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Stepanyuk, L., O. Hrinchenko, B. Slobodian, V. Semka, S. Kurylo y T. Dovbush. "GEOCHRONOLOGY OF LITHIUM-BEARING GRANITOIDS OF INGUL MEGABLOCK (UKRAINIAN SHIELD)". Visnyk of Taras Shevchenko National University of Kyiv. Geology, n.º 3 (82) (2018): 23–28. http://dx.doi.org/10.17721/1728-2713.82.03.
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Rare-metal elements are strategic metals which, in general, are extremely important for economic development or maintenance of defence capability of any country at the modern level. The list of needs for these strategic metals ranges depending on the level of economic development of certain country, but in general it includes such elements as Li, Ta, Nb, Be, Sb, W, REE and others. The majority of these elements has the lithophilous nature and, therefore, is characterized by close genetic relations with granites and pegmatites associated with them. In the world, industrial production of lithium is shared between deposits to lithium-bearing brine of saline depositions of marine basins (Argentina, Chile), some granites (China) and rare-metal pegmatites (Australia, China, Zimmbabve). In pegmatites lithium mineralization is represented mainly by spodumene (LiAlSi2O6), But other lithium-containing metallic minerals can also play an important role in production of this metal – petalite (LiAlSi4O10), minerals of lepidolite (Sa [Li,Al]3[Si,Al]4O10[F,OH]2) and amblygonite-montebrasite (LiAlPO4 [F,OH]) series. Rare-metal pegmatite of Ingul megablock of Ukrainian Shield can be treated as unique (insufficiently studied in world practice) pegmatitic formations in which the main metallic mineral is represented by petalite. In metallogenic interpretations two ore districts can be distinguished within the megablok, that are specialized on rare metals (Li, Rb, Cs, Be, Ta, Nb, Sn) – Polohivka and Stankuvatka. Deposits and numerous ore manifestations of rare metals formed in rather similar geological and tectonic conditions and have many common features – both country rocks composition and mineralogic composition of ores. Within Ingul megablock (Shpola-Tashlyk rare-metal district) a number of lithium rare-metal deposits associated with pegmatites is discovered. In order to determine the age of lithium mineralization in granites of Lypniazhka, Taburyshche massifs and vein bodies of pegmatitic and aplito-pegmatitic granites, which are selected from different localities of this megablock, are dated by U-Pd isotopic method by monazites. It is established that emplacement of vein granites of Ingul megablock occurred within rather narrow age interval – 2040-2020 Ma and it is not significantly separated in time from formation of most granitoids they are spatially associated with. This fact, together with geological evidences, gives grounds to make the assumption that rare-metal lithium pegmatite are formed in the same age interval.
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Steiner, Benedikt. "Tools and Workflows for Grassroots Li–Cs–Ta (LCT) Pegmatite Exploration". Minerals 9, n.º 8 (20 de agosto de 2019): 499. http://dx.doi.org/10.3390/min9080499.
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The increasing demand for green technology and battery metals necessitates a review of geological exploration techniques for Li–Cs–Ta (LCT) pegmatites, which is applicable to the work of mining companies. This paper reviews the main controls of LCT pegmatite genesis relevant to mineral exploration programs and presents a workflow of grassroots exploration techniques, supported by examples from central Europe and Africa. Geological exploration commonly begins with information gathering, desktop studies and Geographic Information System (GIS) data reviews. Following the identification of prospective regional areas, initial targets are verified in the field by geological mapping and geochemical sampling. Detailed mineralogical analysis and geochemical sampling of rock, soil and stream sediments represent the most important tools for providing vectors to LCT pegmatites, since the interpretation of mineralogical phases, deportment and liberation characteristics along with geochemical K/Rb, Nb/Ta and Zr/Hf metallogenic markers can detect highly evolved rocks enriched in incompatible elements of economic interest. The importance of JORC (Joint Ore Reserves Committee) 2012 guidelines with regards to obtaining geological, mineralogical and drilling data is discussed and contextualised, with the requirement of treating LCT pegmatites as industrial mineral deposits.
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Silva, A. L. y E. W. V. Sousa. "New Route of Utilization of Pegmatites Tailings to Application as a Ceramics Raw Materials". Materials Science Forum 820 (junio de 2015): 18–23. http://dx.doi.org/10.4028/www.scientific.net/msf.820.18.
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The proposal to obtain a new route for exploitation of tailings from pegmatite emerged from the need of many companies that showed to reuse of these tailings as raw materials ceramics. The pegmatites represent a large part of available industrial minerals. These can be classified into: kaolin, feldspar, mica, quartz and metallic minerals such as tantalite / columbite and others. The consumer markets for these minerals are glassmaking, ceramic industries, paper, pulp, metallurgy, etc. Order for the product is fit for sale ceramics and metals companies must be of high purity of this raw material. Therefore, the process of separation of these minerals must be carried out as effectively as possible. In this study, surveys have been made to the development of a new process route which facilitates, an optimized manner, separation from pegmatite, concentrated in the waste process of extracting companies, so that a better product shall be passed through the ceramic industry.
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Baranov, P., O. Slyvna y O. Matyushkina. "Eco-aesthetic features of mineral deposits". Journal of Geology, Geography and Geoecology 27, n.º 1 (10 de julio de 2018): 20–29. http://dx.doi.org/10.15421/111826.
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The aim of work is a study of worked out fields, under development and explored deposits of minerals for the purpose eco-aesthetics.The basis of eco-aesthetics is the principle of utility (utility, expediency) and beauty (aesthetics).The criteria for assessing the eco-aesthetics of geological objects are economic, environmental and aesthetic characteristics. Developed deposits cause irreparable damage to the geological environment and the entire ecosystem. Extraction from the bowels of the earth of minerals violates the geochemical systems on many decades and centuries, and on occasion changes the landscape of locality. Developed deposits can be economically profitable, ecologically clean and esthetically attractive due to development to the aesthetic and historical aspects. An example is the Wieliczka mine in Poland, where business, ecology and aesthetics are harmoniously combined. A number of the largest worked out fields and developed fields in Ukraine are in extremely need of the development of this issue. Developed iron ore deposits are one of the important factors of industrial potential of Ukraine. Semiprecious stone material, jaspilite, is the aesthetic aspect of these fields. They have colossal reserves. Using their decorative properties, we have developed the laws of shaping for the design of natural stone, identified the main areas of application of jaspilites in decorative art. Implementation of the idea of creating a Jespilite room will allow Krivbas not only industrial, but also cultural and educational center. The achieved results will qualitatively improve the eco conditions for the local population, the development of stone carving art and will lead to business growth. The explored deposits of spodumene pegmatites in the Western sea of Azov in addition to lithium mineralization contain expansive fields of graphic microcline pegmatites, spodumene and albitic pegmatites. They contain samples of pink spodumene (kunzite), petalite from light green to pink, tourmaline (sherl). Thus, this deposits of spodumene pegmatites in Western Azov today require a comprehensive assessment of minerals, because in addition to ore mineralization there is also a gemstone-colored raw material.
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Zahradník, Jan, Jakub Jirásek, Jaromír Starý y Martin Sivek. "Production, Reserves, and Processing of Feldspar and Feldspathoid Rocks in the Czech Republic from 2005 to 2019—An Overview". Minerals 10, n.º 8 (17 de agosto de 2020): 722. http://dx.doi.org/10.3390/min10080722.
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This paper aims to characterize and interpret the trends in reserves, resources, and mine production of feldspar and feldspathoid rocks during 2005–2019 in the Czech Republic. With over 101 Mt of total resources and 22 Mt of reserves, feldspar belongs to the crucial industrial minerals of the Czech Republic. With annual outputs of approximately 400–450 kt of feldspars and 20–35 kt of feldspathoid rocks (nepheline syenite), the Czech Republic ranks among the top European and world feldspar producers. Most of the production comes from leucocratic granitoid rocks (key active deposit: Krásno-Vysoký Kámen), followed by sedimentary rocks (key active deposit: Halámky), and granitic pegmatites (key active deposit: Luženičky). Nepheline syenite is mined at a single deposit. All deposits are extracted from open pits (quarries). Ongoing geological prospecting and exploration for new deposits are increasing available reserves and resources. The feldspar raw materials are used in the domestic glass and ceramic industries, while more than 50% is exported, generally to Poland and Germany.
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London, David. "Granitic pegmatites". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 87, n.º 1-2 (1996): 305–19. http://dx.doi.org/10.1017/s0263593300006702.
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ABSTRACT:The primary focus of this review is on P-T conditions, mineralogical indicators of melt or fluid composition and textural evolution; lesser treatment is given to pegmatite sources or to pegmatite-wallrock interactions. Investigations of stable and radiogenic isotopes have revealed that the source materials for pegmatites are likely to be more heterogeneous or varied than previously thought, especially for peraluminous pegmatites, but that overall pegmatites bear a clear intrusive relationship with their hosts, as opposed to an origin in situ. The P-T conditions of crystallisation of some lithium-rich pegmatites have been constrained by lithium aluminosilicate stability relations in combination with stable isotope or fluid inclusion methods. Experimental studies have elucidated the effects of components such as Li, B, P and F, which are common in some classes of pegmatites, to liquidus relations in the hydrous haplogranite system. Experimentation has also provided corroboration of an old concept of pegmatite crystallisation—that pegmatites owe their distinctive textures and mineral/chemical zonation to relatively rapid crystallisation of melt from the margins inwards at conditions far from the equilibrium (i.e. from supercooled liquids). The origin of aplites, whether alone, layered, or paired with pegmatites, remains an active area of research. Studies of fluid inclusions, crystal-vapour equilibria and wallrock alteration have helped to define the timing and compositions of vapour phases in pegmatites and to aid in the economic evaluation of deposits.
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Glover, A. S., W. Z. Rogers y J. E. Barton. "Granitic Pegmatites: Storehouses of Industrial Minerals". Elements 8, n.º 4 (1 de agosto de 2012): 269–73. http://dx.doi.org/10.2113/gselements.8.4.269.
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Popov, V. A., M. A. Rassomakhin y S. V. Kolisnichenko. "A Unique Ore Locality of Polyakovite-(Ce) in the Ilmeny Mountains, South Urals – New Finds". МИНЕРАЛОГИЯ (MINERALOGY) 6, n.º 1 (30 de marzo de 2020): 17–32. http://dx.doi.org/10.35597/2313-545x-2020-6-1-2.
