Geochemical relationship between REE and PGE in mafic and ultramafic rocks and their petrogenetic significance - Rare Earth Elements in Ultramafic and Mafic Rocks and their Minerals - page 230

Pd, ppb Pd, ppb

Figure 10.1 Relationships between La and Pd compositions (1), Ce and Pd compositions (2) for rocks
from some mafic-ultramafic massifs of Central Tuva (Russia) (data Tables 10.1 and 10.2).

In order to overcome these difficulties that arise in PGE analysis the
chemists Nikolaeva, Palesskii and Koz'menko (IGM SB RAS Analytical Center,
Novosibirsk, Russia) developed an improved method of sample preparation, which
made it possible to make a comprehensive analysis of REE and PGE by 'Element'
mass-spectrometer (Finnigan MAT, Germany) [Lesnov et al ., 2005b; Palesskii,
2008]. At the same time we took into account the experience of studies on the
subject gained in a number of analytical laboratories [Pearson & Woodland, 2000;
Meisel & Moser, 2004; Zhou et al ., 2005]. The result was a method of sample
preparation that allows achieving a more complete decomposition of the samples
with a weighed sample

0.2-0.4 g. The Pd, Pt, Ru, Os, Ir and Re isotope-shifted
spikes were added into the weighed sample. The necessary characteristics of spikes
were defined beforehand, such as isotopic composition and concentration of the
corresponding element. Decomposition of samples was carried out in sealed Teflon
autoclaves of MARS-5 system by using a mixture of nitric, hydrofluoric and hydro-
chloric acids pre-cleaned by subboiling. After achieving the complete decompo-
sition and isotopic homogenization, the samples were transferred to a solution,
which was divided into two aliquots. The first aliquot was used to measure REE
contents by direct measurement using mass-spectrometer and adding in as an inter-
nal standard. The second aliquot was subjected to the enrichment and separation
of PGE from the matrix by means of chromatographic columns with Dowex cation
resin. Then, the PGE concentrations were measured by isotope dilution with mass-
spectrometric ending.
Testing of the developed method based on the results of control experiments
showed that when using the proposed complex of procedures for sample prepara-
tion the contamination introduced into the sample is insignificant compared to
the content of PGE in the analyzed sample. The exception was Pt, the measure-
ment accuracy of which was reduced due to the fact that the mass-spectrometer
was simultaneously used in analyzing solutions prepared using platinum glassware.
Figure 10.2 show a scheme of procedures of sample preparation and analysis of
REE and PGE by ICP-MS method. Note that when testing this method the control

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