crustal Magnetization of the Phoenix Plate

Abstract

Magnetic contributions to the Earth’s magnetic field within the lithosphere are known as magnetic anomalies. Magnetic anomaly maps provide insight on magnetic properties of subsurface rock, geological structures, and plate tectonic history. A small number of studies have analyzed the Phoenix Plate based on magnetic anomaly data. These focused on its tectonic evolution. Here, we study the crustal magnetization of this region and combine the results with additional information from high-resolution bathymetry and complete Bouguer gravity anomalies. We analyzed the horizontal variation of the magnetization in two spectral domains: one that resolves the medium and long wavelengths magnetization components (20–200 km), and another one that focuses on short wavelengths (7–100 km). The obtained magnetization amplitude for the 20–200 km range reveals the presence of NE–SW and NW–SE high trends in magnetization. We attribute these alignments to induced magnetism. For the range of 7–100 km, the magnetization amplitude shows a progressive decrease towards the southern part of the Phoenix Plate. The obtained magnetization pattern and the integration with additional geophysical and geological information indicates a thermal demagnetization of the oceanic crust in the south, possibly caused by the Pacific mantle outflow present in this region.

Keywords

• magnetization
• heat flow
• gravity anomalies
• magnetic anomalies