Maodeng Cu-Sn deposit (Modon Cu-Sn deposit), West Ujimqin Banner (Xiwuzhumuqin Co.), Xilingol League (Xilinguole Prefecture), Inner Mongolia, Chinai

Regional Level Types
Maodeng Cu-Sn deposit (Modon Cu-Sn deposit)	Deposit
West Ujimqin Banner (Xiwuzhumuqin Co.)	County
Xilingol League (Xilinguole Prefecture)	Prefecture
Inner Mongolia	Autonomous Region
China	Country

Cassiterite-sulfide-silicate veins and stockworks, occurring in the western contact zone of the Alubaogeshan granite porphyry (Rb-Sr isotopic age: 149 Ma). The deposit is hosted in a Jurassic bimodal volcanic sequence, including a lower basalt and upper rhyolite unit, in the Maodeng volcanic basin. The ores occur in veins that are controlled by a NW-trending fault system. The minerals exhibit idiomorphic to hypidiomorphic granular textures and occur as metasomatic fillings, disseminations, masses, veins, veinlets, stockworks and brecciae. Alteration exhibited by the magnetite, cassiterite and sulphide bodies is potassic silicification, greisenization and silicification, respectively. The deposit is interpreted as having forming in hydrothermal conditions at a moderate depth of 1.6 to 2 km, and at moderate temperatures of 450°C to 200°C.
The Maodeng deposit contains large-sized Mo and Bi resources including 162,678 tons of Mo @ 0.07 % and 114,235 tons of Bi @ 0.03 %, along with middle to small-sized Sn (6,400 tons of Sn @ 0.56 %) and Cu (2,200 tons of Cu @ 0.76 %).
The Sn-Cu and Mo-Bi orebodies in the top and lower portions of the Maodeng deposit, respectively, show clear spatial mineralization zones. Mo-Bi orebodies are found in the Dashizhai Formation volcanic breccias as veinlets, stockworks, and disseminated types, hosted in the outer contact of Alubaogeshan pluton. The Mo-Bi orebodies appear approximately circular or oblong in plain view and stratoid or lenticular in cross-section. Four Mo-Bi orebodies (designated as M1, M2, M3, and M4) were delineated and buried below the surface between 500 and 1000 m altitude. The M1 orebody, as the most principal Mo-Bi orebody, mainly varies between 2 and 290 m in thickness with an average of 9.9 m, strikes 315–330°, dips 0–15°, and contains 162,411 tons of Mo @ 0.07 % and 114,050 tons of Bi @ 0.03 %. The Sn-Cu orebodies predominantly occur in the steeply inclining parallel and dense veins in Dashizhai Formation volcanic breccias, and minor occurrences can also be seen in G2, where the ore bodies are hosted in NW-trending faults and joint fissures. Around 232 orebodies including 225 Sn-rich orebodies and 7 Cu-rich orebodies were delineated. The II-204 orebody, as a main Sn-rich orebody, has an average length of 310 m and width of 2.41 m, extends to a depth of 235 m along its dip direction to the NE at 65°, and contains 193 tons of Sn @ 0.63 %. The II-46 Cu-rich orebody has an average length of 165 m and width of 1.80 m, dips 56° to the NE, strikes 331°, and contains 365 tons of Cu @ 1.67 %.

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