The results of a comprehensive study of the Ore Horizon 330 (OH330) sulfide platinum group elements (PGE)-Cu-Ni deposit are presented. OH330 is located within the Sopcha intrusion orthopyroxenites of the layered Monchegorsk pluton (Monchepluton) in the Kola Region (Russia). It is a sill-like body, 3300 m long, 1200 m wide, and 4–6 m thick. The main rock-forming minerals of OH330 were olivine (Fo87–84) and orthopyroxene (En84–83). Light rare-earth element (LREE) fractionation is typical for all OH330 rocks, with the (Ce/Sm)N (where the subscript N indicates normalization to the primitive mantle) values of 1.21 in dunite, 1.33–1.86 in harzburgite, and 1.86–2.15 in orthopyroxenite. The trace elements exhibited positive U and Ta anomalies in dunite and harzburgite and negative Nb and Ta anomalies in orthopyroxenite. The following crystallization parameters of the OH330 rocks were determined: liquidus temperature, 1220 °C; solidus temperature, 1190 °C; and pressure, 2.4 kbar. The SHRIMP (sensitive high-resolution ion microprobe) U–Pb age of magmatic zircon from the OH330 orthopyroxenite is 2492.5 ± 4.1 Ma. This indicates that OH330 was younger than the rocks of the Monchepluton ultramafic subchapter (about 2506 Ma). The calculated parental melt of OH330 has a boninite-like composition with an MgO content of 14 wt

Numerous dyke- and sill-like dunites have been discovered in the Paleoproterozoic Monchetundra mafic intrusion (MMI) located northeast of the Fennoscandian Shield. The subject of our study was a 35-m-thick dunite dyke discovered during exploration drilling of the low-sulfide Pt-Pd Loypishnyun deposit. These dunites contain a xenolith of the amphibolized orthopyroxenite and have undergone uneven, locally intense serpentinization, resulting in serpentinite formation. The host norites and orthopyroxenites underwent tectono-thermal transformations at contact with the dunites in the form of thin zones of serpentine-tremolite, tremolite, and cummingtonite rocks. These dunites are important because they record magmatic events after the formation of the MMI associated with the reactivation of the cratonic mantle. This study reports the mineral composition and the whole-rock major and trace element contents in 23 samples collected from dunite section and host rocks. The primary magmatic minerals in the dunites were olivine (Fo 86.7-92.7 ) with an elevated Ni content (up to 0.57 wt% NiO) and accessory chromite (60-85 %Cr#). Dunites are characterized by high magnesium (80-87 %Mg#), nickel (1590-2990 ppm Ni), chromium (up to 1.7 wt% Cr2O3), and iron oxidation coefficient (82-65 %Fe3+#). They are depleted in rare earth elements (1.3-0.43 ppm REEtot), Ta, Sr, Zr, and Hf and are enriched in U, Th, and Ti. Based on Cr# (Chr)/Fo (Ol) and V/Al2O3 ratios, the parental magma of the dunites formed as a result of partial (30-40 %) melting of the fertile MORB mantle. Dunite crystallization occurred at 1355-1060 degrees C under the control of the FMQ buffer. Comparative analysis showed that the MMI dunites are similar in olivine composition to the alpine-type Pados intrusion and the Phanerozoic ophiolites of Oman, have a closer chromite composition to the Finnish Paleoproterozoic ophiolites, and generally similar in chemical composition to all except for lower SiO2 and CaO contents in the MMI dunites. In the REE patterns, the MMI dunites were closest to those of Pados. We suggest that the formation of MMI dunite dykes was associated with the rise of parental melt through a crack network in the continental crust. This process is likely associated with extensional conditions resulting from the uplift of a mantle diapir. The results obtained indicate that MMI dunites are most likely ophiolite-type intrusive bodies and they characterize the setting of the initial stage of oceanic crust formation in the northeastern Fennoscandian Shield.

