Work

Baddeleyite SK10 ‐3: A Natural Reference Material for Microbeam U‐Pb Geochronology and Hf Isotopic Measurements

Year: 2024

Type: article

Abstract: Baddeleyite is an important U‐Pb geochronometer and Hf isotope tracer that commonly occurs as an accessory phase in silica‐undersaturated igneous rocks of terrestrial and extra‐terrestrial origin. Currently, very few well‐characterised, large sized reference materials are available for baddeleyite U‐Pb geochronology and Hf isotope measurement. In this study, we document a baddeleyite reference material (SK10‐3) of Cenozoic age. SK10‐3 is inclusion‐free and does not contain secondary alteration minerals. The baddeleyite has uniform U‐Pb ages and Hf isotope ratios, within analytical uncertainty, as demonstrated by multiple LA‐ICP‐MS spot analyses (weighted mean 206 Pb/ 238 U age: 31.59 ± 0.11 Ma, MSWD = 0.7, n = 197) and LA‐MC‐ICP‐MS analyses (arithmetic mean 176 Hf/ 177 Hf ratio: 0.282741 ± 59, 2 s , n = 188). Seven ID‐TIMS analyses yielded a weighted mean 206 Pb/ 238 U age of 31.592 ± 0.020/0.022/0.040 Ma ( n = 7, 2 s , MSWD = 2.2). Nine aliquots of MC‐ICP‐MS analyses yielded an arithmetic mean 176 Hf/ 177 Hf ratio of 0.282742 ± 8 (2 s ). We further demonstrate that the method of shallow‐pit (~ 2 μm depth) ablation substantially improves the precision and accuracy of baddeleyite U‐Pb ages. SK10‐3 has a relatively high 176 Yb/ 177 Hf ratio (~ 0.007) compared with most other baddeleyites, allowing the precise measurement of β Yb and may be useful in generating the β Yb ‐β Hf relationship during LA‐MC‐ICP‐MS Hf isotope measurement. SK10‐3 may be a useful addition to previously distributed baddeleyite reference materials for microbeam‐based U‐Pb geochronology and Hf isotope measurements.

Source: Geostandards and Geoanalytical Research

DOI: 10.1111/ggr.12591