The Pizhemskoye titanium deposit is a new object of the nearest development in the Arctic zone of Russia

The Pizhemskoye titanium deposit (Middle Timan) has become one of the most attractive deposits for the industrial development in Russia as a result of the successful protection and approval of reserves at the State Reserves Committee (November 2020). 60 years have passed since the first finds of titanium mineralization in the basin of the Pechora Pizhma and Umba rivers by the thematic teams of the Ukhta Geological Exploration Department and the Komi branch of the Academy of Sciences, and now the deposit is considered one of the largest in Russia and the World. Together with the Yarega oil-titanium deposit, they contain up to 80% of the reserves and predicted resources of titanium in Russia. Timan becomes the largest raw material base of titanium in the world, the intensive development of which is possible for several hundred years. The article highlights the geological structure of the Pizhemskoye deposit (revealed a cellular, bowl-like structure of ore bodies); material and complex polymineral composition of ores; the Neoproterozoic age. The author proves the hydrothermal-metamorphogenic genesis of the ores, considers the sources of the mineral matter and solution of the technological scheme for processing refractory ores. The Pizhemskoye deposit is classified as a new pseudorutile-leucoxene-quartz subtype of primary metamorphogenic deposits.

A new straton in the Late Devonian sedimentation in the Tsil’ma river basin of the Middle Timan

Research subject. Terrigenous rocks of the Sargaevo stage of sedimentation in various structural-facies settings within the Tsilma area (Middle Timan). Material and methods. The composition, structural features of rocks, and the species diversity of spores of higher plants were studied in the most complete natural outcrops proposed as a stratotype of the Paladinskaya Formation – a new straton of the Sargaevo age in the Middle Timan. Over a large area of the region, the deposits contain very few remains of fossil fauna, often indifferent. As a result, palynostratigraphy was selected as the main biostratigraphic method. Results. In the Middle Timan, a new straton, the Paladinskaya Formation, is described, which characterizes the Sargaevo stage of sedimentation in various structural-facies settings within the Tsil’ma area. The new straton has clear lithological and detailed palynological characteristics; a description of the limitotypes was performed.At present, the Paladinskaya Formation is the most complete sequence of Early Frasnian sedimentation in the European North-East of Russia, where it was possible to record regional responses to the global Frasnes event and to determine the position of the controversial level of the boundary between the Middle and Upper Devonian. Conclusions. The name “Ust’e Yarega” Formation in the Middle Timan cannot be considered valid, since it is a homonym of the sediments of the same age in the South Timan. The section is represented mainly by continental, rather than marine, deposits. A new name for the identifed formation is proposed – “Paladinskaya” with a description of the stratum section and limitotype.The Paladinskaya Formation is characterized by subcomplexes of spores (А and Б) of the regional miospore zone Cristatisporites pseudodeliquescens, which made it possible to correlate the marine and continental deposits of the Early Frasnian on the territory of the entire Timan-Pechora region and establish its exact position in the stratigraphic scheme of the Devonian.

Lithogeochemical characteristics of metasandstones of the Chetlas series (Chetlassky Kamen, Middle Timan)

The lithological and geochemical features of the metasandstones of the Svetlinskaya and Vizingskaya formations of the Middle Late Riphean Chetlas series in the Middle Timan, which are a substrate of rare-metal-rare-earth mineralization in several ore occurrences of the Kosyus ore cluster, have been investigated. The interpretation of the results of traditional weight chemical and mass spectrometric inductively coupled plasma (ICP MS) analyses allowed us to identify differences in the material composition of metapesanics, mainly due to changes in the degree of sedimentation maturity of terrigenous material coming from the demolition areas. The composition of metasandstones in various ratios includes both weakly weathered products of destruction of volcanic rocks of intermediate/basic composition, and altered, including under conditions of the weathering crust, metaterrigenous formations. The accumulation of sediments took place in a shallow coastal-marine environment with changing hydrodynamics, which affected the rate of destruction of rocks in paleo-catchments.