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A large crystal of the rarest mineral polyakovite was discovered in 2019 in the carbonatites-pegmatites of pit № 97 of the Ilmeny Mountains. Bodies of carbonatites, glimmerites, glimmerites-pegmatites and carbonatite-pegmatites are located within a small complex body of alkaline ultramafites and carry a unique range of mineral assemblages (rocks), as well as rare-metal and Ree minerals, which is unique for this famous mineral province. Figures 18. Tables 2. References 12. Key words: polyakovite-(Ce), rare-metal and Ree minerals, alkaline ultramafites, carbonatites, glimmerite, carbonatite-pegmatites, South Urals, Ilmen Mountains.
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Nie, Xiao, Zongqi Wang, Lei Chen, Gang Wang y Zengda Li. "Geochemical Contrasts between Late Triassic Rb-Rich and Barren Pegmatites from Ningshan Pegmatite District, South Qinling Orogen, China: Implications for Petrogenesis and Rare Metal Exploration". Minerals 10, n.º 7 (28 de junio de 2020): 582. http://dx.doi.org/10.3390/min10070582.
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The Ningshan pegmatite district in the South Qinling Orogen hosts numerous Rb-(Be) mineralized pegmatites. In this study, whole-rock geochemistry, mineral geochemistry, and zircon U–Pb isotopes of the Rb-rich and barren pegmatites were determined. The barren pegmatites consist mainly of muscovite, microcline, albite, quartz, and garnet, whereas the Rb-rich pegmatites are mainly composed of muscovite, albite, quartz, and beryl, with minor chrysoberyl, cassiterite and columbite-group mineral. The muscovite and albite are the main Rb-bearing minerals. The U–Pb zircon dating of the Rb-rich and barren pegmatites yielding an age of 212–203 Ma, which is similar to that of the neighboring two-mica monzogranites distributed in the Ningshan area. Compared with the two-mica monzogranites, geochemical features, such as the Zr/Hf, Rb/Sr and Nb/Ta ratios and trace element contents indicated that the Rb-rich and barren pegmatites derived from fractionation of the two-mica monzogranites. In combination, the current and previous results suggest that the fractionation of the two-mica monzogranites caused the generation of the affinitive residual melts that, finally, crystallized to form the pegmatites. Compared to those from the barren pegmatites, the apatite from the Rb-rich pegmatites have higher MnO (14.51–19.12 wt.%) and Cl (0.12–0.16 wt.%) contents and lower F/Cl rartios (20–29). We conclude that these differences reflect unique geochemical signatures, and the geochemical composition of the apatite can be used as exploration guidance for rare metal-rich pegmatites.
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Grew, Edward S. "The Minerals of Lithium". Elements 16, n.º 4 (1 de agosto de 2020): 235–40. http://dx.doi.org/10.2138/gselements.16.4.235.
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Lithium is rare in the cosmos, but the formation of continental crust has concentrated lithium into economic deposits. The 124 recognized Li mineral species occur largely in four geologic environments: (1) lithium–cesium–tantalum (LCT) granitic pegmatites and associated metasomatic rocks; (2) highly peralkaline pegmatites; (3) metasomatic rocks not directly associated with pegmatites; (4) manganese deposits. The geologically oldest Li minerals are reported from LCT pegmatites and date to 3,000–3,100 Ma, a critical period in the evolution of the continental crust and the rate of its generation. This suggests a link between the earliest appearance of LCT-family pegmatites and the onset of plate tectonics, consistent with the correlation between the observed abundance of LCT-family pegmatites and supercontinent assembly.
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Feng, Yonggang, Ting Liang, Xiuqing Yang, Ze Zhang y Yiqian Wang. "Chemical Evolution of Nb-Ta Oxides and Cassiterite in Phosphorus-Rich Albite-Spodumene Pegmatites in the Kangxiwa–Dahongliutan Pegmatite Field, Western Kunlun Orogen, China". Minerals 9, n.º 3 (8 de marzo de 2019): 166. http://dx.doi.org/10.3390/min9030166.
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The Kangxiwa–Dahongliutan pegmatite field in the Western Kunlun Orogen, China contains numerous granitic pegmatites around a large granitic pluton (the Dahongliutan Granite with an age of ca. 220 to 217 Ma), mainly including barren garnet-, tourmaline-bearing pegmatites, Be-rich beryl-muscovite pegmatites, and Li-, P-rich albite-spodumene pegmatites. The textures, major element contents, and trace element concentrations of columbite-group minerals (CGM) and cassiterite from three albite-spodumene pegmatites in the region were investigated using a combination of optical microscopy, SEM, EPMA and LA-ICP-MS. The CGM can be broadly classified into four types: (1) inclusions in cassiterite; (2) euhedral to subhedral crystals (commonly exhibiting oscillatory and/or sector zoning and coexisting with magmatic cassiterite); (3) anhedral aggregates; (4) tantalite-(Fe)-ferrowodginite (FeSnTa2O8) intergrowths. The compositional variations of CGM and cassiterite are investigated on the mineral scale, in individual pegmatites and within the pegmatite group. The evolution of the pegmatites is also discussed. The variation of Nb/Ta and Zr/Hf ratios of the cassiterite mimics the Nb-Ta and Zr-Hf fractionation trends in many LCT pegmatites, indicating that these two ratios of cassiterite may bear meanings regarding the pegmatite evolution.
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Roda, E., F. Fontan, A. Pesquera y F. Velasco. "The phosphate mineral association of the granitic pegmatites of the Fregeneda area (Salamanca, Spain)". Mineralogical Magazine 60, n.º 402 (octubre de 1996): 767–78. http://dx.doi.org/10.1180/minmag.1996.060.402.06.
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AbstractIn the Fregeneda area different pegmatitic types can be distinguished on the basis of their mineralogy, internal structure and field relationships. The most common type corresponds with simple pegmatites with a homogeneous internal structure, but Li and Sn-bearing pegmatites are also relatively widespread, besides a minority group of Fe-Mn phosphate-bearing pegmatites that has recently been characterized. These pegmatites are located in an intermediate zone, between the barren pegmatites and the most evolved Li and Sn-bearing bodies, and they carry a complex association of phosphate minerals. The study of these phosphates has allowed the identification of the primary phases as wyllieite, graftonite, sarcopside, triplite-zwieselite and ferrisicklerite; the secondary phosphates are rosemaryite, heterosite-purpurite, alluaudite and väyrynenite. In this study, the main characteristics of these phosphate minerals are reported, including their chemical composition, analysed by electron microprobe, and their unit-cell parameters, calculated using X-ray powder diffraction techniques.A common transformation mechanism in this phosphate association is the oxidation of the transition metal cations at the same time as Na-leaching in wyllieite to generate rosemaryite, and Li-leaching in ferrisicklerite to generate heterosite. The occurrence of sarcopside lamellae in ferrisicklerite and heterosite is evidence of the replacement processes of the former by the latter. A Na-metasomatic replacement of the early phosphates as ferrisicklerite and graftonite, producing alluaudite, is also a well developed process.Phosphate minerals occur in pegmatites with an intermediate degree of fractionation, appearing between the barren and the more evolved pegmatites with Li and Sn, which is in agreement with the pegmatite field zonation established in the literature.
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Hernández-Filiberto, Lorena, Encarnación Roda-Robles, William B. Simmons y Karen L. Webber. "Garnet as Indicator of Pegmatite Evolution: The Case Study of Pegmatites from the Oxford Pegmatite Field (Maine, USA)". Minerals 11, n.º 8 (23 de julio de 2021): 802. http://dx.doi.org/10.3390/min11080802.
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Almandine-spessartine garnets, from the Oxford County pegmatites and the Palermo No. 1 pegmatite, record significant compositional variations according to the degree of evolution of their hosting rock. Garnets from the most fractionated pegmatites (Mt. Mica, Berry-Havey, and Emmons) show the highest Mn, Nb, Ta, Zr, and Hf values, followed by those from the intermediate grade pegmatites (Palermo No. 1) and, finally, garnets from the barren pegmatites show the lowest values (Perham and Stop-35). Iron, Ca, and Mg contents follow an inverse order, with the highest contents in the latter pegmatites. Major element zoning shows increasing Mn values from core to rim in most garnet samples, while trace element zoning is not systematic except for some crystals which show a core to rim depletion for most of these elements. Chondrite normalized HREE (Heavy Rare Earth Elements) spectra show positive slopes for garnets from barren pegmatites, both positive and negative slopes for those associated with the intermediate pegmatite, and negative or flat slopes in garnets from the highly fractionated pegmatites. Ion exchange mechanisms, including Fe2+−1Mn2+1, (Fe2+, Mn2+)−1Si−1Li1P1; and, (Y, Ho3+)2(vac)1(Fe2+, Mn2+)−3, could explain most of the compositional variations observed in these garnets. These compositional variations are the reflection of the composition of the pegmatitic magma (barren pegmatites originate from a more ferromagnesian magma than fractionated pegmatites); and of the coexisting mineral phases competing with garnets to host certain chemical elements, such as biotite, schorl, plagioclase, apatite, Fe-Mn phosphates, Nb-Ta oxides, zircon, xenotime, and monazite.
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Feng, Yonggang, Ting Liang, Ze Zhang, Yiqian Wang, Yi Zhou, Xiuqing Yang, Jinggang Gao, Hui Wang y Kun Ding. "Columbite U-Pb Geochronology of Kalu’an Lithium Pegmatites in Northern Xinjiang, China: Implications for Genesis and Emplacement History of Rare-Element Pegmatites". Minerals 9, n.º 8 (25 de julio de 2019): 456. http://dx.doi.org/10.3390/min9080456.
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The Kalu’an-Azubai pegmatite field, one of the most important rare-metal metallogenic regions in China, contains a large number of pegmatite dikes belonging to spodumene and lepidolite subtypes. Columbite-group minerals (CGMs) collected from three spodumene subtype pegmatites (No. 802, No. 803, and No. 805 pegmatites) were analyzed for major element contents using EPMA (electron probe micro-analyzer) and dated using LA-ICP-MS (laser ablation-inductively coupled plasma mass spectrometer). The crystallization ages of the CGMs from No. 802, No. 803, and No. 805 pegmatites are 209.5 ± 1.4 Ma (2σ), 198.3 ± 2.0 Ma (2σ), and 224.3 ± 2.9 Ma (2σ), respectively. Oscillatory zoning and/or sector zoning along with the associated mineral assemblages suggest that the dated columbite is of magmatic origin. The crystallization ages of the columbite grains thus represent the emplacement ages of the Li pegmatites. Therefore, our dating results indicate that there were three emplacement events of the Li-rich pegmatite-forming melts in a timeframe of ~30 Ma. In combination with previous studies, we conclude that the Li pegmatites were formed before the Be-Ta-Nb pegmatites (~194–192 Ma), which precludes the genesis of rare-metal pegmatites via fractional crystallization of a granitic magma in the Kalu’an-Azubai region.
