Diagram from the article.
Stages of serpentinization during ophiolite formation. (a) Stage 1: Ridge-axis serpentinization during ophiolite formation. (b) Stage 2: Mantle wedge serpentinization in the subduction zone. (c) Stage 3: Meteoric water serpentinization. Credit: Qi et al. [2025], Figure 9
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Geophysical Research: Solid Earth

Magnetic mineral populations that recorded the Earth’s magnetic field during distinct stages of rock formation are often juxtaposed on micrometer-to-millimeter scales. This poses significant challenges for extracting reliable paleomagnetic information because standard methods —which measure the bulk magnetic moment of whole samples— cannot distinguish between magnetic minerals with overlapping demagnetization spectra.

The recently developed Quantum Diamond Microscope (QDM) yield micrometer-scale magnetization images of rock samples, which allow to extract individual magnetization contributions from different structures. Qi et al. [2025] demonstrate the advantage of this new approach with an example from the Troodos ophiolite, Cyprus. QDM measurements of a weakly and a strongly magnetized sample reveal magnetized structures from three distinct serpentinization episodes, from oldest to youngest: ridge-axis serpentinization (strongly magnetized sample, 90-92 Ma), recrystallization zones from mantle wedge serpentinization during subduction (weakly magnetized sample, 5.3-2.6 Ma), and meteoric-water serpentinization following surface exposure (weakly magnetized sample, <2.6 Ma). These episodes are also documented by oxygen isotope measurements indicating distinct alteration temperatures. The QDM technique can be applied to a variety of terrestrial rocks and meteorites with complex magnetization patterns which cannot be disentangled with traditional bulk measurements.

Quantum diamond microscope image of the magnetic field produced by the natural magnetization of minerals inside a rock sample from the Artemis serpentinite diapir, in its untreated from (a) and after demagnetizing the less stable magnetization components with an alternating field (b). Corresponding details from a recrystallization zone formed during subduction (5.3 to 2.6 million years ago) and from a microfracture formed during the latest stage of meteoric water serpentinization, after the rock was emplaced (<2.6 million years ago) are shown in (d, f) and (c, e), respectively. The zoomed details in (h, j) and (g, i) reveal the association between magnetite grains (light-gray structures) and magnetic signals (blue-red hues) in different microstructures. (k-n) Discrete field patterns produced by a single magnetic source, consisting of pairs of positive (red) and negative (blue) anomalies have been fitted with a magnetic dipole model, yielding the magnetization vector orientations shown in the equal area plots with geographical coordinates. Stars show the mean directions for each zone, together with their 95% confidence ellipses. Credit: Qi et al. [2025], Figure 5

Citation: Qi, L., Muxworthy, A. R., Baker, E. B., Cao, X., Allerton, S., Bryson, J. F. J., & Zhang, Y. (2025). Quantifying serpentinization-driven remagnetization from ridge axis to subduction zone using quantum diamond microscopy. Journal of Geophysical Research: Solid Earth, 130, e2025JB031606. https://doi.org/10.1029/2025JB031606

—Ramon Egli, Associate Editor, JGR: Solid Earth

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