Mineralogy and Geochemistry of Ocelli in the Damtjernite Dykes and Sills, Chadobets Uplift, Siberian Craton: Evidence of the Fluid–Lamprophyric Magma Interaction

The study reports petrography, mineralogy and carbonate geochemistry and stable isotopy of various types of ocelli (silicate-carbonate globules) observed in the lamprophyres from the Chadobets Uplift, southwestern Siberian craton. The Chadobets lamprophyres are related to the REE-bearing Chuktukon carbonatites. On the basis of their morphology, mineralogy and relation with the surrounding groundmass, we distinguish three types of ocelli: carbonate-silicate, containing carbonate, scapolite, sodalite, potassium feldspar, albite, apatite and minor quartz ocelli (K-Na-CSO); carbonate–silicate ocelli, containing natrolite and sodalite (Na-CSO); and silicate-carbonate, containing potassium feldspar and phlogopite (K-SCO). The K-Na-CSO present in the most evolved damtjernite with irregular and polygonal patches was distributed within the groundmass; the patches consist of minerals identical to minerals in ocelli. Carbonate in the K-Na-CSO are calcite, Fe-dolomite and ankerite with high Sr concentration and igneous-type REE patterns. The Na-CSO present in Na-rich damtjernite with geochemical signature indicates the loss of the carbonate component. Carbonate phases are calcite and Fe-dolomite, and they depleted in LREE. The K-SCO was present in the K-rich least-evolved damtjernite. Calcite in the K-SCO has the highest Ba and the lowest Sr concentration and U-shaped REE pattern. The textural, mineralogical and geochemical features of the ocelli and their host rock can be interpreted as follows: (i) the K-Na-CSO are droplets of an alkali–carbonate melt that separated from residual alkali and carbonate-rich melt in highly evolved damtjernite; (ii) the Na-CSO are droplets of late magmatic fluid that once exsolved from a melt and then began to dissolve; (iii) the K-SCO are bubbles of K-P-CO2 fluid liberated from an almost-crystallised magma during the magmatic–hydrothermal stage. The geochemical signature of the K-SCO carbonate shows that the late fluid could leach REE from the host lamprophyre and provide for REE mobility.

Pyroxenite as a Product of Mafic-Carbonate Melt Interaction (Tazheran Massif, West Baikal Area, Russia)

Pyroxenite and nepheline-pyroxene rocks coexist with dolomite-bearing calcite marbles in Tazheran Massif in the area of Lake Baikal, Siberia, Russia. Pyroxenites occur in a continuous elongate zone between marbles and beerbachites (metamorphosed gabbro dolerites) and in 5 cm to 20 m fragments among the marbles. Pyroxene in pyroxenite is rich in calcium and alumina (5–12 wt% Al2O3) and has a fassaite composition. The Tazheran pyroxenite may originate from a mafic subvolcanic source indicated by the presence of remnant dolerite found in one pyroxenite body. This origin can be explained in terms of interaction between mafic and crust-derived carbonatitic melts, judging by the mineralogy of pyroxenite bodies and their geological relations with marbles. According to this model, the intrusion of mantle mafic melts into thick lower crust saturated with fluids caused partial melting of silicate-carbonate material and produced carbonate and carbonate-silicate melts. The fassaite-bearing pyroxenite crystallized from a silicate-carbonate melt mixture which was produced by roughly synchronous injections of mafic, pyroxenitic, and carbonate melt batches. The ascending hydrous carbonate melts entrained fragments of pyroxenite that crystallized previously at a temperature exceeding the crystallization point of carbonates. Subsequently, while the whole magmatic system was cooling down, pyroxenite became metasomatized by circulating fluids, which led to the formation of assemblages with garnet, melilite, and scapolite.