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Garate-Olave, Idoia, Encarnación Roda-Robles, Pedro Pablo Gil-Crespo y Alfonso Pesquera. "Phosphate mineral associations from the Tres Arroyos aplite-pegmatites (Badajoz, Spain): Petrography, mineral chemistry, and petrogenetic implications". Canadian Mineralogist 58, n.º 6 (1 de noviembre de 2020): 747–65. http://dx.doi.org/10.3749/canmin.1900102.
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ABSTRACTIn the Tres Arroyos granite-pegmatite system (Badajoz, Spain) a zoned aplite-pegmatite field occurs, with poorly evolved, intermediate, and Li-rich dikes intruded into metasediments, close to the contact with the Nisa-Alburquerque granitic batholith. A large variety of Fe-Mn phosphate minerals occur in the poorly evolved aplite-pegmatites; Al-phosphates occur mainly in the intermediate and Li-rich dikes. The Fe/(Fe + Mn) ratio of the Fe-Mn phosphates is the highest reported for aplite-pegmatite fields in the Central Iberian Zone, suggesting a low degree of fractionation for the poorly evolved aplite-pegmatites that host these minerals. In contrast, the high F contents observed in crystals of the amblygonite–montebrasite series from the intermediate and Li-rich aplite-pegmatites indicates a higher fractionation degree for these dikes. The relatively common occurrence of phosphate minerals in the three types of aplite-pegmatites from Tres Arroyos attests to a significant availability of P in the pegmatitic melt. In this granite pegmatite system, P first started behaving as a compatible element, thus favoring the crystallization of discrete phosphates, during the crystallization of the poorly evolved aplite-pegmatites. In more fractionated melts, where Fe-Mn-(Mg) contents were extremely depleted, P was still available, allowing the crystallization of the Al-phosphates, mainly of the amblygonite–montebrasite series, in the more evolved intermediate and Li-rich aplite-pegmatites. Subsolidus replacement of the early phosphate phases, such as those of the amblygonite–montebrasite series, by lacroixite, together with the presence of late Ca- and Sr-bearing phosphates such as jahnsite-(CaMnFe), whiteite-(CaFeMg), mitridatite, and goyazite, attest to a high activity of metasomatic fluids in the Tres Arroyos granite-pegmatite system. Consequently, variations in the phosphate mineral associations and in their chemical compositions reflect well the fractional crystallization processes suffered by the pegmatitic melts from the poorly evolved up to the Li-rich dikes, as well as the subsolidus history of the Tres Arroyos system.
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Isakov, Leonid V. y Maria L. Isakova. "Location pattern and genetic classification of granite pegmatites of the Ukrainian Shield". Journal of Geology, Geography and Geoecology 28, n.º 4 (22 de diciembre de 2019): 673–91. http://dx.doi.org/10.15421/111964.
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The pegmatites of the Ukrainian Shield, their formation and occurrence are con- sidered. It is shown that the Ukrainian Shield is a pegmatite province encompassing seven regions: Middle Prydniprovia, Western Pryazovia, Eastern Pryazovia, Ingulski, Rosynsko- Tikytski, Dnistersko-Buzki and Volyn, respectively encompassing megastructures of the same names and including pegmatite fields of different mineralogical composition and geochemical specialization. The Volynski, Ingulski, Middle Prydniprovia, Western Pryazovia regions have rare-earth and rare-metal specialization presented by pegmatites of different origin and petrological and mineral composition and occurring in different structural and tectonic conditions, having different formation age, which allows a full classification scheme of the pegmatites of Ukrainian Shield to be given. These structures can be considered as having formed as a result of abyssal magmatic plumes. The geological-structural position of these megastructures with obvious signs of influence of certain abyssal processes on their formation supports this assumption. We present the main geological structural and genetic factors of formation of pegmatite-bearing megastructures of the Ukrainian crystalline core-area, these factors forming the basis of a classification scheme of pegmatites of Pre-Cambrian shields. We have systematized the pegmatites of the Ukrai- nian Shield , and designed their classification scheme . We have distinguished the following groups of pegmatites by the development of pegmatite-generating zones: - three genetic groups of pegmatites: ultrametamorphogenic, magmatogenic and metamorphogenic-meta- somatic; - six genetic subgroups of pegmatites: migmatic; autochthonous granite massifs; metamorphogenic and metasomatic displaced and formed pegmatites; multiphase intrusive granite massifs; multiphase intrusive alkaline massifs; multiphase granite batholiths. By the nature of pegmatite-bearing structures, the following structural groups have been singled out: granite-gneiss regional structures and domes; dome- synclinore and dome-trough plume-structures (subgroups: interdome synclinore and trough structures, in particular greenstone structures; intrusive domes and batholiths); specific tectonic zones of stress tensions.
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Oyebamiji, Abiola, Adeniyi JohnPaul Adewumi, Tehseen Zafar, Adegbola Odebunmi, Philips Falae y Oluwafemi Fadamoro. "Petrogenetic and Compositional Features of Rare Metal Pan-African Post-Collisional Pegmatites of Southwestern Nigeria; A Status Review". Contemporary Trends in Geoscience 7, n.º 2 (1 de diciembre de 2018): 166–87. http://dx.doi.org/10.2478/ctg-2018-0012.
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Abstract This research reviews the geology, petrogenesis, compositional trends and geochronology of the rare-metal pegmatite of southwestern Nigeria. The source of these pegmatites is still presently debated which have been explained as either product of highly fractionated molten material or anatexis of the local crust. However, published works of past authors have been compiled to give a detailed understanding of the formation of the mineral deposits. The basement complex of southwestern Nigeria comprises of Precambrian rocks of amphibolite, the hornblende gneiss and the granite gneisses which were formed as a result of the opening and closing of the ensialic basin with significant, extensive subduction during the Pan-African orogeny. The pegmatites in this region have shown internal zoning and a high degree of evolution from the border zone to the core zone during the crystallization and solidification of the felsic granite to pegmatite melt. The rare-metal pegmatites have distinct chemical compositions and mineralogy, containing quartz, biotite, muscovite, microcline, garnet with localized tourmaline, tantalite and columbite. These pegmatites vary significantly by their bulk-rock and mineral chemistry which indicates a more peraluminous attribute and enrichments of lithophile elements of Rb, Cs, Ta and Ba. Previous K/Ar isotopic ages (502.8±13.0 Ma and 514.5±13.2 Ma) suggest that the pegmatites are related to the post-collisional phase of intensive metasomatism. Adopted from previous studies, a five-stage conceptual model of evolution which is widely accepted have been proposed for the origin of the pegmatites.
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Beurlen, Hartmut, Dwight R. Soares, Rainer Thomas, Lucila E. Prado-Borges y Cláudio de Castro. "Mineral chemistry of tantalate species new in the Borborema Pegmatitic Province, Northeast Brazil". Anais da Academia Brasileira de Ciências 77, n.º 1 (marzo de 2005): 169–82. http://dx.doi.org/10.1590/s0001-37652005000100013.
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Tantalate samples, supposedly of the columbite group, were collected in the Borborema Pegmatitic Province, aiming to test the Mn/(Mn+Fe) and Ta/(Ta+Nb) ratios as geochemical indicators of pegmatite fractionation. Surprisingly, preliminary microprobe data allowed recognizing some species, so far unknown in the Province, namely titanian ixiolite, fersmite, brannerite, strüverite, natrobistantite, plumbo- and stibiomicrolite, plumboand uranpyrochlore. The identification of these exotic tantalates with unusual composition, in addition to its distribution in several pegmatites, far from the classical Alto do Giz and Seridozinho pegmatites, indicate that the elevated degree of fractionation is not restricted to these two occurrences but may be reached in other pegmatite areas of the Province. It indicates also that this degree of fractionation may be very variable between pegmatites in small areas. The zoning patterns observed in the titanian ixiolite, with Ti and Nb enrichment at the borders at expense of Ta enriched in the core, are also quite unusual and reverse in comparison with the normal trend of progressive Ta and Mn enrichment in tantalates with the degree of fractionation. A similar "reverse" trend was observed in titanian wodginite of petalite/pollucite bearing pegmatites of the Separation Rapids Province in Ontario, Canada.
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Andersen, Tom, Muriel Erambert, Alf Olav Larsen y Rune S. Selbekk. "Petrology of nepheline syenite pegmatites in the Oslo Rift, Norway: Zr and Ti mineral assemblages in miaskitic and agpaitic pegmatites in the Larvik Plutonic Complex". Mineralogia 44, n.º 3-4 (1 de julio de 2013): 61–98. http://dx.doi.org/10.2478/mipo-2013-0007.
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AbstractAgpaitic nepheline syenites have complex, Na-Ca-Zr-Ti minerals as the main hosts for zirconium and titanium, rather than zircon and titanite, which are characteristic for miaskitic rocks. The transition from a miaskitic to an agpaitic crystallization regime in silica-undersaturated magma has traditionally been related to increasing peralkalinity of the magma, but halogen and water contents are also important parameters. The Larvik Plutonic Complex (LPC) in the Permian Oslo Rift, Norway consists of intrusions of hypersolvus monzonite (larvikite), nepheline monzonite (lardalite) and nepheline syenite. Pegmatites ranging in composition from miaskitic syenite with or without nepheline to mildly agpaitic nepheline syenite are the latest products of magmatic differentiation in the complex. The pegmatites can be grouped in (at least) four distinct suites from their magmatic Ti and Zr silicate mineral assemblages. Semiquantitative petrogenetic grids for pegmatites in log aNa2SiO5 - log aH2O - log aHF space can be constructed using information on the composition and distribution of minerals in the pegmatites, including the Zr-rich minerals zircon, parakeldyshite, eudialyte, låvenite, wöhlerite, rosenbuschite, hiortdahlite and catapleiite, and the Ti-dominated minerals aenigmatite, zirconolite (polymignite), astrophyllite, lorenzenite, titanite, mosandrite and rinkite. The chemographic analysis indicates that although increasing peralkalinity of the residual magma (given by the activity of the Na2Si2O5 or Nds component) is an important driving force for the miaskitic to agpaitic transition, water, fluoride (HF) and chloride (HCl) activity controls the actual mineral assemblages forming during crystallization of the residual magmas. The most distinctive mineral in the miaskitic pegmatites is zirconolite. At low fluoride activity, parakeldyshite, lorenzenite and wöhlerite are stable in mildly agpaitic systems. High fluorine (or HF) activity favours minerals such as låvenite, hiortdahlite,rosenbuschite and rinkite, and elevated water activity mosandrite and catapleiite. Astrophyllite and aenigmatite are stable over large ranges of Nds activity, at intermediate and low water activities, respectively.
