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Abstract\nKEY POINTSStudies of lithogeochemical dispersion haloes of rare metal pegmatites, particularly those of economic interest, are known to display strong development of haloes of rare alkali elements (Li–Rb–Cs), in particular lithium, into country rocks. The use of these haloes in exploration for pegmatites has had apparently little application in an Australian context, where it has the potential to assist exploration undercover by expanding the known ‘footprint’ of these mineral systems. Dispersion haloes have two parts: proximal (typically of centimetres to metres thickness), characterised by visible changes to mineralogy relating to metasomatism, and distal, where there are typically cryptic geochemical changes, but no changes in host mineralogy. Collation of global data have shown that the lithogeochemical haloes of large rare metal pegmatites can extend laterally at least 200 m, with a few localities giving indications extending several kilometres along strike. Lithium displays the largest haloes, with Rb and Cs typically being less extensive; other elements are mostly localised close to the pegmatite wallrock interface. These haloes are more extensive in mafic host rocks than other host-rock types. Mafic host rocks also provide the best geochemical contrast for rare alkali elements. Of the 22 datasets reviewed here, many are simply ‘proof of concept’ studies based on single sample lines and may not have had their outer limits defined. The actual distribution of these haloes is likely to be controlled by anisotropies that control host-rock permeability in the host units, with fluids emanating from the rare metal pegmatites being commonly channelled into structures or exploiting foliation or bedding. Regional-scale structures are likely to control kilometre-scale haloes. Sheet silicates and amphiboles are the most important hosts for these elements, which consequently accumulate in units or structures rich in these minerals. The actual distributions of these elements are, in most cases, likely to be irregular and complex anomalies of varying three-dimensional shapes, and thus ‘vectoring’ based on systematic changes in concentration away from a source should be treated with caution. It is important to note that given anomaly types do not indicate the presence of particular minerals, such as spodumene. The presence of these haloes in Australian Archean cratons is supported by dispersion haloes in saprolite and saprock units in deep weathering profiles and is potentially applicable to lag sampling over near fresh or unweathered host-rock units in exposed terranes.Lithogeochemical haloes of Li–Rb–Cs represent a simple exploration tool that can be readily integrated into exploration workflows by assay of host rock units in proximity to LCT granitic pegmatites.Haloes extend laterally at least 200 m and show indications of kilometre-scale anomalies relating to structurally controlled fluid flow.Haloes are spatially more extensive and show greater geochemical contrast with backgrounds, in mafic host units.These rare alkali haloes may persist into weathered host-rock units such as saprolite in regolith profiles. [ABSTRACT FROM AUTHOR]

Zirconium (Zr) isotope has significant potential for tracing magmatic processes, particularly late-stage fractionation involving fluids. However, the fractionation of Zr isotopes between magma and fluid is still unclear. In-situ Zr isotope analyses of zircons from three granite-pegmatite suites in the Tibetan plateau show a wide range of δ94/90Zr values (IPGP-Zr) between −0.23 ‰ and +1.38 ‰, with the highest values in hydrothermally altered zircons from pegmatites. A coupled dissolution-reprecipitation process of zircons in a zircon-undersaturated melts is the most plausible mechanism to explain the strong enrichment of heavy Zr isotopes in hydrothermally altered zircons. During the formation of granitic pegmatite, exsolution of F-Na-Si-bearing fluids can enhance zircon solubility and will significantly remove Zr from the melt. Faster diffusion of 90Zr into the fluid channel will result in preferential accumulation of light Zr isotopes in the fluid, and drive the residual melt towards heavier Zr isotopes under disequilibrium conditions. Later, the reprecipitated zircons will inherit the heavy Zr isotope composition of the melt. Rayleigh fractionation models suggest fluid-melt fractionation factors for Zr isotope of about 0.99911–0.99930. This shows the major controls of fluid on Zr isotope fractionation during crystal-magma-fluid differentiation. Thus Zr isotope can be a powerful tracer of the magmatic-hydrothermal transition. [ABSTRACT FROM AUTHOR]

