Further characterization of M257 zircon standard: A working reference for SIMS analysis of Li isotopes

Zircon is the most useful mineral for studies in U-Pb geochronology, Hf and O isotope geochemistry, trace element geochemistry, and increasingly geothermometry. In situ SIMS zircon Li isotope analysis shows potential for studying the genesis of crustal magmas and evolution of the continental crust, but its application has been hampered due to lack of well-characterized zircon Li isotope standards. Reconnaissance SIMS measurement of Li isotope ratio and concentration for several commonly-used zircon U-Pb age standards, including M257, BR266, Plesovice, 91500 and TEMORA 2 zircons are reported here. Of these, the M257 zircon is demonstrated to be homogeneous in Li isotopic composition, with delta Li-7 = 2.1 +/- 1.0 parts per thousand (2SD). It is also relatively homogeneous in Li concentration, with Li concentration = 0.86 +/- 0.18 ppm (2SD). Therefore, we recommend the new M257 zircon standard as a working reference for SIMS Li isotope and concentration measurements in zircons.