Uranium isotope ratios are reported for twenty-nine geological reference materials (RMs) including igneous, metamorphic and sedimentary rocks, as well as sediments. Measurements were conducted on a multi-collector inductively coupled plasma-mass spectrometer (MC-ICP-MS) using the ²³³U-²³⁶U double spike technique. These RMs possess a wide range of matrices with U mass fractions ranging from 0.11 μg g^-1 to 18.7 μg g^-1. The δ^234/238U values (relative to the n(²³⁴U)/n(²³⁸U) ratio at secular equilibrium) show minor fluctuations around the secular equilibrium value except for two Pleistocene speleothem RMs. The δ^238/235U values (relative to the value for NBL CRM 112a (NBS SRM 960)) of igneous rocks and metamorphic rocks are within the range of the continental crust value (-0.29 ± 0.03‰, 95% CI). The δ^238/235U value for sedimentary rock and sediment RMs spans a wide range of 0.98‰, suggesting significant ²³⁸U/²³⁵U isotopic fractionation in low temperature environments. The range of δ^238/235U RMs reported in this study (-0.63‰ to 0.35‰) exceeds that of previous RMs (-0.61‰ to 0.17‰), allowing inter-laboratory calibration of wider ranges of geological and environmental samples.

中文翻译：

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MC-ICP-MS测定29种地质岩石标准物质的铀同位素比值


报告了二十九种地质参考材料 (RM) 的铀同位素比，包括火成岩、变质岩和沉积岩以及沉积物。使用 ²³³ U- ²³⁶ U双尖峰技术在多接收器电感耦合等离子体质谱仪(MC-ICP-MS)上进行测量。这些 RM 具有多种基质，U 质量分数范围从 0.11 μg g ^-1 到 18.7 μg g ^-1 。 δ ^234/238 U 值（相对于长期平衡时的 n( ²³⁴ U)/n( ²³⁸ U) 比率）在长期平衡附近显示出较小的波动值除了两个更新世洞穴化石 RM 之外。火成岩和变质岩的δ ^238/235 U值（相对于NBL CRM 112a（NBS SRM 960）的值）在大陆地壳值范围内（-0.29±0.03‰，95%） CI）。沉积岩和沉积物 RM 的 δ ^238/235 U 值跨越 0.98‰，表明低温环境下存在显着的 ²³⁸ U/ ²³⁵ U 同位素分馏。本研究报告的 δ ^238/235 U RM 范围（-0.63‰ 至 0.35‰）超过了之前的 RM 范围（-0.61‰ 至 0.17‰），允许实验室间校准更广泛的地质和环境样本。