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Popova, V. I., V. A. Popov, A. V. Kasatkin y A. M. Kuznetsov. "Aeschynite Group Minerals from Vishnevye Mountains (South Urals)". МИНЕРАЛОГИЯ (MINERALOGY) 5 (27 de octubre de 2019): 16–25. http://dx.doi.org/10.35597/2313-545x-2019-5-3-16-25.
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The crystals morphology, mineral assemblages and chemical composition of aeschynite group minerals from the Vishnevye Mountains (South Urals, Russia) are presented. Some veins of syenitic pegmatites host aeschynite-(Ce) and «thoroaeschynite». The calcite-aegirine-feldspar pegmatites and quartz-arfvedsonite veins contain nioboaeschynite-(Ce) and «alumoaeschynite». Aeschynite-(Y) and nioboaeschynite-(Y) are found in annite-feldspar aggregates in assemblage with REE silicates and carbonates. The fnd of nioboaeschynite-(Y) is frst in Russia.
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ZAKHAROV, Аnatoliy Vladimirovich. "On the finding of zincohögbomite in the granite pegmatites of the Lipovskiy vein field (Middle Urals)". NEWS of the Ural State Mining University 59, n.º 3 (15 de septiembre de 2020): 27–34. http://dx.doi.org/10.21440/2307-2091-2020-3-27-34.
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The relevance of the work is due to the need to study the mineralogy of granite pegmatites of the Lipovskiy vein field, a unique object that gave the world a large amount of crystal raw materials of colored tourmaline Purpose of the work: study of zincohögbomite found in granite pegmatites of the Lipovskiy vein field (Middle Urals). Research methodology: quantitative analysis of the chemical composition of magnetite was carried out using the X-ray spectral electron probe microanalyzer CAMECA SX 100 (The Zavaritsky Institute of Geology and Geochemistry of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg). The chemical composition of zincohögbomite was determined using the Jeol JSM-6390LV scanning electron microscope with an INCA Energy 450 X-Max 80 energy dispersive attachment from Oxford Instruments (The Zavaritsky Institute of Geology and Geochemistry of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg). Results. When studying the surface of magnetite crystals, pore spaces were found inlaid with flattened grains of an unknown mineral, mainly triangular, less often hexagonal, in shape, up to 2–3 microns in size. Based on the data on its chemical composition, this mineral was assigned to zincohögbomite. Based on crystallochemical calculations, it was found that the mineral corresponds to zincohögbomite-2H2S or zincohögbomite-8H according to the old classification. Conclusions. A new mineral was found for granite pegmatites of the Lipovskiy vein field – zincohögbomite-2H2S. It was found in the form of inclusions in magnetite individuals in common intragranite pegmatites. This is the second find of zincohögbomite in the Urals and, most likely, the first one in the world in granite pegmatites. The formation of zincohögbomite is associated with retrograde metamorphism of amphibolite facies, when primary spinels become unstable and decompose into several mineral phases. Zincohögbomite from Lipovskiy field was formed as a result of the decomposition of primary magnetite during the cooling of granite pegmatite.
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Alexandre, Paul. "Mineral chemistry and geochronology of the Rajasthan emerald deposits, NW India". Canadian Mineralogist 58, n.º 3 (1 de mayo de 2020): 335–46. http://dx.doi.org/10.3749/canmin.1900055.
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ABSTRACT The emerald deposits in Rajasthan, northwest India, are situated in a narrow NE–SW belt in the Aravalli Mountains. The studied deposits were formed by the metasomatic reaction between muscovite (± garnet ± tourmaline) pegmatites and lenticular bodies of altered ultramafic rocks that are hosted by the Delhi Group gneisses. This reaction produced phlogopite schists containing the exometasomatic emeralds, as in all other granite-related emerald deposits. Endometasomatic changes of the mineralogy of the pegmatites is indicated by the geochemistry of the muscovite (phengitic substitution) and the feldspars (disappearance of the potassic feldspar and calcification of the plagioclase). The K-Ar analyses of syngenetic phlogopite (from the phlogopite schist) and muscovite (from the pegmatites) give an age of ca. 790 Ma, close to that of the last major orogeny affecting the region. This is in accordance with the ages of other granite-related deposits, which all formed in conditions of active orogeny. The ages of the biotite are lower than those of the muscovite, indicating limited radiogenic argon loss as a result of deformation.
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Fuchsloch, Warrick C., Paul A. M. Nex y Judith A. Kinnaird. "The geochemical evolution of Nb–Ta–Sn oxides from pegmatites of the Cape Cross–Uis pegmatite belt, Namibia". Mineralogical Magazine 83, n.º 02 (2 de octubre de 2018): 161–79. http://dx.doi.org/10.1180/mgm.2018.151.
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AbstractThe Cape Cross–Uis pegmatite belt, Damara Orogen, north-central Namibia hosts multiple Ta–Nb- and Sn-oxide-bearing pegmatites. Columbite-group minerals, tapiolite, cassiterite and minor ixiolite and wodginite occur in abundance within pegmatites and display various compositional and internal structural mineralogical variations. Ta–Nb oxides display various zonation patterns indicative of multiple crystallisation phases, whereas cassiterite is dominantly homogeneous with minor euhedral columbite-group mineral inclusions. Ta–Nb oxides are mostly rich in Fe, with fractionation patterns in the columbite quadrilateral being sub parallel to the Ta/(Ta + Nb) axis; increasing Ta/(Ta + Nb) with little change in Mn/(Mn + Fe), which is consistent with classical trends in beryl-to-spodumene rare-element pegmatites. In addition, these trends suggest that co-crystallising minerals compete with Ta–Nb oxides for elements such as Mn, preventing Ta–Nb oxides from attaining Mn-rich compositions during the fractionation process. Cassiterite shows similar fractionation patterns with Fe > Mn and notable increases in the Ta content. Minor-element substitution in Ta–Nb oxides shows sharp decreases with increasing fractionation supporting the hypothesis that newly stabilised co-occurring minerals compete with columbite-group minerals for certain elements. Tapiolite shows the same minor-element trend, however, only for Sn and Ti suggesting cassiterite was a dominant competing mineral. Although crystallisation of Ta–Nb oxides from an aqueous fluid at the late-stages of pegmatite genesis is highly debated, significantly elevated Ta contents in metasomatised country rock, compared to unaltered country rock, may give new insight, suggesting that Ta may indeed partition into, and be transported by, an exsolved aqueous fluid. However, further studies of the country rock metasomatic contacts are required as currently the dataset is limited. The degree of fractionation as depicted by Ta–Nb and Sn oxides within pegmatites, indicate that a zonation from primitive to evolved pegmatites surrounding granites is not present and that pegmatites are probably not related to granites in the typical parent–daughter relationship.
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Adeola, Adewole John, Adeyemi Moyosoluwa Odunayo y Omojola Damilola Ifeoluwa. "Geochemical and mineralogical characteristics of clay deposits at Ijesha–Ijebu and its environs, southwestern Nigeria". Global Journal of Pure and Applied Sciences 26, n.º 2 (2 de noviembre de 2020): 119–30. http://dx.doi.org/10.4314/gjpas.v26i2.4.
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Two residual clay deposits and one transported clay deposit in Ijesha-Ijebu area were investigated for their mineralogical, chemical and industrial properties. The investigation was to evaluate their industrial applications and economic importance. The mineralogy of the clay samples was determined using X-ray Diffraction (XRD). The chemical composition of the clay samples was determined using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Physical tests which include; thermal properties, plasticity tests, density measurement, linear shrinkage and water absorption capacity were determined to determine their industrial potentials. The clay within the weathered profiles above banded gneiss and pegmatite at Ijesha-Ijebu is brownish with red spots, while the clays derived from sedimentary terrain is chocolate in colour. The X-ray diffraction results showed that kaolinite is the dominant mineral, while quartz, albite and muscovite are the major non clay minerals. Chemical data showed that the values of SiO2, Al2O3 and Fe2O3 are 66.11%, 20.53% and 3.07%, respectively in weathered banded gneiss, in sedimentary the values of SiO2, Al2O3 and Fe2O3 are 42.12%, 34.43% and 7.37%. In weathered pegmatite, the values of SiO2, Al2O3 and Fe2O3 are 53.17%, 32.7%, 1.44%, respectively. The average percentage of clay in the banded gneiss, pegmatite and sedimentary samples are 50%, 56% and 47% respectively. The clay mouldability ranged between moderate to high. Evaluation of the clay properties and characteristics shows the industrial application of the clay like production of ceramic, building bricks and other structural wares.
Keywords: Clay, Mineralogy, Chemistry, Ceramics, Building bricks.
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Ilevbare, M. y A. Orisamika. "Geochemical Characterization and Economic Potential of Emure and Ijero Ekiti Pegmatites in Southwest Nigeria". Nigerian Journal of Technology 40, n.º 1 (23 de marzo de 2021): 37–43. http://dx.doi.org/10.4314/njt.v40i1.6.
