RioM-1: A new calcite reference material for U-Pb LA-ICP-MS geochronology
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Abstract
Determining absolute ages of carbonate diagenesis, faulting, fossil formation, speleothem growth, carbonate-hosted hydrocarbon deposits, vein mineralisation and hydrothermal alteration has become increasingly accessible through LA-ICP-MS U-Pb dating of calcite, complementing traditional isotope dilution methods still applicable to certain materials (e.g., speleothems via micro-drilling). However, well-calibrated reference materials for LA-ICP-MS calcite geochronology remain scarce. Here, we characterise the Rio Maior calcite, designated ‘RioM-1’, as a potential reference material for U-Pb dating by LA-ICP-MS. Fragments (0.1 to 1 cm3) from a single scalenohedral crystal were analysed by ID-TIMS (U-Pb), LA-ICP-MS (U-Pb and 87Sr/86Sr), and SIMS (O isotopes). RioM-1 displays high U mass fraction and low, though variable, proportions of common Pb. Combined ID-TIMS analyses from two independent laboratories yielded a Tera-Wasserburg lower intercept date of 63.93 ± 0.11 Ma (2s, MSWD = 1.3, n = 16). LA-ICP-MS U-Pb data from three independent laboratories are concordant with the TIMS age, producing a pooled date of 64.10 ± 0.12/1.2 Ma (2s, MSWD = 7.7, n = 708) and an initial 207Pb/206Pb ratio of 0.85 ± 0.01. Other calcite reference materials, when normalised to RioM-1, yielded dates within uncertainty of their published values. SIMS measurements returned a mean 18O/16O of 0.002044450 ± 181 (1s) and δ18OSMOW of 19.57 ± 0.92‰ (1s), while LA-ICP-MS strontium isotope measurement yielded a mean 87Sr/86Sr of 0.708177 ± 9 (2s).
Suggested Citation
Silva, M., Lana, C., Scholz, R., Buick, I., Kamo, S., Roberts, N.M., Gerdes, A., Wiedenbeck, M., Schoene, B., Apen, F.E., and Gaynor, S.P., 2026, RioM-1: A new calcite reference material for U-Pb LA-ICP-MS geochronology: Geostandards and Geoanalytical Research, v. 50, no. 1, p. 181-199, https://doi.org/10.1111/ggr.70018.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | RioM-1: A new calcite reference material for U-Pb LA-ICP-MS geochronology |
| Series title | Geostandards and Geoanalytical Research |
| DOI | 10.1111/ggr.70018 |
| Volume | 50 |
| Issue | 1 |
| Publication Date | October 06, 2025 |
| Year Published | 2026 |
| Language | English |
| Publisher | Wiley |
| Contributing office(s) | Geology, Geophysics, and Geochemistry Science Center |
| Description | 19 p. |
| First page | 181 |
| Last page | 199 |