10:45 〜 12:15
[SGC38-P02] Simultaneous determination of volatile chalcophile and highly siderophile elements in carbonaceous chondrites by triple quadrupole ICP-MS after sealed-glass tube digestion
キーワード：highly siderophile elements、volatile chalcophile elements、triple quadrupole ICP-MS
The origin of volatile elements in Earth remains one of the major unresolved issues in the Earth Science. The late veneer hypothesis may predict that most volatiles in the bulk silicate Earth (BSE) were delivered via late accretion of volatile-rich chondritic material after core formation. However, the amount of volatiles in both BSE and the late veneer are not well-constrained yet. This uncertainty would stem from the fact that the analysis of volatile elements in rocks requires a technique to digest acid-resistant minerals under conditions that do not cause loss or contamination of target elements, resulting in less attraction of geochemical and cosmochemical studies for unknown samples.
In order to overcome this difficulty, we established an analytical method for simultaneously determining elemental abundances of highly siderophile elements (HSEs: Re, Os, Ir, Ru, Pt, Rh, Pd and Au) and volatile chalcophile elements (VCEs: S, Se, Te, As, Ge, Sb and Sn) with isotope dilution-mass spectrometry (ID-MS) after quartz-glass digestion technique. The established method is based on Carius tube digestion technique universally applied for Re-Os dating, and is characterized by its ability to simultaneously quantify multiple elements from samples decomposed to obtain 187Os/188Os ratios. Sample and isotopically enriched spikes of Re, Os, Ir, Ru, Pt, Pd, S, Se, Ge, Sn, Sb, and Te were transferred into quartz glass tubes with inverse aqua regia, and were digested for 72 hours at 240 deg C in an oven. After extracting Os into CCl4, the remaining solution was dried down with additional HF and redissolved in 0.5 M HCl for introducing into triple quadrupole ICP-MS (Thermo Scientific iCAP TQ) without any other chemical separation procedures.
Our results of analytical tests performed on Smithsonian Allende reference powder (4-20 mg) demonstrated that the measurement modes equipped with iCAP TQ efficiently remove multiple interferences on target masses, and successful determination of all HSEs and VCEs including monoisotopic Rh, Au and As was achieved without additional purification steps such as ion exchange column chemistry. Measurements of ten separate dissolutions yielded excellent reproducibilities for the HSEs (RSDs: 6-12%) and VCEs (RSDs: 5-16%), and their weighted mean values were generally consistent with the literature data except for slightly lower Au and higher As [1-4]. Although cause of these discrepancies remain unclear, the developed method will allow multiple element analyses on small sample aliquots used for Re-Os isotope studies, and suitable for obtaining comprehensive data on valuable samples such as CI chondrites and Ryugu.
[1] Walker et al. (2002) GCA 66, 4187–4201. [2] Fischer-Gödde et al. (2010) GCA 74, 356–379. [3] Phelan et al. (2022) GCA 318, 19-54. [4] Makishima and Nakamura (2009) Geostand. Geoanal. Res. 33, 369-384.
In order to overcome this difficulty, we established an analytical method for simultaneously determining elemental abundances of highly siderophile elements (HSEs: Re, Os, Ir, Ru, Pt, Rh, Pd and Au) and volatile chalcophile elements (VCEs: S, Se, Te, As, Ge, Sb and Sn) with isotope dilution-mass spectrometry (ID-MS) after quartz-glass digestion technique. The established method is based on Carius tube digestion technique universally applied for Re-Os dating, and is characterized by its ability to simultaneously quantify multiple elements from samples decomposed to obtain 187Os/188Os ratios. Sample and isotopically enriched spikes of Re, Os, Ir, Ru, Pt, Pd, S, Se, Ge, Sn, Sb, and Te were transferred into quartz glass tubes with inverse aqua regia, and were digested for 72 hours at 240 deg C in an oven. After extracting Os into CCl4, the remaining solution was dried down with additional HF and redissolved in 0.5 M HCl for introducing into triple quadrupole ICP-MS (Thermo Scientific iCAP TQ) without any other chemical separation procedures.
Our results of analytical tests performed on Smithsonian Allende reference powder (4-20 mg) demonstrated that the measurement modes equipped with iCAP TQ efficiently remove multiple interferences on target masses, and successful determination of all HSEs and VCEs including monoisotopic Rh, Au and As was achieved without additional purification steps such as ion exchange column chemistry. Measurements of ten separate dissolutions yielded excellent reproducibilities for the HSEs (RSDs: 6-12%) and VCEs (RSDs: 5-16%), and their weighted mean values were generally consistent with the literature data except for slightly lower Au and higher As [1-4]. Although cause of these discrepancies remain unclear, the developed method will allow multiple element analyses on small sample aliquots used for Re-Os isotope studies, and suitable for obtaining comprehensive data on valuable samples such as CI chondrites and Ryugu.
[1] Walker et al. (2002) GCA 66, 4187–4201. [2] Fischer-Gödde et al. (2010) GCA 74, 356–379. [3] Phelan et al. (2022) GCA 318, 19-54. [4] Makishima and Nakamura (2009) Geostand. Geoanal. Res. 33, 369-384.