In situ U-Pb zircon dating using laser ablation-multi ion counting-ICP-MS

TLDR: In this article, a method using laser ablation-multicollector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) was proposed to overcome complications associated with intricately zoned zircon crystals through in situ sampling of zirmin volumes as small as 12 μm, 25 μm and 40 μm in diameter by about 10 μm.

Abstract: High resolution in situ U-Pb zircon geochronology on zoned grains can obtain isotope signatures from multiple growth or thermal events.We present a method using laser ablation-multicollector-inductively coupled plasma-mass spectrometry(LA-MC-ICP-MS) to overcome complications associated with intricately zoned zircon crystals through in situ sampling of zircon volumes as small as 12 μm,25 μm and 40 μm in diameter by about 10 μm in depth.High precision U-Pb age of a series of zircon standard covering a wide age range of 30 to 1 065 Ma was acquired using LA-MC-ICP-MS.The precision of measured Pb/U ratios in homogeneous zircon is about 2%(2σ),resulting in routinely achieved precision of U-Pb ages obtained by external calibration of～1%(2σ) or better.All masses of interest can be simultaneously recorded with a multi-ion counting system(MIC) operating in static mode,and the short ablation required to achieve such precision results in spatial resolution that is superior to comparable U-Pb zircon analyses by single collector ICP-MS.The resulting present U-Pb age for five zircon reference samples and two geological samples show an excellent agreement with the previously reported ID-TIMS or SHRIMP data.