Examination of the accuracy of SHRIMP U–Pb geochronology based on samples dated by both SHRIMP and CA-TIMS

Abstract. Estimations of the reproducibility U–Pb ages from SHRIMP (Sensitive High-Resolution Ion MicroProbe) instruments are based on data studies that nearly 2 decades old. Since time, refinement analytical procedures and operational improvements have reduced historically identified uncertainties analysis. This paper investigates 36 thermal ionisation mass spectrometry (TIMS) double-dated “real-world” geologic samples a variety igneous rock types to better understand both geological sources disagreement between two dating methods. Geoscience Australia's (GA) use high-precision chemical abrasion (CA-TIMS) for chronostratigraphy in Australian sedimentary basins has produced substantial selection precisely dated zircons, which we can cross-correlate CA-TIMS throughout Phanerozoic. A total 33 were reported with external less than 1 % (95 confidence). Six eight cases where age was outside uncertainty envelope 95 confidence interval below 0.66 uncertainty, suggesting analyses untreated zircon smaller probably overoptimistic. The mean offset TIMS is 0.095 %, but distribution appears bimodal. Geological explanations discrepancies suggested by considering intrusive extrusive results separately. All one sample more 0.25 older volcanic. could be explained single-grain resolution TIMS, allowing identification exclusion antecrysts eruptive population, while does not sufficient precision deconvolve these populations – leading an apparent age. In contrast, plutonic rocks particularly early Paleozoic typically younger same samples, most likely reflecting Pb loss non-chemically abraded zircons prior analysis destroyed or corrected areas loss.