Remote sensing and geophysical exploration for uranium-mineralized breccia pipes in Northwestern Arizona, USA

Abstract

Exploration for uranium-mineralized breccia pipes in northwestern Arizona, USA, has generated interests for several years. These deposits contain high-grade uranium ore and by-products such as Ag, Au, Cu, Pb, Zn, and V. The breccia pipes were formed from the collapse of the overlying sedimentary strata into karst caverns developed in the Mississippian Redwall Limestone. The breccia pipes are known to occur in clusters and are commonly observed along the cliffs of the Grand Canyon and other near-by canyons. On undissected areas of northwestern Arizona part of the Colorado Plateau, the pipes appear as circular features with concentrically inward dipping beds. For most of the known deposits, hydrothermal alteration associated with the uranium- mineralization is concealed under veneer of soil. In this study, digitally enhanced Landsat Thematic Mapper (TM) images were used to identify more than 80% of previously known orebodies as well as additional anomalies. In addition, digital image processing and integration of datasets were used to develop exploration models from airborne electromagnetics (EM) , mangetics and very-low-frequency electromagnetics (VLF-EM) data collected over an area in northwestern Arizona. One of the best models incorporated apparent resistivity and total magnetic; the results of this model outlined 13 anomalous areas for further investigation.