Using the double-dating approach, we have conducted fission-track (FT) and U-Pb age dating on the same zircon grain to evaluate the reliability of the resulting age data. The zircon grains (OD-) used for the investigation were collected from the Mihara Body of the Kawamoto Granodiorite, Shimane Prefecture, Japan. The zircon crystals yielded a FT age of Ma, with a spontaneous FT density of -cm . The U-Pb age data were obtained using inductively coupled plasma-mass spectrometry (ICP-MS) combined with a frequency quintupled Nd-YAG (λ = nm) laser ablation (LA) sample introduction system. The U-Pb age determinations on the zircon samples were performed after chemical leaching using % HF for hrs at room temperature, or after FT etching using a KOH-NaOH eutectic solution for hrs at °C. The resulting U-Pb age of Ma was concordant with the FT age data, suggesting that there was no significant loss of Pb during etching or chemical preparation, thus indicating the feasibility of FT and U-Pb double dating of single zircon grains. The results indicate that the zircon grains (OD-) from the Kawamoto Granodiorite (Mihara Body) can become a new working standard for precise U-Pb age determinations of young zircons.

( 2015 ) Multiple trace element analyses for silicate minerals and glasses by laser ablation-inductively coupled plasma-mass spectrometry ( LA-ICP-MS ) . Bull. Geol. Surv. Japan, vol. 66 ( 9/10 ) , 6 figures, 6 tables.Abstract: Programs were established in the shared research facilities of the Geological Survey of Japan ( GSJ-Lab ) for trace element analysis of silicate minerals and glasses in microspots using laser ablationinductively coupled plasma-mass spectrometry ( LA-ICP-MS ) . National Institute of Standards and Technology ( NIST ) synthetic glasses reference materials ( NIST 613 and NIST 611 ) were used as external calibration standards, and suitable instrumental operation settings were set as follows; 0.5 L min -1 He carrier gas flow rate, 100 μm laser spot diameter, 5 Hz repetition rate, and 40 % laser energy ( fluence ca. 2.0 J cm -2 ) . NIST 615 and NIST 613 were analyzed as unknown samples to evaluate precision and accuracy. Precision was mostly less than 30 % for 45 elements from 45 Sc to 238 U for laser spot diameters ranging from 100 to 10 μm. Accuracy was evaluated according to the difference ( DIF ) between the analytical results and reference values in the literature. Accuracy for the analysis of NIST 613 was DIF < 30 %, except for Sc, Mn, Ni, and Ge. For NIST 615, DIF was less than 30 %, except for Tl with laser spot diameters of 20 and 10 μm, and for Cd with a laser spot diameter of 20 μm. The depths of laser pits for generic conditions for the analysis of clinopyroxene, amphiboles and plagioclase were estimated as extents without penetration of the thin section samples. Two suites of analytical programs ( 34 and 27 elements ) were additionally prepared for general purpose petrological and geochemical discussion and the accuracy of both was evaluated. The DIFs for the suite of 34 elements were mostly less than 30 %, although some for Cr, Mn, Ni, and Cs with laser spot diameters < 40 μm exceeded 30 %. In the suite of 27 elements, the DIFs were < 30 %, except for Sc.

No abstract