Vol 64, No 11 (2019)

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 500°С (early pyrrhotite) and lasts till 150°C (argentopyrite). The late carbonatite assemblages may can be enriched with Au and Ag and be a potential source of formation of alluvial gold.

A kerogen samples set from organic carbon rich rocks of the Middle Frasnian — Early Famennian age (Domanikites) of the Timan-Pechora basin, was characterized by the Rock-Eval pyrolysis data, solid-state ¹³C NMR spectroscopy and Fourier transform IR spectroscopy. Additionally, the spectral characteristics of kerogen isolated from rocks artificially maturated in an autoclave in the presence of water were investigated. In general, the direction of transformation of the kerogen structure with a natural or artificial maturation coincides. For kerogen, subjected to artificial maturation, is characterized by an increase in the concentration of terminal methyl groups in relation to the methylene units. Artificial maturation of kerogen leads to a more rapid rearrangement of aromatic clusters with the accumulation of bridgehead and protonated carbon as compared with natural maturation.

The distribution of dissolved matter (major ions, nutrients, and trace elements) in the Yenisei River estuary and adjacent water area was studied according to the natural observations data from 2009–2016. These results were compared to the literature data of hydrochemical researches of this region. It was shown that transport of major ions (Na, K, Mg, Ca, SO₄) and some trace elements (Li, Rb, Cs, Sr, B, F, Cr, Ge, As, Mo, U) is described by the stable in the long-term period equations of conservative mixing between riverine and seawater masses. Alkalinity also belongs to conservative components; however this parameter exhibits substantial spatiotemporal variability of the distribution caused by complex hydrological structure of the Yenisei Bay and adjoining part of the Kara Sea. Concentrations of P_min, Si, and V in the desalinized waters of photic layer decreases seaward during vegetation period owing to uptake by phytoplankton. The losses of these elements reach 30–57, 30, and 9% of their supply by river runoff, respectively. The content of dissolved P_min and V in the intermediate and near-bottom layers of the Yenisei River estuary strongly increases with increase of salinity due to regeneration of precipitated organic matter, whereas silica remineralization is much less pronounced. Barium in the all estuary is intensively desorbed from river suspended matter in the quantity reaching 20–100% of its dissolved forms input with river runoff depending on seasonal variations of chemical composition of the last. The transport of dissolved forms of heavy metals (Mn, Fe, Pb) and elements-hydrolyzates (Al, Ti, Y, La, Ce, Pr) in the mixing zone between the riverine and seawater masses is probably controlled by the coagulation and flocculation of organic and organomineral colloids, which is indicated by decrease in the concentrations of these elements at the beginning of salinization (for 20–61%) with subsequent approximation to the seawater mass characteristics.

In the plagioperidotite of the ultamafite-mafic Yoko-Dovyren intrusion captured by low-grad metamorphism (NGM) under conditions of the prenite-pumpelliite facies (PPF), mobilization of Ba, Cl and Sr is observed The content of barium in plagioperidotite ranges from 36 to 313 (an average of 130 g / t); strontium – from 25 to 169 (an average of 86 g / t); Ba / Sr value varies from 0.5 to 4 (on average 1.5). Barium minerals – phlogopite and plagioclase; chlorine – chloroferrisadanagite from inclusions in alumochromite, late-magmatic phlogopite, potassium chlorate ferropargassite and chlorapatite in the margins of sulphide nests. During the NGM processes, these minerals were replaced by chlorites, tremolite, diopside, which included very little Ba and Cl. In the areas of barium minerals development, plagioperidotites contain 348–518 g/t of barium and 4–6 g/t of strontium, which indicates the redistribution of Ba and the removal of Sr. Metamorphogenic barium minerals – non-strontium barite and Ba-Fe-Cl mica – chloro-dominant ferrokinochitalit. They coexist with the minerals of the rodingite association — hydrogarnet, tremolite, diopside, chlorite, antigorite, magnetite, hydroxylapatite. Ferrokosnoshitalit replaces phlogopite, plagioclase, sulfides, contains up to 21 wt. % BaO, 31% FeO, 11% Cl and has a iron index of f = 75.8–90.5. The composition of the most chlorine-rich individual responds (Ba_0.83K_0.16)_0.99(Fe²⁺_2.63Mg_0.28Fe³⁺_0.04Al_0.02Cr_0.01Mn_0.01)₃[(Cl_1.86OH_0.12S_0.02)₂/Al_1.86Si_2.14O₁₀]. Since Yoko-Dovyrenskiy ferrokynosalital is chlordominant, this is a new mineral species.