Correlation high-calc undersaturated earth silicon complex of Maymecha-Kotuy province with Siberian flood basalts. New age data of massif Kugda (Polar Siberia)

Perovskite crystals from ore-bearing olivinite and phoscorite of Kugda Massif were analyzed by LA-ICP-MS. Age obtained for alkaline rocks of Kugda Massif is 2576 Ma. It means that Kugda massif was formed simultaneously with the Siberian flood basalts and Guli Massif (2509 Ma) which is the largest pluton in the Maymecha-Kotuy Province and is highly differentiated. The melilite-bearing Kugda Complex was formed synchronously with Siberian Trapps and Guli Massif, which suggests that these rocks might be genetically related.

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

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.

Solid Inclusions in Au-nuggets, genesis and derivation from alkaline rocks of the Guli Massif, Northern Siberia

A total of 112 Au-nuggets, collected from alluvial placer deposits of the Ingarinda River from the Guli massif, located in northem Siberia, Russia, were investigated. The Guli massif consists of a huge dunite-clinopyroxenite complex (the largest complex in the world), an alkaline to highly alkaline rock suite (melilite, nephelinite, ijolite) enveloping the dunite and carbonatite intrusions, associated with disseminated schlieren type chromitite and Au-Ag, Pt placer deposits. The nuggets are characterized by various sizes and shapes and show chemical compositions Au, Au-Ag and AuCu, typical for a derivate of carbon-atites and/or ultramafic complexes. A great variety of oxide, silicate, REE-minerals, carbonate and sulphide inclusions have been detected in the nuggets, which are identical in mineralogy and chemical composition to mineral constituents of the alkaline to highly alkaline rock suite surrounding the Guli dunite core complex thus, considered as the source for Au-nuggets.