TY - JOUR

T1 - Probing the 186Os/188Os Precision Barrier

T2 - New Recommended Values for the DROsS Reference Material and an Assessment of Mixed 1011 and 1012 Ω Amplifier Arrays

AU - Waterton, Pedro

AU - Woodland, Sarah

AU - Pearson, Graham

AU - Serre, Simon Hansen

AU - Szilas, Kristoffer

PY - 2024

Y1 - 2024

N2 - We present high precision negative ion thermal ionisation mass spectrometry (N-TIMS) Os isotope measurement results for the DROsS reference material, to investigate the limits on the precision of TIMS-based 186Os/188Os measurements. We use analytical conditions previously highlighted to optimise precision, present a new flexible data processing protocol, and measure 184Os on a Faraday Cup equipped with a 1012 Ω amplifier. Despite analytical protocols that minimise uncertainty from counting statistics and Johnson-Nyquist noise, the intermediate measurement precision of our approach does not significantly improve on previous high precision Os isotope measurements, with the exception of 184Os/188Os. This is probably due to uncertainties in measured amplifier gain factors, which are greater when using mixed arrays of 1011 and 1012 Ω amplifiers than when using 1011 Ω amplifiers alone, though Faraday Cup deterioration could also contribute. We propose that multi-dynamic Os isotope measurements could largely eliminate both of these uncertainties. Our 184Os/188Os measurement results are the most precise yet, yielding 184Os/188Os = 0.0013036 ± 0.0000007 (2s, n = 38). Additionally, we average our data with published data to recommend the following composition for DROsS: 186Os/188Os = 0.1199319 ± 0.0000024, 187Os/188Os = 0.1609227 ± 0.0000022, 189Os/188Os = 1.219709 ± 0.000010, 190Os/188Os = 1.983793 ± 0.000011.Supporting Information

AB - We present high precision negative ion thermal ionisation mass spectrometry (N-TIMS) Os isotope measurement results for the DROsS reference material, to investigate the limits on the precision of TIMS-based 186Os/188Os measurements. We use analytical conditions previously highlighted to optimise precision, present a new flexible data processing protocol, and measure 184Os on a Faraday Cup equipped with a 1012 Ω amplifier. Despite analytical protocols that minimise uncertainty from counting statistics and Johnson-Nyquist noise, the intermediate measurement precision of our approach does not significantly improve on previous high precision Os isotope measurements, with the exception of 184Os/188Os. This is probably due to uncertainties in measured amplifier gain factors, which are greater when using mixed arrays of 1011 and 1012 Ω amplifiers than when using 1011 Ω amplifiers alone, though Faraday Cup deterioration could also contribute. We propose that multi-dynamic Os isotope measurements could largely eliminate both of these uncertainties. Our 184Os/188Os measurement results are the most precise yet, yielding 184Os/188Os = 0.0013036 ± 0.0000007 (2s, n = 38). Additionally, we average our data with published data to recommend the following composition for DROsS: 186Os/188Os = 0.1199319 ± 0.0000024, 187Os/188Os = 0.1609227 ± 0.0000022, 189Os/188Os = 1.219709 ± 0.000010, 190Os/188Os = 1.983793 ± 0.000011.Supporting Information

U2 - 10.1111/ggr.12532

DO - 10.1111/ggr.12532

M3 - Journal article

VL - 48

SP - 109

EP - 132

JO - Geostandards and Geoanalytical Research

JF - Geostandards and Geoanalytical Research

SN - 1639-4488

IS - 1

ER -