The Lobash copper-molybdenum-porphyry mineralization of the Lobash deposit. Northern Karelia, Russia, is located in the apical portion of the 2.715 Ga Lobash granitic intrusion and at its exocontact in an Upper Archean greenstone rock sequence. Molybdenite mineralization is confined to a quartz vein at the massif margin, while disseminated-streaky mineralization is confined to a stockwork in host rock sequences. The gold-base metal mineralization of the Lobash-1 deposit lies to the north of the molybdenum deposit. Mineral associations of ores and their geochemical characteristics were studied by microprobe analysis and the ICP-MS method. At the Lobash deposit, molybdenite is associated with pyrite, chalcopyrite and zonal scheelite-molybdoscheelite. The ore mineralization of the Lobash-1 deposit is confined to schistosity zones and rhyodacite dyke contacts. It consists of pyrrhotite, sphalerite, chalcopyrite, galena, gold, electrum, hessite, bismuth, bismuthine and various bismutotellurides. The ore mineralization of the Lobash Ore Field formed at a temperature which decreased from 440 to 145 ℃.

Gold–copper–sulfide, noble-metal–copper–uranium and noble-metal–copper–uranium–vanadium mineralization in Paleoproterozoic structures of the Karelian Craton is associated with the evolution of the large regional Lapland–Onega rift structure in the Svecofennian. A characteristic feature of the deposits and ore occurrences that formed at the orogenic stage is the appearance of selenium minerals. On the territory of Karelia, ore objects of the separate Onega, Kumsinskaya, Pergubskaya, Severo-Vygozero, Lekhta and Elmozersko-Segozero structures were studied and materials on the ore mineralization of Paana-Kuolajarvi structure were generalized. The element concentrations in ores and near-ore metasomatites were determined by ICP-MS analysis, and the contents of individual elements was determined by X-ray fluorescence analysis. Ore minerals were studied by scanning electron microscopy. It has been established that the ores of the studied deposits and ore occurrences are represented by a geochemical assemblage of elements, including Cu, Au, Ag, Pb, Mo, Pd, Pt, Co, Ni, U, Se, Bi, Te, As, V, REE, Ba, and Fe ( in various proportions). Vein-disseminated ore mineralization is accompanied by low-temperature metasomatites: alkaline (albitites, eisites), ferromagnesian, mica or beresites, confined to deformation zones in the host Paleoproterozoic sequences. Basalts, quartzite sandstones, and carbonate deposits of the Jatulian suprahorizon; carbonaceous, mafic, and ultramafic sequences of the Ludicovian suprahorizon, as well as gabbrodolerites intruding them, were subjected to alteration. The ore mineralization of noble-metal–copper–uranium–vanadium and noble-metal–copper–uranium deposits and occurrences (in which the noble metals are predominantly Au, Pd) is represented by copper sulfides and selenides, lead, silver, gold, palladium; less frequently, platinum, native gold; more rarely, bismuth, bismuth tellurides; as well as uraninite, vanadium micas, molybdenite, REE minerals, hematite, and goethite, which are typomorphic minerals of these deposits and occurrences. Among hydrothermal selenides, clausthalite, naumannite, fischesserite, palladseite, padmaite, sudovikite, bogdanovichite, paraguanahuatite, eukairite, umangite, klockmanite, timannite, tyrrelite, and cadmoselite have been established, as well as selenium-bearing sulfides (Se-malyshevite, weibullite, selenogalena, Se-bearing bornite, chalcocite, and molybdenite). Native selenium and selenates were found in oxidation zones. Typomorphic assemblages of Au–Cu sulfide deposits and occurrences in the more eroded central part of the Karelian Craton are represented by chalcopyrite, bornite, pyrite, galena, molybdenite, silver sulfides, gold, electrum, Se-bearing chalcocite, and hematite. Selenides are less common in these ores—among them clausthalite, naumannite, bogdanovichite, and fischesserite have been identified.

—In the present paper we demonstrate that most sulfides of the studied deposits of the Archean Sumozero–Kenozero greenstone belt within the Karelian Craton on the Fennoscandian Shield have nonzero Δ33S values. This indicates that proportions of seawater sulfate and elemental sulfur in Mesoarchean, included into the ores and resulting from UV photolysis, are different. Our results show that systematics of sulfur isotopes of sulfides generally reflects the mixing of mass-independently fractionated sulfur reservoirs with positive and negative Δ33S values. Pyrite is depleted in 34S isotope, which was interpreted as evidence for microbial sulfate reduction. Variations in the positive Δ33S anomalies of the Leksa deposit and the general tendency for Δ33S sulfide content to increase with stratigraphic levels in certain boreholes most likely reflect the change in temperature and the fluid mixing throughout the life of the hydrothermal system. The presence of sulfides with strongly negative Δ33S anomalies suggests that atmospheric sulfur and seawater sulfate, rather than volcanic sulfur, were the prevailing source for mineral systems of the studied deposits. The presented data require the Mesoarchean seawater to contain sulfates at least locally.

