Unravelling complex shrimp U-Pb zircon ages for Palaeozoic and Mesozoic magmatic rocks: fact or artefact

Abstract

U-Pb zircon geochronology is one of the most widely used tools to determine the crystallization ages of magmatic rocks and the timing of high grade metamorphism. The mineraI zircon is particularly robust and retains information about crustaJ history even through melting events. There are now a variety of analytical methods available to determine U-Pb ages, and the more widely used methods are: (1) conventional wet chemistry, isotope dilution thermal ionisation mass spectrometry (IDTIMS), (2) Sensitive High Resolution Ion Microprobe (SHRIMP) and (3) laser ablation ICP MS (LAM-ICP). Each method has it particular strengths, and weaknesses, but it is our contention that the particular complexities to be discussed in this paper are a consequence of geological processes resulting in multiple generations of zircon crystaJlisation over relatively short periods of time.