AEROMAGNETIC DATA PROVIDE A FRAMEWORK FOR CONCEALED MINERAL RESOURCE POTENTIAL OVER AN ACCRETED ISLAND-ARC SETTING IN SOUTHWEST ALASKA

Southwest Alaska presents a challenging environment for mineral exploration as the bedrock geology is largely concealed beneath Quaternary sediments. Regional-scale aeromagnetic data provide a continuous set of observations and show contrasting patterns over the igneous rock suites hosting a number of different mineral deposit types in the region. Combined with surface geological data and regional metallogenic constraints, aeromagnetic data, filtered to enhance the anomalous magnetic field and map magnetic domains, were used to produce a mineral potential map. The reduced-to-pole, upward continuation, and total horizontal gradient transform maps show anomalies that could represent porphyry-epithermal deposits within the intra-oceanic and continental arc terranes. Three dimensional magnetic inversion models indicate that the magnetic source for these anomalies extends to deep crustal levels. The tilt derivative transform highlights lineaments within the back-arc that may represent zones with potential for volcanogenic massive sulfide deposits. The truncations of tilt derivative lineaments outline a major magnetic domain boundary between the back-arc and craton margin, which is prospective for granitoid Sn-W deposits. Annular tilt derivative highs outline granitoids that could be associated with intrusion-related Au deposits within the craton margin. Shallow, magnetite-rich Alaska-type ultramafic-mafic complexes are mapped by their short-wavelength, high-amplitude anomalies. Using metallogenic models to help interpret aeromagnetic data is an effective way to understand concealed geology and mineral resource potential across an accreted island-arc margin.