Understanding processes that occur during pegmatite crystallization are important for understanding magma evolution and enrichment processes of e.g. strategic and rare metals in pegmatites. Several processes are involved in the formation of pegmatites, and among these the timing of fluid saturation and exsolution is a critical area of investigation. The primary question focuses on if the timing of these processes influences pegmatite crystallization and the concentration of elements. The understanding of the relationship between fluid dynamics and mineralization is essential to develop comprehensive models of pegmatite formation. The unidirectional tourmaline prisms and quartz-tourmaline intergrowths (QTIs), composed of a central tourmaline surrounded by skeletal tourmaline intergrown with quartz are anisotropic textures, linked to disequilibrium crystallization at high degrees of undercooling. This study aims to trace fluid saturation and evolution in the outer zones of internally zoned pegmatites and to provide more accurate temperature constraints for their crystallization, using the Emmons pegmatite (Maine, USA) as a case study. The methodology comprises detailed inclusion petrography, microthermometric analyses, Raman spectroscopy, and LA-ICP-MS analyses. The results indicate that localized fluid saturation occurs early during the magmatic stage of pegmatite crystallization. At this point, the crystallizing mineral assemblages are composed of feldspar, muscovite, quartz, tourmaline, and minor garnet. The exsolved fluid is similar throughout the host tourmalines and is characterized by an H 2 O-NaCl-CO 2 -(N 2 -CH 4) composition. Temperatures, which are obtained from primary fluid inclusion isochores vary between 315 °C and 440 °C and confirm that the pegmatite crystallized at undercooled conditions. A decrease in temperature occurs on a centimeter scale between the central tourmaline and the skeletal tourmaline of the QTIs, which could be caused by a nucleation delay within individual boundary layers that are formed around the central tourmaline of the QTI. The higher concentration of water and other incompatible components, including fluxes, in the boundary layer led to fluid exsolution localized at the crystal-melt interface. The increased concentration of fluxes causes a nucleation delay, increasing the degree of undercooling and consequently leading to the skeletal morphologies seen in the QTIs. Furthermore, studied melt inclusions indicate that a compositionally modified melt was present during tourmaline crystallization, confirming the existence of a boundary layer at centimeter to decimeter scale. [ABSTRACT FROM AUTHOR]

With the advancement of the global economy, the significance of cutting-edge technology and the pre- servation and development of future energy can be decisive in ensuring national energy security, homeland security, and economic development. Dispersed elements play an indispensable role in high-tech industries, but their unique characteristics contribute to their scarcity in the earth's crust and limited reserves. The research on the geochemical behavior of dispersed elements is relatively weak, and there is considerable controversy regarding their metallogenic mechanisms. With the progress of research, it has been found that the anomalous enrichment of dispersed elements shows a strong correlation with granite and pegmatite in both mineralization time and spatial distribution. Nevertheless, different dispersed elements exhibit significantly different geochemical behaviors during the enrichment process. During magmatic evolution, indium is influenced by the content of dark minerals and their iron and magnesium minerals and shows a strong correlation with tin. In the later stages of precipitation, indium enrichment is closely related to sphalerite and its iron and cadmium content. When present in granitic pegmatite, gallium shows a strong correlation with niobium, tantalum, lithium, and rubidium, mainly enriching in muscovite and microcline in pegmatite. In the later stages of magmatic evolution, germanium tends to enrich in highly volatile components but primarily associates with organic mat- ter to form germanium-containing organic compounds or complexes or dynamically recrystallizes in sphalerite to enrich. Tellurium mainly coexists with bismuth. Recently, large quantities of tellurium bismuth compounds have been found in pegmatite and tungsten deposits closely related to granite. The outlook of the research on dispersed element deposits is made, including the relationship between dispersed metals and primary minerals, detailed characterization of the migration and enrichment processes of dispersed metals, and detection technologies for enriched dispersed element deposits. These studies will provide new data and theoretical guidance for the further development and utilization of dispersed metals. [ABSTRACT FROM AUTHOR]