Geochemical characteristics of the Late Devonian basaltoids of the Kanin Peninsula and the Middle Timan

The petrochemistry and geochemistry of dolerites and basalts of the Late Devonian Kanin-Timan complex of the Kanin Peninsula and the Middle Timan are considered. Petrochemically, the rocks of the Kanin-Timan complex of the Kanin Peninsula and the Tsilma river area of the Middle Timan correspond to basaltoids of the normal range of alkalinity and partially to moderately alkaline varieties, and belong to the tholeiitic series. The least differentiated varieties are dolerites of the southeastern Kanin Peninsula, the most differentiated are the basalts of the river Tsilma of the Middle Timan. The lowest REE concentrations were found in the rocks of the central part of the Kanin Peninsula (36.5-56.8 g/t); in the same samples, the lowest LaN/YbN values were recorded (1.85 and 2.4, respectively), which indicates an increased degree of melting of the source. The highest REE concentrations were found in basalts from the river Tsilma (77.13-88.33 g/t), LaN/YbN values (2.49-2.7, respectively). The influence of the crustal component in the formation of melts from which rocks of the Kanin-Timan complex were formed, was established. The source of the melt was spinel-garnet lherzolite, the degree of melting varied from 10 to 30%. The maximum degree of melting was 30%, at which melts were formed, that gave rise to the least differentiated rocks of the Northern Timan and the central part of the Kanin Peninsula. The mantle source, that gave rise to the melts from which the rocks of the Kanin-Timan complex were formed, was enriched with subduction and crustal components, a similar type of source is characteristic of the basaltoids of the No-rilsk trough.

Typomorphism of сhromespinelides from the Holocene psephites of the Kyvvozhskoye gold-placer field (Volsko-Vymskaya ridge, Middle Timan)

The results of the study of accessory chrome spinels from heavy mineral concentrates of gold-bearing psephites of the Kyvvozhsky gold-placer field (Volsko-Vymskaya ridge, Middle Timan) are presented. As a result of the study of the typochemistry of chromspinelides, their genetic relationship with rocks of mainly alkaline-ultrabasic composition — analogues of Timanian Late-Riphean-Vendian ultramafites and Early-Middle Devonian alnoites is substantiated. The formation of magmatic sources of chrome spinels occurred in a wide range of geotectonic settings — from passive (platform) to active (island-arc subduction zones), which are more characteristic of the bulk of chrome spinels. The crystallization of chrome spinels, found as microinclusions in lherzolite pyropes in the same shlich samples of the Kyvvozhskaya gold-bearing area, is associated with the conditions of rift zones (spreading of the seabed). We made a conclusion about probable local (intra-valley) position of main magmatic sources of chrome spinels. The revealed chrome spinels, containing microinclusions of nickel and copper sulfides, are considered by the authors as indicators of igneous rocks containing platinum group minerals.

Study and Diagnostics of Convergent Rocks on the Example of Carbonated Fluid-Explosive Ultramaphic Dyke Complex (Middle Timan)

Fluid-explosive rocks of the dike complex are identified in the Middle Timan. The rocks have convergent properties due to a combination of explosive and metasomatic processes. The study of the petrographic features of the rocks revealed their explosive nature. Further study of the chemical composition of rock-forming minerals established the source of the mantle material and the paragenetic relationship with carbonatite magmatism. The fluid-explosive rocks of the dyke complex have a long-term multistage formation history. The fluids caused fenitization of the host strata and its disintegration. Solid-gas material of the mantle-crustal compound fills the cracks. At the last stage of formation of fluid-explosive rocks, the rare-metal, rare-earth, and sulfide mineralization took place.

New data on titanium mineralization in fenitized precambrian carbonate rocks of Middle Timan bystrinskaya series

Fenitized Precambrian carbonate rocks (Middle Timan) are parent rocks for bauxite — phosphate weathering crusts. Therefore, the mineral composition of fenites, characterized by rich and varied mineralization, is of great interest. Titanium minerals especially attract attention, since their high concentrations are noted in bauxite-phosphate weathering crusts. For example, in the bauxites of the Verkhne-Shchugorsk area, the amount of rutile may reach 6000—7000 g/t. Titanium mineralization is represented by titanite, rutile, anatase, and cassite.