Geologic environments of uranium deposits in Quaternary volcano-sedimentary basins in Central Italy

High U and Th values have been measured in the volcanites belonging to the Roman Comagmatic Province, which consists of a perpotassic magmatic suite. This volcanic province was formed during the Quaternary along the coastal plain between the Tyrrheniam Sea and the Appenninc Range, as extensional tectonic features which were connected by the collapse of the Tyrrhenian Basin. Continental volcano-sedimentary formations were deposited at the borders of the volcanic belt against the walls of the enclosing graben system and peneconcordant layers of uranium deposits have been detected in the formations. Uranium is disseminated in beds of kaolinezed tuffites associated with iron sulphide. The genetic interpretation is that the U mobilized from the volcanic rocks and concentrated in the ground water in the volcano-sedimentary basins. Along faults limiting the basins, H2S exhalation occurred, and the gases, dissolved in the ground waters, caused the precipitation of the uranium. The ore-forming control was due to the structural evolution of the volcano-sedimentary basins and to the hydrodynamic conditions of the ground waters. (author)