Manganese

The radioactive isotope ⁵³Mn is formed by the interaction of protons, produced by cosmic rays, on iron in rocks. The accumulation of ⁵³Mn, having a half-life of 3.7×10⁶ years, at the Earth’s surface enables determination of exposure ages of landforms to cosmic rays and quantification of erosion rates. For example, Schaefer et al. [211] measured 13 samples from nine dolerite (igneous rock containing plagioclase, pyroxene, and olivine) surfaces in the Dry Valleys, Antarctica. They found that the terrestrial ⁵³Mn concentrations correlate well with cosmic-ray-produced ³He and ²¹Ne concentrations in the same samples (Fig. IUPAC.25.1), which suggests that ⁵³Mn is produced continuously in place and retained over millions of years without loss. Their results suggest that ⁵³Mn concentrations in rocks can be used to monitor Earth-surface processes on time scales exceeding 10×10⁶ years.

⁵¹Mn, ⁵²Mn and 52mMn (with half-lives of 46 min, 5.6 days, and 21 min, respectively) are radioactive isotopes that emit positrons that are used in positron emission tomography (PET) imaging [212], [213]. The m in the superscript of 52mMn indicates a metastable state of the isotope.