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The paper presents the first SIMS SHRIMP U-Pb data for zircon from an olivine horizon within the Nyud intrusion of the ore-bearing layered Monchegorsk pluton (Monchepluton) in the Kola Region, Russia. A 100–150 m-thick olivine horizon occurs nearly horizontally between the melanocratic and mesocratic norite of the Nyud intrusion, which disturbs its normal cumulus stratigraphic sequence. In addition, the pyroxene-plagioclase hornfelses are present at the upper contact with the olivine horizon. Twenty-three zircon grains were extracted from the large-volume olivine plagio-orthopyroxenite sample and clustered into two populations. The first population of magmatic zircon (n = 8) has a concordant and weighted average 207Pb/206Pb age of 2484.3 ± 5.6 Ma, which characterizes the formation time of the olivine horizon rocks. This serves as evidence of the olivine horizon that forms as a result of additional magma injection, which does not contradict the geological data. The 207Pb/206Pb age of single-grain zircon is 2414 ± 25 Ma, which indicates the time of postmagmatic transformations. The second population of zircon (n = 16) has a concordant and weighted average U-Pb age of 2700.6 ± 4.6 Ma, which indicates zircon absorption by olivine horizon magma probably from the rocks of the Archean greenstone belt.

The sulfide PGE-Cu-Ni deposit "Ore horizon 330" (OH330) of the reef type is located within the orthopyroxenite of the Sopcha intrusion, which is part of the Paleoproterozoic layered Monchegorsk pluton (Monchepluton) in the Kola Region. OH330 is a sill-like body with a thickness of 4-6 m, traced along the entire perimeter of the Sopcha intrusion at a distance of 3.3 km and a width of 1.2 km. The OH330 deposit was studied in two wellexposed sections of its western flank. Here, OH330 is a thinly layered horison that lies among the host olivine orthopyroxenite. It consists of interlayers of dunite, harzburgite, and orthopyroxenite containing fine sulfide dissemination with increased contents of Ni (1290-5220 ppm), Cu (up to 2320 ppm), and platinum group elements (PGE) (0.43-1.40 ppm of the PGEtot). It is assumed that the OH330 parental magma was significantly contaminated with crustal material, saturated with sulfur and chalcophile elements. The separation of immiscible sulfide droplets during cooling led to the development of ore sulfide concentrations. The association of platinum group minerals (PGM) in harzburgite is represented by the predominant Pt-Fe alloys and subordinate PGE bismuth-tellurides, arsenides, and tellurides. Compared to harzburgite, PGE bismuth-tellurides and tellurides are widely distributed in orthopyroxenite, whereas arsenides, Pt-Fe alloys, and sulfides are minor. The PGE-Cu-Ni ore formed in a relatively wide temperature range from 1000 to 900 degrees C (base metal sulfides) to 900-600 degrees C (PGE sulfides and arsenides, and Pt-Fe alloys) and ended at a temperature of 600-400 degrees C with a crystallization bismuth-tellurides and tellurides of Pt and Pd.

It is shown that the uneven cooling of hot-rolled coiled material leads to inconsistent lengthwise characteristics of metal in a strip from one coil, welded joint zone included. One of the consequences of using this flat bar without controlled coil chilling (CCC) is an uneven relation of the mechanical properties of the main metal and the welded joint, which raises doubt about the possibility to eliminate this inconsistency by subsequent heat treatment. The study results show the need for optimizing the chilling of finished hot-rolled coiled material to reach a stable level of physical mechanical properties of items, where this material is used as the source material for producing cold-rolled products, pipes, metalware, etc.

Аннотация.В результате проведенного исследования изучены петро-геохимические особенности интрузии Плотичья Варака (ИПВ) комплекса роговообманковых мафит-ультрамафитов.В основном она сложена кортландитами (60 об.%), шрисгеймитами (10 об.%) и габброноритами (30 об.%).Химический состав шрисгеймитов и кортландитов характеризуется высокой отрицательной корреляцией между содержаниями MgO и остальными петрогенными элементами, за исключением содержания FeO tot , с которым у MgO положительная корреляционная связь.Для спектра РЗЭ в этих породах свойственен отрицательный наклон и незначительные отрицательные Eu аномалии.Распределение элементов-примесей характеризуется отрицательными аномалиями Ta, Nb, Ba, Hf и Y, а также положительными аномалиями Sr. Получен новый U-Pb возраст кортландитов ИПВ равный 1913 ± 5 млн лет

