Details

Autor(en) / Beteiligte

• Sano, Yuji
• Koyama, Yuta
• Takahata, Naoto
• Matsuzaki, Takuya
• Koike, Mizuho
• Haba, Makiko K.
• Sakata, Shuhei
• Kuwahara, Hideharu
• Irifune, Tetsuo

Titel

Hf-W dating of zircon in mesosiderite with high-pressure sintered standard

Ist Teil von

• Journal of analytical science and technology, 2024-12, Vol.15 (1), p.24-11, Article 24

Ort / Verlag

Singapore: Springer Nature Singapore

Erscheinungsjahr

2024

Quelle

Elektronische Zeitschriftenbibliothek (Open access)

Beschreibungen/Notizen

• New standard zircons applicable to in situ analysis of Hf/W ratio by Nanoscale secondary ion mass spectrometer (NanoSIMS) were prepared and applied to Hf-W dating of a differentiated meteorite classified as mesosiderite. The standard zircons were synthesized by high-pressure experiment from starting materials which were mixture of hafnium oxide, tungsten oxide and high-purity zircon powder. The mixed powders were stirred and pulverized by a high-energy ball mill. They were then sintered at 1000 °C and 6 GPa using multi-anvil apparatus. Homogeneity of Hf/W ratios of synthesized zircons was examined by SEM–EDS, EPMA, and Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICPMS). Hf/W ratios of the same zircons were measured by a NanoSIMS with 2 nA oxygen primary beam and mass resolving power of 10,000. The relative sensitivity factor (RSF) of Hf/W ratio was determined by comparing zircon data measured by LA-ICPMS and NanoSIMS. Observed RSF (Hf/W) of zircon is 0.585 ± 0.180 (hereafter all error 2σ) consistent with 0.855 ± 0.468 of previous work within experimental error margin. The value is higher than observed RSF of glass matrix, 0.301 ± 0.062, and significantly higher than glass data of 0.21–0.22 in references. Based on the RSF, the Hf/W ratios of zircons extracted from mesosiderite “Asuka 882,023” were measured together with W isotopic compositions by NanoSIMS. Observed data in 180 Hf/ 186 W– 182 W/ 186 W diagram are fitted by a straight line, yielding a slope ( 182 Hf/ 180 Hf) of 8.19 ± 3.50 × 10 –6 . This slope is converted into an absolute zircon Hf-W age of 4536.5 +4.6 –7.2  Ma using the age anchor of CV3 chondrite. This age agrees well with a reference value of 4532.0 +11.4 –20.8  Ma.