Time-Of-Flight ICP-MS Laser Ablation Zircon Geochronology: Assessment and Comparison Against Quadrupole ICP-MS
Uranium–lead (U-Pb) dating is an established radiometric dating method in Earth sciences. The method is commonly applied to the mineral zircon which incorporates U and Th but rejects Pb during crystallization. The method relies on two decay series; 238U to 206Pb with a half-life of 4.47 billion years, and 235U to 207Pb with a half-life of 710 million years. In U-Pb dating of zircon by LA-ICP-MS, there is a need for high precision and accurate measurements of these two elements and their isotopes.
This study by Thompson et al. compares U-Pb zircon dating by laser ablation coupled to a time-of-flight inductively coupled plasma mass spectrometer (LA-ICP-TOFMS) and a quadrupole mass spectrometer (LA-ICP-QMS). The results show that both ICP-MS types produce similar levels of precision and accuracy for most U-Pb ages in zircon, especially if the 235U decay series is considered. The advantage of TOFMS is that trace element concentrations (e.g. rare earth elements) in zircon are measured simultaneously along with the U-Pb isotope data.