REGIONAL GRAVITY SURVEY TO AID IN DETERMINING THE REE POTENTIAL OF THE PEA RIDGE MINE AND THE SURROUNDING AREA, SOUTHEAST MISSOURI

The Pea Ridge mine and surrounding area in Southeast Missouri is historically known for large magnetite and hematite deposits hosted in Precambrian granitic rocks that have produced significant amounts of iron ore in the past. Airborne magnetic studies that were conducted from the 1930s through the 1950s originally located a number of these deposits but lack the data quality to fully delineate the nature of the deposits. Renewed interest in these deposits occurred with the discovery of iron-oxide, heavy rare earth elements (REE) within breccias pipes approximately 300-400 meters in depth within the Pea Ridge mine. To further investigate the REE potential of the Pea Ridge mine and the surrounding Precambrian terrane, a geophysical investigation was undertaken to determine if gravity and electromagnetic data can delineate additional REE deposits. The available gravity data which contains as few as three and rarely more than a dozen points per 7.5 minute topographic quadrangle within and surrounding the Pea Ridge deposit, show a small amplitude gravity minimum corresponding to the magnetic high over the Pea Ridge deposit. To enhance this database, a regional gravity survey of this area was undertaken to both improve the general regional gravity anomaly map in this poorly studied area, and to investigate the magnitude and extent of previously identified anomalies that may be related to breccia pipes that may contain REE. The analysis of gravity data will include the construction of residual gravity anomaly maps, a variety of derivative maps and 2.5- and 3-dimensional models constrained by density measurements from surface and subsurface samples.