Geodynamic, Tectonic, and Magmatic Indicators of Large Uranium Clusters of the Transbaikal–Mongolia–North China Province

Abstract

The Transbaikal–Mongolia–North China province of East Asia is ranked as the most productive uranium province. Its area contains hundreds of occurrences, dozens of deposits of different (endo-, exo-, and polygenic) types, and several large uranium-bearing clusters and districts. The largest F–Mo–U clusters were revealed in the Mongol–Argun and Inshan–Liaohe volcanoplutonic zones (VPZ) in the western and southwestern periphery of the Great Xingan belt, respectively. Tectonic data on the Late Mesozoic (J2–K) Tulukuev (Southeastern Transbaikalia), Dornod (East Mongolia), and Guyuan–Duolung (Inshan–Liaohe, China) depressions of the above-mentioned VPZ are analyzed to distinguish their important structural details, which are responsible for the distribution of uranium-bearing fields and deposits in the volcanic rocks. Some of the deposits are associated with paleovolcanic necks, extrusive rocks, subvolcanic bodies, and dikes and have complex morphology. Other deposits are localized in stratified volcanic–pyroclastic rocks or within the basement rocks of the depressions. Recent geochronologic, geophysical, and seismotomographic data indicate not only the synchronous formation of the ore clusters in the Early Cretaceous (Valanginian), but also their localization within a crust of moderate (36–42 km) thickness above the periphery of a stagnant slab in the mantle transition zone. The coincidence of the slab boundary projections and area of their influence with the spatial position of large F–Mo–U ore clusters (Streltsovka, Dornod, and Guyuan–Duolung) separated from each other by hundreds and thousands of kilometers is regarded as evidence for the possible influence of deep geodynamics on the formation of the corresponding mineralization. Some of the aforementioned and similar clusters of the province seem to be insufficiently studied. This refers, in particular, to the exploration of the thick volcanic–pyroclastic fields associated with volcanic paleocenters within the clusters, as well as the basement rocks of the basin.