Sandyites from Ilmenogorsky miaskite massif (South Ural)

The paper presents new data on mineralogy and geochemistry of sandyites (melanocratic variety of miaskites) from the Ilmenogorsky massif. Sandyites form extended bodies in amphibole miaskites. The sandyites are distinct from host amphibole miaskites in 1) higher Ca, Fe, Mg and REEs contents and lower Si and Аl contents, 2) increase in amount of amphiboles, titanites and apatites and decrease in amount of nephelines, and 3) lower Fe value, lower Аl, Ca and K contents and higher Si, Mg and Na contents in composition of amphibole and biotite. The increase in LILEs and HFSEs contents in sandyites indicates the influence of fluid activated by shear deformations. Sandyites are the products of metasomatic alteration of amphibole miaskites with participation of the fluid due to tectonic activity in the shear zone.