EVIDENCE OF THE PARTICIPATION OF MATERIAL FROM DEEP SOURCES IN THE GENESIS OF SELIGDAR-TYPE APATITE ORES

Abstract

Here we shall discuss new information on carbon and strontium isotopes in calcites and apatites of the Ust' Chul'man ore node. It shows that existing theories on the crustal source of Seligdar-type ore material are by no means always confirmed by the factual evidence. The new Rb-Sr dates of ores determined on micas also are important in themselves, as are the new Pb-Pb dates determined on apatite and zircon. For the first time among Seligdar-type deposits, we have found a carbonatite body whose calcites and apatites are similar in strontium-isotope composition to those of the Arbarastakh pluton, the genotype for the Aldan shield. In terms of δ 13C, though, the Birikeen ore calcites differ significantly from calcites of the fringing metamorphic carbonate rocks, being isotopically 'heavier', so we conclude that the ore carbonates were formed from material derived from deep sources. There also was a time lag in late-stage ore deposition in ore clusters of the Nimnyr structural metallogenic zone, from south to north. The above data on carbon and strontium isotopes show that in the Medvedevka, the Nimnyr, the Zolotoy and the Ust' Chul'man areas there certainly is evidence that carbon and strontium from deep sources participated in the deposition of the Seligdar-type apatite ores.