Detrital-appearing uraninite grains in the Shinarump member of the Chinle Formation in northern Arizona

Abstract

A sample of uranium-bearing conglomerate from the Shinarump member of the Chinle formation in northern Arizona was disaggregated in an ultrasonic separator. The sample, weighing 187 grams, contained about 60 grains of uraninite (from 0.1 to 1 mm diameter) which have the sphericity and polish suggestive of detrital grains. The detrital-appearing grains are associated with abundant interstitial uraninite, sphalerite, and pyrite, which presents conflicting evidence as to the origin of the uranium deposit. No definite conclusions are presented for the occurrence of these grains. However, the evidence strongly suggests that they are probably not detrital in origin, but are uraninite replacements of detrital grains; the original mineral may have been quartz. (auth)