Gamma-ray absorption coefficients and chemical composition of tertiary volcanic rocks

Summary

Gamma-ray absorption coefficients$\mu _{Cs^{137} }$ for a set of 83 Teritary volcanic rocks from the Bohemian Massif were measured; the set of samples included a broad range of related rock types from alkaline rocks of trachytic and phonolitic composition to basic and ultrabasic alkaline rocks of basaltic and nephelinitic composition. The values of$\mu _{Cs^{137} }$ varied in the range from 0.1775 cm⁻¹ to 0.2464 cm⁻¹. The dependence of$\mu _{Cs^{137} }$ on the density ϱ could be expressed by the linear relation μ=0.0730ϱ+0.0124. The correlation of the absorption coefficient with the content of several oxides confirmed, in accordance with [1], that the absorption coefficient increased with the content of oxides bound to dark minerals (Fe₂O₃, FeO, MgO, CaO), as well as with the colour index, and decreased with the increasing content of oxides bound to light minerals (SiO₂, Al₂O₃, Na₂O). Specific behaviour of phonolites was observed in several cases.