Geochemical Characteristics And Genesis Of Haoyaoerhudong Gold Deposit In Inner Mongolia

The Haoyaoerhudong gold deposit is located in the northern margin of the North China plate,and is situated in the Urad Middle Banner area of Inner Mongolia in C hina.This deposit is a large tonnage and lower-grade deposit with a reserve of about 148 tons o f gold at about 0.82g/t Au.This thesis is based on the collection of the previous results,combined with several geological surveys and a large number of indoor research work,bringing together the regional geological background,the geological characteristics of ore deposit,the main elements and trace elements and rare earth elements of magmatite,the S and Pb isotopic characteristics of ore and the ⁴⁰Ar/³⁹Ar isotopic ages of biotite etc,in order to discusses the geochemical characteristics and genesis of Haoyaoerhudong gold deposit.The orebody of the deposit presented as layered and stratoid,controlled strictly by the tectonic fracture zone and extrusion schistositilization.The deposit generates in carbonaceous fine sandstone,slate and phyllitic slate of the Bilute Formation.The folds and faults in the mining area are well developed,and there are a large number of Hercynian granitic rocks and dikes.According to the graph analysis based on the data of the main elements,trace elements and rare earth elements?REE?of magmatite in the mining area,we come to these conclusions: the main rock types of magmatic rock in Haoyaoerhudong gold deposit are diorite,granite,gabbro,diorite,biotite granite and so on,and all the rocks are high-k calc alkaline series.All kinds of rocks show the relative enrichment of LILE and the relative loss of HFSE,also show the enrichment of LREE and the obvious fractionation between LREE and HREE.Using the main elements,trace elements and REE data to have graph analysis es of tectonic environment,we found that intermediate-acid intrusive rocks in the Haoyaoerhudong gold mining area are mainly formed in the precollisional--syncollisional tectonic environment.It is closely related with the collison movement between North China plate and Siberia plate.Therefore,the invasion of the rock mass in the precollisional-syncollisional period has played a key role in the formation of Haoyaoerhudong gold deposit.The biotite ⁴⁰Ar/³⁹Ar isotopic plateau age of the quartz vein in the mining area is?260.1 ± 2.9?Ma,the inverse isochron age is?260.9 ± 3.4?Ma,these ages can accurately indicate the mineralization age of the Haoyaoerhudong gold deposit,namely the Late Permian.It is consistent with the geological age fact of a large number of hercynian magmatic rocks,and also proved that the deposit's gold mineralization is closely related to Hercynian tectonic-magmatic activity.The ?³⁴S values of pyrites and pyrrhotites in ores showed that the sulphur was derived from a relatively uniform source,and most probably derived from carbonate contaminated granite magma.The lead isotopic results showed that the characteristics of Haoyaoerhudo ng deposit have a mixed source of crust and mantle,and reformed by later seawater sedimentation.