Shihuiyao Rb-Nb-Ta-(Be-Li) deposit, Xilinhot City (Xilinhaote Co.), Xilingol League (Xilinguole Prefecture), Inner Mongolia, Chinai

Regional Level Types
Shihuiyao Rb-Nb-Ta-(Be-Li) deposit	Deposit
Xilinhot City (Xilinhaote Co.)	County
Xilingol League (Xilinguole Prefecture)	Prefecture
Inner Mongolia	Autonomous Region
China	Country

Six Rb-rich plutons, which are composed of siderophyllite monzogranite, muscovite granite, zinnwaldite granite and zinnwaldite-amazonite granite, intruded into the Permian Linxi Formation in the Shihuiyao mining area. The Nb-Ta mineralization mainly occurs in the Pluton III and IV, while Nb-Ta minerals appear as a small number of accessory minerals in other plutons. Fifteen ore bodies were determined in the Shihuiyao deposit, including ten in Pluton III and five in Pluton IV. The largest Nb-Ta orebody occurs in the east of the Pluton III, accounting for 75 % of the total reserves of Nb + Ta in the Shihuiyao deposit.
In the large Shihuiyao Rb-Nb-Ta-Be deposit, a beryl-bearing granite was identified with three texturally different zones that show an increasing degree of fractionation, including the albite granite (bottom zone), albite granite with pegmatite pockets (intermediate zone), and intercalation of granite and pegmatite layers (top zone). Beryl occurs both in the intermediate and top zones.
In the Shihuiyao area, seventeen Be ore bodies (grading at 0.164–0.314 wt% BeO) were discovered, mainly hosted in Pluton Ⅲ and Ⅳ. These Be orebodies occur in greisenized granite, and beryl is the only beryllium-bearing mineral present. We investigated in detail the No. 17 Be orebody, which occurs on the apical parts of Pluton Ⅳ. This orebody is approximately 3 m thick and 30 m long and particularly well exposed in an exploratory trench at the top of the pluton. The trench can be divided into three subzones based on petrographic variations, from bottom to top: granite (bottom zone), granite with pegmatite pockets (intermediate zone), and layered aplite-pegmatite body (top zone).

The Shihuiyao deposit shows great potential for rare polymetallic exploration and mining, with proven reserves of exceeding 870,000 tons of Rb2O with grades ranging from 0.17 to 0.93 wt.% (average 0.55 wt.%). Additionally, associated (Nb, Ta)2O5 reserves are approximately 16.21 million tons with grades of 0.02% Nb2O5 and 0.015% Ta2O5. Seven plutons, collectively covering about 3 km2 in surface area, are delineated and named Pluton I to VII. Plutons I and V are the two main Rb–Ta–Nb–Be ore bodies, covering approximately 10% of the total deposit. The dominant lithology consists of fine- to medium-grained monzogranite and greisen, with the granite undergoing strong albitization and greisenization. Notably, a pegmatite shell occurs at the top of Pluton I. In contrast, Plutons II, III, IV, VI, and VII primarily host Rb-bearing ore bodies. Plutons II, III, and IV are located in the central part of the deposit. Pluton II is predominantly composed of amazonite monzogranite with albitization and greisen, along with pegmatite veins. Plutons III and IV are primarily medium- to fine-grained monzogranites. Plutons VI and VII are situated in the northeastern section, with lithologies consisting of medium- to fine-grained biotite monzogranites, exhibiting albitization, and locally developed amazonite pegmatite veins. Pluton I is located in the southwestern part of the Shihuiyao deposit. It has a length of 815 m, a width of 110–280 m, and a thickness of 33.40–135.30 m, covering an area of approximately 0.15 km2 of altered Yanshanian granite. The estimated resources of (Nb, Ta)2O5, Li2O, and Rb2O are @ 0.015%–0.035%, average @ 0.0186%, @ 0.034%–0.236%, average @ 0.096%, and @ 0.10%–0.39%, average @ 0.137%, respectively. Minority samples displayed high Sn and WO3 contents, with maximum values of 0.0081% and 0.05%, respectively.

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References