Quantifying serpentinization-driven remagnetization from ridge axis to subduction zone using quantum diamond microscopy

Journal article

Diachronous ferromagnetic (sensu lato) mineral populations are often juxtaposed on micrometer-to-millimeter scales. This poses significant challenges for extracting reliable paleomagnetic information because standard methods measure bulk magnetic moments and cannot distinguish between magnetic minerals with overlapping demagnetization spectra. However, the recently developed Quantum Diamond Microscope (QDM) enables micrometer scale magnetization imaging of samples with complex remagnetization events. Here we use the QDM to quantify diachronous remagnetizations resulting from serpentinization episodes throughout the life of ophiolites, from the ridge axis where ophiolites form to the subduction zone where they are emplaced. Representative samples with contrasting bulk magnetic properties are selected from the Troodos ophiolite, Cyprus, including weakly and highly magnetic samples. QDM imaging of the weakly magnetic sample suggests that diachronous magnetizations are associated with magnetite-filled microfractures and serpentine recrystallization zones. Dipole fitting of these two zones suggests that microfracture-related magnetization corresponds to the low-field component, while serpentine recrystallization associated magnetization corresponds to the high-field component. QDM imaging of the highly magnetic sample shows magnetic signals associated with magnetite-filled veins, carrying stable magnetization different from the weakly magnetic sample. From oldest to youngest, we interpret the highly magnetic sample as recording magnetization from ridge-axis serpentinization at 90–92 Ma. In the weakly magnetic sample, magnetization in serpentine recrystallization zones reflected mantle wedge serpentinization in the subduction zone at 2.6– 5.3 Ma, while microfracture-related magnetization resulted from meteoric-water serpentinization following the surface exposure of ultramafic rocks between 0.78 and ~2.6 Ma. These different serpentinization episodes are supported by various serpentine δ 18 O values, indicating distinct temperatures.

Authors: Qi, L; Muxworthy, A; Baker, E; Cao, X; Allerton, S

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Geophysical Union
• Journal: Journal of Geophysical Research (JGR): Solid Earth
• Volume: 130
• Issue: 10
• Article number: e2025JB031606
• Publication date: 2025-10-09
• Acceptance date: 2025-10-02
• DOI: 10.1029/2025jb031606
• EISSN: 2169-9356
• ISSN: 2169-9313
• Language: English