The paper reports first comprehensive geological, petrographic, mineralogical, and geochemical data on one of the world’s oldest Tiksheozero ultramafic‒alkaline‒carbonatite complex (~1.99 Ga), which belongs to the Mid-Paleoproterozoic igneous province of the Baltic Shield. The complex was formed in three intrusive phases. The first phase is composed of the low-alkali mafic‒ultramafic rocks: dunites, wehrlites, clinopyroxenites, and gabbro. The rocks of the second phase are alkaline ultramafic rocks represented mainly by jacupirangites (alkaline clinopyroxenites) and foidolites (melteigites, ijoliltes, and urtites), with subordinate olivinites, alkaline gabbro, and nepheline syenites. The third intrusive phase is made up of carbonatites. Geochemical and mineralogical data indicate that all three phases were derived from different primary melts. It is shown that the nepheline syenites were obtained by fractionation of foidolites. A model of formation of such complexes through decompressional melting of mantle plume head enriched in carbonate fluid is proposed.

МИНЕРАЛЬНО-СЫРЬЕВАЯ БАЗА КАРЕЛЬСКОЙ АРКТИКИ - ПЕРСПЕКТИВЫ РАЗВИТИЯ И ОСВОЕНИЯ В. И. Иващенко, В. В. Щипцов Институт геологии ФГБУН ФИЦ Карельский научный центр РАН (Петрозаводск, Российская Федерация) Статья поступила в редакцию 1 апреля

The Tiksheozero ultramafic–alkaline–carbonatite intrusive complex, like numerous carbonatite-bearing complexes of similar composition, is a part of a large igneous province related to the ascent of a thermochemical mantle plume. The geochemical and isotopic data indicate that the formation of the ultramafic and alkaline rocks was related to crystallization differentiation of a primary alkali picritic melt, whereas carbonatite magmas were derived from an independent mantle source. We suggest that the origin of parental magmas of the Tiksheozero Complex, as well as other ultramafic–alkaline–carbonatite complexes, was provided by two-stage melting of the mantle-plume head: (1) adiabatic melting of its inner part generated moderately alkaline picrites, the subsequent fractional crystallization of which led to the appearance of alkaline magmas, and (2) incongruent melting of the upper cooled margin of the plume head under the influence of CO2-rich fluids, which arrived from underlying adiabatic melting zone, gave rise to carbonatite magmas.

Shungite rocks are widespread in Zaonezhye, Republic of Karelia, where they constitute dozens of carbonaceous rock deposits of the Paleoproterozoic Onega structure with predicted carbon resources of more 4 billion tons. The lower age boundary is of 2.1 Ga. Shungite rocks belong to carbonaceous rock class. These rocks metamorphosed in greenshcist facies of muscovite-chlorite-biotite subfacies are unique natural, noncrystalline, non-graphitized, fullerene-like carbon. They have various structural-mineralogical levels: (a) supramolecular, (b) molecular, (c) electron-energetic, (d) structural-physical and (e) geologic-genetic (parametric). Shungite rocks contain shungite carbon (shungite matter) and a variety minerals, microminerals and nanominerals. The applications of shungite rocks are determined with regard for their natural types. Authors had shown their intergrated application in ore-thermal processes.

Magmatic oxide mineralization widely developed in syenite–gabbro intrusive complexes is an important Fe and Ti resource. However, its origin is hotly debatable. Some researchers believe that the oxide ores were formed through precipitation of dense Ti-magnetite in an initial ferrogabbroic magma (Bai et al., 2012), whereas others consider them as a product of immiscible splitting of Fe-rich liquid during crystallization of Fe–Ti basaltic magma (Zhou et al., 2013). We consider this problem with a study of the Middle Paleoproterozoic (2086 ± 30 Ma) Elet’ozero Ti-bearing layered intrusive complex in northern Karelia (Baltic Shield). The first ore-bearing phase of the complex is mainly made up of diverse ferrogabbros, with subordinate clinopyroxenites and peridotites. Fe–Ti oxides (magnetite, Ti-magnetite, and ilmenite) usually account for 10–15 vol %, reaching 30–70% in ore varieties. The second intrusive phase is formed by alkaline and nepheline syenites. Petrographical, mineralogical, and geochemical data indicate that the first phase of the intrusion was derived from a moderately alkaline Fe–Ti basaltic melt, while the parental melt of the second phase was close in composition to alkaline trachyte. The orebodies comprise disseminated and massive ores. The disseminated Fe–Ti oxide ores make up lenses and layers conformable to general layering. Massive ores occur in subordinate amounts as layers and lenses, as well as cross-cutting veins. Elevated Nb and Ta contents in Fe–Ti oxides makes it possible to consider them complex ores. It is shown that the Fe–Ti oxide mineralization is related to the formation of a residual (Fe,Ti)-rich liquid, which lasted for the entire solidification history of the first intrusive phase. The liquid originated through multiple enrichment of Fe and Ti in the crystallization zone of the intrusion owing to the following processes: (1) precipitation of silicate minerals in the crystallization zone with a corresponding increase in the Fe and Ti contents in an interstitial melt; and (2) periodic accumulation of the residual melt in front of this zone. Unlike liquid immiscibility leading to melt splitting into two phases, this liquid dissolved the residual components of the melt. Correspondingly, such an Fe-rich liquid has unusual properties and requires further study.

