SA01: a new potential reference material for zircon in situ (U–Th)/He and U–Pb double dating

Abstract

The zircon in situ laser (U–Th)/He and U–Pb double dating technique has been proven to be a powerful and efficient tool for sedimentary provenance studies. The recently developed laser microanalysis technique offers some advantages over conventional bulk crystal chemical methods such as higher spatial resolution, more productivity, and higher safety by avoiding the usage of concentrated hydrofluoric acid. To achieve this, matrix-matched zircon reference materials with a homogeneous composition (especially parent nuclides such as U, Th, and Sm isotopes) and (U–Th)/He age are urgently needed. In this study, a new natural zircon reference material SA01 is reported for in situ (U–Th)/He and U–Pb double dating by laser microbeam techniques. Three randomly selected shards yielded weighted mean in situ (U–Th)/He ages of 350.4 ± 18.8 Ma (N = 5, MSWD = 0.66), 369.6 ± 11.4 Ma (N = 12, MSWD = 0.60), and 368.6 ± 14.4 Ma (N = 7, MSWD = 0.59), respectively, which were consistent with traditional single-crystal laser fusion He determination and U–Th isotope dilution (U–Th)/He ages of 358.5 ± 9.1 Ma (N = 17, MSWD = 1.3) and 363.7 ± 13.6 Ma (N = 8, MSWD = 1.7) from two different laboratories. All the in situ analyses yielded a concordia age of 535.2 ± 7.1 Ma (N = 32, MSWD = 5.1) and weighted mean U–Pb age of 535.4 ± 7.1 Ma (N = 32, MSWD = 0.96), which was indistinguishable with published isotope dilution thermal ionization mass spectrometry (ID-TIMS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb ages. Raman spectrometry analysis suggested that the SA01 zircon experienced a low degree of radiation damage. All the results suggest that the SA01 zircon could serve as a new potential reference material for in situ (U–Th)/He, U–Pb double dating and traditional solution (U–Th)/He dating techniques.