Geological Characteristics And Deposit Origin Of The Huogeqi No.2 Deposit Of Langshan District In Inner Mongolia

The Huogeqi ore field is located in the western section of the north margin of the North China Craton,which is the largest Cu polymetallic deposit in Langshan,Inner Mongolia.The Huogeqi ore field is composed of three large and middle-sized deposits,The No.2 deposit ore bodies are obviously controlled by strata.The ore bodies and mineralization are mainly distributed in the second formation of Langshan group,and occurred in a set of Hydrothermal sedimentary silicalite rocks and Hydrothermal metasomatism in marl.The occurrence of Cu,Pb and Zn bodies are in accordance with the strata.Meanwhile,the bodies are layered,quasi layered,lentoid,and with a clear boundary with the roof and floor rocks.Based on plenty of articles about this deposit,a large number of documents were consulted and data were analyzed to find out the geochemical characteristics,finally summarized the genesis of ore deposit.The Co/Ni ratio of pyrite in the No.2 deposit ranges between 0.40?2.60%,and the Se is small.They are suited to sediment-reconstruction deposit and hydrotherma estrogenic deposit.The Co/Ni ratio of pyrrhotite is 0.13?1.54,the Se is very small.The Trace elements of pyrite and pyrrhotite are very similar,giving evidence that the origin of pyrrhotite is similar to pyrite.The analysis of Pyrite single mineral shows that,The Co/Ni ratio of pyrite ranges between 0.40?2.60%,one of the samples shows the characteristics of volcanogenic.The Co-Ni-As of magnetite in No.2 deposit show they have characters of metamorphic hydrothermal.The REE of magnetite are characterised by Eu of positive anomaly and Ce of low positive anomaly,which are completely opposite to Eu of low negative anomaly and Ce of low negative anomaly in Pine Lake VMS deposit.The No.2 deposit does not have the characteristics of VMS deposit in rare earth elements.The?³⁴S of stratiform pyrite in Huogeqi ore field values+10.6?20.0‰,is close to the?³⁴S of seawater sulfate.and own the features of exhalation-sediment.The?³⁴S of veined pyrite is among-3.1?+23.5‰,the limit of variation of?³⁴S in veined pyrite is larger than that in stratiform pyrite,caused by later magmatic hydrothermalism.The lead isotopes in Huogeqi ore field range between the evolutionary line of orogenic belt Mantle and there are some points falling in the Mantle,showing lead had multisource features.The above geochemical characteristics indicate that the No.2 deposit in Huogeqi ore field are an exhalative sedimentary deposit,reformed by later regional metamorphism and magmatic hydrothermalism.