GEOCHEMISTRY AND ORIGIN OF THE POTASSIC M AGMATIC ROCKS OF THE CENTRAL ALDAN

Geochemical features (about 40 elements) of the Late Mesozoic potassic magmatic rocks of the Central Aldan are studied. The composition of t he primitive rock varieties (lamproites, leucitites, shonkinites, monz onites) indicates that their parent magmas have a mantle origin. The r ocks are variable in mineralogy and alkalies concentration but they ha ve similar geochemical features: low Ti, Zr, Nb, Hf and Ta and high K, Rb, Ba concentrations. The lithospheric mantle is suggested to be a s ource of these magmas. Apparently such mantle rocks were metasomatised during the Precambrian subdiction processes. The geodynamic processes that took place at the S-E part of Siberian platform in Mesozoic coul d be considered only like a trigger of potassic magma emplacement of t he Central Aldan region.