The Barroso–Alvão region is an excellent setting for studying Li mineralization associated with granitic pegmatites and developing Li exploration techniques. Among the distinguished pegmatite types in this pegmatite field, the spodumene-bearing dyke from Alijó is a representative example of an Iberian Li–Cs–Ta (LCT) pegmatite currently under exploitation. In this work, we examine the internal evolution of the Alijó dyke and its external metasomatic effect on the surrounding metasediments, contributing to lithium exploration techniques. Electron microprobe analyses provided clues about the crystallization conditions and the degree of differentiation of the pegmatitic melt, whereas the external metasomatism induced by the spodumene-bearing pegmatite was studied through whole-rock geochemistry. The obtained results indicate that the primary crystallization of the studied dyke likely occurred at temperatures between 450–500 °C, with emplacement at shallow crustal levels of about 2–3 kbar. The high concentrations of trace elements such as Li, Cs, Rb, Be, Sn, Nb, Ta, Ge, U, and Tl in the pegmatitic melt suggests high availability of these elements, allowing their partitioning into an early exsolved fluid phase. The exsolution of this fluid phase, subtracting components such as F and B, from the pegmatitic melt would cause a significant undercooling of the melt. Moreover, the interaction of this expelled fluid with the country rock generated a metasomatic overprint in the surrounding metasedimentary host rocks. The metasomatic effect in Alijó is strongly influenced by the nature of the host metasediments, with a significantly higher grade of metasomatism observed in pelitic (mica-rich) samples compared to psammitic (mica-poor) samples collected at same distances from the dyke. The greisen developed close to the pegmatite contact reflects this metasomatic signature, characterized by the mobilization of at least B, F, Li, Rb, Cs, Sn, Be, Nb, Ta, and Tl. We cautiously suggest that whole rock Li concentrations greater than 300 ppm, combined with a minimum value of 1000 ppm for the sum of B, F, Li, Rb, Cs, and Sn in pelitic metasediments of Barroso–Alvão, may be indicative of a mineralized pegmatite in this region. [ABSTRACT FROM AUTHOR]

The granite pegmatites of Hmrat El Sorwhyia, situated in the northern Egyptian-Nubian Shield, are predominantly hosted within the central areas of syenogranitic bodies, with limited occurrences noted along the marginal sites. The Hmrat El Sorwhyia granitic pegmatites represent a notable example of rare-metal mineralisation. This study introduces novel bulk- rock compositions, including major, trace, and rare earth elements, to investigate and constrain the origin and mechanisms influencing the genesis of the Hmrat El Sorwhyia granitic pegmatites and their rare-metal mineralisation. The studied pegmatites exhibit diverse morphologies, featuring lenticular pockets that contain the highest radioelement concentrations. The maximum (equivalent uranium) eU value is 760 ppm while the maximum (equivalent thorium) eTh value is 5552 ppm. These pegmatites have granitic composition and peraluminous characteristics, indicative of A-type affinity associated with post-collisional tectonic settings, and are categorised as niobium–yttrium–fluorine-type pegmatites. The formation of granite pegmatites through fractional crystallisation during the late-stage magmatic processes involved the concentration of U, Th, rare earth elements, Zr, Y, and Nb. This concentration facilitated the crystallisation of thorite, uranothorite, columbite, cerianite, and zircon. Additionally, assimilation-fractional crystallisation mechanisms led to the exchange of accessory phases between successive injections of pegmatite and the surrounding wallrock, resulting in variable mineral concentrations. These open-system processes were responsible for the development of these pegmatites. [ABSTRACT FROM AUTHOR]