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Global demand increase for rare metals deposits has re-enacted the search for economically viable deposits. Precambrian pegmatites occurring as near dykes and massive types were studied for Emure-Ekiti and Ijero-Ekiti respectively, with the aim of characterizing them geochemically and determining their possible economics values. A total of twelve samples comprising seven from Emure-Ekiti, three whole rock muscovite extract for Ijero-Ekiti were analysed for major and trace elements using X-ray fluorescence method. Thin sections prepared for the Emure-Ekiti pegmatites show that quartz, microcline are major mineral constituents. The geochemical results reveals that the Emure-Ekiti and the whole rock samples of Ijero-Ekiti are considerably siliceous, with an average value of 68.72% and 68.6% respectively, while the muscovites extracts average 48.86%. Mean values of major oxides for the Emure, Ijero[whole rock, muscovite] are as follows; Al2O3 - 20.42%, [13.74%, 35.15%]; Fe2O3 - 1.83%, [1.24%, 2.19%]; MgO - 0.013%, [0.029%, 1.04%]; CaO - 0.02%, [0.34%, 2.4%]; Na2O – 1.01%, [4.40%, 1.045%]; K2O – 3.17%, [2.77%, 11.07%]. Trace and rare-earth elements result shows that the Emure-Ekiti pegmatites is “barren” – depleted in rare metals Ta, Nb, Cs, Sn, Rb, etc, and compare favourably with Apomu, Ago-Iwoye and Ijebu-Ife barren pegmatites. On the other hand, two of the whole rock samples are mineralized – fairly enriched in rare metals Ta, Nb, Rb while the remaining sample and the muscovite extract are barren; as depicted by the Rb vs Rb plot and when compared to the other rare metal pegmatites across the world.
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Cardoso-Fernandes, Joana, João Silva, Mônica M. Perrotta, Alexandre Lima, Ana C. Teodoro, Maria Anjos Ribeiro, Filipa Dias, Odile Barrès, Jean Cauzid y Encarnación Roda-Robles. "Interpretation of the Reflectance Spectra of Lithium (Li) Minerals and Pegmatites: A Case Study for Mineralogical and Lithological Identification in the Fregeneda–Almendra Area". Remote Sensing 13, n.º 18 (15 de septiembre de 2021): 3688. http://dx.doi.org/10.3390/rs13183688.
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Reflectance spectroscopy has been used to identify several deposit types. However, applications concerning lithium (Li)-pegmatites are still scarce. Reflectance spectroscopic studies complemented by microscopic and geochemical studies were employed in the Fregeneda–Almendra (Spain–Portugal) pegmatite field to analyze the spectral behavior of Li-minerals and field lithologies. The spectral similarity of the target class (Li-pegmatites) with other elements was also evaluated. Lepidolite was discriminated from other white micas and the remaining Li-minerals. No diagnostic feature of petalite and spodumene was identified, since their spectral curves are dominated by clays. Their presence was corroborated (by complementary techniques) in petalite relics and completely replaced crystals, although the clay-related absorption depths decrease with Li content. This implies that clays can be used as pathfinders only in areas where argillic alteration is not prevalent. All sampled lithologies present similar water and/or hydroxide features. The overall mineral assemblage is very distinct, with lepidolite, cookeite, and orthoclase exclusively identified in Li-pegmatite (being these minerals crucial targets for Li-pegmatite discrimination in real-life applications), while chlorite and biotite can occur in the remaining lithologies. Satellite data can be used to discriminate Li-pegmatites due to distinct reflectance magnitude and mineral assemblages, higher absorptions depths, and distinct Al–OH wavelength position. The potential use of multi- and hyperspectral data was evaluated; the main limitations and advantages were discussed. These new insights on the spectral behavior of Li-minerals and pegmatites may aid in new Li-pegmatite discoveries around the world.
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Dolníček, Zdeněk, Karel Malý, Jana Ulmanová, Jaroslav Havlíček y Luboš Vrtiška. "Minerály kontaminovaných granitových pegmatitů z lomu Pohled u Havlíčkova Brodu (moldanubikum), část I: oxidy, karbonáty, silikáty a fosfáty". Bulletin Mineralogie Petrologie 28, n.º 1 (2020): 132–51. http://dx.doi.org/10.46861/bmp.28.132.
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In the Pohled quarry near Havlíčkův Brod town (central part of Czech Republic), granitic pegmatites form dikes or irregular bodies cementing breccia of host metamorphic rocks (paragneisses, amphibolites) belonging to the Monotonous (Ostrong) Group of the Moldanubicum of the Bohemian Massif. Pegmatites exhibit coarse-grained textures and very simple mineral composition, which, however, was in places strongly modified by superimposed hydrothermal alterations and locally also by crystallization of ore minerals. K-feldspar, plagioclase (An0-38), biotite (phlogopite), apatite (fluorapatite to hydroxylapatite), zircon, allanite-(Ce) and part of quartz undoubtedly originated during magmatic stage. Products of hydrothermal alterations include younger quartz, Fe-Mg chlorites (older clinochlore and younger chamosite with an admixture of Ca-smectite), prehnite, clinozoisite, amphibole (actinolite), titanite, calcite, and very probably also ilmenite (with up to 22.5 mol. % of pyrophanite), rutile, anatase and V-Cr-Fe-rich grossular with 13 - 25 mol.% of goldmanite and 12 - 24 mol.% uvarovite. The elevated contents of Mg, Ca, V and Cr found in some minerals are associated with a material contamination by the surrounding metamorphic rocks (especially amphibolites, serpentinites and perhaps also graphitic lithologies), which took place with varying intensity during both magmatic and hydrothermal stages of evolution of the studied pegmatites. Geochemically, they are poorly fractionated pegmatites, whose origin was probably connected with anatexis of the host Moldanubian metamorphic rocks, which was likely associated with emplacement of adjacent small body of the Pohled Granodiorite.
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Khromykh, Sergey V., Tatiana A. Oitseva, Pavel D. Kotler, Boris A. D’yachkov, Sergey Z. Smirnov, Alexey V. Travin, Alexander G. Vladimirov et al. "Rare-Metal Pegmatite Deposits of the Kalba Region, Eastern Kazakhstan: Age, Composition and Petrogenetic Implications". Minerals 10, n.º 11 (16 de noviembre de 2020): 1017. http://dx.doi.org/10.3390/min10111017.
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The paper presents new geological, mineralogical, and isotope geochronological data for rare-metal pegmatites in the Kalba granitic batholith (Eastern Kazakhstan). Mineralization is especially abundant in the Central-Kalba ore district, where pegmatite bodies occur at the top of large granite plutons and at intersections of deep faults. The pegmatites contain several successive mineral assemblages from barren quartz-microcline and quartz-microcline-albite to Li-Cs-Ta-Nb-Be-Sn-bearing cleavelandite-lepidolite-spodumene. Ar-Ar muscovite and lepidolite ages bracket the metallogenic event between 291 and 286 Ma. The pegmatite mineral deposits formed synchronously with the emplacement of the phase 1 Kalba granites during the evolution of hydrous silicate rare-metal magmas that are produced by the differentiation of granite magma at large sources with possible inputs of F and rare metals with fluids.
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Dutra, Cláudio V. "A geoquímica analítica em Minas Gerais: de Gorceix ao Geolab: a contribuição do ITI". Rem: Revista Escola de Minas 55, n.º 3 (septiembre de 2002): 185–92. http://dx.doi.org/10.1590/s0370-44672002000300005.
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É apresentada a recuperação da memória histórica da Geoquímica Analítica em Minas Gerais desde os primeiros trabalhos de Henri Gorceix, em 1881. São descritos os trabalhos dos órgãos antigos, como o Serviço da Produção Mineral, a Secretaria da Agricultura do Estado de Minas Gerais e o Instituto de Tecnologia Industrial, órgãos cujos geoanalistas descreveram novos minerais, se especializaram na análise de tântalo-niobatos e minerais radioativos de nossos pegmatitos, fizeram cronogeologia, introduziram métodos espectroquímicos nos estudos de elementos-traços em rochas e deram suporte aos estudos da apatita e do pirocloro de Araxá. São realçados os trabalhos pioneiros do GEOLAB, o primeiro laboratório geoquímico de serviço no país.
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Kudryashov, Nikolay M., Oksana V. Udoratina, Matthew A. Coble y Ekaterina N. Steshenko. "Geochronological and Geochemical Study of Zircon from Tourmaline-Muscovite Granites of the Archaean Kolmozero–Voronya Greenstone Belt: Insights into Sources of the Rare-Metal Pegmatites". Minerals 10, n.º 9 (27 de agosto de 2020): 760. http://dx.doi.org/10.3390/min10090760.
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In order to determine the U-Pb crystallization age of zircon from the tourmaline-muscovite granites of the Kolmozero–Voronya greenstone belt located in the northeastern Fennoscandian Shield (Kola Peninsula), an isotope-geochronological study of the zircon grains was performed using a SHRIMP-RG microprobe. The belt is represented by the Archaean volcano-sedimentary rocks (2.9–2.8 Ga). Deposits of rare-metal pegmatites (Li and Cs with associated Nb, Ta, and Be) occur within the belt and on its margins. The age of the pegmatites within the belt was estimated at 2.7–2.6 Ga. Until now, there has been no generally accepted view on the genetic relation of the pegmatites with granite. Various authors have suggested that the pegmatites could potentially be associated with many type of granitoids within the region, i.e., plagiogranites, tonalites, amphibole-biotite granodiorites, microcline granites, alkaline granites, or muscovite-tourmaline granites. Zircon crystals from the muscovite-tourmaline granites are heterogeneous; they have less altered cores and strongly altered rims. The zircon cores are slightly enriched in U at a value of 173–1030 ppm, Th/U = 0.1–0.4. The zircons’ rims are heavily enriched in U at a value of 700–3300 ppm, Th/U = 0.03–0.08, indicating metasomatic processes. Zircon characteristics show that it crystallized from a melt enriched in a fluid phase. Fluid activity lasted after zircon crystallization as reflected in the irregular composition of the mineral and its rare earth element (REE) patterns that are typical of a metasomatic zircon. The computed zircon crystallization temperature in the tourmaline-muscovite granites is in the range of 650–850 °C. The discordant age calculated for five analyzed points of the zircon crystal cores is 2802 ± 13 Ma. The discordant age for four analyzed points of the zircon crystal rims is found to be 2728 ± 14 Ma. On the basis of the obtained isotope-geochronological data, we conclude that the tourmaline-muscovite granites located in the immediate vicinity of rare-metal pegmatite veins are the most probable source of matter for the pegmatites.
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FLOWERDEW, M. J., J. S. DALY, P. G. GUISE y D. C. REX. "Isotopic dating of overthrusting, collapse and related granitoid intrusion in the Grampian orogenic belt, northwestern Ireland". Geological Magazine 137, n.º 4 (julio de 2000): 419–35. http://dx.doi.org/10.1017/s0016756800004209.
