GEOCHEMICAL EVOLUTION OF CARBONATITE MELT S IN POLAR SIBERIA

Geochemistry of major, trace, and rare-earth elements in the Gull Mass if, Maimecha-Kotui Province, Polar Siberia, is examined. The contents of Si, Fe, Ti, P, and Al decrease from the earliest rocks (phoscorite) to later calcite and dolomite carbonatite simultaneously with an incr ease of the Ca content (which then decreases again in the dolomite car bonatite). The content of Mg decreases from the phoscorite to the carb onatite and increases from the calcite to the dolomite carbonatite. Th e contents of elements of the Fe group (Cr, Ni, V; and Co), P, Zr, Hf, Nb, U, Th, and REE declined during the evolution of the Gull carbonat ite system, This evolution was predominantly controlled by concurrent crystal fractionation and cumulation and by the hydrothermal transport ation of trace elements.