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Date submitted2022-08-22
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Date accepted2023-02-02
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Date published2023-08-28
Wodginite as an indicator mineral of tantalum-bearing pegmatites and granites
- Authors:
- Viktor I. Alekseev
In the composition of tantalum-niobates, the tin-bearing wodginite group minerals (WGM) were found: wod-ginite, titanowodginite, ferrowodginite, ferrotitanowodginite, lithiowodginite, tantalowodginite, “wolframowodginite”. We reviewed the worldwide research on WGM and created a database of 698 analyses from 55 sources including the author's data. WGM are associated with Li-F pegmatites and Li-F granites. Wodginite is the most prevalent mineral, occurring in 86.6 % of pegmatites and 78.3 % of granites. The occurrence of WGM in granites and pegmatites differs. For instance, titanowodginite and “wolframowodginite” occur three times more frequently in granites than in pegmatites, whereas lithiowodginite and tantalowodginite do not appear in granites at all. The difference between WGM in granites and pegmatites is in finer grain size, higher content of Sn, Nb, Ti, W, and Sc; lower content of Fe 3+ , Ta, Zr, Hf; higher ratio of Mn/(Mn + Fe); and lower ratio of Zr/Hf. The evolutionary series of WGM in pegmatites are as follows: ferrowodginite → ferrotitanowodginite → titanowodginite → “wolframowodginite” → wodginite → tantalowodginite; in granites: ferrowodginite → ferrotitanowodginite → “wolframowodginite” → wodginite → titanowodginite. WGM can serve as indicators of tantalum-bearing pegmatites and granites. In Russia the promising sources of tantalum are deposits of the Far Eastern belt of Li-F granites containing wodginite.
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Date submitted2022-02-26
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Date accepted2022-04-27
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Date published2022-07-26
Type intrusive series of the Far East belt of lithium-fluoric granites and its ore content
- Authors:
- Viktor I. Alekseev
The evolution and ore content of granitoid magmatism in the Far East belt of lithium-fluoric granites lying in the Russian sector of the Pacific ore belt have been studied. Correlation of intrusive series in the Novosibirsk-Chukotka, Yana-Kolyma and Sikhote-Alin granitoid provinces of the studied region allowed to establish the unity of composition, evolution, and ore content of the Late Mesozoic granitoid magmatism. On this basis, a model of the type potentially ore-bearing intrusive series of the Far East belt of lithium-fluoric granites has been developed: complexes of diorite-granodiorite and granite formations → complexes of monzonite-syenite and granite-granosyenite formations → complexes of leucogranite and alaskite formations → complexes of rare-metal lithium-fluoric granite formation. The main petrological trend in granitoid evolution is increasing silicic acidity, alkalinity, and rare-metal-tin specialization along with decreasing size and number of intrusions. At the end of the intrusive series, small complexes of rare-metal lithium-fluoric granites form. The main metallogenic trend in granitoid evolution is an increasing ore-generating potential of intrusive complexes with their growing differentiation. Ore-bearing rare-metal-granite magmatism of the Russian Far East developed in the Late Cretaceous and determined the formation of large tungsten-tin deposits with associated rare metals: Ta, Nb, Li, Cs, Rb, In in areas with completed intrusive series. Incompleteness of granitoid series of the Pacific ore belt should be considered as a potential sign of blind rare-metal-tin mineralization. The Far East belt of lithium-fluoric granites extends to the Chinese and Alaskan sectors of the Pacific belt, which allows the model of the type ore-bearing intrusive series to be used in the territories adjacent to Russia.
