A Matrix‐Matched Reference Material for Validating Petroleum Re‐Os Measurements

Abstract

This study presents two matrix‐matched reference materials developed for petroleum Re‐Os measurements. We present the Re and Os mass fractions and 187Re/188Os and 187Os/188Os values (ratio of the number of atoms of the isotopes) for repeatedly measured aliquots (ca. 120–150 mg test portions) of the NIST Research Material 8505 (RM 8505) crude oil, and its asphaltene and maltene fractions, and ~ 90 g of homogeneous asphaltene powder isolated from this oil. Measurements were performed using the Carius tube‐isotope dilution negative‐thermal ionisation mass spectrometry methodology. The RM 8505 crude oil contains 1.98 ± 0.07 ng g−1 Re and 25.0 ± 1.1 pg g−1 Os, with Re‐Os isotope amount ratios of 452 ± 6 for 187Re/188Os and 1.51 ± 0.01 for 187Os/188Os (n = 20, 95% conf.). The homogeneous asphaltene sample contains 16.52 ± 0.10 ng g−1 Re and 166.0 ± 0.9 pg g−1 total Os, and possesses isotope amount ratios of 574 ± 3 for 187Re/188Os and 1.64 ± 0.01 for 187Os/188Os (n = 24, 95% conf.). The intermediate precision of these data makes the RM 8505 whole oil and the (~ 90 g) homogenised asphaltene appropriate petroleum matrix‐matched reference materials for Re‐Os measurements. The asphaltene fraction of the oil is the main carrier of Re and Os of the RM 8505 whole oil, and caution is suggested in using asphaltene and maltene fractions of a single oil for Re‐Os geochronology.

Rhenium–osmium (Re–Os) geochronology of crude oil from lacustrine source rocks of the Hailar Basin, NE China

“…The average blanks during this study were 3.4 picogram for Re, and 0.02 picogram for Os. For the present analyses, the measured Re and Os concentrations of homogenised asphaltene isolated from NIST Research Material 8505 (RM 8505) crude oil were 16.128-16.699 parts per billion (ppb, 10 -9 ) and 162.31-166.88 parts per trillion (ppt, 10 -12 ), with 187 Re/ 188 Os and 187 Os/ 188 Os ratios of 571.6-573.2 and 1.612-1.640, respectively (Table 1), consistent with previously published data by Liu and Selby (2018). The Re-Os mass fractions and isotopic compositions of asphaltene fractions from the terrestrial crude oils in the Hailar Basin are presented in Table 2.…”

“…Providing temporal constraints on the evolution of a petroleum system within a sedimentary basin is of fundamental importance to exploration targeting by industry. The rhenium-osmium (Re-Os) geochronometer is a promising absolute dating technique for organic-rich rocks and their associated hydrocarbon derivatives (see reviews in Cohen 2004;Stein and Hannah 2015;Li et al 2017;Liu and Selby 2018). Both Re and Os are redox-sensitive and organophilic, and can be enriched in hydrocarbon source rocks, tar sands, crude oil, and bitumen.…”

“…, values that are significantly lower than asphaltene fractions separated from crude oils in USA (Lillis and Selby 2013; Liu et al 2019), UK(Finlay et al 2011), Venezuela(Liu and Selby 2018), and the Persian Gulf(Liu et al 2019)…”

Analytical Methods for Os Isotope Ratios and Re-PGE Mass Fractions in Geological Samples

“…Rhenium and the PGE mass fractions are usually measured by ICP-MS with ID method. Some labs use NTIMS for determination of Re (e.g., Markey et al, 2007 ; Liu and Selby, 2018 ). When NTIMS is used, it should be noted that trace amount of Re is probably present in the Pt filament (e.g., Day et al, 2003 ), and thus often Ni filament is applied with Ba(NO 3 ) 2 as an ion emitter.…”

“…NIST RM 8505 whole oil and its homogenized powered asphaltene separates were recommended as Re-Os matrix-matched oil RMs by Liu and Selby (2018) . Hurtig et al (2020) also reported Re-Os data for NIST RM 8505 crude oil and another oil RM, NIST RM 1634c.…”