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In the Grampian (Ordovician) orogenic belt in northwestern Ireland the Dalradian Supergroup abuts and interleaves with an enigmatic psammite-dominant unit, with relict latest Precambrian granulite-facies assemblages, known as the Slishwood Division. These two units were most likely tectonically juxtaposed during the D3 phase of Dalradian deformation. Using Ar–Ar, Rb–Sr and Sm–Nd methods, 53 new mineral ages have been obtained from both rock units, and from pegmatites intruding them, in an attempt to constrain the timing of their juxtaposition and the history they subsequently shared. Prior to D3 (c. 480 Ma), retrograde hornblende poikiloblasts grew in granulite-facies metabasite pods within the Slishwood Division. Tectonic juxtaposition (D3) with the Dalradian is loosely constrained between 479 Ma and 459 Ma but is likely to have occurred between 470 Ma and 459 Ma. Dalradian peak metamorphic conditions were attained shortly after D3, at around 460 Ma. Extensional collapse of the orogen, with rapid uplift and exhumation, is dated by an abundance of mineral cooling ages between 460 Ma and 450 Ma. Orogenic collapse is also dated, more precisely, by widespread pegmatite intrusion into both rock units at about 455 Ma. Initial 87Sr/86Sr ratios suggest that these pegmatites are partial melts from Dalradian metasediments. A second suite of pegmatites were intruded, along with the Ox Mountains Granodiorite, much later at or around 400 Ma during sinistral shearing.
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Sebastian, Ansom y Martine Lagache. "Experimental study of the equilibrium between pollucite, albite and hydrothermal fluid in pegmatitic systems". Mineralogical Magazine 54, n.º 376 (septiembre de 1990): 447–54. http://dx.doi.org/10.1180/minmag.1990.054.376.10.
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AbstractPollucite is a silicate mineral of the rare element caesium, occurring in granitic pegmatites. Experiments have been carried out at 450, 600, and 750°C, 1.5 kbar, to study the equilibrium between pollucite, albite and the co-existing hydrothermal solution. When pollucite co-exists with albite, the alkaline composition of the solution is buffered. The Cs/Na ratio of the solution has been determined to be 0.11 at 450°C 0.22 at 600°C and 0.23 at 750°C. Pollucite contains about 15 mol.% of sodium, whereas albite is almost purely sodic. In nature, pollucite with more than 82 mol.% caesium has never been found. This can be explained by the absence of solutions in granitic pegmatites having a higher Cs/Na ratio than those determined by us.
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Ulmanová, Jana y Zdeněk Dolníček. "Minerály pegmatitových hnízd z okolí Jablonce nad Nisou (krkonošsko-jizerský pluton) - část I. silikáty". Bulletin Mineralogie Petrologie 28, n.º 2 (2020): 466–82. http://dx.doi.org/10.46861/bmp.28.466.
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We have studied silicate minerals in pegmatite nests from the Tanvald Granite (4 sites) and the Liberec Granite (1 site) in the vicinity of Jablonec n. Nisou, situated within the Variscan Krkonoše-Jizera Pluton. They contain major quartz, K-feldspar and plagioclase (An0-11), subordinate biotite, muscovite and locally schorl. Accessory phases include garnet (spessartine-almandine), andalusite, Hf-rich zircon and thorite. In addition, zinnwaldite was found in a single sample. The studied pegmatites show simple internal structure including aplitic, granitic and coarse-grained “blocky” units; the central zone commonly contains miarolitic cavity which is sometimes filled by tourmaline. The mineral composition and fractionation degree largely reflect those of the host granite; the more fractionated are pegmatites hosted by the Tanvald Granite. The pegmatite nest from Nová Ves nad Nisou II exhibits distinct mineral assemblage with zinnwaldite, pure albite and lack of biotite and garnet, therefore we suggest here a substantial modification of mineral assemblage by superimposed processes. Moreover, tourmaline (schorl) composition with local increasing of Mg toward rim indicates a possible contamination derived from adjacent rocks during tourmaline crystallization.
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Kurуlo, S. I., N. M. Lуzhachenko, S. M. Bondarenko, V. O. Syomka y O. V. Hrinchenko. "Ta-Nb mineralization in rare-metal pegmatite from north-western frame of Lypniazhka granite-migmatite structure". Geochemistry and ore formation 41 (2020): 32–41. http://dx.doi.org/10.15407/gof.2020.41.032.
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The three type of rare-metal pegmatites are know in Stankuvatske ore field (Ingul megablock, the Ukraianian Shield), such as: Li-bearing, Bi-As-U and Ta-Nb pegmatites. For the first time Ta-Nb mineralisation from Ta-Nb bearing albite-K-Feldspar rare metal pegmatite have been described. Investigated pegmatite is located on the Norh-West frame of the Lypnazky granitemigmatite massive among hosted amphibolites. Rare-metal pegmatite doesn’t have obvious zonality and consist of alkaline feldspar, biotite, muscovite, dark to black colour quartz, blue-greenish apatite, nigerite, gachnite, tourmaline, monazite. The primary ferrocolumbite and Nb-rutile-II have undergone strong hydrothermal alteration. Thus primary rutile-II decomposed with formation of skeletal intergrowths of secondary cassiterite and rutile-III with a much lower volume of Nb and Ta under the influence of hydrothermal fluid. Primary homogenous Nb-rutile-I (Nb2O5+Ta2O5 from 33,5 to 42,9 wt.%) exsolved a fine trellis-like pattern and lamellar of Nb-pure rutile-III, cassiterite and Mn-rich ilmenite. The Nb-rutile-II is occurred in tabular grains with unclear internal zonation. Primary ferrcolumbite breakdown to Ti-ixiolite and Nb-rutile-III. Primary oscillatory zonality is transformed into irregularly patchy and veinlety. Recrystallized ferrotantalite is secondary and uncommon mineral. Ferrocolumbite contains 2.93 to 4.74 wt.%TiO2, and titanian ixiolite 7,33-10,76 wt.%. The (Ti,Nb)>Ta mineral assemblages, and compositional trend of columbite with very low Ta/(Ta+Nb) and Mn/ (Mn+Fe) imply a general low level of fractionation in comparison with typical beryl-columbite rare-metal pegmatites.
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Mikhailova, Julia A., Yakov A. Pakhomovsky, Olga F. Goychuk, Andrey O. Kalashnikov, Ayya V. Bazai y Victor N. Yakovenchuk. "Pre-Pegmatite Stage in Peralkaline Magmatic Process: Insights from Poikilitic Syenites from the Lovozero Massif, Kola Peninsula, Russia". Minerals 11, n.º 9 (7 de septiembre de 2021): 974. http://dx.doi.org/10.3390/min11090974.
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The Lovozero peralkaline massif (Kola Peninsula, Russia) is widely known for its unique mineral diversity, and most of the rare metal minerals are found in pegmatites, which are spatially associated with poikilitic rocks (approximately 5% of the massif volume). In order to determine the reasons for this relationship, we have investigated petrography and the chemical composition of poikilitic rocks as well as the chemical composition of the rock-forming and accessory minerals in these rocks. The differentiation of magmatic melt during the formation of the rocks of the Lovozero massif followed the path: lujavrite → foyaite → urtite (magmatic stage) → pegmatite (hydrothermal stage). Yet, for peralkaline systems, the transition between magmatic melt and hydrothermal solution is gradual. In the case of the initially high content of volatiles in the melt, the differentiation path was probably as follows: lujavrite → foyaite (magmatic stage) → urtitization of foyaite → pegmatite (hydrothermal stage). Poikilitic rocks were formed at the stage of urtitization, and we called them pre-pegmatites. Indeed, the poikilitic rocks have a metasomatic texture and, in terms of chemical composition, correspond to magmatic urtite. The reason for the abundance of rare metal minerals in pegmatites associated with poikilitic rocks is that almost only one nepheline is deposited during urtitization, whereas during the magmatic crystallization of urtite, rare elements form accessory minerals in the rock and are less concentrated in the residual solution.
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Garate-Olave, Idoia, Encarnación Roda-Robles, Pedro Pablo Gil-Crespo, Alfonso Pesquera y Jon Errandonea-Martin. "The Tres Arroyos Granitic Aplite-Pegmatite Field (Central Iberian Zone, Spain): Petrogenetic Constraints from Evolution of Nb-Ta-Sn Oxides, Whole-Rock Geochemistry and U-Pb Geochronology". Minerals 10, n.º 11 (12 de noviembre de 2020): 1008. http://dx.doi.org/10.3390/min10111008.
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Abundant Li-Cs-Ta aplite-pegmatite dykes were emplaced in the western Central Iberian Zone of the Iberian Massif during the Variscan Orogeny. Their origin and petrogenetic relationships with the widespread granitoids have led to a currently rekindled discussion about anatectic vs. granitic origin for the pegmatitic melts. To deal with these issues, the aplite-pegmatite dykes from the Tres Arroyos area, which constitute a zoned pegmatitic field related to the Nisa-Alburquerque granitic batholith, have been studied. This work comprises a complete study of Nb-Ta-Sn oxides’ mineralogy, whole-rock geochemistry, and U-Pb geochronology of the aplite-pegmatites that have been grouped as barren, intermediate, and Li-rich. The most abundant Nb-Ta-Sn oxides from Tres Arroyos correspond to columbite-(Fe), columbite-(Mn) and cassiterite. Niobium-Ta oxides show a marked increase in the Mn/(Mn+Fe) ratio from the barren aplite-pegmatites up to the Li-rich bodies, whereas variations in the Ta/(Ta+Nb) ratio are not continuous. The probable factors controlling fractionation of Mn/Fe and Ta/Nb reflected in Nb-Ta oxides may be attributed to the crystallization of tourmaline, phosphates and micas. The lack of a progressive Ta/Nb increase with the fractionation may be also influenced by the high F and P availability in the parental pegmatitic melts. Most of the primary Nb-Ta oxides would have crystallized by punctual chemical variations in the boundary layer, whereas cassiterite formation would be related to an undercooling of the system. Whole-rock composition of the distinguished lithotypes reflects similar tendencies to those observed in mineral chemistry, supporting a single path of fractional crystallization from the parental Nisa-Alburquerque monzogranite up to the most evolved Li-rich aplite-pegmatites. The age of 305 ± 9 Ma, determined by LA-ICP-MS U-Pb dating of columbite-tantalite oxides, reinforces the linkage of the studied aplite-pegmatites and the cited parental monzogranite.
