See the oscillatory zoning domains surrounded or invaded by lobate structurless grey or luminescent rims. In these rock-types the Ordovician-Silurian ages represent clusters connected to a recrystallization event being the protoliths Neoproterozoic-Cambrian in origin. Zircon imaging All crystals were inspected under transmitted light and by SEM Scanning Electron Microscope in order to investigate their morphology and collect high-resolution images unravelling the internal microstructures. Inherited cores may give a mixed false age when the age of crystallization is sought.
That would take the zircons on a straight line back to zero on the concordia diagram. This is called Discordia. The high-resolution images of internal zoning patterns of zircons were realized by CL Cathodoluminescence and by VPSE Variable Pressure Secondary Electrons detectors, the last used in high vacuum conditions. Calibration of u—pb detrital zircon u—pb dating. It is also resistant to metamorphism, which is when heat or pressure causes a rock to change its composition or structure.