Li Shengxiang and Yu Hengxu report that this case study provides considerations related to the application of UNFC-2009 to estimates of uranium resources in the Yili Basin, north west China. The uranium resources of this basin were originally classified according to the China Mineral Reserves and Resources Classification System (CMRRCS) and this case study demonstrates that the quantities may be transparently mapped and transferred to UNFC-2009. In this context, consideration may now be given to the possible development of a Bridging Document between the CMRRCS and UNFC-2009 classification systems.
The Yili Basin, situated in the western part of the Tianshan Tectonic Belt, north west China, is a Meso-Cenozoic intermountain basin developed on the basement of an old Precambrian block (Figure 1). The coordinates of the centre of the Yili Basin are E81°05, N43°50. The uranium mineralization is mainly hosted in the coal-bearing clastic rocks of the Shuixigou Group (J1-2sh), the Lower-Middle Jurassic (Figure 1). The ore-hosting Shuixigou Group (J1-2sh) can be further divided into three formations, namely, Badaowan Formation (J1b), Sangonghe Formation (J1s) and Xishanyao Formation (J2x) [5, 6].
Uranium prospecting work began in this region in the early 1950s. During the 1950s and 1960s, the prospecting focused on coal type uranium resources; two coal type deposits – the Daladi Deposit and the Mengqiguer Deposit – were discovered during that time. After being suspendedfor about 20 years, prospecting work restarted in the early 1990s and focused on in situ leach (ISL) amenable sandstone type uranium deposits in the southern margin of the Yili Basin. Following 25 years of geological exploration, five in situ leachable sandstone type uranium deposits – the Mengqiguer, Zhajistan, Wukuerqi, Kujiertai and Honghaigou Deposits – have been delineated, with the total uranium resources amenable to ISL extraction estimated at over 30,000 tU (tonnes (metric tons) of uranium).
Uranium production and trial production activities using the ISL method are currently ongoing in the Mengqiguer, Zhajistan, Wukuerqi and Kujiertai Deposits, forming the largest uranium production centre in China. The total production capacity of the four deposits is around 400 tU per annum, and will expand to 500 tU per annum in the near future. Exploration work continues in the existing deposit extensions and their adjoining areas.
Mengqiguer Deposit
The Mengqiguer Deposit is the largest uranium deposit in the Yili Basin. The deposit accounts for about 45 per cent of the total uranium resources of the basin. The uranium ore bodies are mostly hosted in the Xishanyao Formation and the Sangonghe Formation. The uranium mineralization discovered during the 1950s and 1960s was found to be hosted in coal beds (named as Mengqiguer-1). The quantity is small. Since this material is difficult to process, this kind of coal type uranium mineralization is considered as “development not viable” with categories E3.3 F2.3 G2, E3.3 F2.3 G3 The uranium mineralization discovered after 2000 was found in permeable sandstone layers, which allows the uranium to be extracted with the ISL method (named as Mengqiguer-2). The ISL-amenable uranium resources of the deposit account for about 43 per cent of the total resources of the basin. Since the on-going trial uranium production with the ISL method in the deposit shows positive commercial results, this type of sandstone type uranium mineralization is considered as “on production” with categories E1.1 F1.1 G2, E1.1 F1.1 G3 (Table 3). More geological work needs to be carried to increase the geological confidence of these resources.
Kujiertai Deposit
The Kujiertai Deposit is the second largest uranium deposit, the first ISL-mining uranium deposit in the Yili Basin, and also the first commercial ISL uranium production centre in China. The deposit accounts for about 23 per cent of total uranium resources of the basin. It was discovered in the early 1990s and the uranium ore bodies are mostly hosted in the permeable sandstone layers of the Xishanyao Formation and the Badaowan Formation. The uranium production of the deposit began in middle of 1990s using the ISL method. The uranium mineralization is considered as “on production” with categories E1.1 F1.1 G1, E1.1 F1.1 G2, E1.1 F1.1 G3.
Zhajistan Deposit
The uranium ore bodies of the Zhajistan Deposit are mostly hosted in the Xishanyao Formation and the Sangonghe Formation with the uranium resources constituting about 10 per cent of the total resources of the basin. The uranium mineralization is hosted in permeable sandstone layers and is being mined with the ISL method, in which case the uranium resources are considered as “on production” with categories E1.1 F1.1 G1, E1.1 F1.1 G2, E1.1 F1.1 G3.
Wukuerqi Deposit
The uranium ore bodies of the Wukuerqi Deposit are mostly hosted in the Xishanyao Formation and the Sangonghe Formation with the uranium resources constituting about 7 per cent of the total uranium resources of the basin. The uranium mineralization is hosted in permeable sandstone layers and is being mined with the ISL method, so the uranium resources are considered as “on production” with categories E1.1 F1.1 G2, E1.1 F1.1 G3. However, more geological work needs to be carried out to increase its geologic confidence.
Daladi Deposit
The Daladi Deposit is the earliest discovered uranium deposit in the Yili Basin. The uranium ore bodies are mostly hosted in the Xishanyao Formation and the Sangonghe Formation with the uranium resources being less than 3 per cent of the total resources of the basin. The uranium mineralization is hosted in the coal beds and is difficult to process, so these uranium resources are considered as “development not viable” with categories E3.3 F2.3 G2, E3.3 F2.3 G3.
Honghaigou Deposit
The Honghaigou Deposit is a new deposit that was discovered in recent years, and the exploration and the pre-feasibility studies are still ongoing in the deposit. The uranium ore bodies are mostly hosted in the Upper Jurassic and the Xishanyao Formation with the uranium resources constituting about 12 per cent of the total resources of the basin. The uranium mineralization is classified into “333” in the current CMRRCS. However, considering that the uranium mineralization is hosted in permeable sandstone with similar mineralization characteristics to that of the Kujiertai Deposit, and that the deposit can be mined using the ISL method, the uranium resources are considered as “development pending” with categories E2 F2.1 G3.
Conclusions
From this case study on the application of UNFC-2009 to the uranium resources in the Yili Basin, it can be concluded that if a comprehensive consideration of the project socio-economic viability and project status and feasibility is undertaken, the mapping of CMRRCS Classes to UNFC-2009 Classes will be relatively easy and straight forward. UNFC-2009, in particular with its Sub-classes, is a very useful uranium resources categorization tool because it can provide an overall picture of a uranium project. Additionally, UNFC-2009 can express the project more comprehensively and more precisely than UNFC-1997 and CMRRCS, especially in relation to project status and feasibility.
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