Publication Date:
2017-06-09
Description:
We present a double-spike technique for precise determination of mass-dependent fractionation of tungsten (W) stable isotopes. Instrumental mass bias effects and isotope fractionation during W separation are corrected for by means of a W-180-W-183 double-spike added prior to sample dissolution. The separation of W from the matrix is achieved via three-step anion-exchange chromatography. Tungsten stable isotopic compositions were determined by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). Results are expressed relative to the NIST SRM 3136 W standard as the permil difference in W-186/W-184 (delta W-186). The external reproducibility of the NIST SRM 3163 W standard is +/- 0.05 parts per thousand with an average composition of -0.01 parts per thousand on W-186/W-184 (2s.d., n = 171). Tungsten stable isotope compositions for USGS standard reference materials are as follows: AGV-2 (andesite; delta W-186 +/- 0.18 +/- 0.05 parts per thousand, 2s.d., n = 6), SDC-1 (mica schist; delta W-186 = 0.36 +/- 0.05 parts per thousand, 2s.d., n = 6), SDO-1 (shale; delta W-186 = 0.26 +/- 0.06 parts per thousand, 2s.d., n = 6), and manganese nodules NOD-A-1 (delta W-186 = 0.07 +/- 0.05 parts per thousand, 2s.d., n = 10) and NOD-P-1 (delta W-186 = 0.31 +/- 0.04 parts per thousand, 2s.d., n = 7). The long-term external reproducibility (2s.d.) for these rock standards is +/- 0.05 parts per thousand.
Type:
Article
,
PeerReviewed
Format:
text
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