Study On Material Composition And Genesis Of The Chaobuleng Fe Polymetallic Deposit,Inner Mongolia

Located in the middle section of the Xing'an-Mongolia orogenic belt,the Chaobuleng Fe polymetallic deposit is a skarn deposit containing iron,zinc,copper,lead,bismuth,tungsten,tin,gold,silver,gallium,indium,cadmium and other elements.The ore minerals in the deposit are mainly magnetite,chalcopyrite,pyrite,galena,sphalerite,arsenopyrite,pyrrhotite,loellingite,natural bismuth,cosalite,bismutinite,bornite and chalcocite.The skarn minerals are mainly garnet,pyroxene,rhodonite,epidote,hornblende,mica and chlorite.According to the relationship between minerals,the mineralization process can be divided into skarn period,sulfide stage and supergene stage.The four generations of sphalerite in the deposit have four different internal reflection colors due to different Fe content.They are dark red,mahogany,brown and yellow respectively.The average Fe content is 12.34%,7.82%,4.37% and 3.11%,respectively.According to the relationship between Fe content and formation temperature,sphalerite is mainly formed in the middle and high temperature environment with a large temperature range.The formation temperatures of sphalerite in four generations decrease successively.The garnets in the deposit belong to an andradite-grossular series,however,generally higher in andradite.According to the sequence of minerals,the garnets are divided into two periods.Fe in the first period garnet is richer but Mg is richer in the second period garnet.The REE partition pattern of the first period garnet is rich in LREE,positive Eu abnormal.The REE partition pattern of the second period garnet is rich in HREE,negative Eu abnormal.The first period garnet is magmatic hydrothermal origin,while the second period garnet is metasomatic origin.The REE partition pattern of the rhodonite is rich in LREE,positive Eu abnormal or rich in MREE,positive Eu abnormal slightly.The REE partition patterns of the diopside and the magnetite are similarly negative Eu abnormal and negative Ce abnormal.The rhodonite is magmatic hydrothermal origin or metasomatic origin.The diopside and the magnetite are metasomatic origin with the addition of sea water to the ore-forming fluid.Stable isotope studies show that the sulfur in ore minerals is mainly derived from mixed magma of crust and mantle materials.Later,there is the addition of sea salt,sulfur or formation sulfur.Lead in ore minerals is the mixture of magmatic hydrothermal solution and ore bearing surrounding rock.Comprehensive studies have suggested that the formation of the deposit in the early Cretaceous during the Yanshanian Tectonic Period has undergone a gradual change from the high temperature oxidation environment to the low temperature reduction environment.