The investigating results are given for the kyanite concentrate using in both the refractory and the facing materials for the iron founding and for the stone casting, as well as for the Investment shells in the precision steel casting.Ill.2. Ref. 20. Tab. 2.

The crisis of the Belomorian pegmatite province mica sector and perspectives of its overcoming causes and consequences of the mica sector crisis in the North-West Belomorie related to studies and a production of lamellar micaceous pegmatite is discussed. The alternative importance of the unique deposit in the Mezhozernoe (Eastern Hizovaara, Northern Karelia) - primary source of scarceness lamellar light mica is confirmed. The results of mineralogical and technological researches show that it is a promising target for mining and processing a small ferrous flake muscovite.

Был изучен циркон из титаноносного среднепалеопротерозойского Елетьозерского расслоенного интрузивного комплекса ультраосновных-основных-щелочных пород и карбонатитов, а также Sm-Nd система породообразующих минералов образца феррогаббро из этого комплекса. Циркон, выделенный из образцов сиенитов и феррогабброидов, имеет сходное строение и претерпел два главных независимых эпизода вторичного преобразования. В процессе первого из них магматический циркон с осцилляторной зональностью частично или полностью замещался пористым цирконом со сложной нерегулярной внутренней структурой, а во время второго – зерна как первичного, так и пористого циркона обрастали каймой гомогенного в катодной люминисценции циркона. Для исходного магматического циркона характерно распределение РЗЭ с повышенным содержанием тяжелых и пониженным легких лантаноидов, а также Се-максимум. Пористый же циркон характеризуется повышенным содержаниями легких РЗЭ, Са, Ti и часто – Th. Обе разновидности циркона в основном обеднены U. Распределение РЗЭ для гомогенного циркона оболочек подобно таковому в магматическом цирконе, но отличается заметно более низким уровнем концентрации РЗЭ, особенно тяжелых и средних. Пористый циркон содержит микровключения торита, барита, иттриалита, а также других редкометалльных и редкоземельных минералов (кальциосамарскита, пирохлора и гатчетолита), свидетельствующих о том, что зерна циркона подверглись переработке флюидами, содержащими не только F и Th, но и Y, U, Nb, Ta, Ba, Fe, Ti и Са. По-видимому, эти компоненты высвобождались в процессе метаморфизма при замещении магматических минералов метаморфическими парагенезисами с весьма ограниченной изоморфной емкостью. U-Pb геохронологические исследования циркона (SHRIMP-II) показали, что его возраст варьирует в широких пределах и коррелирует с особенностями внутренней структуры зерен, что объясняется характером наложенных процессов. Однако во многих случаях эти оценки возраста имеют более низкие значения, особенно для участков зерен вдоль границы с пористой разновидностью или при “проникновении” в них материала оболочек. По-видимому, наиболее близки времени формирования интрузива самые древние оценки возраста, т.е. 2086 ± 53 и 2086 ± 30 млн лет для сиенитов и 2070 ± 24 млн лет – для феррогабброидов. По геологическим данным, сиениты прорывают габброиды, поэтому как оценка возраста формирования интрузива в целом более предпочтителен возраст, полученный для сиенитов, т.е. 2086 ± 30 млн лет. Оценки возраста пористого циркона также варьирует в широких пределах, что объясняется присутствием реликтов (доменов) вещества циркона первичных зерен в пористой матрице. Мы полагаем, что наиболее близки возрасту кристаллизации пористого циркона минимальные из полученных датировок, т.е. этот циркон образовался 1.9–1.8 млрд лет назад. Это время проявления свекофеннских тектоно-метаморфических процессов, в которые, по-видимому, были вовлечены и породы Елетьозерского комплекса, что привело к метаморфизму всех пород комплекса в условиях эпидот-амфиболитовой фации и сопровождалось образованием пористого циркона. Формирование светлых (в катодной люминисценции) оболочек зерен, по-видимому, происходило еще позже, в результате взаимодействия циркона с внутрикоровым флюидом, и уже было связано с событиями в мезо- и неопротерозое, или даже в каледонское время. Возраст феррогабброидов, определенный Sm-Nd изохронным методом (1988 ± 63 млн лет), в пределах погрешности сопоставим с результатами U-Pb датирования пористого циркона, подтверждая тот факт, что магматические породы испытали существенные вторичные преобразования в ходе свекофеннской орогении. Среднепалеопротерозойский Елетьозерский комплекс является древнейшим проявлением титаноносного умеренно-щелочного магматизма на Карельском кратоне.