Аннотация.В результате проведенного исследования изучена кумулусная стратиграфия и петрохимические особенности пород расслоенной интрузии Поаз, которая слагает крайнюю восточную часть Мончегорского плутона (Мончеплутона).Разрез интрузии состоит из двух зон: нижней и верхней, мощностью 70-120 и 250-260 м, соответственно.Нижняя зона представлена меланократовыми норитами-плагиоортопироксенитами с ортопироксеновым кумулусом и плагиоклазовым интеркумулусом и относятся к ортокумулатам.Верхняя зона сложена лейко-мезократовыми норитами с кумулусными ортопироксеном и плагиоклазом и редкими пойкилопорфиробластами клинопироксена, которые являются мезокумулатами.На отдельных интервалах присутствуют прослои габброноритов, а также сложенные переслаиванием норитов и габброноритов.Различие между породами верхней и нижней зон интрузии Поаз подчеркивается особенностями их химического состава.Снизу вверх по разрезу происходит снижение содержаний MgO, FeOtot и SiO

We present the results of a study of loveringite found in two Paleoproterozoic layered intrusions of the Fennoscandian Shield: the Syöte block, Koillismaa intrusion, Finland, and the Nyud intrusion of the Monchegorsk pluton (Monchepluton), Russia. Loveringite is found in various rock types: 1) in non-cumulative gabbronorite (NcG) of a later phase from the middle zone of the Syöte block of the Koillismaa intrusion and 2) in orthopyroxene orthocumulates from lower zone of the Nyud intrusion. The loveringite morphology is diverse. It occurs as euhedral, anhedral, and corroded grains. Loveringite from the Syöte block, in contrast to that of the Nyud intrusion, is characterized by increased contents of Ti, Ca, V, and Zr, the presence of U and Th, and also reduced contents of REE. The loveringite composition is not strictly controlled by the stratigraphy of the layered intrusions, but is related the composition of residual liquid. The ilmenite reaction rims with baddeleyite and chrome-spinel are constantly present around the loveringite. Thinnest rims are observed around euhedral loveringite, whereas the thickest rims are observed around corroded grains, which indicates that the rim formation is due to reaction of the grain with residual liquid. Loveringites were formed at the late magmatic stage, after crystallization of cumulus orthopyroxene in the Nyud intrusion and pyroxene-plagioclase assemblage in the Syöte block. The presence of incompatible elements (Zr, U, Th, and REE) in the loveringite composition indicates crustal contamination for its genesis.

During the recent exploration of the Monchegorsk ore district (MOD) in the Arctic western sector, the platinum potential of known Cu–Ni deposits (Nittis-Kumuzhya-Travyanaya (NKT), Nyud, Ore Horizon 330 (OH330), and Terrasa) has been assessed, and new sulfide PGE–Cu–Ni deposits (Western Nittis) and manifestations (Moroshkovoe Ozero, Poaz, and Arvarench), and low-sulfide Pt–Pd deposits (Loipishnyun, Southern Sopcha, and Vuruchuaivench) have been discovered. All of them are confined to Paleoproterozoic (ca. 2.5 Ga) layered intrusions (the Monchegorsk pluton (Monchepluton) and the Monchetundra massif) and are divided into two types according to their structural position: basal, located in the marginal parts of intrusions, and reef-type (stratiform). All types of ores show Pd specialization. Platinum group minerals (PGM) have a limited composition in sulfide PGE–Cu–Ni ores and are represented by predominant Pt and Pd compounds with Bi and Te and subordinate PGE arsenides and sulfides. Low-sulfide Pt–Pd ores are characterized by a significant variety of PGM, with a predominance of PGE sulfides, bismuthide-tellurides, and arsenides. Sulfide PGE–Cu–Ni deposits and manifestations (Western Nittis, NKT, Nyud, Moroshkovoe Ozero, Poaz, and Arvarench) formed through the accumulation of base metal sulfides and PGE in immiscible sulfides and their subsequent segregation in commercial contents. The reef-type OH330 deposit and Terrasa manifestation resulted from the injection of additional portions of sulfur-saturated magma. The basal-type low-sulfide Pt–Pd deposits (Loipishnyun and Southern Sopcha) formed from residual melts enriched in ore components and fluids separated and crystallized during long-term oreforming processes. The reef-type Vuruchuaivench deposit is the result of deep fractionation of the parental magma with the formation of a sulfide liquid enriched in Cu and PGE. Significant reserves and large predicted resources of sulfide PGE–Cu–Ni and low-sulfide Pt–Pd ores are a reliable mineral resource base for the development of the mining industry in the Kola region of the Arctic western sector.

