Interlaboratory Comparison of PGE and Re in a Mid-Ocean Ridge Basalt
Abstract
An interlaboratory comparison of PGE (Os, Ir, Ru, Pt, Pd) and Re contents in a mid-ocean ridge basalt has been carried out. The purpose of the study was to address long-standing analytical problems for analyzing low-level PGE contents in basalts. The reference material (RM) used was EN026 10D-3, which is a MORB dredged from the Mohns Ridge (Greenland Sea). It was prepared at URI and was distributed to seven laboratories in Europe and the United States. More than 30 analyses have been completed using various methods of dissolution/leaching (i.e. Carius tube reverse aqua regia attack with and without an HF attack step; high pressure asher reverse aqua regia attack; NiS fusion; and hot plate closed-PFA beaker HF attack). All laboratories used isotope dilution - ICP-MS in their analytical protocol, but they differed in spike calibration methods, interference corrections, and blank levels. The interlaboratory range of values obtained were (in ppt): Os = 12 to 18; Ir = 17 to 36; Ru = 41 to 64; Pt = 320 to 830; Pd = 716 to 1745; Re = 516 to 1643. The Os 187/188 ratio measured ranged from 0.1449 to 0.1603. These results so far indicate that there appear to be some systematic analytical differences between laboratories. Although progress is being made on understanding problems of low-level PGE analyses in basalts it is still difficult to separate interlaboratory bias related to various sources of error such as:(a) mass interference correction or elimination during analysis; (b) spike calibrations; (c) dissolution/equilibration/leaching methods; (d) procedure blank levels; and (e) differences between splits of the RM. Also, it is not yet clear whether a desilicification step (i.e. HF attack) is required for low-PGE-level basalts, however, the evidence presented here points to this need. An additional and more rigorous and detailed analytical study in progress will resolve this issue. Thus, more work is needed on this RM and other, more widely distributed RM basalts such as TDB-1, with possible exchange of calibration and spike solutions, and RM batches. A limited amount of EN026 10D-3 RM is available (through the principal author) to other investigators interested in low-PGE-level geochemistry.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSM.V51B..02K
- Keywords:
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- 1065 Trace elements (3670);
- 1094 Instruments and techniques