Optimization of standard zircon U–Pb dating: insights into high-temperature thermal annealing

The weighted average 206 Pb/ 238 U ages for unannealed and annealed Plešovice zircons (photomicrographs are shown in (a) and (b)) using LA-ICP-MS are shown in (c) and (d) and Sri Lanka zircons using SIMS are shown in (e) and (f).