Properties of Magmatism, Hydrothermal-Metasomatic and Filtration-Transport Processes in Uranium-Bearing Volcanogenic Structures

Abstract

Creation of a refined conceptual model for the formation of volcanogenic uranium deposits includes researches of the nature of magmatic, hydrothermal-metasomatic and filtration-transport processes, as well as physico-chemical conditions for the transfer and deposition of uranium. We considered these issues using the examples of the Streltsovskaya caldera and the ore field of the same name in Eastern Transbaikalia, the Xiangshan volcanic structure in South China, and the McDermitt caldera in the western United States (Oregon and Nevada states). According to the IAEA classification [Geological Classification …, 2018], these ore fields and deposits belong to the volcanogenic (volcanic-related) type. In the Streltsovsky and Xiangshan ore fields, a combination of volcanogenic in the cover and granitic (granite-related) in the basement types of deposits is observed. The main part of uranium industrial deposits of volcanic type in these regions was formed during the Mesozoic and Cenozoic epochs (although more ancient, Paleozoic, objects are known in the world). Despite different time intervals of the ore-bearing volcanogenic structures formation, many features of magmatic, hydrothermal, and filtration-transport processes in them are very similar. It is assumed that these features are due to the general influence of intraplate tectonic regimes or the evolution of the outer parts of the ocean-continent zones where magmatic activity produced volcanism of the bimodal series in the predominant sequence mafic ‒ felsic volcanics ‒ mafic, and the migration of uranium-transporting fluids was set by the joint action of seismogeodynamic and thermoconvective processes.