The sulfur isotope anomalies ∆33S and ∆36S known today in ancient rocks exhibit common geochemical patterns reflected in the existence of a correlation like ∆36S ≈ –∆33S for sulfides from Archean formations of Australia, Africa, and America. To understand the scale of this phenomenon, we investigated the pattern of sulfur isotope fractionation in sulfides from rocks of the Irkut Block of the Sharyzhalgai Uplift of the basement of the Siberian Craton, as well as the Leksa ore occurrences located in the Karelian Province. It was shown that the objects of our study held ∆33S and ∆36S isotope anomalies. This leads to the conclusion that the geochemical processes responsible for the generation of sulfur isotope anomalies are much more widespread than was assumed until now and allows us to recognize them as a phenomenon of planetary significance. The fact that the relationship between ∆36S ≈ –1.0 ∆33S isotope anomalies demonstrates the same characteristics as in other Archean rocks of the most ancient shields worldwide indicates the similar conditions and mechanisms for fractionation of sulfur isotopes at the stages of its transformation in an atmospheric photochemical cycle.

В представленном исследовании мы показываем, что большинство сульфидов в исследованных месторождениях Сумозеро-Кенозерского зеленокаменного пояса Карельского кратона Фенноскандинавского щита имеют ненулевые значения Δ33S. Это указывает на различные пропорции сульфата в морской воде и элементарной серы, образовавшихся в результате УФфотолиза, и включенных в руды. Наши результаты показывают, что систематика изотопов серы сульфидов в основном отражает смешение между массово-независимо фракционированными резервуарами серы с положительным и отрицательным Δ33S. Пирит обеднен изотопом 34S, что было интерпретировано как свидетельство микробного восстановления сульфата. Вариации положительных аномалий Δ33S месторождения VHMS Лекса и общая тенденция увеличения содержания сульфида Δ33S со стратиграфической высотой в отдельных скважинах, скорее всего, отражают изменение температуры и перемешивание флюидов на протяжении жизни гидротермальной системы. Присутствие сульфидов со значительными отрицательными аномалиями Δ33S предполагает, что атмосферная сера и сульфат морской воды, а не вулканическая сера, были доминирующим источником для минеральных систем изученных месторождений. Представленные здесь данные требуют, чтобы мезоархейская морская вода, по крайней мере локально, содержала сульфаты.

The paper presents results of the first geochronologic study (LA-ICP-MS zircon method) of metasedimentary rocks that host the banded iron formation (BIF) and the metarhyolites (halleflinta) of the Gimoly Group in the Kostimuksha greenstone belt,Karelian Craton. Felsic magmatism that produced the rhyolite sills and dikes was dated at 2759 ± 19–2743 ± 15 Ma. The clearly predominant group of zircons in the schists (metagraywacke) has an isotope age of 2753 ±19 Ma, and scarce zircon grains of these rocks vary in age from 3.1 to 2.8 Ga. Geochemically, zircons from metarhyolites fall into three types (1) Eu-depleted and Ce-enriched, (2) Eu- and Ce-enriched, and (3) LREE- and MREE-enriched. The zircons of geochemical types (1) and (2) are also predominant in the sediments. The morphology and structure of zircon crystals in the rhyolites and sediments are also identical. The rhyolites were thus a major source of zircons for the metagraywacke, which alternates with BIF, while the Mesoarchean rocks played a subordinate role. The BIF of the Gimoly Group in the Kostomuksha Greenstone Belt was formed simultaneously with felsic volcanism at 2760–2740 Ma.

