Quantitative Constraints on Mid- to Shallow-Crustal Processes using the Zircon (U-Th)/He Thermochronometer

Despite the potential of zircon He thermochronometry for constraining rock thermal histories, it remains less commonly exploited than the apatite He chronometer. In part, this is due to the more challenging analytical techniques required to extract He, U and Th. Here we present a new method for the routine determination of zircon (U-Th)/He ages, and demonstrate how it can be used to constrain thermal histories and to quantify cooling in different tectonic settings. We present zircon (U-Th)/He ages that place a firm upper limit on the extent of denudation-induced cooling (c. 3 km) on the SE Australian passive margin; a region where synrift apatite fission-track and apatite (U-Th)/He ages have previously prevented quantitative constraint. We have also used the zircon (U-Th)/He thermochronometer to quantify the cooling of early Tertiary mafic plutons from Skye, Scotland, where the rate and timing of cooling cannot be determined using other thermochronometers.