Geochemical Characteristics And Metallogenic Model Of Banded Iron Formations From Macheng Deposit,Eastern Hebei

The Macheng sedimentary metamorphic iron deposit is located in the east side of the Sima long duplex syncline,which is a large-scale iron deposit discovered in recent years.The paper firstly studys the magnetite quartz rock collected from the same drilling hole.The mineral compositions of Macheng iron deposit are magnetite and quartz.The main components of ore in Macheng iron deposit are Si O2?Fe2O3 and Fe O with an average of about 90%.Iron ore is mainly chemical sedimentary rocks that have suffered from regional metamorphism.Light rare earths are relatively loss,medium and heavy rare searths are relatively rich.The whole shows Eu,Y positive anomaly,and high Y/Ho value.Macheng Iron Ore Quartz has the characteristics of hot-water-forming features,which suggests that the metallogenic material of the BIFs iron ore deposits in Macheng probably originated from the discharge of hydrothermal fluids and water in the bottom of the sea.The epidote amphibolite facies metamorphism is the main period of fluid inclusions.During the peak period,type Ib gas-rich two-phase and type III carbon dioxide-rich three-phase inclusions are developed with a uniform temperature of 335~580?,salinity 2.90wt%~18.55wt%Na Cleqv;after the epidote amphibolite main development Ia rich two-phase and IV type sub-inclusions.The uniform temperature and salinity are 159~>580? and 1.55wt%~5.99wt%Na Cleqv,which shows they are very poor.This area has suffered multiple phases of fluid alteration.The type II secondary inclusions are generally developed in the late hydrothermal alteration stage.The uniform temperature and salinity are 131 ? ~239 ?,1.4wt%~21.6wt%Na Cleqv,which is characterized by low salinity,the formation of iron-rich ore is related to such inclusions.The ore-forming fluid system is H2O-Na Cl-CO2±N2,the fluids related to the iron-rich ore have both the characteristics of magmatic and metamorphic hydrothermal fluids.Through the systematic study of the Macheng iron deposit,combining with the geological characteristics,it explores the genesis and establishes the corresponding metallogenic model.