Carbonatites and ultrabasic-alkaline rocks of the maimecha-kotui region, N. Siberia

The structural position, geology, petrography, petrochemistry, and petrogenesis of one of the world's greatest carbonatite provinces situated in North Siberia are recorded. Three groups of Late Permian-Early Triassic magmatites are briefly discussed: effusives, dikes, and intrusives of complex central type. Carbonatite and congenetic rocks are related to kimberlites, but are genetically unrelated to tholeiitic basalts and trachybasalts. The genetic development and diagnostic features of ultrabasic-alkaline rocks and carbonatites are formulated.