Re–Os and Lu–Hf isotopic constraints on the formation and age of mantle pyroxenites from the Bohemian Massif

Sample decomposition using inverse aqua regia at elevated temperatures and pressures (e.g., Carius tube or high‐pressure asher) is the most common method used to extract highly siderophile elements (HSEs: Ru, Rh, Pd, Re, Os, Ir, Pt and Au) from geological samples. Recently, it has been recognised that additional HF desilicification is necessary to better recover HSEs, potentially contained within silicate or oxide minerals in mafic samples, which cannot be dissolved solely by inverse aqua regia. However, the abundance of interfering elements tends to increase in the eluent when conventional ion‐exchange purification procedures are applied to desilicified samples. In this study, we developed an improved purification method to determine HSEs in desilicified samples. This method enables the reduction of the ratios of isobaric and polyatomic interferences, relative to the measured intensities of HSE isotope masses, to less than a few hundred parts per million. Furthermore, the total procedural blanks are either comparable to or lower than conventional methods. Thus, this method allows accurate and precise HSE measurements in mafic and ultramafic geological samples, without the need for interference corrections. Moreover, the problem of increased interfering elements, such as Zr for Pd and Cr for Ru, is circumvented for the desilicified samples.

Section: Resultssupporting

confidence: 89%

A Method to Suppress Isobaric and Polyatomic Interferences for Measurements of Highly Siderophile Elements in Desilicified Geological Samples

Zhou

Tanaka

Yamanaka

et al. 2019

“…, Ackerman et al . ), compared with our measurement results for CT digestions of 0.2–1.0 g test portions. Our CT digestion method provides highly reproducible results (RSD < 2%) with an average value of 0.689 ± 0.023 ng g −1 (2 s , n = 43), and the results show good agreement with previously published values obtained by the same digestion method (Ishikawa et al .…”

Section: Resultsmentioning

confidence: 90%

“…, Ackerman et al . ). Based on these observations, we conclude that BIR‐1a is a relatively homogeneous basaltic reference material in terms of Re‐Os isotopic compositions for test portion sizes of > 0.4 g. It is therefore recommended as a quality control material for mafic geological samples.…”

Section: Discussionmentioning

confidence: 97%

Rhenium‐Osmium Isotope Measurements of Geological Reference Material BIR‐1a: Evaluation of Homogeneity and Implications for Method Validation and Quality Control

Long

Sun

et al. 2017

To evaluate the homogeneity of geological reference material BIR‐1a (basalt; United States Geological Survey, USGS) for Re‐Os isotopic studies at the 0.2–1.0 g test portion size level, sixty‐three precise measurement results of Re and Os mass fractions and isotope amount ratios were obtained over an 18‐month period. These data reveal that the reference material has higher Re (0.691 ± 0.022 ng g−1, 2s, n = 63) and lower Os mass fractions (0.343 ± 0.089 ng g−1, 2s, n = 63) than UB‐N (serpentinite, CRPG) and is homogeneous in 187Os/188Os isotope amount ratio (0.13371 ± 0.00092, 2s, n = 63) at the 0.2–1.0 g test portion size level. The results are essentially consistent with previous views indicating that BIR‐1a gives precise measurement results for Re‐Os isotope amount ratio measurements at the 1 g test portion size level (Ishikawa et al., Chemical Geology, 2014, 384, 27–46; Meisel and Horan, Reviews in Mineralogy and Geochemistry, 2016, 81, 89–106). Based on these new Re‐Os data and previous studies, we propose BIR‐1a as a useful reference material that can be used in method validation and quality control and interlaboratory comparisons for studies dealing with mafic geological samples at test portion sizes of > 0.4 g.

“…Published data from Ackerman et al . () and Chu et al . () are associated with relatively poor precision, with values from 0.1322 ± 46 to 0.1334 ± 37 measured with a secondary EM.…”

Section: Resultsmentioning

confidence: 87%

High‐Precision Measurement of ¹⁸⁷Os/¹⁸⁸Os Isotope Ratios of Nanogram to Picogram Amounts of Os in Geological Samples by N‐TIMS using Faraday Cups Equipped with 10¹³ Ω Amplifiers

Wang

Vollstaedt

2019

N(187Os)/N(188Os) ratios of six geological reference materials were measured using static Faraday cups (FCs) with 1013 Ω amplifiers by N‐TIMS. Our results show that the repeatability precision was 2–3‰ (2 RSD, n = 3), when taking ~ 1 g of BHVO‐2 with 76 pg g−1 of Os mass fraction and ~ 2 g of BCR‐2 with 21 pg g−1 of Os mass fraction for each sample, whether measured by FCs or by secondary electron multiplier. The repeatability precision measured by FCs was 1–0.2‰ (2 RSD, n = 3) when taking ~ 1 g of BIR‐2 with 350 pg g−1 of Os mass fraction, ~ 1 g of WGB‐1 with 493 pg g−1 of Os mass fraction or ~ 0.5 g of WPR‐1 with 13.3 ng g−1 of Os mass fraction for each sample, which is much better than those measured by secondary electron multiplier. Instead, when taking ~ 2 g of AGV‐2 with 4 pg g−1 Os mass fraction, the repeatability precision measured by secondary electron multiplier is 3–4‰ (RSD, n = 3), which is better than those measured by FCs. Of the six reference materials analysed, WPR‐1 and BIR‐1a are the most homogeneous with regard to Os isotopic composition (2 RSD of 0.08% and 0.23%, respectively) when test portion masses are 0.5–1 g.