Relation of topaz rhyolite volcanism to uranium mineralization in the western United States of America.

Tertiary rhyolites containing topaz are widespread in the eastern Basin and Range Province and Rio Grande Rift areas in the western USA as well as in the central plateau region of N Mexico. In several topaz rhyolite occurrences, including those of the best known Spor Mountain-Thomas Range area, western Utah, devitrification and weathering (leaching) of fluorine-rich tuffs appear to have been responsible for economic uranium mineralization in underlying clastic sediments. Similar leaching may have been responsible for the large, low-grade uranium deposits in tuffaceous, F-, Li- and Mn-enriched lake sediments at the Anderson uranium mine, west-central Arizona. Topaz rhyolites, including the associated tuffs, may therefore be regarded as promising source rocks for sediment-hosted uranium ores in regional prospecting. -from Authors