The paper presents a study of zircon from the Middle Paleoproterozoic Elet’ozero high-Ti layered ultramafic-mafic-alkaline intrusive complex with carbonatites and Sm-Nd isotope system of rock-forming minerals in ferrogabbro sample from this complex. Zircons extracted from syenite and ferrogabbro samples have similar pattern and experienced two main independent episodes of secondary transformation. The first episode was accompanied by the partial or complete replacement of the magmatic zircon with oscillatory zoning by porous zircon with a complex irregular inner structure, while a rim of CL-homogenous zircon around primary and porous zircons was produced during the second episode. The primary magmatic zircon is characterized by the elevated HREE, lowered LREE contents and positive Ce anomaly. The porous zircon is enriched in LREE, Ca, Ti, and frequently, in Th. While both varieties are mainly depleted in U. The REE distribution pattern in a homogenous zircon shell is similar to that of the magmatic zircon, but differs in much lower REE, especially HREE and MREE contents. The porous zircon contains microinclusions of thorite, barite, yttrialite, as well as other rare-metal and rare-earth minerals (calciosamarskite, pyrochlore, and hatchettolite), which indicates it was reworked by fluids containing not only F and Th, but also Y, U, Nb, Ta, Ba, Fe, Ti, and Ca. These components were presumably released during metamorphism-related replacement of magmatic minerals by metamorphic assemblages with fairly limited isomorphic capacity. U-Pb SHRIMP-II geochronological study of zircon showed its age varies within a wide range and correlates with peculiarities of its inner structure, which is explained by a style of superimposed processes. However, age estimations, especially for the domains dispersed alongside with porous zircon or “penetration” of shell material, often have younger values. The oldest ages (2086 ± 53 and 2086 ± 30 Ma for syenites and 2070 ± 24 Ma for ferrogabbroids) are presumably closest to the crystallization age of the intrusion. According to geological data, syenites intrude gabbroids. Therefore, the age obtained for syenites (2086 ± 30 Ma) seems to be the more preferable for the real formation age of the intrusion. Age values of porous zircon also widely vary, which is explained by the presence of relics (domains) of primary zircon in a porous matrix. We suggest that the minimum obtained dates (1.8–1.9 Ga) are the closest to the crystallization age of porous zircon. This age coincides with the Svecofennian tectonometamorphic processes, which presumably spanned the rocks of the Elet’ozero Complex, caused the metamorphism of all kind of rocks under the epidote-amphibolite facies conditions and formation of porous zircon. CL-light zircon shells were presumably formed later by interaction of zircon with a crustal fluid during the Meso- and Neoproterozoic, and even Caledonian events. The age of ferrogabbroids determined by Sm-Nd isochron method (1988 ± 63 Ma) is comparable within error with results of U-Pb dating of porous zircon, thus confirming that magmatic rocks of the complex underwent intense secondary transformations during the Svecofennian orogeny. The Middle Paleoproterozoic Elet’ozero Complex is the oldest manifestation of the high-Ti moderately alkaline magmatism at the Karelian Craton.