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Singh, Abhimanyu y Vinod K. Singh. "New observations of Tin Mineralization Potential Vis-à-Vis Ore Petrographic, Alteration and Geochemistry in the Southeastern part of Bastar Craton, Central India". Journal of Geoscience, Engineering, Environment, and Technology 4, n.º 2-2 (30 de junio de 2019): 43. http://dx.doi.org/10.25299/jgeet.2019.4.2-2.2144.
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The Tin mineralizations occur around the Katekalyan area, hosted in the acid magmatic rocks. The evolution differentiating granitic magma shows residual melt enrichment where end products intruded as pegmatites into the rocks. The different kind of pegmatite occur as simple unzoned, recrystallized (granitic pegmatite), and metasomatic greisenised and albitised pegmatites which emplaced within the pre-existing rocks of metabasic intrusive, granite (KG), granite gneiss (KGG). Sometimes it also found in metasediments as mineralised and non-mineralised characters along the fractures and foliation planes trending N-S, E-W and more frequently are observed NNW-SSE trends. Cassiterite is most important Tin-ore mineral and associated with pegmatites. Some cassiterite samples exhibit colourless to brown shades zoning which indicate multi stage growth. The cassiterite samples contain significant amounts of Sn, Nb, Ta with minor W.
The partial melting model shows that the variation 5 to 50% partial melting of bulk continental crust for KG as well as KGG rocks but bulk distribution coefficient for Sr (DSr) shows low i.e. <<10. The upper limit of partial melting of bulk crust estimates ~50 % for KG and KGG rocks are consistent with required rheological, critical melt percentage to leave the source region has decreased granite melt which were capable to mineralised tin ore elements. It is interesting to note that the SnF4 and SnCl4 probably not stable in presence of water under geologically reasonable conditions.
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Baldwin, J. R., P. G. Hill, O. von Knorring y G. J. H. Oliver. "Exotic aluminium phosphates, natromontebrasite, brazilianite, goyazite, gorceixite and crandallite from rare-element pegmatites in Namibia". Mineralogical Magazine 64, n.º 6 (diciembre de 2000): 1147–64. http://dx.doi.org/10.1180/002646100549940.
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AbstractReplacement phenomena in amblygonite–montebrasite in rare-element pegmatites from the Karibib-Usakos area, Namibia, have been investigated using the electron microprobe. The first African occurrence and analysis of the very rare mineral natromontebrasite NaAl(PO4)(OH,F) is reported from the Daheim pegmatite. In the Okatjimukuju pegmatite, montebrasite has been replaced by a number of phases including crandallite CaAl3(PO4)2(OH)5·H2O and brazilianite NaAl3(PO4)2(OH)4. In one example, montebrasite has been almost completely replaced by brazilianite which has also been found to contain not only crandallite but also its solid solution analogues: goyazite SrAl3(PO4)2(OH)5·H2O and gorceixite BaAl3(PO4)2(PO3OH)(OH)6. Apatite is common at the contacts with montebrasite and associated minerals and texturally is intimately intergrown with crandallite, goyazite and gorceixite at Okatjimukuju. The occurrence of these minerals offers insight into the chemistry of post-magmatic fluids in these pegmatites.
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Oliveira Santos, Raissa Yohana, Vinicius Anselmo Carvalho Lisboa, José Ramilson Santos Oliveira, Tiago Sales Costa Barros, Thales José Cordeiro Santos y Paulo Sales Costa Barros. "Mapeamento Geológico do Pegmatito Alto do Urubu, município de Picuí (PB), Faixa Seridó, Província Pegmatítica da Borborema". Revista Principia - Divulgação Científica e Tecnológica do IFPB 1, n.º 43 (13 de diciembre de 2018): 222. http://dx.doi.org/10.18265/1517-03062015v1n43p222-233.
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The Alto do Urubu Pegmatite is located in the municipality of Picuí, northern of Paraíba, in Borborema Pegmatitic Province (PPB), the area that has the greatest concentration of pegmatites in the Brazilian Northeast, corresponding to the eastern part of the Seridó Belt. PPB is known worldwide for the abundance of pegmatites, with some incidence of mineralized bodies. In the region we studied, 42 outcrops were described, in each of them the main textures and mineralogical aspects of rock were described. The geological mapping made it possible to observe the predominance of the rocks of the Seridó Formation. Schists and pegmatites intruded in the form of dikes and sills are very common in the place. The schists of the region present a dark, grayish coloration, fine to medium granulation, and are composed mainly of quartz, biotite, muscovite and granade porphiroblasts, in some cases, there are cordierite centimeter nodules. It is possible to observe in these rocks foliation Sn and Sn+1, as well as crenulations. The studied pegmatite has an elongated shape, it is about 106 meters long and 18 meters wide and N-S direction, in agreement with the foliation of the schist. It shows a well defined mineral zoning, namely: i) border zone (zone I); ii) zone III and iii) quartz core. Zone I corresponds to the outermost part of the body, measuring about 30 cm in width and consisting essentially of muscovite. Zone III is composed of quartz, feldspar and mica and it is where the majority of the minerals of economic interest (especially tantalite and beryl) are concentrated, in a smaller quantity there is the occurrence of arrojadita and espersatita. In the innermost part of the pegmatite, there is the quartz nucleus, composed of milky and rosacea quartz. The observed mineral zoning enables us to classify it as a heterogeneous pegmatite type.
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Tomašić, Nenad, Radek Škoda, Vladimir Bermanec y Marin Šoufek. "Crystal chemistry and microfeatures of gadolinite imprinted by pegmatite formation and alteration evolution". American Mineralogist 105, n.º 11 (1 de noviembre de 2020): 1647–55. http://dx.doi.org/10.2138/am-2020-7355.
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Abstract Gadolinite [REE2Fe2+Be2Si2O10] is a common mineral in certain types of rare element and rare earth element (REL-REE) pegmatites. Changes in pegmatite environment during and after gadolinite formation may be devised by studying its crystal-chemical properties and a thorough observation of microfeatures in the mineral matrix. Post-crystallization processes in pegmatite might trigger alteration mechanisms in gadolinite like in other REE-rich pegmatite minerals, whereby various late-magmatic or metasomatic events may affect mineral chemistry. Three gadolinite samples originating from various pegmatite occurrences in southern Norway offer an excellent opportunity in studying post-crystallization evolution of the pegmatites; by determining their crystallographic, chemical, and micro-textural features, imprints of the related processes in the pegmatites have been characterized in this study. Relevant mineral information was collected in recrystallization experiments of fully or slightly metamictized gadolinite samples and subsequent XRD analyses. Micro-Raman spectroscopy, electron microprobe analysis (EMPA), and scanning electron microscope–backscattered electron–energy-dispersive X-ray spectroscopy (SEM-BSE-EDS) analyses were employed to retrieve micro-chemical properties and related micro-textural features of the mineral matrix. With a reference to the gadolinite supergroup, a general alteration path can be envisaged outlining the pegmatite evolution and suggesting the occurrence of the secondary REE mineral phases: altered gadolinite domains prove Ca enrichment with a tendency toward the hingganite composition, while a slight fluorine increase and sporadic secondary fluorite occurrence imply a significant role of fluorine as a complexing agent in the dissolution-reprecipitation mechanism of metasomatic alteration in the mineral. Micro-Raman spectra show improved vibration statistics for the altered gadolinite domains, which could be linked to the substitution of rare earth elements (REE) by Ca and a possible increase of structural ordering within the gadolinite structure, being at the same time an indication of structural healing of metamictized domains by metasomatic processes. A study of microfeatures in the complex silicates like gadolinite proves to be an excellent tool to trace post-crystallization processes in a pegmatitic environment. With a slight redistribution of radionuclides during an alteration in gadolinite, a moderate precaution has to be taken when selecting gadolinite for U-Th-Pb dating.
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Chiarenzelli, Jeffrey, Marian Lupulescu, George Robinson, David Bailey y Jared Singer. "Age and Origin of Silicocarbonate Pegmatites of the Adirondack Region". Minerals 9, n.º 9 (23 de agosto de 2019): 508. http://dx.doi.org/10.3390/min9090508.
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Silicocarbonate pegmatites from the southern Grenville Province have provided exceptionally large crystal specimens for more than a century. Their mineral parageneses include euhedral calc–silicate minerals such as amphibole, clinopyroxene, and scapolite within a calcite matrix. Crystals can reach a meter or more in long dimension. Minor and locally abundant phases reflect local bedrock compositions and include albite, apatite, perthitic microcline, phlogopite, zircon, tourmaline, titanite, danburite, uraninite, sulfides, and many other minerals. Across the Adirondack Region, individual exposures are of limited aerial extent (<10,000 m2), crosscut metasedimentary rocks, especially calc–silicate gneisses and marbles, are undeformed and are spatially and temporally associated with granitic pegmatites. Zircon U–Pb results include both Shawinigan (circa 1165 Ma) and Ottawan (circa 1050 Ma) intrusion ages, separated by the Carthage-Colton shear zone. Those of Shawinigan age (Lowlands) correspond with the timing of voluminous A-type granitic magmatism, whereas Ottawan ages (Highlands) are temporally related to orogenic collapse, voluminous leucogranite and granitic pegmatite intrusion, iron and garnet ore development, and pervasive localized hydrothermal alteration. Inherited zircon, where present, reflects the broad range of igneous and detrital ages of surrounding rocks. Carbon and oxygen isotopic ratios from calcite plot within a restricted field away from igneous carbonatite values to those of typical sedimentary carbonates and local marbles. Collectively, these exposures represent a continuum between vein-dyke and skarn occurrences involving the anatexis of metasedimentary country rocks. Those of Ottawan age can be tied to movement and fluid flow along structures accommodating orogenic collapse, particularly the Carthage-Colton shear zone.
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Badanina, E. V., M. A. Sitnikova, V. V. Gordienko, F. Melcher, H. E. Gäbler, J. Lodziak y L. F. Syritso. "Mineral chemistry of columbite–tantalite from spodumene pegmatites of Kolmozero, Kola Peninsula (Russia)". Ore Geology Reviews 64 (enero de 2015): 720–35. http://dx.doi.org/10.1016/j.oregeorev.2014.05.009.
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Dill, Harald G. y Frank Melcher. "Nigrine a heavy mineral aggregate indicative of pegmatites and their siliceous root zones". Zeitschrift der Deutschen Gesellschaft für Geowissenschaften 160, n.º 2 (13 de julio de 2009): 191–99. http://dx.doi.org/10.1127/1860-1804/2009/0160-0191.
