Aeromagnetic analysis of the post-collisional Homrit Waggat ring pluton, southeastern Desert, Egypt: Evidence for cauldron subsidence in mid crustal magma chamber

The post-collisional Homrit Waggat ring pluton exposed in southeastern Egypt preserves a record of events in the magma plumbing system at mid-crust depths (∼ 11 km). The pluton consists of two successive granite rings: an inner syenogranite ring (ca. 630–626 Ma) and an outer alkali granite ring (ca. 635 Ma). High-resolution aeromagnetic data in total magnetic intensity were used to construct vertical cross-sections through the pluton to configure its subsurface geometry and internal structure. A reduced-to-pole (RTP) filter was applied to the total magnetic intensity data to position magnetic anomalies directly above their sources. Several derivation techniques were applied to the RTP data, including the tilt-derivation filter (TDR) to highlight the subsurface structural contacts and faults, the analytical signal (AS) technique to delineate the concentric magnetic rings, and both 3D Euler deconvolution and 2D aeromagnetic modeling to analyze the aeromagnetic data and identify the depths of subsurface magnetic sources. Integration of aeromagnetic and petrological data suggests that the ring structure of the Homrit Waggat pluton reflects subsurface cauldron subsidence within a mid-crustal magma chamber, likely driven by the leakage of accumulated hydrous melts and volatiles from the interior of the magma chamber. These findings imply that cauldron subsidence at mid-crustal levels may play a critical role in the emplacement of ring-dyke plutons in orogenic belts without associated volcanic activity.