Hidra aeschynite-(Y): a potential natural reference material for microbeam Pb-Pb and Lu-Hf geochronology

Abstract

Niobium (Nb) is a critical strategic metal essential for advanced industrial and aerospace technologies. As aeschynite represents one of the primary natural sources of Nb, its geochronological characterization is of significant interest. In situ microbeam geochronology of aeschynite can provide a direct approach to constraining the timing of niobium mineralization and regional geological evolution. Accurate and precise in situ microbeam dating using SIMS or LA-ICP-MS requires well-characterized matrix-matched reference materials to correct for matrix-induced elemental fractionation. However, a critical gap exists due to the current absence of natural aeschynite reference materials. To address this deficiency, we propose the Hidra aeschynite-(Y) from the Urstad Feldspar Mine, Norway as a candidate of natural reference material for Pb-Pb and Lu-Hf dating. Multiple SIMS spot analyses demonstrate that it has a homogeneous age with the arithmetic mean 207Pb/206Pb age of 902.1 ± 21.3 Ma (2SD; n = 46), corroborated by three LA-ICP-MS/MS analytical session (arithmetic mean 207Pb/206Pb age = 902.5 ± 22.5 Ma, 2SD; n = 55). Six ID-TIMS analyses yield an arithmetic mean 207Pb/206Pb age of 912.8 ± 6.9 Ma (2SD), recommended as the best estimate of the crystallization age. In addition, in situ LA-ICP-MS/MS Lu-Hf analyses of Hidra aeschynite-(Y) calibrated with NIST SRM 610 yield an isochron age of 912.5 ± 6.5 Ma (2σ; MSWD = 1.4; n = 68). The convergence of microbeam 207Pb/206Pb ages with the high-precision ID-TIMS benchmark, combined with reproducible Lu-Hf results, establishes Hidra aeschynite-(Y) as the first potential matrix-matched reference material for microbeam in situ Pb-Pb and Lu-Hf geochronology of aeschynite.