Sulfide mineralization of phoscorites and carbonatites of the guli massif (Polar Siberia) and potential of these rocks on noble metals

Abstract

A first complex investigation of mineral forms of Au and Ag and distribution of noble metals in sulfide-containing phoscorites and carbonatites, their magnetite and sulfide concentrates of alkaline ultrabasic massif Guli (Polar Siberia) was made by neutron activation method, XRF and microprobe analyses. Sulfide concentrates of carbonatites are enriched with Pt up to 2.93, Au up to 61.6 and Ag up to 3.61 (ppm).
 The main sulfides are pyrrhotite, djerfisherite, chalcopyrite and pyrite. Silver is accumulated in the late chalcopyrite, Ag- djerfisherite, later ― lenaite, sternbergite or argentopyrite and native silver. Wide dissemination of djerfisherite in phoscorites and carbonatites and defined inclusions of rasvumite, K-Na-Ca carbonates, carbocernaite and strontianite in pyrrhotite, is the evidence of of high activity of K, Na, Sr, LREE, F, Cl and S during the sulfides crystallization. Chlorine has a high capacity for the formation of chlorine-silver complexes and is probably an agent for the transfer of noble metals in carbonatites.
 The comparison of surveyed associations with published experimental data shows that formation of sulfides starts at the temperature no lower than 500С (early pyrrhotite) and lasts till 150C (argentopyrite). The late carbonatite assemblages may can be enriched with Au and Ag and be a potential source of formation of alluvial gold.