Direct dating of gold by radiogenic helium
Natural isotopic variations amongst the noble gases result from both radiogenic and nucleogenic production processes.
Because of their unique properties, it is useful to distinguish them from the conventional radiogenic isotope systems described above. Some He is not affecting the concentration or noble gas ratios of the mantle.
It has been observed that He is stored in the planet is under investigation, but it is associated with the mantle and is used as a marker of material of deep origin.
Hence, during melting of the mantle, rhenium is stripped out, and prevents the osmium–osmium ratio from changing appreciably.
This locks in an initial osmium ratio of the sample at the time of the melting event.
Osmium–osmium initial ratios are used to determine the source characteristic and age of mantle melting events.
Lead is created in the Earth via decay of transuranic elements, primarily uranium and thorium.
Lead isotope geochemistry is useful for providing isotopic dates on a variety of materials.