Аннотация.Молибденовое и золото-полиметаллическое месторождения рудного поля Лобаш приурочены к зеленокаменным толщам позднеархейского возраста, которые прорываются разновозрастными интрузиями габброидов, дайками дацитов-риодацитов и двухфазной гранодиорит-гранит-порфировой интрузией.На молибденовом месторождении Лобаш в ореоле не выходящей на поверхность гранит-порфировой интрузии формируются эпидозиты по габбро; пропилиты -по базальтам, андезитам; окварцевание и альбитизация развиваются по кислым породам (дайкам); биотитизация -по всем типам вмещающих оруденение пород.В минеральном и химическом составе ведущих типов метасоматитов (пропилитов и биотититов

Аннотация.В работе рассмотрен состав шеелитов из медно-молибден-порфировых месторождений и проявлений Карелии, локализованных в архейских зеленокаменных поясах, на примере рудного поля Лобаш и Ялонвара.Шеелиты разных месторождений изучались с использованием электронного сканирующего микроскопа VEGA II LSH (Tescan) c энергодисперсионным микроанализатором INCA Energy-350; руды -c помощью ICP-MS-анализа.Шеелит из молибденовых месторождений часто содержит Mo 6+ , изоморфно замещающий W 6+ , при этом образуются зональные молибдошеелиты (Лобаш, Ялонвара) и шеелиты, содержащие вростки молибденита (Ялонвара).Шеелит золоторудного месторождения Лобаш-1 не образует значительных

Аннотация.Район дер.Кондобережская в Онежской палеопротерозойской структуре известен тем, что здесь в результате поисковых работ, проводимых ПО «Северкварцсамоцветы» в 80-е годы прошлого века, было открыто уникальное для докембрия проявление пестроцветных яшм и карнеол-агатов.Проявление приурочено к шунгитоносным породам заонежской свиты людиковия.Карнеол-агаты представлены концентрически зональными оранжево-красными обособлениями размером до 30 см.При обследовании западного участка проявления выяснилась, что карнеол-агатовая минерализация приурочена к СЗ зоне окварцевания по шунгитоносным породам

Минеральные ассоциации золото-медно

The Maksovo metasapropelite deposit, which contains shungite matter and is called maksovite, is located in the eastern Onega structure. The deposit is a diapiric fold which formed ca. 2070±10 Ma ago. It is underlain by carbonate rocks and overlain by tuff siltstones and is cross-cut by 1956±5 Ma gabbro-dolerites. Unaltered maksovites are pelitomorphic rocks with a massive to mildly layered texture and moderate concentrations of all petrogenic components and Сorg of about 30%. Fe-Mg rich and alkaline metasomatic rocks evolve after maksovites and mafic and carbonate tuff siltstones in the northwestern part of the deposit within a multiple ridge-like fold after brecciation zones. They differ from unaltered sedimentary rocks in heterogeneous (brecciated, streaky) textures, mineral and chemical composition and are saturated with numerous sulphide, carbonate, quartz and albite veinlets. They are identified by intense biotitization, chloritization and the presence of calcite, microcline metacrystals, albite-carbonate metacrystals with apatite and carbonate-quartz metacrystals with sulphides and rutile, veinlets and disseminated mineralization. Na concentration rises to 5.67% and K concentration to 7.57%. P and Ti concentrations, accompanying alkaline metasomatism, as well as Mg-Fe and ore-bearing components (often incompatible), increase locally. Metasomatic rocks evolve heterogeneously and are represented by breccia zones. Their slightly elevated radioactivity disturbs the qualitative characteristics of primary maksovite as a useful mineral. Maksovites were dated at 1558±61 Ma by the Re-Os method from sulphides.

The concentration of production of rare earth elements (REEs) outside the United States raises the important issue of supply vulnerability.REEs are used for new energy technologies and national security applications.Two key questions of interest to Congress are: (1) Is the United States vulnerable to supply disruptions of REEs? (2) Are these elements essential to U.S. national security and economic well-being?There are 17 rare earth elements (REEs), 15 within the chemical group called lanthanides, plus yttrium and scandium.The lanthanides consist of the following: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.Rare earths are moderately abundant in the earth's crust, some even more abundant than copper, lead, gold, and platinum.While more abundant than many other minerals, REEs are not concentrated enough to make them easily exploitable economically.The United States was once self-reliant in domestically produced REEs, but over the past 15 years has become 100% reliant on imports, primarily from China, because of lower-cost operations.U.S.-based Molycorp has begun production at its Mountain Pass mine and anticipates production at full capacity (19,050 metric tons) in 2014.Molycorp also operates a separation plant at Mountain Pass, CA, and sells rare earth concentrates and refined products from newly mined and previously mined above-ground stocks.Molycorp announced its purchase of Neo Materials Technology (renamed Moly Canada), a rare earth processor and producer of permanent magnet powders which has facilities in China.Some of the major end uses for rare earth elements include use in automotive catalytic converters, fluid cracking catalysts in petroleum refining, phosphors in color television and flat panel displays (cell phones, portable DVDs, and laptops), permanent magnets and rechargeable batteries for hybrid and electric vehicles, generators for wind turbines, and numerous medical devices.There are important defense applications, such as jet fighter engines, missile guidance systems, antimissile defense, space-based satellites and communication systems.World demand for rare earth elements was estimated at 136,000 tons per year, with global production around 133,600 tons in 2010.The difference was covered by previously mined aboveground stocks.World demand is projected to rise to at least 160,000 tons annually by 2016 according to the Industrial Minerals Company of Australia.Some mine capacity at Mt. Weld Australia has come on-stream in 2012, but far below the projected 11,000 metric tons of capacity.Other new mining projects could easily take as long as 5-10 years to reach production.In the long run, however, the U.S. Geological Survey expects that global reserves and undiscovered resources are large enough to meet demand.In March 2012, the Obama Administration announced the filing of a World Trade Organization case against China, citing unfair trade practices in rare earths.A final decision is expected to be announced in early 2014.Several legislative proposals have been introduced in the 113 th Congress in the House and Senate to address the potential of U.S. supply vulnerability and to support domestic production of REEs and other critical minerals because of their applications for national security/defense systems and clean energy technologies.

