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The research summarized by the slide show was conducted by the U. S. Geological Survey during the years 1969-1980. During that period, the research focused on three topics: beryllium mineralization in the volcanic environment, volcanic history of Spor Mountain, and uranium in volcanic rocks at Spor Mountain.
Initial research focused on the processes that formed deposits of fine-grained, disseminated beryllium minerals in volcanic rocks. The Spor Mountain district was selected for study because it contained large, newly-discovered deposits of beryllium in volcanic rocks, of a deposit type never before recognized. Studies were conducted to identify and map alteration minerals in the Spor Mountain beryllium deposits and to map trace element anomalies in tuff, with the twin goals of better understanding mineralization processes and of developing exploration guides.
The initial research on mineralization processes at Spor Mountain was conducted using existing geologic information, including maps and descriptions from earlier research by the U. S. Geological Survey. As the investigation proceeded, the need for new geologic information, including radiometric ages and better understanding of the volcanic history the area, became evident. During previous investigations, radiometric dating of rocks was in its infancy and the ages of volcanic rocks related to mineral deposits at Spor Mountain remained largely unknown. Also, the caldera cycle of volcanism was a new concept and the relation between plate tectonics, structural style, and mode of volcanism in the western United States was still being discovered. The Thomas caldera at Spor Mountain had been recognized, but its relation to mineralization, if any, had not been determined because the complete time-stratigraphic sequence of volcanism, structural events, and mineralization was not known. To understand the geologic environment of beryllium mineralization at Spor Mountain, much of the volcanic terrane was remapped, a new volcanic stratigraphy was developed, radiometric ages of many rock units were obtained, and the history of volcanism and mineralization was reinterpreted. As it turned out, the mineral deposits at Spor Mountain were not formed during caldera-related volcanism, but during later basin-range faulting and associated bimodal basalt-rhyolite volcanism.
The revision of the history of volcanism and mineralization at Spor Mountain was conducted at about the time of renewed interest in uranium exploration, during the years 1975-1980. Discoveries of possibly economic deposits of uranium in volcanic rocks of northern Mexico, the presence of numerous uneconomic occurrences in volcanic rocks of the western United States, and earlier discovery of the Yellow Chief uranium mine at Spor Mountain, spurred intense exploration for uranium in the Spor Mountain area. Samples collected previously by industry during exploration and samples collected for research by the U. S. Geological Survey were reanalyzed for uranium and other elements. The age of uranium mineralization was dated by radiometric methods, and the role of alternative mineralizing processes in volcanic rocks was evaluated using the newly generated data.
Since completion of work on the mineral deposits at Spor Mountain by the U. S. Geological Survey, additional research has been conducted by university staff. Much of the new work addresses the chemical evolution of topaz rhyolite magma, thought to be the source of beryllium and other elements concentrated at Spor Mountain.
Field scenes were photographed by the author; specimens and illustrations were photographed by Louise Hedricks.