Macroscopically-Zoned Grandite from the Garnetite Skarn of Meka Presedla (Kopaonik Mountain, Serbia)

摘要

The macroscopically-zoned grandite from the garnetite skarn of Meka Presedla(Kopaonik Mountain,Serbia) was studied with optical microscopy,electron microprobe analysis(EMPA),Fourier transform infra-red(FT-IR),and Raman methods.The EMPA results indicate that the main core-rim compositional variations(Ca2.93-2.97Mn0.05-0.06Mg0.00-0.01Al1.14-1.26Fe3+0.72-0.83Ti0.00-0.02Si2.97-3.02O12) slightly differ along the zones,showing evidence for a quasi-cyclic alternation of the oscillatory zoning nature.Among this,considerable variation is observed only by the Al-Fe3+ substitutions in the octahedral site.The EMPA also indicate that the grandite zones compositionally vary,mostly within ±1 and ±2 mol% of the homogeneity level range,that is,Grs64±1Adr36±1Sps2(A),Grs62±1Adr38±1Sps2(B),Grs59±2Adr40±2Sps2(C),Grs58±2Adr41±2Sps2(D),and Grs58±1Adr41±1Sps2(E).Therefore,the investigated garnet can be considered as relatively highly homogeneous.The majority of compositions lie within the narrow miscibility region of 0.58±2