Conductivity-elevated by brucite amorphization and implication for electrical anomalies in shallow subduction zones

Pervasive high-conductivity anomalies in shallow cold subduction zones (40–70 km depths, corresponding to 1–2 GPa) remain unexplained by conventional mechanisms (e.g., dehydration fluids). Here we report a dramatic enhancement in brucite’s electrical conductivity at 1.2–2.0 GPa and 300–400 °C: conductivity rises sharply by 2–3 orders of magnitude over just 100 °C, ultimately reaching peak values of ~10−2 S/m, through integrated multi-anvil press experiments and in situ impedance spectroscopy analysis. Comprehensive post-experiment characterization of quenched samples confirms brucite preservation with no detectable dehydration byproducts (e.g., periclase). High-resolution transmission electron microscopy identifies high temperature-triggered distinct amorphous regions along grain boundaries above 300 °C, indicating conductivity enhancement arises from amorphization-facilitated proton transport in brucite. This result implies that high-conductivity anomalies in most shallow cold subduction zones likely originate from the amorphization of hydrous minerals (e.g., brucite), shedding light on the global water cycle and Earth’s deep electrical structure. The amorphization of brucite can increase its conductivity at 1 − 2 GPa and 300 − 400 °C, thereby causing high-conductivity anomalies in shallow cold subduction zones, as revealed through integrated multi-anvil press experiments and in situ impedance spectroscopy analysis.