A modified model based on classical nucleation theory was applied to a natural hydrous peraluminous pegmatite composition and tested against crystallization experiments in order to further investigate the quantification of nucleation delay in felsic melts. Crystallization experiments were performed in a piston-cylinder apparatus at 630 MPa and temperatures between 650 and 1000 °C for durations ranging from 0.3 to 211 h. Experimental run products were investigated by scanning electron microscopy paired with energy dispersive spectroscopy analyses of both crystalline and quenched liquid phases, the results of which were compared to an established theoretical nucleation delay model from the literature. The experiments showed good agreement (within a factor of 5) with the model for quartz, while it showed moderate agreement (within a factor of 10) with the model for sodic feldspar. Other crystals also nucleated, demonstrating abundant features of disequilibrium. Our research further demonstrates the potential of the model to predict nucleation delay, showing promising results for the quantification of the nucleation delay of quartz and feldspar in natural felsic melts, thus adding to previously published studies on hydrous, metaluminous, felsic melts and dry basaltic melts. [ABSTRACT FROM AUTHOR]

It is widely accepted that the complexation of Sn with Cl in magmatic-hydrothermal fluids is critical for the formation of endogenic Sn deposits. However, Sn abundance as high as 0.4 wt% has been found in some chlorine-poor but silicate-rich fluid inclusions associated with a Sn-mineralized pegmatite. To examine the role of silicate solutes in Sn mineralization, we measured the solubility of cassiterite in alkaline silicate-rich fluids by direct observation of single crystal cassiterite dissolution in a hydrothermal diamond anvil cell at 540–900 °C and 5.5–13.6 kbar. Experimental results indicated that a significant amount of cassiterite could be dissolved in both Na 2 Si 3 O 7 –H 2 O and Na 3 AlSi 5 O 13 –H 2 O fluids, and SnO 2 solubility was positively correlated with the concentration of silicate solutes, the Na/(Si + Al) ratio of the fluid and temperature. In Na 2 Si 3 O 7 –H 2 O fluids at ∼680 °C with 24 to 45 wt% silicate solute, SnO 2 solubility increased from 0.65 to1.67 wt%. In Na 3 AlSi 5 O 13 –H 2 O fluids at ∼715 °C with 21 to 52 wt% silicate solute, the solubility increased from 0.49 to 1.19 wt%. These values are comparable to cassiterite solubilities in HCl solutions and Li 2 CO 3 solutions, and are much higher than those in NaCl solutions, 0.1 mol/kg NaOH solution, and 14 wt% SiO 2 solution. In situ Raman spectra collected on fluids demonstrated the presence of silicate monomers and oligomers, and the complexation of Sn with these Si-(Al)-Na clusters or with (OH)− could explain the observed high SnO 2 solubility. Comparison with SnO 2 solubility in peraluminous melt suggests that Sn can be significantly enriched in alkaline silicate-rich fluids. Modeling of progressive fluid-melt unmixing successfully reproduces the observed high Sn abundance in silicate-rich fluid inclusions. Alkaline silicate-rich fluids can therefore serve as an effective agent, alternative to chlorine-rich fluids, for Sn mobilization and mineralization, especially in pegmatite systems. [ABSTRACT FROM AUTHOR]

The anisotropic textures, including unidirectional solidification textures and graphic intergrowths, characteristic for pegmatites, are interpreted to result from disequilibrium crystallization at high degrees of undercooling. Experimental studies have revealed the existence of thin boundary layers surrounding the rapidly growing crystals. Here, tourmaline-bearing samples from the outer zones of the Emmons pegmatite (Maine, U.S.A.) are used to examine if a boundary layer can also occur in natural samples. Crystal morphology is linked with geochemistry to understand the evolution of pegmatite melts and to constrain disequilibrium conditions at large degrees of undercooling. Petrographic studies and semiquantitative micro-X-ray fluorescence element mapping were conducted to identify crystal morphology and zonation, complemented with electron microprobe analyses to determine major and minor element compositions and LA-ICP-MS analyses of selected trace elements. Three textural groups were identified: comb-like tourmaline, quartz-tourmaline intergrowths, and radiating tourmaline. The intergrowths are optically coherent and are split into three different morphologies: central, second tier, and skeletal tourmaline. Most tourmaline is schorl, but chemical variation occurs on three different scales: between textural groups, between different morphologies, and intracrystalline. The largest scale geochemical variation is caused by the progressive evolution of the melt as it crystallized from the borders inwards, while the intracrystalline variations are attributed to sector zoning. A model is suggested where the systematic variation of Mg, Mn, and Fe within individual intergrowths is proposed to be the result of crystallization from a boundary layer, rich in water and other fluxing elements (e.g., Li, P, B), formed around the rapidly growing central tourmaline. Here, we show the first examples of boundary layers in natural pegmatites. Furthermore, the results bring into question whether boundary layer tourmaline can be used as a bulk melt indicator in pegmatitic melts. [ABSTRACT FROM AUTHOR]