Аннотация.Представлены результаты комплексных геологических и минералого-геохимических исследований дунитов, входящих в состав Мончетундровского базитового массива (МБМ) Кольского региона.Дуниты образуют серию дискордантных жильных тел мощностью от 10 до 50 м среди ортопироксенитов и норитов нижней зоны МБМ, реже метагабброидов верхней зоны.Они содержат ксенолит вмещающих ортопироксенитов и активно воздействуют на вмещающие породы.Оливины и хромшпинели дунитов по составу сходны с таковыми альпинотипного массива Падос.В качестве акцессорного минерала в дунитах присутствует аваруит (Ni 3 Fe), который является типоморфным минералом офиолитовых комплексов.По химическому составу дуниты МБМ близки серпентинитам офиолитов Финляндии

The analysis of technology for the production of hot-rolled strip steel in coils has shown that the technological instructions for this metallurgical processing stage finishes at the stage of winding a finished hot strip into a coil. The development and implementation for technology to control the cooling of hot-rolled strip coils in accordance with the grade-and-size assortment, as well as with customer’s requirements, are necessary.

The article presents the results of studying the chemical composition of ore-bearing rocks, as well as the mineralogy of base metal sulfides and platinum group elements (PGE), of the Nyud-II sulfide PGE–Cu–Ni deposit in the southwestern part of the Nyud massif of the Monchegorsk Pluton (Monchepluton). The ores of the deposit are represented by vein-disseminated and nest-schlieren types. They are characterized by significant predominance of Pd over Pt, fractionation of low-melting PGE (PPGE subgroup) with respect to high-melting ones (IPGE subgroup), and close correlations of Ni and Cu with S in the presence of increased As, Se, Te, and Bi contents. The S/Se ratios in ore (3470−3530) correspond to the mantle values. Among the platinum group minerals (PGM), the most widespread are Pt and Pd bismuth–tellurides and tellurides (merenskyite, michenerite, and moncheite), subordinate amounts of Pt–Fe alloys and sperrylite, and native osmium and Ir, Rh, and Pt sulfoarsenides (irarsite, hollingworthite, and platarsite). The formation of ore sulfide concentrations resulted from separation of an immiscible sulfide liquid upon cooling of a sulfur-saturated silicate magma with a mafic composition. Subsequent fractional crystallization of the sulfide liquid contributed to the uneven distribution of Ni, Cu, and PGE. PGE–sulfide ore formation took place in a fairly wide temperature range, starting at 1100−1000°C and ending at 600−400°C. At an early stage, IPGE minerals (native osmium and erlichmanite) separated. Upon cooling to a temperature of 1000−900°C, the sulfide liquid fractionated with the formation of monosulfide solid solution (mss), in which compatible IPGE were concentrated, and a residual sulfide liquid enriched in Ni, Cu, PtPGE, and chalcophile elements. With a further decrease in temperature (to 600°C), Pt–Fe alloys, sperrylite, and IPGE + Pt sulfoarsenides crystallized, with separation of the residual sulfide melt enriched in Cu, PPGE and chalcophile elements. At 600−400°C, ore formation ended with the complete crystallization of base metal sulfides and the formation of Pt and Pd bismuth–tellurides and tellurides.