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Date submitted2022-03-03
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Date accepted2022-04-27
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Date published2022-07-26
Peculiarities of rare-metal mineralization and genetic relationship of mineral associations in the eastern rim of Murzinsko-Aduysky anticlinorium (the Ural Emerald Belt)
- Authors:
- Mikhail P. Popov
The paper presents features of the location and composition, as well as a generalization of data on the age of rare-metal mineralization developed at the deposits and occurrences of rare metals and gemstones in the eastern rim of Murzinsko-Aduysky anticlinorium, within the Ural Emerald Belt, which is a classic ore and mineralogical object and has been studied for almost two hundred years. With a significant number and variety of prospecting, research and scientific works devoted mainly to emerald-bearing mica complexes and beryl mineralization, as well as rare-metal pegmatites, scientific literature has so far lacked generalizations on the formation of numerous mineral associations and ore formations that represents a uniform genetic process in this ore district. The aim of the work is a comprehensive geological-mineralogical analysis of mineral associations of the eastern rim of Murzinsko-Aduysky anticlinorium and studying their age, formation conditions and characteristic features to determine the possibility of expanding and using the mineral resource base of the Urals through developing new prognostic and prospecting criteria for rare-metal and gemstone ore formations and creating the new devices for promising objects prospecting
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Date submitted2022-04-18
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Date accepted2022-05-25
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Date published2022-07-26
U-Pb (SHRIMP-RG) age of zircon from rare-metal (Li, Cs) pegmatites of the Okhmylk deposit of the Kolmozero-Voron’ya greenstone belt (northeast of the Fennoscandian shield)
The results of isotopic and geochronological study of zircon from rare-metal pegmatites of the Okhmylk deposit are presented. There were no reliable data on the age of lepidolite-spodumene-pollucite pegmatites of this and the other deposits spatially located within the Archean Kolmozero-Voron’ya greenstone belt. The earlier estimates of the pegmatite age indicate a broad time range from 2.7 to 1.8 Ga. Zircon in the studied pegmatites is characterized by inner heterogeneity, where core and rim zones are distinguished. Minor changes are observed in the core zones, they have a spotted structure and contain numerous uranium oxide inclusions. According to X-ray diffraction analysis, zircon crystallinity is preserved completely in these areas. Complete recrystallization with modification of the original U-Pb isotopic system occurred in the zircon rims. New U-Pb (zircon) isotopic and geochronological data of 2607±9 Ma reflect the time of crystallization of pegmatite veins in the Okhmylk deposit. Isotopic data with ages of ~1.7-1.6 Ga indicate later hydrothermal alteration. The obtained results testify to the Neo-Archean age of the formation of the Okhmylk deposit 2.65-2.60 Ga, reflecting the global age of pegmatite formation and associated the world's largest rare-metal pegmatite deposits.
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Date submitted2019-10-17
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Date accepted2020-01-24
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Date published2020-04-24
Composition and probable ore igneous rocks source of columbite from alluvial deposits of Mayoko district (Republic of the Congo)
The article presents the results of optical, electron microscopic and electron microprobe studies of columbite group minerals, collected during heavy mineral concentrate sampling of alluvial deposits in the Mayoko region (Republic of the Congo). The aim of the study is revealing tantalum niobates ore body in this region. We found that these minerals in loose deposits are represented by two grain-size groups: less than 1.6 mm (fine fraction) and 1.6-15 mm (coarse fraction). The grains of both fractions belong mainly to columbite-(Fe), less often to columbite-(Mn), tantalite-(Mn) and tantalite-(Fe), contain impurities of Sc, Ti, and W. The crystals have micro-scaled zoning (zones varies slightly in the Ta/Nb ratio values) and contains a lot of mineral inclusions and veins represented by zircon, pyrochlore supergroup minerals and others. Columbite-(Fe) and columbite-(Mn) are characterized by an increased content of Ta 2 O 5 up to the transition to tantalite-(Fe) and tantalite-(Mn). This allows us to exclude the formation of subalkaline rare-metal granites, their metasomatites (albitites and greisenes) and carbonatites, from the list of possible columbite ore rocks source in the Mayoko district. Thus, beryl type and complex spodumene subtype rare-element pegmatites of the mixed petrogenetic family LCT-NYF (according to P.Černý) should be considered as a probable root source. The results of the research should be taken into account when developing the methodology for prospecting in this area.
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Date submitted2010-07-18
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Date accepted2010-09-16
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Date published2011-03-21
Two genetic types of peristerites in iridescent plagioclases
- Authors:
- M. A. Ivanov
- A. P. Simakov
Physico-mathematical modeling has shown that color of iridescent depends on spacing of peristerite lattice. The more spacing lattice, the color of iridescent is higher. The phenomenon of iridescent in plagioclases has an interferential nature. We can select two genetic types of peristerites: peristerites of decomposition and segregation peristerites. Segregation peristerites are formed from postcrystallizational consolidation of peristerites of decomposition. The form of segregation pertisrerites is one of the reasons of polychromatic iridescent genesis in plagioclases.