Uranium Deposits in Collapse Breccia Pipes in the Grand Canyon Region, Colorado Plateau, USA

By Franz J. DAHLKAMP With 4 figures and 1 table in text Received 1989, November 10th

Introduction The uranium district is located in the Arizona Strip area, to the north and south of the Grand Canyon, northwestern Arizona. Numerous solution collapse breccia pipes (not to be confused with diatreme pipes) crop out on the plateaus and in the canyons. Some contain economic Cu, Pb, Zn, Ag, and/or U mineralization. Mining in breccia pipes started at the end of the last century, at the beginning primarily for copper (ore grades <15% Cu). Later, during the 1950's and 1960's, the Orphan Lode (headframe still visible a short distance to the west of Grand Canyon village on south rim of the Grand Canyon) was exploited for uranium with Cu and Ag as byproducts (production ca. 1900 t U3OS at an ore grade of 0.43% U3O8, 3000 t Cu, 3400 kg Ag). Revived exploration in the 1970's and 1980's resulted in new discoveries of uranium ore bearing pipes which are shown in Figure 1. Mineable breccia pipes contain uranium reserves in a range from a few hundreds to about 2500 t U3OS. Total reserves discovered so far are in the order of about 14000 t U3Ü8 contained in about 15 pipes. Production grades are high averaging from 0.4 to 0.8% U3O8 and locally more. Ag, Cu and V are recoverable from some of the lodes. The following presentation is a synopsis of a chapter in „Uranium Ore Deposits", DAHLKAMP 1990, Springer Verlag, and the reader is referred to this book for details of breccia pipe uranium deposits including extentive bibliography, and for other uranium deposits as wel