SA01 – A Proposed Zircon Reference Material for Microbeam U‐Pb Age and Hf‐O Isotopic Determination

Abstract

A new natural zircon reference material SA01 is introduced for U‐Pb geochronology as well as O and Hf isotope geochemistry by microbeam techniques. The zircon megacryst is homogeneous with respect to U‐Pb, O and Hf isotopes based on a large number of measurements by laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) and secondary ion mass spectrometry (SIMS). Chemical abrasion isotope dilution thermal ionisation mass spectrometry (CA‐ID‐TIMS) U‐Pb isotopic analyses produced a mean 206Pb/238U age of 535.08 ± 0.32 Ma (2s, n = 10). Results of SIMS and LA‐ICP‐MS analyses on individual shards are consistent with the TIMS ages within uncertainty. The δ18O value determined by laser fluorination is 6.16 ± 0.26‰ (2s, n = 14), and the mean 176Hf/177Hf ratio determined by solution MC‐ICP‐MS is 0.282293 ± 0.000007 (2s, n = 30), which are in good agreement with the statistical mean of microbeam analyses. The megacryst is characterised by significant localised variations in Th/U ratio (0.328–4.269) and Li isotopic ratio (−5.5 to +7.9‰); the latter makes it unsuitable as a lithium isotope reference material.

Further Characterization of the BB Zircon via SIMS and MC-ICP-MS for Li, O, and Hf Isotopic Compositions

“…Correction for molecular interferences (e.g., 160 Gd 16 O) was not made due to low light to middle rare earth element contents in zircon. Zircon reference materials Mud Tank and SA01 analyzed during the same session gave grand mean 176 Hf/ 177 Hf values of 0.282507 ± 0.000032 (2SD, n = 15) and 0.282287 ± 0.000020 (2SD, n = 15), consistent with the reported results [23,38].…”

“…The heterogeneity of Li isotopic compositions and concentrations revealed by this study indicates that BB zircon is unusable as a reference material for micro-beam Li isotopic analysis. Several zircon reference materials used in U-Pb geochronology, including 91500, BR266, TEMORA 2, SA01, Plešovice, Penglai, and Qinghu, have been checked for the homogeneity of Li isotopic compositions, and all of them were shown to have large ranges in δ 7 Li values and Li concentrations [14,38,39], which were ascribed to fast diffusion velocity of Li ion in zircon [14]. At present, only M257 and M127 have been documented to have homogenous Li isotopic compositions and concentrations [31,39].…”

“…However, a matrix-matched reference material is necessary for accurate micro-beam isotope measurements to correct for instrument-induced mass bias and to assess external reproducibility. A number of natural zircons were identified as reference materials by previous number of natural zircons were identified as reference materials by previous studies, like SL7 [15], CZ3 [16], SL13 [17], 91500 [18], Temora [19], BR266 [20], GJ-1 [21,22], Mud Tank [23], M257 [24], Plešovice [25], Sri Lanka [26], OG1/OGC [27], Penglai [28], Qinghu [29], OD-3 [30], M127 [31], BB [32,33], LGC-1 [34], GZ7/GZ8 [35], LKZ-1 [36], GHR1 [37], and SA01 [38]. However, most of them are just used as a reference material for U-Pb geochronology, and the homogeneity of Li, O, and Hf isotopic compositions was not elaborately evaluated [15,17,26,30,34,35].…”

New Evidence for 4.32 Ga Ancient Silicic Volcanism on the Moon

“…Zircon standard Plesovice was used to calibrate this instrument (Sláma et al., 2008). Another standard zircon (SA 01; Huang et al., 2020) was also analyzed as an unknown sample to monitor the reliability of the entire procedure. The measured 204 Pb was used for the common Pb correction, which was assumed to be surface contamination from the sample preparation, and the composition of the sample was calculated according to the two‐stage evolution model (Stacey and Kramers, 1975).…”

The Pre-Grenvillian assembly of the southeastern Laurentian margin through the U–Pb–Hf detrital zircon record of Mesoproterozoic supracrustal sequences (Central Grenville Province, Quebec, Canada)

“…1017/S0016756821001023). The following weighted mean 176 Hf/ 177 Hf values were obtained: BB9 zircon (0.281666 ± 26, MSWD = 1.5, n = 9, 2s, ϵHf value of −27.2 ± 1.2), Maniitsoq (0.280865 ± 15; MSWD = 0.9, n = 10, 2s, ϵHf value of −0.28 ± 0.9), Munzirc12c (0.282129 ± 12; MSWD = 1.3, n = 17, 2s), Munzirc02a (0.282160 ± 8, MSWD = 1.5, n = 18, 2s), Munzirc32c (0.282150 ± 19; MSWD = 2, n = 14, 2s), Munzirc42b (0.282164 ± 14; MSWD = 0.3, n = 11, 2s), Plešovice (0.282475 ± 6; MSWD = 0.6, n = 30, 2s, ϵHf value of −3.5 ± 0.6), SA01 (0.282296 ± 24; MSWD = 1.5, n = 11, 2s, ϵHf value of −5.7 ± 1.5), GJ-1 (0.282006 ± 16; MSWD = 0.6, n = 17, 2s, ϵHf value of −14.3 ± 1.1) and Mudtank (0.282528 ± 11; MSWD = 1.5, n = 16, 2s, ϵHf value of þ7.1 ± 1) (Morel et al 2008;Sláma et al, 2008;Fisher et al 2011;Santos et al 2017;Gain et al 2019;Marsh et al 2019;Huang et al, 2020). The reproducibility (2s) of the secondary reference materials varies from 0.004 to 0.029 %.…”