JPD-analysis as a New Approach for Studying the Zircon Texture with Micron Spatial Resolution with Application to Geochronology

Resumo

The polygenic and polychronous character of the texture (heterogeneity of the chemical and isotope composition, degree of crystallinity, stress, etc.) of zircon is the key source of information on the conditions of its growth and secondary alterations. The JPD method of processing of the BSE and CL images including plotting of JPD histogram and JPD map of grains was developed and tested in this research for quantitative study of the internal texture of zircon grains with micron spatial resolution and its application in geochronometry. Based on the concentration of impurities (Cameca SX100 micoanalyzer), the parameters of the Raman spectra, and photoluminescence (Horiba LabRam HR800 Evolution spectrometer), the nomenclature for distinguishing individual zones on the generalized diagram (BSE vs. CL) is suggested for zircons of a wide range of the conditions of the formation, age, size, texture types, and degrees of structure disordering. The JPD-analysis of the zoned texture of zircon grains is applied for interpretation of the nature of variations in the BSE and CL intensities within an individual heterogeneous grain on the quantitative level, and between the different grains, on the qualitative level, as the preliminary stage during geochronological studies increasing the reliability of the local electron microprobe and mass spectrometry isotope studies of the mineral.