Analysis of platinum group elements and gold in geological materials using NiS fire assay and Te coprecipitation; the NiS dissolution step revisited

被引:67
作者
Gros, M [1 ]
Lorand, JP [1 ]
Luguet, A [1 ]
机构
[1] Museum Natl Hist Nat, CNRS FR 32, Lab Mineral, F-75005 Paris, France
关键词
platinum group elements; ICP-MS; NiS fire assay; Te coprecipitation;
D O I
10.1016/S0009-2541(01)00405-3
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The NiS fire assay-Te coprecipitation separation procedure for inductively coupled plasma mass spectrometry (ICP-MS) analyses of platinum-group elements (PGE) in silicate rocks has been revisited with the aim of reducing volatile PGE losses (Os, Pd). The NiS bead was dissolved in 20.2% HCl, in an open system allowing H2S to escape without loss of HCl. Yield, accuracy and reproducibility were tested by replicate analyses of a CANMET reference material (UMT1), a mantle lherzolite (FON B 93), prepared as in-house standard, and abyssal harzburgites, analysed as unknowns. The yields as estimated from UNIT1 range from 97% (Ir) to 93-94% (Rh, Pt, Pd) and 91% (An). The Os value (7.13 +/- 1.4 ppb) is equal within 1 sigma level, to the CANMET provisional value. The mean Os content of FON B 93 (3.42 ppb) Fits the Os concentration inferred for the terrestrial mantle very well, as does the Os/Ir ratio (1.053 vs. 1.063) while Pd concentrations are increased by 18% compared to previous analyses after open-beaker dissolution steps. The abyssal harzburgites also yield consistent Os contents (3.28 +/- 0.19 ppb) and a perfectly chondritic Os/Ir ratio (1.07). Thus modified, the NiS fire-assay method allows Os to be nearly completely recovered, while greatly reducing the volatility of Pd. Moreover, the PGE analyses of coarse-grained rocks are highly reproducible (1% for Rh, Pt, Pd; 4% for Ir, 5% for Ru, 6% for An), if performed from large-sized powder aliquots. (C) 2002 Elsevier Science B.V. All rights reserved.
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页码:179 / 190
页数:12
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