The Tiksheozero ultramafic-alkaline rock and carbonatite intrusion and the Eletozero pyroxene-gabbro-alkaline intrusion in northern Russian Karelia are a Paleoproterozoic component of the continental crust of the Fennoscandian Shield. U-Pb ID-TIMS age of the Tiksheozero carbonatite: expression of 2.0 Ga alkaline magmatism. The age also emphasizes the fact that not all members of the Kola alkaline province are of Paleozoic age. Those complexes are shown to host industrial minerals such as apatite, calcite, olivine, ilmenite, titanomagnetite as well as alkaline and nepheline syenites as the sources of feldspar. Geological-technological and economic assessment of the integrated use of carbonatites from the Tiksheozero complex were tested. The Suurivaara ilmenitic ore occurrences is very attractive. Another essential industrial mineral occurrence is the Eletozero central part of nepheline syenite massif. Based on the geological and technological data obtained on ilmenitic and titanomagnetitic ores and law-iron feldspatic concentrates from nepheline syenites. These occurrences can be evaluated. And the mineral reserves are assumed to be accessible from modern geological, technological, economic and environmental points of view.

Geological survey and study of the Tiksheozero alkali-gabbroid massif, North Karelia, have revealed apatite-bearing carbonatite which is of interest as an industrial raw material.Available data on the geological structure, petrographic and mineralogical characteristics and technological and economic value of apatite-bearing rocks were analyzed. It is shown that high-quality apatite and calcite concentrate, magnetite and mica can be produced.The industrial application of rocks from the Tiksheozero carbonatite massif and their conversion products industries with regard for their characteristics and technical requirements for various types of raw materials was preliminarily assessed. Undressed rock can be used for lime

The Tiksheozero carbonatite in northern Russian Karelia is a transitional type between alkaline ultramafic — carbonatitic and alkaline gabbroic suites. The complex is dominated by pyroxenite with a variety of subordinate mafic and ultramafic phases and nepheline syenite. Carbonatite occurs in a main central body and in veins. In this study we have obtained a reliable age for the complex by single grain ID-TIMS U-Pb analyses of zircon and baddeleyite. The age of 1999 ± 5 Ma is important because it places the emplacement of the alkaline complexes in the context of craton-wide extension and break-up events which preceded the initiation of a major Paleoproterozoic orogenic cycle. The Paleoproterozoic age also emphasizes the fact that not all members of the Kola alkaline province are of Paleozoic age.

A technology for manufacturing refractory ramming mixtures for the runners of blast furnaces is proposed based on the use of schungite in place of the conventional coke. The resistance of the lining to attack by molten metal and slag and its service life improved significantly using silicon carbide produced from schungite.

The article presents a systematic review of industrial minerals of Karelia ranged according to the most important geological events in the history of the Earth's crust of the Fennoscandian Shield. Polygenic and polytypic deposits and occurrences were distinguished, including operated and potential ones. The important role of industrial minerals in the economics of mineral raw materials is emphasized taking into account that the state of the world market is sufficiently stable and has a tendency to grow. Karelia possesses favorable geological conditions and prerequisites for the development and use of various types of mineral raw materials.

Requirements placed on the quartzite-based lining of crucible-type induction furnaces are discussed. The properties of Pervoural'skii and Karel'skii quartzites (P- and K-quartzites) are studied. Mineral impurities (in particular, mica) and their effect on properties of quartzite mixtures are considered. Industrial tests show that the fine-grained, predominantly intergranular mica is mainly responsible for the high wear resistance of K-quartzites. A characterization of the Metchangjarvi quartzite deposit is given and its commercial potential for production of refractory materials is discussed.

This paper describes investigations of the geology and processing of Karelian quartz occurrences, Russia. Different types of quartz were studied, such as quartz from mica and ceramic pegmatites of Saamian formations of Belomorian mobile zone, quartz from veins of Saamian, Lopian, Sariolian and Jatulian formations including placers, quartzites of Lopian and Jatulian formations. The quartz samples were refined and Al, Fe, Na, K, Ca, Mg and Ti were analyzed by a Swedish laboratory Analytica Abh and a Japanese laboratory in Tokio. The tests were done in the processing laboratory of Partek Nordkalk (Virkkala, Finland) and the laboratory of the Institute of Geology (Petrozavodsk, Russia). The outcome was that Karelian quartz could be of interest for high-purity quartz after different purification procedures.