The energy transition challenges faced by modern civilization have significantly enhanced the demand for critical metals like lithium resulting in improved methods to explore, extract, and utilize these metals. In this comprehensive review, we discuss the different types of lithium resources, factors, and mechanisms controlling lithium enrichment in various geological settings including terrestrial and marine environments. Diverse exploration strategies including geological, geophysical, mineralogical, geochemical, and remote sensing techniques including drone-based techniques for lithium exploration studies in different terranes are summarized. An overview of the mining techniques, including beneficiation and extraction, and their principles, mechanisms, operations, and comparison of the various approaches and compatibility with different types of lithium deposits for obtaining maximum yield are evaluated. Lithium isotopic studies are useful in understanding geological processes such as past weathering events and riverine input into the oceans, as well as in understanding the source of lithium in diverse types of deposits. We also highlight the recent developments in other areas such as recycling, environmental impact, and state-of-the-art analytical techniques for determining lithium in different lithium ore deposits and other geological materials. Our overview provides the latest developments and insights in the various sectors related to lithium and prompt further developments to meet the growing demand for this valuable metal as the world transforms to clean energy.

Kaolin (mainly composed of kaolinite, whose chemical formula is Al2Si2O5(OH)4), serves as a versatile raw material widely used in various industries including production of ceramics, paper, paints, cosmetics, pneumatics, building materials, and hazardous waste storage. In the northern part of Vietnam, due to favorable geological conditions, there are diverse deposits of high quality kaolin of different origin and scale. Decades of research indicate the diversity of kaolin sources in the region, with special attention paid to hydrothermally altered and exchange types of kaolin, the formation of which is associated with complex processes of weathering, hydrothermal alteration and reprecipitation. The aim of this study was to characterize three different types of kaolin derived from different sources in Northern Vietnam (from weathered pegmatites, weathered felsic effusives, and hydrothermal-metasomatic altered rocks). The main focus was to analyze the thermal behavior of these samples during calcination in the temperature range from 300 °C to 1,100 °C. The comprehensive characterization was performed by X-ray diffraction (XRD), FT-IR spectroscopy (FT-IR), thermal analysis (thermogravimetry / differential thermogravimetry (TG / DTG)) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The results showed that kaolinite with particle size less than 2 μm was identified in all samples. Minor amounts of muscovite and montmorillonite are present in some samples, and pyrophyllite is present in a sample from the hydrothermally altered rocks. Kaolinite morphology in all the samples showed typical forms including hexagonal and pseudohexagonal. The main chemical constituents of the samples are SiO2 and Al2O3; in addition to these, K2O + Na2O, TiO2 and iron are present in smaller quantities. Thermal analysis allowed to reveal the formation of metakaolinite phase at temperatures around 494 °C and 507 °C in the two studied samples from weathered rocks, while the pyrophyllite-bearing sample undergoes this transition at a higher temperature of 653.8 °C. The onset of metakaolinization was observed at about 500 °C for the weathered rock samples and about 700 °C for the pyrophyllite-bearing sample. In addition, mullitization leading to the formation of mullite was evident at 1,100 °C. The study findings allow concluding that the studied kaolins can be used in traditional ceramics production.

