Mineralogy Of Graphite In Weathering Alteration Zone Of Typical Graphite Deposits

Graphite is a non-metallic mineral with a layered structure,which has excellent high temperature resistance,electrical and thermal conductivity,good peelability,lubricity and high chemical stability.Graphite of different origins and different genetic types may have certain differences in crystal grain diameter,the ratio of diameter to thickness,the degree of crystallization and the structural defects.Therefore,graphite with different weathering degree in different weathering zones also has some differences in crystal structure,spectral parameters,physical and chemical properties.However,there are few reports in the literature.Three graphite mining areas including Yunshan in Luobei,Liumao in Jixi and Pinghe in Nanjiang were studied in our work.Through the geological investigation in the field,graphite samples from typical sections of weathered alteration zones are collected from the surface weathering of graphite deposits,and the mineralogical characteristics of weathered graphite ores are systematically studied.Based on the knowledge of mineralogy,mineralogy,crystal chemistry and crystal physics,the crystal structure,spectral characteristics and physical and chemical properties of weathered graphite ores and weathered graphite are investigated by using modern analytical techniques such as XRD,FT-IR,Raman,SEM-EDS,four-probe tester and contact angle tester.Spectral characteristics and physical and chemical properties of weathered graphite were explored to reveal the weathering and alteration mechanism of graphite in nature,which provided the mineralogical basis for the oxidation mechanism of graphite.The mineral composition of graphite ore in the three mining areas is similar.In addition to graphite,the common and associated minerals are mainly quartz,biotite,potassium feldspar,calcite,chlorite,etc.The Nanjiangpinghe graphite deposit also contains a large amount of pyrite.The chemical composition of the ore is mainly Si O2,Al2O3,K2 O,Fe2O3,Mg O,Ti O2,and the mineral components are basically the same.The paper systematically studied the mineralogical characteristics of weathered graphite ore in three mining areas,including the texture and structure of ores,natural type of ore,mineral composition and embedding characteristics,chemical composition of ores,etc.2The morphology of weathered graphite in three mining areas was obtained from the SEM images.The edges of weathered graphite samples in Yunshan and Liumao graphite deposits in Luobei and Jixi are generally wrinkled and bent,forming two-dimensional pores with different sizes and different shapes,which are easily broken along the graphite structure layer.The graphite structure layer is partially connected to the oxygen-containing functional group,which results in the changes of the chemical bond length and makes the surface of the weathered graphite sample pleated obviously.Weathered graphite in Pinghe Graphite Mine of Nanjiang,Sichuan Province is relatively fragmented,with relatively small particle size and the graphite weathering boundary is obvious.XRD pattern analysis shows that the d002 value of graphite single mineral sample increases with the ore weathering degree,,and the peak shape of diffraction is asymmetric,with tends to broaden to a lower angle.Raman spectra showes that the D peak of weathered graphite samples appears and gradually increases.The intensity integral ratio(R)of ID/IG increases gradually indicating the decrease of crystal structure perfection.In particular,the graphite samples of Pinghe in Nanjiang show obvious characteristics of graphite oxide.XPS and FT-IR analysis show that the components of each sample contains different contents of O,and in addition to the sp2 hybrid type bonding carbon atoms,there are also carboxyl groups(COOH)and carbonyl groups(C=O),and epoxy groups(C-O-C)and hydroxyl(C-OH),which has similar surface chemical structure with graphite oxide.The oxidation temperature range of the graphite samples in the three mining areas is relatively close,ranging from 750 to 1025?.With the deepening of weathering degree of graphite ore,the initial temperature of graphite sample decreases,and the exothermic peak shows a broad peak shape.The resistivity of graphite samples in Hei longjiang Province is lower than that of Pinghe graphite samples in Nanjiang,On the whole,the resistivity increases with the deepening of weathering degree.The surface wetting properties of graphite samples are tested.The contact angles of the two mines in Luobei Yunshan and Jixi Liumao are larger than those in the weathered graphite samples in Nanjiang.The higher the degree of weathering,the smaller the surface bulge,the smaller the contact angle,and the stronger the hydrophilicity.Compared with the artificial graphite oxide,the weathering degree of natural weathered graphite samples is about GO-0.1-0.5 times of the oxidation degree of artificial graphite oxide.Based on the characteristics of crystal structure and chemical bonding of graphite,and the practice of preparing graphite oxide in laboratory,this paper explores the possible changes of crystal structure and spectral parameters of natural graphite in the course of geochemical superimposition in the later stage of nature,and reveals the weathering and alteration mechanism of graphite under natural conditions.The research scope of graphite mineralogy and crystal chemistry has been expanded,which has important theoretical significance for the utilization of weathered graphite deposits.