U th he dating of apatite a potential thermochronometry
Helium diffusion from apatite is a sensitive function of the volume fraction of radiation damage to the crystal, a quantity that varies over the lifetime of the apatite. (2006) The influence of natural radiation damage on helium diffusion kinetics in apatite. By incorporating the RDAAM into the He FTy computer program, we explore its implications for apatite (U–Th)/He thermochronometry.Using recently published laboratory data we develop and investigate a new kinetic model, the radiation damage accumulation and annealing model (RDAAM), that adopts the effective fission-track density as a proxy for accumulated radiation damage. We show how (U–Th)/He dates predicted from the model are sensitive to both effective U concentration (e U) and details of the temperature history.The conodonts have CAI values of 1-1.5, indicating maximum burial temperatures of ≤ 90 °C.First, the conodonts yield He dates substantially younger than their depositional age, indicating that the ≤ 90 °C temperatures were sufficient to cause He loss, and therefore implying that the conodont He closure temperature is no higher than the conventional apatite He system (70-80 °C).The (U-Th)/He picking and grain measurement facilities were funded through JSG start-up funds to Stockli and are also used for U-Pb (LA-ICP-MS and TIMS) and other geochronologic sample preparation.Automated He Extraction Line for (U-Th)/He Dating The UT (U-Th)/He laboratory houses three state-of-the-art, all metal, ultra-high vacuum noble gas extraction and purification lines for measuring 4He.UT (U-Th)/He Laboratory Picking and Grain Measurement Facilities This facility is housed in a complete renovated laboratory space at the UT JSG.Mineral grains are handpicked and screened for inclusions using customized Nikon SMZ-U/100 stereomicroscopes with a rotating stages.
Conodonts are toothlike bioapatite structures common in Paleozoic through early Mesozoic marine carbonates and shales. They suggest relative tectonic quiescence in the latest Cretaceous through mid-Tertiary and provide no evidence for rapid unroofing of the block during this period. Detailed reviews by Trevor Dumitru and Mark Brandon greatly improved this paper. Helium ages are strongly correlated with elevation and record the latest low-temperature thermal evolution of the range.Considerations of the data indicate removal of up to 9 km overburden since the Palaeozoic.Thermal modelling reveals a protracted rapid cooling event commencing during the early Carboniferous (ca.