Investigation on the occurrence of magnetite ore minerals in Emure – Ekiti, Southwestern Nigeria was carried out by integrating magnetic and very low frequency electromagnetic (VLF-EM) methods on the suspicion that the major part of the magnetite ore being sought lies in the subsurface. Eight traverses in total were established with five traverses occupied in the northeast–southwest direction and the other three in the northwest–southeast direction. Six traverses were established across the exposed part of the pegmatite (magnetite) veins to serve as a control. Inter-station spacing of 1 m was chosen, so as not to miss any significant ore occurrence. The VLF-EM profile is a plot of the real and filtered real components. The KH-filter geophysical software was used to invert real data into a two-dimensional subsurface map that revealed variations in conductivity. The results of the geophysical interpretation for both methods indicate anomalous signatures observed on the exposed section of the pegmatitic veins, which are indicative of magnetite ore. These anomalous signatures align with certain zones along the Tr4 and Tr8 transects. Some of the high magnetic anomalies observed on traverse 5, 6, and 7 coincide with low conductivity suggesting the concentration of minerals such as quartz, microcline, plagioclase, and biotite, which are commonly associated with magnetite. The study has not only enhanced the mapping of the subsurface characterisation of the deposit but also confirms the reliability and suitability of using magnetics and VLF-EM geophysical methods for mapping magnetite deposits. [ABSTRACT FROM AUTHOR]

This study has investigated the effect of particle size of non-plastic components of quartz and pegmatite on some technological properties of wall tile bodies. For this, quartz-pegmatite mixtures were further milled up to 90 min. before adding into the body composition unlike the standard body composition, where quartz and pegmatite were used as-received. The physical and mechanical properties of the bodies were investigated and compared with the standard values. Thermal expansion coefficient and moisture expansion values were determined by a dilatometer. Phase analyses were carried out by X-ray diffraction and microstructural characteristics were studied using a scanning electron microscope. Changes in various technological properties with reducing particle size of the non-plastic components were reported, particularly the increased green and fired strength. It was discussed that using finer particle size non-plastic raw materials of quartz and pegmatite would enable not only increased industrial productivity but also increased producibility of thinner large format wall tiles. [ABSTRACT FROM AUTHOR]

Bimbowrieite, NaMgFe3+5(PO4)4(OH)6⋅2H2O, is a new mineral found in a mineralogically zoned rare-element bearing pegmatite at the White Rock No.2 quarry, Bimbowrie Conservation Park, South Australia, Australia. Crystals are dark olive green to greenish brown and are bladed with dimensions of up to 150 μm. Crystals occur as aggregates up to 0.4 mm across associated with ushkovite, bermanite, leucophosphite and sellaite. Bimbowrieite is pleochroic, biaxial (+), with α = 1.785(5), β = 1.795(5), γ = 1.805(5) and 2V(meas.) = 89.4(5)°. The average of 28 chemical analyses gave the empirical formula: (Na0.81Ca0.19)Σ1.00(Mg0.75Mn2+0.19Fe2+0.05)Σ0.99(Fe3+4.99Al0.01)Σ5.00(PO4)3.97(OH)5.88⋅2.05 H2O based on 24 oxygen atoms. Bimbowrieite is monoclinic, space group C 2/c with a = 25.944(5), b = 5.1426(10), c = 13.870(3 Å, β = 111.60(3)°, V = 1720.4(7) Å3 and Z = 4. The crystal structure was refined to R 1 = 1.97% for 1060 observed reflections with F 0 > 4σ(F 0). Bimbowrieite is isostructural with dufrénite. The structure is based on a trimer of face-sharing octahedra in which an M 2 octahedra shares two trans faces with two M 4 octahedra. Trimers link in the c -direction by sharing corners with two M 3 octahedra and with T 1 and T 2 tetrahedra. Linkage in the a -direction is via corner-sharing M 1 octahedra and linkage in the b -direction is via corner-sharing T 1 and T 2 tetrahedra. [ABSTRACT FROM AUTHOR]

