Metamorphism Degree Of BIF Deposits In Eastern Hebei Province Constraints From The Mineralogical Characteristics

The BIF iron deposit in the eastern Hebei province is one of the important iron resources in China.The larger BIF iron deposits in the area include the Macheng iron deposit,the Shirengou iron deposit,the Shuichang iron deposit,the Douzigou iron deposit,and the zhalanzhangzi iron deposit.The ore is mainly magnetite quartzite with banded structure.In this paper,magnetite quartzite samples from the Macheng iron deposit,Shirengou iron deposit,Shuichang Iron deposit,Douzigou iron deposit,and Zhalanzhangzi iron deposit are selected for petrography,mineral typology,and fluid inclusions to obtain relationship between the metamorphicgrade of BIF iron deposits and mineral typomorphic characteristics,further we infer the relationship between the metamorphicgrade and ore grade.The high-metamorphicgrade of BIF iron deposit ore structures has changed from banded structures to gneissic structures,massive structures,and the particle size of the ore minerals has increased,indicating that the degree of metamorphism has an obvious transformation effect on the ore structure.The X-ray diffraction analysis of quartz showed a positive correlation between the cell parameters and the metamorphicgrade.It is speculated that the metamorphicgrade is closely related to the ore grade.Electronic probe analysis of magnetite,amphibole,biotite and chlorite,the data show that the metamorphicgrade can affect the Fe O content in the mineral,the ore with high Fe O content has a higher metamorphicgrade.The amphibole is a magnesium-rich and ironpoor amphibole,the biotite from the original magma,The Fe O content in chlorite is negatively correlated with Mg O and Si O2.Fluid inclusions are classified into class I secondary inclusions,class II gas-liquid two-phase inclusions,class III submineral inclusions and class IV CO2 three-phase inclusions.Among them,The class II,III and IV belongs to metamorphic formation of inclusions,the uniform temperature was positively correlation with metamorphicgrade.Figure 23;Table 23;Reference 67...