REMOTE SENSING OF CARBONATE-RICH ULTRAMAFICS IN SOUTH-EAST MISSOURI

The Avon Volcanic District (AVD) is a ~200 km² area in south-east Missouri's St. Genevieve and St. Francois counties that hosts an ultramafic dike and diatreme complex reported to be a melilitite-alnöite-carbonatite assemblage. Researchers suggest that over eighty intrusions are in the area, yet no comprehensive map or description of these rocks has been published. The currently accepted apparent age of ~390 Ma sets the AVD apart from the majority of ultramafic intrusions globally because of the lack of prominent tectonic activity during the period. The AVD magmatism does not appear to correlate with any major orogenic event, but it might have been penecontemporaneous with deep basement faulting associated with the adjacent St. Genevieve Fault Zone which is normal to and terminates at the Precambrian Reelfoot Rift. The AVD is also located within the south-east Missouri lead-zinc-copper-iron district, host to the nearby Pea Ridge REE deposits. Given the potential insight possible through a detailed understanding of the AVD, our aims are to 1) develop a spectral reflectance database using field and laboratory spectroscopy, 2) locate unidentified dikes and diatremes of the AVD by integrating high spatial resolution hyperspectral and regional gravity data with the spectral database. A mineralogical analysis is conducted on samples from 10 outcrops spanning the district. Qualitative and quantitative analysis is performed using XRD and ICP-MS, which contributes to the validation of spectral signature sources as well as the overall understanding of the AVD. A significant challenge to hyperspectral remote sensing in the study area is the dense vegetative land cover present. Synthetic Aperture Radar (SAR) data is used to address this issue by extracting under canopy geological features associated with the rocks and minerals of interest. In the current environment of growing demand for rare minerals and need for ecologically sensitive exploration, remote sensing is of increasing value. This study presents a novel, non-destructive way of identifying carbonate-rich ultramafics using remote sensing techniques.