Accurate U‐Pb Age and Trace Element Determinations of Zircon by Laser Ablation‐Inductively Coupled Plasma‐Mass Spectrometry

Abstract

Various zircons of Proterozoic to Oligocene ages (1060‐31 Ma) were analysed by laser ablation‐inductively coupled plasma‐mass spectrometry. Calibration was performed using Harvard reference zircon 91500 or Australian National University reference zircon TEMORA 1 as external calibrant. The results agree with those obtained by SIMS within 2s error. Twenty‐four trace and rare earth elements (P, Ti, Cr, Y, Nb, fourteen REE, Hf, Ta, Pb, Th and U) were analysed on four fragments of zircon 91500. NIST SRM 610 was used as the reference material and 29Si was used as internal calibrant. Based on determinations of four fragments, this zircon shows significant intra‐and inter‐fragment variations in the range from 10% to 85% on a scale of 120 μm, with the variation of REE concentrations up to 38.7%, although the chondrite‐normalised REE distributions are very similar. In contrast, the determined age values for zircon 91500 agree with TIMS data and are homogeneous within 8.7 Ma (2s). A two‐stage ablation strategy was developed for optimising U‐Pb age determinations with satisfactory trace element and REE results. The first cycle of ablation was used to collect data for age determination only, which was followed by continuous ablation on the same spot to determine REE and trace element concentrations. Based on this procedure, it was possible to measure zircon ages as low as 30.37 0.39 Ma (MSWD = 1.4; 2s). Other examples for older zircons are also given.

Geochronological and geochemical constraints on the petrogenesis of Middle Paleozoic (Kwangsian) massive granites in the eastern South China Block

“…The standard CN92-2, 91500 and GJ zircons were used to calibrate the U-Th-Pb ratios and absolute U abundance. Raw count rates were measured for 29Si, 204 Yuan et al (2004). The errors for individual U-Pb analyses are presented with 1σ error in Supplementary Dataset 1 and Concordia diagrams, and uncertainties in age results are quoted at the 95% level (2σ).…”

Late Miocene provenance change on the eastern margin of the Yinggehai-Song Hong Basin, South China Sea: Evidence from U–Pb dating and Hf isotope analyses of detrital zircons

“…The Temora was used as the age standard ( 206 Pb/ 238 U ¼ 416.8 Ma) (Black et al, 2003). Details of analytical procedure, precision and accuracy are similar to those of Jackson et al (2004), Yuan et al (2004) and Liu et al (2010).…”

Provenance of Upper Miocene to Quaternary sediments in the Yinggehai-Song Hong Basin, South China Sea: Evidence from detrital zircon U–Pb ages

“…Traceelement concentrations were obtained by normalizing count rates for each analyzed element to those for Si, and assuming SiO 2 to be stoichiometric in zircon. The details of precision, accuracy and analytical procedure are described in Jackson et al (2004), Yuan et al (2004) and Liu et al (2010).…”