Quantifying Contributions of Magnetic Inclusions Within Silicates to Marine Sediments: A Dissolution Approach to Isolating Volcanic Signals for Improved Paleoenvironmental Reconstruction

Abstract

Silicate-hosted magnetic inclusions are a widespread fine grained magnetic component in marine sediments. However, their paleomagnetic and paleoenvironmental significance remains elusive as they are often overshadowed by unprotected detrital and biogenic magnetic components. We developed a protocol to extract silicate inclusions from sediments sampled from the central Pacific and the Okhotsk Sea. Our results show that the threshold condition (hydrochloric acid 10 mol/L with a reaction time of 24 h) can efficiently remove biogenic and unprotected magnetic phases and preserve silicate hosted magnetic inclusions that manifest a wide coercivity spectrum ranging between 10 and 300 mT with a median coercivity of ∼100 mT based on systematic rock magnetic analyses. This approach was applied to the Okhotsk Sea sediments, whose magnetic phases are dominantly derived from surrounding volcanic formations, spanning the last interglacial period. The residues after dissolution present a similar temporal variation compared to the bulk magnetic signal despite significant drops in amplitude. This suggests that the preserved signals of silicate inclusions can qualitatively represent the volcanic component. We suggest that when applied to sediments with complex magnetic components, this approach has the potential to extract volcanic components for paleoenvironmental reconstructions.