ウズベキスタン共和国メシェティンスカヤ地域における 砂岩型ウラン鉱床の発見について

抄録

Japan Oil, Gas and Metals National Corporation (JOGMEC) and the State Committee of the Republic of Uzbekistan on Geology and Mineral Resources (GKG) started to jointly conduct an exploration on sandstone-type uranium deposits in the Meshetinskaya area, Navoi Region of the Republic of Uzbekistan in August 2016. The Meshetinskaya area northwardly straddles the Kyzylkum basin, where most of the sandstone-type deposits in the country are distributed, the Bukantau range and the Syr Darya basin. The area is approximately 2,057 km². Although the potentiality of the sandstone-type uranium deposits had been suggested in this area, the detailed survey has not conducted before.

JOGMEC and GKG have been carrying out a drilling campaign (35,780 m / 135 holes in total) up until now. As a result, favorable sandstone-type deposits with the redox front formation have been discovered in the Upper Cretaceous Maastrichtian, which are located less than 200m from the surface.

The uranium deposits in the Meshetinskaya area are hosted in unconsolidated sand with good water permeability and sandstones in the Maastrichtian, laying between impermeable layers, such as marlstones, silty sandstones and siltstones. It turns out that this is the roll-front sandstone-type uranium deposits with the redox front formed through the infiltration of oxidized groundwater containing uranium from the east-northeastern project property. The reasons are that 1) uranium mineralization is recognized over the boundary between gray-colored reduced sand containing pyrite and carbonaceous material and light yellow-colored oxidized sand, 2) distribution of mineralization and the shape of deposits shown in the cross section, 3) distribution of the associated elements. The mineralization zone is continuously distributed along the extension of strike, running approximately 4.4 km long and a few to 300 m width. With resource estimation conducted in this targeted area, the scale of resource is confirmed approximately more than 2,000 tU, which is categorized as C2 in the resource classification of Uzbekistan.

In terms of the development of uranium deposits in the Meshetinskaya area, the cost-competitive ISL (In-Situ Leaching) method is expected. The acquisition of various physical property values as applicable index and its evaluation were launched in 2019, and it is indicated that the ISL is an appropriate method as a preliminary result. In addition, it is confirmed that sulfuric acid leaching method is also suitable for the area due to the high recovery rate in the leaching test using sulfuric acid for the collected drilled cores.

Since many of the areas along the extension of strike with the redox front have not yet explored, the further increase in the uranium resource will be expected. As a future plan, additional drilling campaigns to acquire and confirm the uranium resource, technical reviews, including Push-Pull tests and In-Situ tests, and economic evaluations toward the development will be conducted.