Preliminary test of the potential in magnetic scanning of cold-water coral using Quantum Diamond Microscope

Cold-water coral (CWC) provides critical insights into annual-to-decadal environmental changes in intermediate/deep oceans. The Quantum Diamond Microscope (QDM) enables high-sensitivity magnetic detection at nano-to-micron scales， offering a novel approach for examining the magnetic characteristics of CWCs. In this study， we explore the magnetic properties of a CWC sample (SY185-9) collected from the Ganquan Seamount in the South China Sea by the "Shenhai Yongshi" HOV. Analysis of the hysteresis loop， isothermal remanent magnetization (IRM) acquisition curve， and first-order reversal curve reveals that the magnetic minerals in coral SY185-9 are primarily low-coercivity detrital magnetite. Magnetic scanning performed under a 100 mT IRM field using the QDM reveals a quasi-symmetrical fluctuation pattern， with axial distribution of magnetic minerals aligning with vessel-like structures. Comparison with elemental data shows a strong correlation between the IRM record and the Mg/Ca ratio， suggesting that seawater temperature could be a primary driver of magnetic variability. These findings indicate that detrital magnetite in SY185-9 might represent contamination， while the vessel-like magnetic enrichment possibly reflects a connection to the metabolic activity of CWCs. Based on these observations， this study highlights the potential of magnetic mapping as an alternative method for investigating CWC growth and intermediate/deep ocean dynamics.