ORIGINAL RESEARCH article
Front. Earth Sci.
Sec. Geomagnetism and Paleomagnetism
This article is part of the Research TopicGeophysical Electromagnetic Exploration Theory, Technology and ApplicationView all 13 articles
Low-Temperature Magnetic Properties of Deeply Buried Gas Hydrate Bearing Sediments: A Case Study from IODP Expedition 375 Site U1519C in the Hikurangi Subduction Zone, New Zealand
Provisionally accepted
- Guilin University of Technology, Guilin, China
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The diagenetic pathways, mineral types, and products of magnetic minerals in gas hydrate-bearing sediments are closely linked to burial depth. During IODP Expedition 375, drilling at the northern Hikurangi margin recovered 83.09 m of core from the gas hydrate stability zone (518.4–640.0 m depth) at Site U1519C. This provides an exceptional opportunity to investigate progressive diagenesis and fluid-driven late-stage diagenesis in deeply buried gas hydrate-bearing sediments. We conducted low-temperature magnetic measurements on 13 samples from this interval, including: (i) Low-temperature cycling (LTC) cycles, (ii) Zero-field-cooled (ZFC) and field-cooled (FC) curves, (iii) Low-temperature hysteresis loops, and (iv) Low-temperature alternating current (AC) magnetic susceptibility. Using features such as low-temperature transitions and curve trajectory patterns, we determined the types, concentrations, and assemblages of magnetic minerals, analyzed the origins of magnetic particles. Key results reveal: (1) Deeply buried sediments exhibit notably low SIRM intensity, indicating scarce magnetic minerals dominated by superparamagnetic (SP) and single-domain (SD) particles. This indicates that the deeply buried sediments experienced extensive pyritization under sustained reducing diagenetic conditions; (2)Despite the dominance of SP signals in the low-temperature FC/ZFC curves, the observation of the Verwey transition at ~118 K—a characteristic low-temperature phase transition stemming from magnetite's structural transformation—provides definitive evidence for the presence of trace magnetite even at such depths (>580 mbsf); (3) A double Verwey transition (~106 K and ~118 K) was observed in some samples, which indicates the coexistence of biogenic magnetite and nearly stoichiometric magnetite; (4) Authigenic Greigite (Fe₃S₄), an intermediate product of pyritization (FeS₂), is detected. Some greigite likely exists as SP particles, while a low index of hysteresis parameters (DJH) indicates limited contributions from stable SD greigite among ferrimagnetic minerals.This study provides low-temperature magnetic evidence for diagenetic processes affecting magnetic minerals in deeply buried gas hydrate-bearing sediments. It reveals partial magnetite preservation, greigite formation and transformation, and ultimate pyritization, offering new insights into magnetic mineral evolution in such environments.
Keywords: Gas hydrate-bearing sediments, Low-temperature magnetism, magnetic mineraldiagenesis, Northern Hikurangi margin, IODP Expedition 375
Received: 15 Jul 2025; Accepted: 28 Nov 2025.
Copyright: © 2025 Liu, Li and Xu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Xuesen Li
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