Pages: 261 - 270
Abstract: Zircon is an uncommon but widespread accessory mineral in Hercynian barren to beryl-columbite rare-element granitic pegmatites of the Central Western Carpathians, Slovakia. BSE images show either homogeneous composition, or irregular to oscillatory zoning, and locally also two-stage crystal growth. Electron-microprobe analysis reveals elevated Hf, locally also P, Y, REE, Al, Fe and Ca. Hafnium content and Zr/Hf ratio are proportional to the fractionation degree of the host pegmatite; zircon from the barren pegmatites attains 1 to 8 wt. % HfO2 (average 3 wt. %), zircon from the beryl-columbite pegmatites contains 2 to 22 wt. % HfO2 (average 7 wt. %). HfZr-1, Al3+P5+Si4+-2 and (Y,HREE,Fe)3+P5+(Zr,Hf)4+-1Si4+-1 are the possible substitution mechanisms. Calculation of the temperature of zircon saturation gave TS ≈ 700 to 580 °C, which corresponds to a primary magmatic origin of the zircon.
Keywords: Western Carpathians, geochemistry, temperature of crystallization, granitic pegmatite, zirconDownload PDF document Show Text Version