CONDITIONS AND SEQUENCE OF FORMATION OF MINERALS OF APATITE-MAGNETITE ORES OF THE TOMTOR MASSIF

This paper presents the results of a study of the mineral composition of phoscorites of the Tomtor massif based on materials from wells 801 and 59. In the course of studying the mineral composition of phoscorites using optical, electron scanning microscopy and microprobe analysis, the relationships of minerals were determined, the conditions and sequence of their formation were established. It has been established that the formation of foscorites took place in 4 stages: magmatic, metasomatic, hydrothermal, hypergene. During the magmatic stage, with the participation of liquid immiscibility, the Fe-P melt was separated from the silicate (foidolite) melt, from which apatite-magnetite ores were formed, in some cases with the participation of crystallization differentiation. At the contact of silicate (Si, K) and Fe-P (Fe) rocks, with the participation of metasomatism, massive biotite deposits (Si, Al, K + Fe, LE) were formed. Later, hydrothermal processes were superimposed on the rocks, introducing sulfide and carbonate (and associated REE) mineralization. Like the entire massif, the foscorites were subject to hypergene changes of oxidative and reduction stages, which determined their final appearance in near-surface conditions, transforming them into limonite-francolite lateritic weathering crusts.