Determination of Lu and Hf Mass Fractions and 176Hf/177Hf Ratios in Mafic‐Ultramafic Rock Reference Materials by Multi‐Collector Inductively Coupled Plasma‐Mass Spectrometry

• Published in: Geostandards and geoanalytical research 2023-12, Vol.47 (4), p.869-891
• Main Authors: Ma, Qian, Yang, Yue‐Heng, Yang, Zhi‐Ming
• Format: Article
• Language: English
• Subjects: 176Hf/177Hf ratio; bomb and bench‐top dissolution; ID‐MC‐ICP‐MS; Lu and Hf mass fractions; mafic‐ultramafic rock reference materials; Mass spectrometry; Mass spectroscopy; Peridotite; Reference materials; Rocks; Ultramafic rocks
• ISSN: 1639-4488; 1751-908X
• DOI: 10.1111/ggr.12513

Reported data for Lu, Hf mass fractions and 176Hf/177Hf isotopic ratios of mafic‐ultramafic rock reference materials (RMs) are rare at present, hampering the comparison of data quality between difference laboratories. Herein, we measured the Lu and Hf mass fractions and the 176Hf/177Hf isotopic ratios of ten mafic‐ultramafic rock RMs, including OKUM (komatiite), WPR‐1 (serpentinised peridotite), NIM‐N (norite), NIM‐P (pyroxenite), UB‐N (serpentinised peridotite), JP‐1 (peridotite), NIM‐D (dunite), MUH‐1 (serpentinised harzburgite), HARZ01 (harzburgite), DTS‐2b (dunite), which contain extremely low amounts of Lu and Hf (Lu, 2–150 ng g−1; Hf, 5–500 ng g−1). All measurements were conducted on a Neptune Plus multi‐collector inductively coupled plasma‐mass spectrometer employing an Aridus II desolvator inlet system and Jet sample/X skimmer cone configuration. The following RMs, OKUM, WPR‐1, UB‐N, JP‐1, NIM‐D, HARZ01 and DTS‐2b, have 176Hf/177Hf precision of less than 60 ppm (2s) at test portions of 0.06 to 0.3 g, and are good ultramafic RMs for Lu‐Hf systems. In contrast, significant Hf mass fraction and isotopic variability were observed in NIM‐N, NIM‐P and MUH‐1 at test portion masses of 0.1 to 0.3 g. Collectively, our study provides a new database that can be used by the geochemical community for evaluating the Lu‐Hf system of mafic‐ultramafic rocks. Key Points Lu and Hf mass fractions and 176Hf/177Hf isotope ratios of ten mafic‐ultramafic reference materials obtained by ID‐MC‐ICP‐MS are reported. Use of the bomb digestion method is essential to acquire valid Lu‐Hf data in mafic‐ultramafic rocks. OKUM, WPR‐1, UB‐N, JP‐1, NIM‐D, HARZ01, and DTS‐2b are suitable RMs for validation of Lu‐Hf data.