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Hrinchenko, O., S. Bondarenko y T. Mironchuk. "GRANITOIDS, RARE-METAL PEGMATITES AND Ta-Nb MINERALIZATION OF SHPOLIANO-TASHLYK ORE AREA (INGUL MEGABLOCK, UKRAINIAN SHIELD)". Visnyk of Taras Shevchenko National University of Kyiv. Geology, n.º 4 (83) (2018): 24–29. http://dx.doi.org/10.17721/1728-2713.83.03.
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Composition of granites, genetically associated pegmatites and superimposed metasomatites distributed within Shpoliano-Tashlyk ore area (Ingul megablock) is considered. It is established, that on the basis of similarity in their petrographic and petrochemical features granitoids of the area can be related to single complex. Features of ore mineralization are defined by both composition of granitoids (Sgranites) after which rare-metal pegmatites are formed and intensity of superimposed metasomatic alterations. Main minerals-concentrators of Ta and Nb mineralization in granitic pegmatites and metasomatites are represented by minerals of three isomorphic series – columbite-tantalite (Fe,Mn)(Nb,Ta,Ti)2O6, ilmenorutile-struverite (Ti,Nb,Ta)O2 and pyrochlore-microlite (Ca,Na)2Ta2O6(O,B,OH,F). Depending on geological setting such ore minerals as tapiolite, ixiolite, cassiterite, uraninite, nigerite, gahnite are commonly found in association with these minerals. Chemical composion of tantalo-niobates sampled from ore-bearing pegmatites and metasomatites is investigated by microprobe analysis. Most minerals of columbite-tantalite series are characterized by distinct and rhythmic internal zonality and contrasting mosaic structure which are related to considerable heterogeneities of their chemical composition. Within one aggregate mineral phases with wide range of values – from 9,80 to 71,0 % for Ta2O5 and from 10,6 to 70,1 % for Nb2O5 – are established. Among minerals ferruginous varieties which composition relates to Fe-columbite-tantalites (Nb2O5/Ta2O5 = 1–1,2; FeO/MnO = 2,5–6) prevail. Columbite-tantalites are characterised by high contents of admixture elements present (%): TiO2 – to 5,88; WO3 – to 3,70; SnO2 – to 9,20; Sc2O3 – to 5,40. Scandium ores occur as scandium-rich minerals that are mostly confined to the minerals of columbite-tantalite series found in Polohivka ore field. On the Ukrainian Shield high contents of Sc2O3 in tantalo-niobates are established for the first time. Minerals of ilmenorutile-struverite series do not quantitatively yield to minerals of columbite-tantalite series. For minerals of this series Nb2O5/Ta2O5 ratio varies in the range of 0,6-1,4. Among characteristic admixture-elements are prevailed (%): SnO2 – to 3,1, V2O5 – to 5,05; FeO – to 11,51, Cr2O3 – to 1,20. Minerals of pyrochlore-microlite series are of subordinate importance. For the first time by results of U-Pb dating of columbite-tantalites from Mostove ore manifestation (Shpoliano-Tashlyk area) the age of Ta-Nb mineralization is established to be about 1965 ± 25 million years.
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Dill, Harald G. y Frank Melcher. "Erratum: Nigrine a heavy mineral aggregate indicative of pegmatites and their siliceous root zones". Zeitschrift der Deutschen Gesellschaft für Geowissenschaften 160, n.º 3 (1 de septiembre de 2009): 295. http://dx.doi.org/10.1127/1860-1804/2009/0160-0295.
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Grew, Edward S., James J. McGee, Martin G. Yates, Donald R. Peacor, Roland C. Rouse, Joep P. P. Huijsmanns, Charles K. Shearer, Michael Wiedenbeck, Douglas E. Thost y Shu-Chun Su. "Boralsilite (Al16B6Si2O37); a new mineral related to sillimanite from pegmatites in granulite-facies rocks". American Mineralogist 83, n.º 5-6 (1 de junio de 1998): 638–51. http://dx.doi.org/10.2138/am-1998-5-624.
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Smeds, Sten-Anders. "Regional trends in mineral assemblages of Swedish Proterozoic granitic pegmatites and their geological significance". Geologiska Föreningen i Stockholm Förhandlingar 112, n.º 3 (1 de septiembre de 1990): 227–42. http://dx.doi.org/10.1080/11035899009454769.
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McNeil, Alysha G., Robert L. Linnen, Roberta L. Flemming y Mostafa Fayek. "An experimental approach to examine fluid-melt interaction and mineralization in rare-metal pegmatites". American Mineralogist 105, n.º 7 (1 de julio de 2020): 1078–87. http://dx.doi.org/10.2138/am-2020-7216.
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Abstract Niobium and tantalum, rare metals and high field strength elements (HFSEs) that are essential to modern technologies, are concentrated among others in lithium-cesium-tantalum (LCT) pegmatites and rare metal granites. The most important hosts for Nb-Ta in these types of deposits are the columbite group minerals (columbite-tantalite), but at some ore deposits significant Ta is also contained in wodginite, microlite, and tapiolite. Previous solubility experiments of HFSE minerals have been limited to high temperatures because of the slow diffusivities of HFSEs in granitic melts. An experiment protocol is described herein that allows HFSE mineral solubilities to be determined at lower temperatures, more in line with the estimated solidus temperatures of LCT pegmatites and rare metal granites. This is achieved through the interaction of a melt that is enriched in high field strength elements (e.g., P and Nb or Ta) with a fluid enriched in a fluid-mobile element (FME, e.g., Mn). A starting glass enriched in a slow diffusing HFSE was synthesized, and HFSE mineral saturation is obtained via the diffusion of a FME into the melt via interaction with a fluid. This interaction can occur at much lower temperatures in reasonable experimental durations than for experiments that require diffusion of niobium and tantalum. The solubility product of columbite-(Mn) from the fluid-melt interaction experiment in a highly fluxed granitic melt at 700 °C is the same as those from dissolution and crystallization (reversal) experiments at the same P-T conditions. Thus, both methods produce reliable measurements of mineral solubility, and the differences in the metal concentrations in the quenched melts indicates that the solubility of columbite-(Mn) follows Henry's Law. Results show that columbite-(Mn) saturation can be reached at geologically reasonable concentrations of niobium in melts and manganese in hydrothermal fluids. This experimental protocol also allows the investigation of HFSE mineral crystallization by fluid-melt interactions in rare-metal pegmatites. Magmatic origins for columbite group minerals are well constrained, but hydrothermal Nb-Ta mineralization has also been proposed for pegmatite-hosted deposits such as Tanco, Greenbushes, and granite-hosted deposits such as Cínovec/Zinnwald, Dajishan, and Yichun. This study shows that columbite-(Mn), lithiophilite, and a Ca-Ta oxide mineral (that is likely microlite) crystallized from experiments in fluid-melt systems at temperatures as low as 650 °C at 200 MPa. It is important to note that HFSE minerals that crystallize from fluid-melt interactions texturally occur as euhedral crystals as phenocrysts in glass, i.e., are purely magmatic textures. Therefore, crystallization of HFSE minerals from fluid-melt interactions in rare metal granites and pegmatite deposits may be more widespread than previously recognized. This is significant because the formation of these deposits may require magmatic-hydrothermal interaction to explain the textures present in deposits worldwide, rather than always being the result of a single melt or fluid phase.
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Defnet, Peter A., Michael A. Wise, Russell S. Harmon, Richard R. Hark y Keith Hilferding. "Analysis of Garnet by Laser-Induced Breakdown Spectroscopy—Two Practical Applications". Minerals 11, n.º 7 (29 de junio de 2021): 705. http://dx.doi.org/10.3390/min11070705.
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Laser-induced breakdown spectroscopy (LIBS) is a simple and straightforward technique of atomic emission spectroscopy that can provide multi-element detection and quantification in any material, in-situ and in real time because all elements emit in the 200–900 nm spectral range of the LIBS optical emission. This study evaluated two practical applications of LIBS—validation of labels assigned to garnets in museum collections and discrimination of LCT (lithium-cesium-tantalum) and NYF (niobium, yttrium and fluorine) pegmatites based on garnet geochemical fingerprinting, both of which could be implemented on site in a museum or field setting with a handheld LIBS analyzer. Major element compositions were determined using electron microprobe analysis for a suite of 208 garnets from 24 countries to determine garnet type. Both commercial laboratory and handheld analyzers were then used to acquire LIBS broadband spectra that were chemometrically processed by partial least squares discriminant analysis (PLSDA) and linear support vector machine classification (SVM). High attribution success rates (>98%) were obtained using PLSDA and SVM for the handheld data suggesting that LIBS could be used in a museum setting to assign garnet type quickly and accurately. LIBS also identifies changes in garnet composition associated with increasing mineral and chemical complexity of LCT and NYF pegmatites.
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Bulakh, Andrei, Georgii Popov, Svetlana Yanson y Mikhail Ivanov. "New data on the granite pedestal of the monument to Peter the Great “The Bronze Horseman” in Saint Petersburg". Journal of Mining Institute 248 (25 de mayo de 2021): 180–89. http://dx.doi.org/10.31897/pmi.2021.2.2.
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In order to expand and popularize knowledge about the stone decoration of Saint Petersburg, we present new data on the mineralogy and petrography of the famous Thunder-Stone, the parts of which were the basis for the monument to Peter the Great – the legendary “Bronze Horseman”. In the course of studying geological documentation of the monument's granite base, we examined the mineral composition and internal structure of granite, as well as the fragments of a pegmatite vein and veinlets found in it. 25 single-mineral samples were collected from the available micro-scaled shear fractures within the pedestal surface and studied by electron microscopy, electron probe and X-ray phase analysis. It was established that K-Na feldspar in the granite composition was represented by microcline, whereas micas were represented by annite-siderophyllite and muscovite. Accessory minerals included monazite, xenotime, thorite, zircon, rutile, apatite, fluorite, Ti-, Nb-, Ta-bearing minerals, uranium phosphates. The presence of topaz is characteristic of pegmatites. The revealed structural and textural features of four granite boulders in the monument pedestal, as well as mineralogical and chemical composition of their rock-forming and accessory minerals, showed the similarity of this rock to Precambrian biotite-muscovite granites and topaz-containing pegmatites (stockscheiders) of the late formation phase of the Vyborg rapakivi granite massif. The research results are considered as the basis for further geological and mineralogical study of the Thunder-Stone origin and determining the place of its separation from the primary source.