Максовское месторождение метасапропелитов (максовитов), содержащих шунгитовое вещество, расположено в восточной части Онежской структуры — бассейна, заложившегося и формировавшегося в палеопротерозое в юго-восточной части Фенноскандинавского щита. Залежь максовитов представляет собой диапировую складку, сформировавшуюся около 2050±10 млн лет назад; она подстилается карбонатными толщами, перекрывается туфоалевролитами и прорвана габбродолеритами (1956±5 млн лет). Неизмененные максовиты — это пелитоморфные породы с массивной или неяснослоистой текстурой, с содержанием Сорг около 30%. Наложенные на максовиты и на подстилающие толщи туфоалевролитов изменения развиваются в пределах гребневидной складки по зонам брекчирования. Эти изменения представлены щелочно-железо-магнезиальными метасоматитами с брекчированными текстурами, неоднородным минеральным и химическим составом; выделяются по интенсивной биотитизации, хлоритизации, развитию альбит-карбонатных с апатитом и карбонат-кварцевых с сульфидами прожилков. В зонах изменения повышается содержание Na, K, Р, Ti, Mg-Fe и рудогенных компонентов. Время формирования метасоматитов, установленное Re-Os методом по сульфидам — 1558±61 млн лет.

The results of the study of ore mineralization in the Paleoproterozoic layered massifs of North Karelia conducted by various researchers (Lukkulaisvaara, Kivakka, Travyanaya Guba, Panfilova Gora, and Klimovskoye occurrences), are reported.Attention is focused on platinum-group metal minerals.

Pyrite ores have been formed on the Earth from the Archean to the present. The most important component, sulfur, can be provided by the following three sources: igneous, sedimentary, and sulfates of seawater. Studies of contemporary hydrothermal systems of the seabed, which are considered to be the ore-generating mechanism responsible for the oldest pyrite deposits, have shown that magmatic sulfur and seawater sulfate make the major contribution to the total sulfur budget in ore formation [1–3]. The question of the influence of the simplest forms of life on the processes of ore formation, which is especially important and debatable for the Archaean deposits, is also widely discussed. However, our understanding of the processes occurring at the early stage of the Earth’s development is limited to a few available well-preserved geological samples, while the overwhelming majority of Archean rocks have experienced some degree of metamorphic changes.

The Maksovo shungite-bearing metasapropelite (maksovite) deposit is located in the eastern part of the Onega Basin that was initiated and formed in the Paleoproterozoic in the southeastern Fennoscandian Shield. The maksovite deposit represents a diapiric fold formed about 2050 ± 10 Ma ago. It is underlain by carbonate sequences and, in turn, overlain by tuffaceous siltstones and intruded by gabbro-dolerites (1956 ± 5 Ma). Unaltered maksovites represent pelitomorphic rocks with a massive or obscure-layered structure containing about 30% C org . Alterations superimposed on the maksovites and underlying tuffaceous siltstone sequences are developed along brecciation zones within the ridge-shaped fold. The alterations are represented by alkaline Fe–Mg metasomatites with brecciated structures, as well as heterogeneous mineral and chemical compositions. They differ in terms of intense biotitization, chloritization, and development of the apatite-bearing albite–carbonate and sulfide-bearing carbonate–quartz stringers. Alteration zones are enriched in Na, K, P, Ti, Mg, Fe, and other ore components. Based on the Re–Os dating of sulfides, the age of metasomatites is estimated at 1558 ± 61 Ma.