Аннотация.Изучены офитовые габбронориты, вскрытые в результате бурения в основании массива Кумужья, являющегося средней частью массива Ниттис-Кумужья-Травяная (НКТ) палеопротерозойского Мончегорского плутона (Мончеплутона).Они слагают силлоподобное тело мощностью около 70 м с вертикальным подводящим каналом.Комплексное исследование офитовых габброноритов показало, что они являются более молодой интрузивной фазой, относительно основного объема массива НКТ.Для них характерно присутствие зонального ортопироксена, состав которого меняется от бронзита ) в ядре до гиперстена (En 74.3-57.0 ) в краевой части, что обусловлено резким снижением температуры кристаллизации тела в результате сравнительно быстрого охлаждения.Между офитовыми габброноритами и вышележащими меланоноритами происходил процесс диффузионного метасоматоза, который фиксируется в возрастании

The Sopcha massif, which is part of the Paleoproterozoic layered Monchegorsk Pluton (Monchepluton), contains an ore horizon with an average thickness of ca. 4 m within the homogeneous orthopyroxenite sequence. This horizon has a layered internal structure with variations in composition from dunite to orthopyroxenite and sulfide mineralization enriched in platinum group elements (PGE). All the rocks of the ore horizon include accessory chrome-spinels, which demonstrate a high variability of the composition and are divided into two groups based on their optical properties and chemical composition. Group I chrome-spinels belong to Al-chromites. They occur as homogeneous grains in fine-to-medium-grained orthopyroxenite at the top of the horizon and form cores of zoned chrome-spinels in the medium-to-coarse-grained orthopyroxenite and harzburgite. Group II chrome-spinels belong to Fe-chromites. They form homogeneous grains in dunite and harzburgite and rims of zoned grains in harzburgite. Chemical compositions of Group I chrome-spinels are characterized by high contents of Al2O3 and Cr2O3, an increased MgO but low contents of FeOtot and values of Cr#= Cr/(Cr + Al) and Fe3+# = Fe3+/Fetot. Group II chrome-spinels have low Al2O3 and MgO contents, and sharply increased values of Cr# and Fe3+#. This variability in the composition of chrome-spinels is caused by decreasing melt temperature in the process of its cooling during two stages of magmatic crystallization. At the first stage, cumulus crystallization of Group I chrome-spinels and subsolidus diffusion between spinel and olivine (“mineral-mineral” reaction) occurred at a temperature of about 1170 °C. At the second stage, reactions between Group I chrome-spinels and intercumulus melt (“mineral-melt” reactions) resulted in the formation of a rims of zoned chrome-spinels and homogeneous Group II chrome-spinels at a temperature of 1070–970 °C.

Аннотация.Определен химический состав и U-Pb возраст дунитов и хромовых руд Сопчеозерского хромового месторождения (СХМ), приуроченного к Дунитовому блоку Мончегорского плутона (Мончеплутона).Составы дунитов и хромовых руд укладываются в общие эволюционные тренды петрогенных элементов, при этом, между содержаниями MgO и SiO 2 существует тесная положительная корреляционная связь и резко отрицательная между MgO, Cr 2 O 3 и FeOtot.Суммарные содержания РЗЭ в дунитах не превышают 2 г/т и возрастают до 5 г/т в хромовых рудах.Для спектра РЗЭ в дунитах и рудах характерен отрицательный наклон за счет фракционирования ЛРЗЭ.Распределение элементов-примесей в дунитах и хромовых рудах характеризуется наличием повышенных содержаний U, Th, Nb и Ta, положительными аномалиями Ti, Sr и Y, отрицательными аномалиями Hf и Zr.Возраст дунитов СХМ U-Pb методом по циркону определен в 2500 ± 10 млн.лет, а богатой хромовой руды в 2500 ± 2 млн.лет, что свидетельствует о синхронности их образования.

