EXPERIMENTAL STUDY OF THE SOLUBILITY OF URANINITE IN GRANITIC MELTS AND FLUID SOLUTIONS AT HIGH PRESSURES AND TEMPERATURES

Abstract

Many geologists believe that uraniferous hydrothermal solutions arise from deep-seated granite magmas in late stages of development. Smirnov considers this a paragenetic relationship (indirect or fraternal), making postmagmatic deposits and magmatic bodies derivatives from a common source. This viewpoint has not yet received physicochemical confirmation, as it is based mainly on the space and time relationships between uranium deposits and magmatism. The present paper is intended to fill this gap. The authors have performed a wide range of preliminary experiments, have determined the uranium saturation concentrations for model granitic melts with controlled oxygen fugacity, and have examined the distribution of uranium between coexisting fluid and melt, and have also examined the solubilities of uraninite in hot halide solutions. They find that saturation levels for uranium in the melts exceed the contents generally found in natural magmas and the partitioning of uranium always favors the melts over aqueous fluids. Aqueous fluids in equilibrium with the final batches of melt may carry significant quantities of uranium and are probably involved in ore deposition. 22 references.