A Magnetic Signature of Volcanogenic Massive Sulphide (VMS) Deposits: An Example from the Hawiyah Area, Western Saudi Arabia

This study examines the magnetic signature of subsurface structures associated with volcanogenic massive sulphide mineralization in the Hawiyah area, in western Saudi Arabia, through an integrated analysis of ground magnetic surveys and magnetic susceptibility measurements. High analytic signal amplitudes are primarily concentrated in the western and central parts of the study area, largely coinciding with the surface expression of the main ore body. In contrast, the eastern greenstone belt shows subdued responses with minimal magnetic variation. The analytic signal, supported by self-potential data, reveals a central linear negative self-potential anomaly that closely aligns with magnetic anomalies, indicating a strong geophysical expression of mineralization. Depth estimations derived from the Werner and analytic signal methods indicate that magnetic sources are predominantly shallow (less than 4.9 m), with near-vertical apparent dip geometries. Amplitude factor analysis reveals variability across the mineralized zone. Magnetic susceptibility measurements from core samples support these findings, showing elevated values in fresh massive sulphide rocks (average value of 67.41 × 10⁻³ SI), declining progressively in transition and oxide zones. Lithological controls are evident, with greenschist, intermediate dikes, and quartz veins exhibiting distinct susceptibility patterns tied to alteration states. The study results demonstrate that integrating ground magnetic data and magnetic susceptibility measurements offers a powerful approach for delineating near-surface sulphide mineralization, providing a framework for targeting sulphide-rich zones in similar geological settings across the Arabian Shield.