Phosphate-fluoride-carbonate mineralization in lamproite rocks of the Ryabinovy pluton (Central Aldan): mineralogical and geochemical features and origin
I.F. Chayka, A.E. Izokh
Carbonate and apatite-fuorite mineral assemblages are studied in lamproite rocks from high-K Ryabinovy intrusive (Central Aldan, Russia). It is concluded that these assemblages are genetically related and belong to the same apatite-fuorite-carbonate mineralization. It is shown that this mineralization was formed in the course of silicate-carbonate immiscibility, when primary magma was separated on p, f, and SO4-bearing carbonatite melt and silicate fraction. The carbonatite melt was further separated on immiscible sulfate-carbonate and sulfate-phosphate-carbonate fractions. Study of trace element composition of this mineralization showed that, during silicate-carbonate immisci-bility of the ultrabasic potassic lamproite magma, the carbonatite melt can concentrate LREEs, U, Th, Ba and Sr. The key role in this process belongs to f and p. Silicate melt becomes rich in HfSEs. The separation of primary carbonatite melt on immiscible fractions leads to the formation of apatite-fuorite veins, which contain REE-bearing apatite and LREE carbonates (f-bearing carbonates). This «secondary» immiscibility results in depletion of carbonatite in trace elements and enrichment of phosphate-fuoride system in LREEs, U, and Th.
Figures 8. Tables 3. References 14.
Key words: apatite, fuorite, dolomite, carbonatite, Ryabinovy intrusive, Aldan.
МINERALOGY № 1 2017