Magnetic Fabric Analysis in Geoscience

Magnetic fabric analysis employs the directional dependence of a rock’s magnetic properties to infer its internal structure and deformation history. Central to this approach is the measurement of anisotropy of magnetic susceptibility (AMS), which quantifies how mineral alignment under stress or flow imparts preferred magnetic orientations. By mapping magnetic foliation and lineation at centimetre to regional scales, researchers can reconstruct tectonic strain, sedimentary stress fields and magma transport pathways. Applications span from dating pulses of crustal shortening in mountain belts to unravelling magma flow dynamics in sills and dykes, and to probing fault zone processes such as frictional heating and fluid percolation. Advances in three-dimensional magnetic imaging and in-phase versus out-of-phase susceptibility measurements now allow fine dissection of sub-fabrics carried by different mineralogies. The growing integration of magnetic fabric data with microstructural, petrological and geochronological evidence underpins its role in deciphering Earth’s structural evolution, with implications for seismic hazard assessment, resource exploration and basin analysis.

Research from Nature Portfolio

Studies of cone-sheet intrusions in central Sweden have shown that oblate magnetic fabrics aligning parallel to sheet orientations can arise not only from primary magma flow but also from post-emplacement sheet closure. A conceptual framework now guides the systematic separation of these processes, integrating AMS with detailed geological mapping to yield more reliable reconstructions of magma transport. In a contrasting structural setting, microstructural analyses of a small-scale shear zone in marble revealed that localisation of deformation produces inverse AMS fabrics controlled by the crystallographic preferred orientations of calcite and Fe-dolomite. Numerical modelling demonstrated that increasing strain leads to a progressive angular deviation between macroscopic foliation and magnetic fabric, emphasising the need to couple magnetic measurements with petrographic context when interpreting strain magnitudes.

Magnetic Fabric Analysis in Geoscience publication trend

The graph below shows the total number of articles in magnetic fabric analysis in geoscience across all publications each year (not limited to Nature Index journals).

Technical terms

Anisotropy of Magnetic Susceptibility (AMS): A measure of the directional dependence of a rock’s magnetic susceptibility, used to infer mineral alignment and strain.

Anisotropy of Out-of-Phase Magnetic Susceptibility (opAMS): The component of magnetic susceptibility that is out of phase with an alternating field, sensitive to magnetically viscous minerals and sub-fabric detection.

Magnetic fabric: The spatial arrangement and orientation of magnetic minerals within a rock that produce measurable anisotropy.

Magnetic foliation and lineation: Planar (foliation) and linear (lineation) features defined by the principal axes of the magnetic susceptibility ellipsoid, corresponding to flattening and elongation fabrics respectively.

References

1. High‐Velocity Slip and Thermal Decomposition of Carbonates: Example From the Heart Mountain Slide Ultracataclasites, Wyoming. Journal of Geophysical Research: Solid Earth (2023).
2. Anisotropy of Magnetic Susceptibility (AMS) Analysis of the Gonjo Basin as an Independent Constraint to Date Tibetan Shortening Pulses. Geophysical Research Letters (2020).
3. Magma transport in sheet intrusions of the Alnö carbonatite complex, central Sweden. Scientific Reports (2016).
4. Anisotropy of Out-of-Phase Magnetic Susceptibility and Its Potential for Rock Fabric Studies: A Review. Geosciences (2022).
5. Localization effect on AMS fabric revealed by microstructural evidence across small-scale shear zone in marble. Scientific Reports (2019).