Study On Mineralogical Characteristics And Genesis Of Phlogopites In "Ganlan Jade" Ore In Ji'An,Jilin

Based on the main research object of phlogopites in the“Ganlan jade”ore in Ji'an,Jinlin province,this thesis makes an in-depth analysis of its occurrence characteristics,mineral assemblages,major and trace elements characteristics,as well as spectral characteristics such as infrared spectra and Raman spectra,and discusses the information of genesis of different types phlogopites such as material sources,formation and evolution process,which provides an effective basis for revealing the mineralization and evolution of“Ganlan jade”ore.The“Ganlan jade”ore in research region is mainly composed of high-Mg olivine and serpentine,which belongs to a kind of serpentinized dunite.The oligoclasite mainly composed of Na-rich oligoclase intrudes into the“Ganlan jade”orebody in form of dikes,and forms a contact band with the“Ganlan jade”.According to the occurrence characteristics of phlogopites in“Ganlan jade”ore,phlogopites can be classified into three types:Contact-band-type phlogopite occurs in the contact zone between the“Ganlan jade”and oligoclasite.The vein-type phlogopite occurs in veinlet or thin aggregate filled in the fissure of“Ganlan jade”orebody.The single granular interstitial phlogopite occurs in interstice of serpentine and olivine in“Ganlan jade”.On the major elements,the phlogopites in“Ganlan jade”ore has the characteristics of rich in Si and Al generally.The contact-band-type phlogopite is rich in Fe,Ti,K,Cl but poor in Mg,Na and F compared to the vein-type and interstitial phlogopites.On the trace elements,the phlogopites are generally rich in Li,Ba,Rb,Mn,V,Zn,Nb and Ta,which show a gradually decreasing trend from contact-band-type phlogopite to vein-type and interstitial phlogopites of“Ganlan jade”.With regards to the characteristics of infrared spectra,the phlogopites in“Ganlan jade”ore are generally similar,with infrared absorption peaks at 455cm^-1,605cm^-1,686cm^-1,723cm^-1,819cm^-1,999cm^-1 and 3710cm^-1 respectively.The Raman spectra of phlogopites in“Ganlan jade”ore are also generally similar,with characteristic Raman peaks near 100cm^-1,155cm^-1,193cm^-1,278cm^-1,360cm^-1,656cm^-1,681cm^-1,820cm^-1 and 1027cm^-1 respectively.However,the characteristic peaks near 193cm^-1,360cm^-1 of Fe-rich contact-band-type phlogopite may shift to the lower frequency region,and appear around 187cm^-1 and 348cm^-1 respectively.In additional,other characteristic peaks appear around 551cm^-1,639cm^-1,727cm^-1 and 783cm^-1 respectively.The genesis of phlogopites in“Ganlan jade”ore are hydrothermal filling metasomatism.In the“Ganlan jade”orebody,intrusive oligoclasite magma could release water-bearing hydrothermal fluid during its evolution process.A part of hydrothermal fluid firstly fills the contact zone between oligoclasite and“Ganlan jade”,then crystallizes and precipitates contact-band-type phlogopite after making metasomatic reaction with surrounding rock,and the other part fills fissures of the“Ganlan jade”orebody and the interstices of constituent minerals of“Ganlan jade”,and forms vein-type phlogopite and interstitial phlogopite respectively after replacing serpentine.The formation and evolution of phlogopites in“Ganlan jade”ore indicates that the eastonite in oligoclasite has the characteristics of hydrothermal genesis and the hydrothermal fluid released by oligoclasite magma is rich in trace elements.It also provides effective evidences for the factors,which influence the quality of“Ganlan jade”caused by modification of hydrothermal fluid,such as the increase of serpentinized degree,color deepening and enrichment of inclusions of“Ganlan jade”ore.