MINERALOGY AND GEOCHEMISTRY OF APATITE-MAGNETITE ORES OF THE TOMTOR MASSIF (NORTHWESTERN YAKUTIA)

Abstract

The apatite-magnetite ores within the Tomtor Massif have been known since 1975. Our predecessors (E. N. Ehrich, G. I. Porshnev, L. S. Egoroy, et al.) have revealed the Onkuchakh deposit, studied the morphology, genesis, and substance composition of the formation, with special attention focused on geologo-genetical aspects, petrology, and petrography of the host rocks. Mineralogically, only rock-forming minerals (magnetite, apatite) are studied in detail. Beyond study were secondary and accessory minerals as well as new varieties generated at subsequent hypogenetic changes and during hypergenesis. To bridge this gap and to continue the earlier research, we studied features of apatite-magnetite mineralization not only of the known Onkuchakh deposit, but also of newly recognized ore bodies, mainly, in the central massif, in the field of development of carbonatites. We attempted to compare apatites and magnetites from the main petrographic complexes. As a result, new minerals not typical of this type of ores (cobaltite, bornite) were recognized and described. Based on analysis of the scheme of step-by-step mineralization of complex apatite-magnetite ores, an attempt was made to recognize precarbonatite, postcarbonatite and s.s. hypergenic stages of origination and transformation of apatite-magnetite ores of the Tomtor Massif.