Geochemical Characteristics And Genesis Of The Shuangqing Iron Deposit In Dulan,qinghai Province

The iron ore deposit of Shuangqing is located in Xiangride town 2km of Dulan County,Qinghai Province,which study degree is very lower.This paper discuss the genesis by field geological work,indoor research on characteristics of ore deposit geology,element geochemical characteristics,fluid inclusions and stable isotope study.Ore bodies of Shuangqing iron deposit form general is lenticular and hosted in the interlayer of greenschist and marble rock formations or parallel distributed.Based on the hand specimens and mineral microscope system identification,nonmetallic mineral is a typical alteration silicate mineral association,and the main metallic minerals composition of the ore is ilmenite,molybdenite,pyrite,pyrrhotite,chalcopyrite,sphalerite,galena,total mineral is covellite,limonite and lead-vanadium.Magnetite are main mineral,with a small amount of metal sulfide magnetite ore;The structure of ore are mainly for the massive and dense disseminated,and the ore textures are mainly automorphic,hypidiomorphic and xenomorphic textures,zonal texture,metasomatic relict texture,including texture,metasomatic relict texture,vein-staggered mesh texture and solid separation texture.Wall rock alteration are silicon card lithification,carbonatization,silicification and sericitization.According to the mineral interaction interspersed relationship and fabric characteristics,ore-forming process will be divided into skarn stage,quartz sulfide stage and supergene stage.According to the study on ore characteristics of major element,trace element and REE element,Primitive mantle standardized trace element distribution plots showed consistency,the content of siderophile elements,chalcophile elements?Cu,Zn,Co,Ni?is higher,enrichment in high field strength elements?HFS?such as Y,Ga,Th,Zr,Hf and depletion in lithophile element?LILE?such as Rb,Sr,Ba,which show that the deposit have similar contact metasomatic genesis of granitic magma.REE elements shows the LREE enrichment,and the HREE depleted type of linear fractional pattern to the right,and the LREE and HREE occurred significant differentiation.Total REE in rock is higher,the amount of REE in ore is low,from ore to the surrounding rock,the total REE increased gradually,the Eu from the positive anomaly to negative anomaly,which show that the ore inherits the REE characteristics of ore-forming hydrothermal solution with the ore precipitation.The triangle genesis diagram of electron probe TiO₂-Al₂O₃-?MgO+MnO?on magnetite indicated that the deposit belongs to the genesis of skarn type.Total REE in magnetite is low,the LREE and HREE occurred significant differentiation,and no obvious Eu and Ce anomalies.The spider diagram of trace elements show high consistency,the content of siderophile elements,chalcophile elements is higher,and enrichment in high field strength elements?HFS?and depletion in lithophile element?LILE?.The content of Co and Ni is higher,and the value of Co/Ni is greater than 1,which indicated that the formation of metallogenic material source of magnetite is deep and related to the mineralization of deep granitic intrusive rocks.The metal sulfide standard chemical is calculated by electron probe,The successively generating relation of Molybdenite,pyrite,chalcopyrite,sphalerite,galena and covellite can be seen that the value of S is decreased in succession,which explain the mineral formation of reductive environment gradually weakened.Middle-high temperature?250³00??type is determined through the Zn/Fe ratio of sphalerite,through the calculation of the average temperature is about 284.9?,the deposit belongs to the middle-high temperature type of sphalerite.According to the Characteristic analysis of fluid inclusions and stable isotopes,and investigating the ore-forming materials and ore-forming fluids sources,it point out that the ore-forming materials are mainly derived from the deep focus of granite magma.The ore-forming fluid is mainly magmatic water,and then large amount of atmospheric precipitation joins in.The ore-forming fluid is a kind of fluid with medium-high temperature,low salinity and low density.On the basis of comprehensive research on geological features and geochemical characteristics of the ore deposit,it shows that the genesis of mineral deposit is related with granitic magmatic activity in deep mantle.This deposit belongs to contact metasomatic skarn type iron deposit.