EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Cosmogenic 3He in detrital Pt-alloy grains: tracing the accumulation of critical metals

Olga Yakubovich1,2, Finlay Stuart3, Alexander Mochalov2, and Roman Palamarchuk4
Olga Yakubovich et al.
  • 1St Petersburg University, Saint Petersburg, Russian Federation (
  • 2Institute of Precambrian Geology and Geochronology RAS, Saint-Petersburg, Russian Federation
  • 3SUERC, Glasgow, UK
  • 4Saint Petersburg Mining University, Saint-Petersburg, Russian Federation

The application of cosmogenic noble gases (3He and 21Ne) in detrital grains to quantify sediment transport rates and storage timescales is largely undeveloped. We have previously shown that cosmogenic He can be measured in single grains (Yakubovich et al. 2019). The low He diffusion rate and the chemical and/or physical robustness of metal alloys (eg Au, Ag, Cu, Pt, Fe) means the technique has potential to determine how critical metals accumulate at the Earth surface.  In an effort to determine how long detrital Pt-alloy grains spend travelling to placer deposits we have measured cosmogenic3He concentrations in 60 (0.5–7 mg) grains of isoferroplatinum (Pt3Fe) from the world largest alluvial Pt placer deposits in the Kondyor-Uorgalan rivers in Khabarovsk region, and the Is-Turinsk and Nyas’ma river systems in Middle Urals, Russia.

In both systems, there are no significant cosmogenic 3He in the grains from the low order streams that drain the source rock. 3Hecosconcentrations in Pt grains from distant placers (30 km) varies in order of magnitude from 0.3 to 30 x 107at g-1in grains in Uorgalan river, 5 to 40 x 107at g-1in Glubokinskoe placer deposit (Is river) and 20 to 70 x 107at g-1in the Generalka deposit (Nyas’ma river). Converting this to surface residence times (P = 25 at g y-1, Yakubovich et al., 2019) yields model exposure durations of0.1­–10, 3–20 and 13–38 Myr for grains from the Uorgalan, Glubokinskoe and Generalka deposits respectively. Assuming that all grains were extracted from shielded locations this exposure ages indicate the total time of transport and residence of the grains on river bed surface prior to final deposition.

Pt grains are added to the river system constantly. If we assume that the average transport conditions are essentially identical for all grains, then the difference between the maximum and minimum exposure ages within the same location indicates the total duration of placer supply from the source rock. For the Urals it is equal for 17–25 Myr, while for Kondyor-Uorgalan placer it is 10 Myr. This is in a good agreement with geological observations. Within Kondyor-Uorgalan placer deposit the age of the alluvium varies from Neogene to Quaternary, while in the Urals Pt-bearing Jurassic, Neogene and Quaternary fluvial sediments are distinguished within the placers.

Paleo peneplain surfaces are established nearby the Kondyor massif and pre-date the most productive platinum sands. Several stages of peneplenisation are evident in the Urals from thick weathering crusts. The exposure ages indicate10’s million-year scale of transport/deposition histories of detrital Pt alloys, which might result of multiple redeposition of material during long term accumulation of cosmogenic 3He during peneplenisation.  

Yakubovich O., Stuart F.M., Nesterenok A. and Carracedo A. (2019). Chem. Geol. 517, 22-33.

How to cite: Yakubovich, O., Stuart, F., Mochalov, A., and Palamarchuk, R.: Cosmogenic 3He in detrital Pt-alloy grains: tracing the accumulation of critical metals, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10247,, 2021.


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