DON’T CALL IT A COMEBACK: MINERAL RESOURCES OF THE REACTIVATED REELFOOT RIFT, THE ARKANSAS ALKALINE PROVINCE, AND INSIGHTS FROM NEW HIGH-RESOLUTION AIRBORNE MAGNETIC DATA

The Arkansas alkaline province (AAP) encompasses a series of mid-Cretaceous alkaline and carbonatitic intrusive complexes located near the intersection of the late Paleozoic Ouachita orogenic belt and the northwestern margin of the failed late Precambrian Reelfoot rift in the southern Midcontinent, USA. Intrusions exposed at the surface have been studied extensively and are recognized to be significant critical mineral production sites with active and historic mining. Critical minerals present in the province include Al, Ba, Ti, V, Nb, Li, and the carbonatites are permissive for rare earth elements. Also notable is the diamondiferous lamproite at Prairie Creek, which hosts the Crater of Diamonds State Park. The northwest margin of the Reelfoot rift is lined by mafic-to-ultramafic intrusions, some of which have been mapped at the surface while others are inferred from geophysical data and confirmed by drilling. The intrusions are marked by coincident positive magnetic and gravity anomalies. The Reelfoot rift axis includes the active New Madrid Seismic Zone. These features are products of recurrent tectonic activity during multiple Wilson Cycles. Extension and re-activation of the Reelfoot rift are thought to have resulted in a thinned, weakened crust that facilitated mantle upwelling and emplacement of the AAP alkaline and carbonatitic intrusions. The magnetic intrusive rocks strongly contrast with the relatively non-magnetic sedimentary country rocks of the Ouachita orogen, resulting in distinct anomalies over the AAP intrusions. New airborne magnetic data acquired by the United States Geological Survey in 2022-2023 improve upon the resolution of legacy data by more than double (800 m vs 300 m flight-line spacing). The high-resolution data reveal new intrusive features interpreted to be related to the AAP and subtle changes associated with known but mostly concealed breccias and dikes that have been only partially mapped due to cover and erosion. The modern survey data reveal finer details within the larger mineralized alkaline intrusive complexes at Magnet Cove and Granite Mountain. Insights revealed by the new aeromagnetic data have implications for the mineral resource potential across the province.