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Osmium isotope analysis

One of the main applications of CEZA is the characterisation of iron objects and the associated deposits. For geoscientific questions, Os isotope analysis is part of various applications (e.g. rhenium-ismium isotope analysis, platinum-ismium isotope analysis).



One of the main applications in archaeometry is determining the origin of iron. Archaeological iron objects are often very heavily, sometimes even completely corroded. However, osmium is not mobile, i.e. the Os isotope signature of the ferrous metal is also retained in the corrosion products. For comparison with potential ore deposits, comprehensive comparative data has already been collected for some regions as part of various projects. However, serial analyses of metal objects from a site also provide an overview of how many possible sources of supply or imported goods were represented at this site (e.g. Heuneburg).

Other materials that are suitable for origin studies using Os isotope analysis are (raw) clays, fired clays and ceramics as well as marble.


Os isotope ratios are also used in the geosciences as an indicator of origin, e.g. in research into mantle-crust interaction. Here, however, it is often necessary to correct for the increase in radiogenic osmium since the genesis of the rocks. This requires additional rhenium concentration determinations. We have calibrated Re-Os spike solutions for this application.

Another application in the geosciences is the investigation of surface processes. Such “source tracer” studies investigate, for example, the input of anthropogenic pollutants into the atmosphere.

Other applications

Forensic applications in the field of material fingerprinting, batch identification or related issues are also possible using Os isotope analysis. For example, it is possible to distinguish between different steel suppliers and thus verify the origin of safety-relevant metal parts in plant or aircraft construction.


The isotope ratios of chemical elements in natural rocks and cultural-historical artefacts can vary. One of the most common causes of the variations that occur is the radioactive decay of unstable isotopes for most heavy elements.

Osmium is one of a total of 6 platinum group elements (PGE). It has a total of seven natural isotopes, two of which can be formed by the radioactive decay of other elements (Re or Pt). In this way, for example, stable 187Os is formed from 187Re via β-decay. The abundance of the other osmium isotopes is not changed by the decay of 187Re. Both elements – Re and Os – are siderophiles. Nevertheless, they behave differently during melting and mineralisation processes. Rhenium is a highly incompatible element, it accumulates in the melt. Osmium, on the other hand, is the most compatible element in the 6th period and prefers to remain in the Earth’s mantle. This behaviour leads to an extreme fractionation of rhenium compared to osmium, whereby the Re-Os ratio in the earth’s crust is very high to extreme. These conditions favour the differentiation of rock types and rock formation processes. Furthermore, the scattering of the Re/Os ratio is the reason why osmium isotope ratios show a significantly greater variation than other radiogenic isotope systems (e.g. rubidium-strontium), which makes Os isotope analysis very suitable as an indicator of origin.

Osmium is often present in very low concentrations in most ores and materials, making this isotope system very challenging to analyse.


The lower limit for determining Os isotope ratios using our thermionic mass spectrometer (NTIMS) is 1 pg Os total. In Mannheim, we prepare the samples in a so-called Carius tube, which allows the use of a maximum of 2 g of sample. However, the possible sample quantity can vary greatly, e.g. for rock powder the sample limit is approx. 2g, whereas for peat the limit is 200 mg. For the Os isotope analysis of iron we use 50 mg of iron, for iron ore between 500 mg and 1 g of sample powder.

Sample composition

  • Metals (iron, copper, steel, etc.): min. 50 mg metal shavings or max. 4 mm wide strips
  • Corrosion (e.g. of iron): if possible 100 – 200mg compact corrosion
  • Marble: 2 – 3g granules of max. 4mm diameter
  • Rocks: 5g powder and -if possible- the contents of MgO
  • Peat: 1g powder or loose material
  • Ton oder KClay or ceramic: 3 – 4 g of pulverised material
  • Ores: 2 – 3g of pulverised material
  • odern iron alloys, steel: 1 g drilling chips or max. 4 mm wide strips
  • ther materials on request.