ISTOPIC COMPOSITION (H, O AND C) OF NATURAL WATERS OF THE NOVOSIBIRSK CITY AGLOMERATION

The paper presents the first data on the regional distribution of the isotopic composition of oxygen and hydrogen in waters, as well as the carbon of water-dissolved carbon dioxide in natural surface and underground infiltration waters of the Novosibirsk urban agglomeration. For the presented sample of samples, the vector of changes in the values of δD and δO in the studied region was obtained from -112 to -126 ‰ and from -14 to -16 ‰, respectively. The water-dissolved carbon dioxide of the studied waters has the expected biogenic genesis, the isotopic composition of carbon (δC from -14.0 to -7.0 ‰) indicates its participation in the processes of silicate-carbonate weathering.

New reagent regimes for potash flotation

The article presents the results of the VNII Galurgii’s studies into development of reagent regimes for flotation of potash ores of the Upper Kama deposit in fat solutions of potassium and sodium chlorides. The influence of the temperature of the saline solution and the content of magnesium chloride in it on the efficiency of aliphatic amines—collector of sylvin—was investigated. An alternative ethoxylated sludge collector for flotation de-sludging of potash ores is tested. The effect of a modified sludge depressant obtained by the synthesis of urea and formaldehyde is studied. The developed reagents are tested in full-scale processing of potash ore with variable composition and an increased content of sludge-forming silicate-carbonate and anhydrite water-insoluble impurities have been carried out. It is shown that the process stability and the production performance improve. Application of the sludge depressant in flotation of potash ore of variable composition allows stabilization of sylvin flotation and reduction in potassium chloride loss owing to stimulation of potassium chloride flotation from coarse tailings, which enables the decrease in the sylvin collector consumption and favors improvement of the process performance.

Polygenic Nature of Olivines from the Ultramafic Lamprophyres of the Terina Complex (Chadobets Upland, Siberian Platform) Based on Trace Element Composition, Crystalline, and Melt Inclusion Data

Olivine from the deep mantle-derived rocks, such as ultramafic lamprophyres, carries important information about the composition of the mantle source, the processes of mantle metasomatism, the origin of specific silicate-carbonate melts, as well as the composition and mechanisms of crystallization of these rocks. Textures and compositions of olivine from the carbonate-rich ultramafic lamprophyres (aillikites) of the Terina complex, along with their mineral and melt inclusions, exposed that olivines have different sources. Two populations of olivines were considered: macrocrysts (>1 mm) and groundmass olivines (<1 mm). Groundmass olivines are phenocrysts and characterized by weak variations in Mg# (84–86.5), a sharp increase in Ca and Ti contents, and a decrease in Ni and Cr from core to rim. They have higher concentrations of Li, Cu, Ti, and Na compared to macrocrysts. Among the macrocrysts, the following populations are observed: (1) high-Mg olivines (Mg# 89–91) with high Ni and low Ti contents, which are interpreted as xenocrysts from the slightly depleted lherzolite mantle; (2) high-Ca olivines (Mg# 84–88, CaO 0.13–0.21 wt %), which have patterns similar to groundmass olivines and are interpreted as cumulates of early portions of aillikite melt; (3) macrocrysts with wide variations in Mg# (73–88), low CaO contents (0.04–0.11 wt %), and positive slope in Ca vs. Al and negative slope in Ca vs. Mn, which are interpreted as disintegrated megacrysts from the Cr-poor megacryst suite. The megacryst suite could have been formed in the pre-trap period during the melting of the metasomatized subcontinental lithospheric mantle (SCLM). The aillikite melt evolution is traced by secondary melt inclusions in olivine macrocrysts: early phlogopite-diopside-calcite-apatite association, containing Ti-magnetite and ilmenite, is followed by an association with magnetite and sulfides (pyrrhotite and pentlandite); finally, at a late stage, inclusions with a predominance of Ca-Na-carbonates and sulfates and enriched in U, Th, Y, REEs, Sr, and Ba were captured.

