Results of Uranium Hydrogeochemical and Stream Sediment Reconnaissance of the San Juan Area, Southwestern Colorado

摘要

During June-July 1976, 1706 water samples and 1982 sediment samples were collected from 1995 sites in the San Juan Mountains area and analyzed for uranium. The area includes the southern third of the Colorado mineral belt which has yielded rich ores of gold, silver, copper, lead, zinc, and molybdenum. The broadly domed mountains are capped by 2500 m of Tertiary volcanics, deeply eroded to expose a Precambrian crystalline core. Adjacent plateaus underlain by Mesozoic sedimentary rocks were included in the reconnaissance. Average value of uranium in water samples from mountains was less than 0.5 ppb, from plateaus was 1 to 2 ppb, and from Mancos shale areas exceeded 2 ppb. Anomalous sediment samples, 40 ppM uranium, came from near Storm King Mountain and upper Vallecito Creek. Other anomalous areas, including the Lake City mining district, were well defined by 4 to 30 ppM uranium in sediment and 3 to 30 ppB uranium in water. Above-average concentrations of uranium not previously reported indicate areas favorable for detailed exploration. (ERA citation 02:045102)