Abstract Anisotropy of Magnetic Susceptibility (AMS) and Anisotropy of Magnetic Remanence (AMR) are critical petrofabric tools for investigating the evolution of volcano‐magmatic, tectonic, and surface process systems. These highly sensitive techniques can distinguish multiple magnetic fabrics within individual samples, crucial in assessing archives of emplacement and deformation in granitic intrusions where magmatic and tectonic processes occur concurrently or successively. However, mineral phases that dominate AMS and AMR signals are highly susceptible to hydrothermal alteration that may overprint pre‐existing petrofabrics. Despite this, the mechanisms and extent to which hydrothermal alteration modifies magnetic fabrics remain poorly understood, raising concerns about the reliability of interpretations in studies involving hydrothermally altered rocks. This study assesses the significance of magnetic fabrics preserved in a hydrothermally altered fault zone that crosscuts a granitic pluton. Data are collected from unaltered granodiorite peripheral to the fault, the fault damage zone and the fault core to assess the impact of hydrothermal alteration on magnetic fabrics associated with magmatic and tectonic processes. Our integrated magnetic and hyperspectral approach to characterizing alteration type and intensity, combined with measurement of AMS and AMR fabrics, reveal a distinctive magnetic fabric associated with hydrothermal alteration that overprints earlier magmatic and tectonic fabrics. While composite magnetic fabrics are well documented in igneous systems, fabrics that directly record hydrothermal alteration imparting a systematic, measured fabric is incredibly rare and this paves the way for further work on the tracing of fluid flow in fault zones using rock magnetic fabrics as a paleoflow indicator.
Latimer et al. (Sun,) studied this question.