REE, U, Th, and Hf distribution in zircon from Western Carpathian Variscan granitoids: A combined cathodoluminescence and ion microprobe study

Abstract

A cathodoluminescence (CL) investigation on individual zircon crystals from Variscan S-type granites from the Western Carpathians has been combined with ion microprobe rare earth element (REE) and trace element analyses to explore possible connections between the CL emission of natural zircon crystals and their chemical composition. The work was supported by single zircon U-Pb dating, both by thermal ionization mass spectrometry (TIMS) and ion microprobe, which helped to identify inherited zircon cores derived from related protoliths and to constrain the ages of inheritance and anatexis. Neither the REE nor trace elements such as Y or Th were found to have any direct correlation with the CL brightness. The intensity of the CL signals was not directly reflected in the REE concentrations or the shape of the REE patterns. Uranium is probably the element responsible for quenching or suppressing the CL signals. Zircon cores inherited from different protoliths were distinguished by their REE patterns. This enabled, within a particular geological area, the identification of inherited cores which possibly originate from the same protolith and therefore might lie on the same discordance line, thereby improving the accuracy of inheritance ages inferred from TIMS single zircon analyses.