Cambridge University Press. How is age determined on ancient rocks? Combining all of these attributes, it is often possible to measure both the time of crystallization and the time of second melting in different parts of the same grain or in different selected grains from the same rock. The ratio of lead versus uranium in the zircon is what is used to determine the age of the rock. Geochronology - Methods and Case Studies. These ages have been interpreted as effect of a recrystallization event assisted by fluids [ 16187 ]. Contributions to Mineralogy and Petrology4:
The same spot size and integration intervals were considered on both standard and studied zircons.
Zircon Chronology: Dating the Oldest Material on Earth
First, its crystal structure allows a small amount of tetravalent uranium to substitute for zirconium but excludes with great efficiency the incorporation of lead. Join the Community. That way, scientists know the exact composition of that tiny sample. The zircon formation may have occurred tens to hundreds of thousands of years before the eruption and deposition. Geology professors Darrell Henry of Louisiana State University and Paul Mueller of the University of Florida are expert practitioners of several techniques that can extract precise age information from zircons.