Geological And Geochemical Characteristics And Genesis Of Heiyuting Co-iron Deposit In Kuandian,Liaoning Province

The Heiyuting Co-Iron Deposit is located in the central depression of the east Liaoji Rift,in Kuandian,Liaoning Province.In this paper,through the research methods of petrography,ore microscopy,XRF,ICP-MS,EPMA and fluid inclusions,we have analyzed the geological and geochemical characteristics of Heiyuting Co-Iron Deposit,explored the source of metallogenic minerals and fluids,determined the genesis type and metallogenic process of the deposit,and then we hope to provide scientific basis for exploration of Co-Iron deposits in Liaoji Rift.?1?The Co-containing pyrite-magnetite granulites occurs in the Lower Lieryu Formation of the Liaohe Group of Paleoproterozoic.Its geochemical characteristics show that the original rock is dacite,and the rare earth element?REE?patterns are obviously right dip,with relative enrichment of lithophilic elements such as Rb?K and relative lack of highfield strong elements such as Ta?Nb?Ti?Zr?Hf,with indicates the continental margin arc tectonic environment.?2?The ore bodies of Heiyuting Co-Iron Deposit are distributed in EW direction.There are 6 ore types,and the most importent are massive magnetite ore,laminated pyrite-magnetite ore and disseminated pyrite-magnetite ore.The metallic minerals mainly are magnetite,cobaltic pyrite,pyrrhotite and chalcopyrite,while the main non-metallic minerals are quartz and feldspar.The types of wall rock alteration are silicification,pyritization,carbonation,chloritization and epidotization.The formation of the deposit is mainly divided into three stages:deposition stage,hydrothermal stage and oxidation stage.?3?The characteristics of main elements in ores are basically consistent with the global BIF type deposits,though the content of Al₂O₃ is slightly higher.The content of total rare earth element??REE+Y?is low,and the Post Archean Australian Shale?PAAS?-normalized REE patterns of ores show the slight enrichment of light REE,with positive Eu anomaly,slightly negative Y anomaly and weakly negative Ce anomaly.Y/Ho ratio is between that of submarine hydrothermal solution and modern seawater.Trace elements are characterized by high Ba,V,Cr,Co,Ni,Cu,Pb,Zn and W,low K,Nb,Sr,Ti,Zr and Hf.In a word,the ore-forming material source of Heiyuting Co-Iron Deposit may be the combination of seawater and submarine low-temperature hydrothermal mixing,and the formation of the deposit is related to submarine hydrothermal vents.?4?The micro-temperature test results of inclusions in quartz of ores show that the ore-forming fluid of deposition stage is H₂O-NaCl system with shallow,medium low temperature,medium low salinity and medium density,and the salinity is higher than the normal seawater salinity,reflecting that the formation of laminar ores is affected by medium low temperature hydrothermal solution.?5?The content of magnetite trace elements in ore is generally higher than that of the global BIF and related iron deposits,and the Co/Ni ratio and Ni/Cr ratio are both greater than 1.The characteristics of REE are basically consistent with the magnetite characteristics in global BIF,which are characterized by extremely low?REE,loss of LREE,slight negative Ce anomalies,positive Eu and Y anomalies.The ore-forming materials are derived from the mixture of anoxic paleo-sea water and low-temperature hydrothermal solution,and the formation of iron-rich ore bodies is modified by the later reductive middle-low temperature shell-source fluid.?6?Based on the above study,it is concluded that the genesis type of Heiyuting Co-Iron Deposit is the iron deposit of sedimentary-metamorphic and hydrothermal type,the ore-forming material and fluid source are related to submarine volcanic jet,and the formation of iron-rich ore body is related to the metamorphism of the later reductive middle-low temperature shell-source fluid.