Descriptive Model of Solution-Collapse Breccia Pipe Uranium Deposits

Uranium (Nuclear Minerals) / Exploration, Mining, Marketing, & Acquisitions

Date posted: 02/18/15

Warren I. Finch of the USGS in Denver describes a number of special types of uranium occurrences, such as - collapse breccia pipe deposits, sedimentary breccia pipe deposits, Orphan Lode-type deposits. Uraninite and associated sulfide, arsenide, sulfate, and arsenic-sulfosalt minerals occur as disseminated replacements and minor fracture fillings in distinct bodies in near-vertical cylindrical solution-collapse breccia pipes, 30-175 m in diameter and 1,000 m in length. Pipes located in flat-lying upper Paleozoic and Triassic rocks restricted to the Grand Canyon region in the southwestern part of the Colorado Plateau. One of two dominant high-grade sources of United States uranium production in 1987, which are expected to be major source of future uranium production within the United States. Pipes are found within and along the southwest margin of the Colorado Plateau, in a stable block existent since the Precambrian and resistant to tectonic forces acting on the western part of the North American plate. Wall rocks of pipes were deposited on a stable marine platform. Pipes apparently originated along and at intersections of N. 50 degrees E.- and N. 45 degrees W.- trending joint or fracture sets, roughly parallel to orthogonal Colorado River - N. 45 degrees E., Zuni - N. 45 degrees W, and related lineaments shown by Green - 1988, that developed in the Precambrian and rejuvenated in later periods. No igneous rocks are found in the pipes. Orebodies occur as discontinuous pods mainly in the core of the breccia pipe but some are also found in the annular-ring structure and may occupy as much as a 200-m vertical interval, mainly as replacement and sparse open-space filling. Pyrite and marcasite and base-metal sulfides occur locally associated with pyrobitumen, which form a discontinuous massive sulfide cap above the uranium deposits in many pipes. Uranium, vanadium, and copper roughly zoned within some deposits.