DIFFERENTIATION FEATURES OF ALKALINE ROCKS IN ILMEN MIASKITE MASSIF: NEW MINERALOGICAL AND GEOCHEMICAL DATA

The Ilmen miaskite massif located in the Southern Urals remains largely understudied from mineralogical and geochemical standpoints, while the theories of its formation are still debatable. The article presents new data on mineral associations of miaskite varieties and REE-rich minerals. Microchemical studies determined pyroxene-amphibole miaskites as the most promising variety on REE mineralization (REE content at ca.1500 μg/g). These rocks showed distinct positive Nb anomalies combined with a negative Pb anomaly. The temperatures of feldspar exsolution indicate their following formation sequence within miaskite varieties (from higher temperature to lower temperature ones): pyroxene-amphibole miaskite → garnet-amphibole miaskite → amphibole miaskite → biotite miaskite.