Abstract: Laodonggou gold deposit located in Ejinaqi, Inner Mongolia, consists of mainly goldpolymetal ore veins, of which the most important No. 98 and No. 1 veins are being mined. These veins occur mainly in Pingtoushan group dolomite marble of Jixian system and are controlled by nearly E-W and WNW-trending faults. The primary mineralizations is related to diorite porphyrite dykes in origin. The primary ore minerals are arsenopyrite, pyrite, galena (±sphalerite), native gold, native silver, argentite, etc. Gold grade of the ores ranges from 0.1×10^-6 to 5.0×10^-6. The oreveins were suffered from oxidizing-leaching in various degree by meteoric water and groundwater for a long time after these veins had been formed. As observed at open pits of No. 98 vein, within the oxidized-leached zone of 50m from the surface, with the exception of residual galena, the sulfide minerals have been oxidized and formed earth and foveolateores. The mineral assemblage of the oxidized ore is scorodite+beudantite+limonite+goethite+austinite+adamite+native gold+native silver+quartz+calcite+opal, etc. The secondary leached-enriched zone of gold is between 10 and 30 m from the surface. The average grade of gold is 10×10^-6 to 15×10^-6.
Thus Laodonggou mineable gold orebodies are considered as oxidized-leached type ore deposit.