Environmentally benign recycling of gold-bearing silicate–carbonate mill tailings

The bulk of the global gold reserves concentrate in mining and processing waste. This gold represents very fine and scattered particles, which complicates recovery. Implementation of a new method for dispersed micro-size gold in a patent-protected machine, including heating, melting, post-cooling milling and gravity separation, in the tests of rebellious silicate–carbonate ore has proved dissociation of gold and coarsening of gold particles. As a consequence, gold recovery in gravity separation can be largely improved, especially in case of reduced number of particle sizes and when close-cut fractions are processed separately. Cyanation after thermal treatment allows all gold to be extracted. On the other hand, melting of waste produces slag to be recycled as well. Recycling alternatives of any manmade products, and, in particular, slag, should base, for the first turn, on the environmental impact analysis, especially, regarding soil. The chemical composition of slag is compared with reference allowable concentrations of toxic substances in soil and with governmental standards set for feed for different process flows. The environmentally safe flow chart is proposed for integrated processing of gold-bearing silicate–carbonate mill tailings by thermal treatment which recovers disperse micro-size gold while slag is usable as an aggregate in backfill mixtures and as a corrective ingredient in the cement industry. The proposed flowchart is applicable to recycling of mining waste in different processing scenarios of goldbearing silicate–carbonate ore. The study was carried out under agreement with the Ural Mining University, State Contract No. 0833-2020-0008 Development and Ecological Feasibility Study of Mining and Metallurgy Disturbed Land Reclamation Using New-Type Improvers and Fertilizers, in association with and using the equipment of the Shared Use Canter at the Federal Research Center for Biological Systems and Agrotechnologies of the Russian Academy of Sciences, Accreditation Certificate No. Ross RU.0001.21 PF59, Unified Russian Shared Use Center Register, http://www.ckp-rf.ru/ckp/77384.

Melt inclusions in olivines from phoscorites and olivinites of the Kovdor massif.

&lt;p&gt;The Kovdor massif is a part of the Paleozoic Kola alkaline province and located in the eastern part of the Baltic Shield. Kovdor carbonatites host a unique complex baddeleyite-apatite-magnetite deposit from which iron ores and zirconium have been mined. New data on melt inclusions in olivine crystals from phoscorites and olivinites of the ore complex are presented in this contribution. Daughter minerals in crystallized melt inclusions were identified by Raman spectroscopy and scanning electron microscopy. The trace element composition of inclusions was determined using LA-ICP-MS.&lt;/p&gt;&lt;p&gt;Melt inclusions in olivine from Kovdor phoscorites are negative crystal or round in shape, with sizes ranging from 5 to 50 microns. They form groups or line up. According to the mineral composition, two types of melt inclusions can be distinguished: carbonate and silicate-carbonate. In the first type, Ca-Na-Mg- (Sr?) - REE carbonates are dominant among daughter phases. In the second one, silicate phases (phlogopite, monticellite, diopside), Ca-Na-Mg carbonates and magnetite are found together. Melt inclusions in olivine from olivinites are isometric or elongated, 5&amp;#8211;25 &amp;#956;m in size. They form groups or occur as isolated inclusions. Benstoneite, geylussit, ankerite, calcite and hydroxyl-bastnesite along with phyllosilicates (phlogopite, paragonite?) were identified among daughter minerals.&lt;/p&gt;&lt;p&gt;The rare earth elements composition of melt inclusions from both types of rocks is characterized by the predominance of light REE. The content of REE, especially light ones, in inclusions from phoscorites is higher. Strontium and barium contents in most melt inclusions have negative correlations with niobium and zirconium concentrations.&lt;/p&gt;&lt;p&gt;Melt inclusions from phoscorites and olivinites contain carbonate and silicate mineral phases in various proportions, which may imply heterogeneous trapping of crystalline phases and two immiscible melts, silicate and carbonatite. Inclusions from phoscorite represent a more evolved magma with higher concentrations of rare metals.&lt;/p&gt;&lt;p&gt;This work was supported by the Russian Science Foundation, grant No 19-17-00013.&lt;/p&gt;