In-situ 230Th/U dating of Quaternary zircons using LA-MCICPMS

Zircon is the most widely used mineral for geochronology purposes, as parts of it can behave as a closed system for billions of years and resist most geochemical alteration; yet, its use in Quaternary geochronology has been largely overseen, and limited to few laboratories. Here we present a new simple methodology to obtain precise and accurate 238U-230Th-232Th composition from zircons using LA-MCICPMS, which permits obtaining meaningful ages of well constrained Pleistocene and Holocene volcanic samples from Mexico. The results are compared with that of alternative instrumental techniques, such as SIMS, and other radiogenic dating methods (40Ar/39Ar, 36Cl and 14C). Our results show that the technique presented here is superior to SIMS in terms of precision, and analysis time, and equivalent in terms of sensitivity and spatial resolution. Moreover, the 230Th/U ages obtained here are also consistent with those obtained by other radiogenic dating methods, as well as the geological and geochemical constrains imposed by comparing ages from different mineral phases. The 230Th- 232Th- 238U analysis of zircons by LA-MCICPMS allows to obtain significantly richer isotope information from any set of Quaternary zircons, opening a window into the temporal evolution of crustal magma chamber.