За последнее время в пределах Мончегорского рудного района (МРР) западного сектора Арктики была выполнена оценка платиноносности известных Cu-Ni месторождений (НКТ, Нюд, РП330 и Терраса) и выявлены новые месторождения (Западный Ниттис) и проявления сульфидных ЭПГCu-Ni руд (Морошковое озеро, Поаз и Арваренч), а также месторождений малосульфидных Pt-Pd руд (Лойпишнюн, Южная Сопча и Вуручуайвенч). Все они приурочены к палеопротерозойским (около 2.5 млрд. лет) расслоенным интрузиям: Мончегорскому плутону (Мончеплутону) и Мончетундровскому массиву и по структурному положению делятся на два типа: базальные и рифовые. Первые из них (Западный Ниттис, НКТ, Нюд, Морошковое озеро, Поаз, Арваренч, Лойпишнюн и Южная Сопча) локализованы в пределах нижних краевых зон интрузий, имеют сложное строение рудных тел с невыдержанной мощностью и неравномерным распределением элементов платиновой группы (ЭПГ). Месторождения рифового типа (РП330, Терраса и Вуручуайвенч) характеризуются выдержанной мощностью и более равномерным распределением полезных компонентов. Для всех типов руд характерна ярко выраженная палладиевая специализация. В сульфидных ЭПГ-Cu-Ni рудах минералы платиновой группы (МПГ) имеют ограниченный состав и представлены преимущественно соединениями Pt и Pd c Bi и Te, а также подчиненными арсенидами и сульфидами ЭПГ. Для малосульфидных Pt-Pd руд характерно значительное разнообразие МПГ с преобладанием сульфидов, висмуто-теллуридов и арсенидов ЭПГ. Образование сульфидных ЭПГ-Cu-Ni руд происходило при величине R-фактора от 3000 до 5000 и модельном содержании сульфидов около 5 % в результате контаминации исходной магмы коровыми породами, насыщения ее серой и последующим выделением несмешивающегося сульфидного расплава, обогащенного ЭПГ. Процесс малосульфидного Pt-Pd рудообразования протекал при величине R-фактора 10000 и модельном содержании сульфидов около 1 % и обусловлен отделением с последующей кристаллизацией остаточного, богатого флюидами и рудными компонентами остаточного расплава. Значительные запасы и крупные прогнозные ресурсы сульфидных ЭПГ-Cu-Ni и малосульфидных Pt-Pd руд служат надежной минеральносырьевой базой для развития добывающей промышленности в Кольском регионе западного сектора Арктики.

The paper presents results of comprehensive studies of the rock association composing the lower zone of the northeastern part of the Monchetundra mafic massif in the Monchegorsk ore district. The zone consists of orthopyroxenite, plagioorthopyroxenite, and norite, which are variably amphibolized and host numerous gabbroid injections from the upper zone of the massif. The chemical composition of the dominant rock-forming minerals of the rocks was studied. The orthopyroxenes of the lower zone of the Monchetundra massif (LZMM) notably differs from those of the Monchegorsk pluton (Monchepluton) in containing lower aluminum concentrations because of differences in the P–T parameters of their crystallization. According to mineral geothermobarometric data, the LZMM rocks crystallized at 1200–1000°C and approximately 6 kbar, at a depth of about 20 km, whereas the Monchepluton rocks crystallized at an average temperature of 1230°C and a pressure of 3 kbar in shallow conditions. The LZMM rocks are characterized by moderate magnesium and silica contents and by elevated iron and low titanium concentrations, are enriched in the light rare earth elements (LREE) and LILE (Rb, Ba, and Sr) but are depleted by HFSE (Nb and Ta). The behavior of major components in the rocks is similar to that in analogous rocks in the bottom axial part of the Monchetundra massif, lying at its basement. Moreover, all petro- and geochemical parameters of the LZMM rocks are close to those of the analogical rocks of the Monchepluton. The paper presents new U–Pb isotope-geochronological data on individual zircon grains from the LZMM rocks. The age of the orthopyroxenite is 2496.3 ± 2.7 Ma, and that of the norite is 2500 ± 2 Ma, which indicates that these rocks crystallized simultaneously (within the error). The orthopyroxenite has an age of 2452 ± 85 Ma and positive εNd(T) = +1.7, and the model age of the protolith T(DM) is 2.76 Ga according to data on the Sm–Nd of isotopic systematics. The possible parental melt of the rocks may have been komatiite contaminated with crustal material. The obtained results indicate that the Monchetundra massif is a composite intrusion, whose lower zone is similar to the layered intrusions and the upper one is made up of rocks belonging to the gabbro–anorthosite complex. The massif was formed by at least three pulses of magmatic activity (at 2.50, 2.47, and 2.45 Ga).