Prydz Bay is an important part of the Pan-African high-grade tectonic mobile belt. The focus of this investigation, by applying zircon LA-ICP-MS U-Pb geochronology, zircon Lu-Hf isotope systematics, and whole-rock geochemistry, is on Pan-African pegmatites in the Larsemann Hills of Prydz Bay, East Antarctica, their association with country rocks, and the formation conditions. Based on the obtained results, it is concluded that the pegmatites exhibit elevated levels of silica and alkali and possess peraluminous features. These pegmatites originated during the late Neoproterozoic–Early Cambrian (Pan-African) event, specifically in the D2–D4 stages. The D2 stage occurred between 546 and 562 Ma, followed by D3-stage pegmatites around 534 Ma. The pegmatites from the D2–D3 stages are considered to originate from Paleoproterozoic crustal materials, while there are at least two phases of pegmatites in the D4 stage (~517 Ma and ~521 Ma). The D4-1 pegmatite (~521 Ma) suggested both Paleo–Mesoproterozoic crustal origin, perhaps connected to extension. The D4-2 pegmatite (~517 Ma) originated from the crust layers. In the Larsemann Hills, Pan-African pegmatites formed in a recurring regime of tension. Therefore, the obtained data elucidate that a Pan-African stretching process might have occurred in Prydz Bay. [ABSTRACT FROM AUTHOR]

In the county of Pedra Lavrada – PB, various mineral occurrences of pegmatite are observed with prominence at Alto Dois Irmãos – PB, where quartz, feldspar and mica are mined. The understanding of mineral constituents is fundamental to define their industrial employment and to implement improvements in the beneficiation process. The proposal of this research is the detailed characterization and proof of that part of the ore (quartz) considered waste, presenting low poisoning (Fe2 O3 ) and high silica (SiO2) content, to enable its industrial use. Besides that, to minimize the environmental impact through the reuse of this waste, and to determine the correct utilization of the milling equipment. For the pegmatite characterization, done were density determination tests, mineralogical identification by X-ray diffraction (XRD), chemical analysis by fluorescents X-rays and morphological analysis by scanning electron microscopy (SEM/EDS). Then tests were done for the Work Index (WI) calculous and consequently the empirical determination of the dimensions (LxD) of the pebble mill. The sterile presented a medium density of 2.66g/cm³, majority chemical composition of silicon and oxygen and quartz as the main mineralogical stage, indicating that this material has high purity. The. The Work Index (WI) was 15.9 kwh/t showing that this material can be considered resistant to breaking in the grinding process. The necessary energy to the milling was defined in 11.52 kwh/st, that corresponds to 57.28 HP. This power allowed the mill selection with diammeter and length of 1.83m, that provides the production maximization and the energy saving. [ABSTRACT FROM AUTHOR]

In this paper we present textural and compositional data for columbite group minerals (CGMs) and associated Nb-Ta-Sn oxides from lithium-beryllium-tantalum pegmatite deposits of the Kolmozero–Voronja belt, NW Russia, with the aim of deciphering these characteristics for minerals from deposits with different mineral signatures and lithium ore grade. Minerals from four deposits, including two of world-class (Kolmozero and Polmostundra), are examined. The main controlling factors for CGM compositional ranges are the diversity and rate of magmatic fractionation, hydrothermal overprint and mineral paragenesis, following the specific geochemical signature of the different pegmatite deposits. CGM from Kolmozero include several mineral species (columbite-(Fe), columbite-(Mn), tantalite-(Fe), and tantalite-(Mn)), showing large compositional variations, mainly controlled by Nb-Ta fractionation (Ta/(Ta + Nb) = 0.16–0.70; Mn/(Mn + Fe) = 0.45–0.63). Textural patterns are various (oscillatory, homogeneous, and patchy); spongy domains and overgrowing Ta-rich rims are also observed somewhere. This indicates the involvement of numerous magmatic and hydrothermal processes. The Polmostundra CGMs are represented by columbite-(Fe) with Ta/(Ta + Nb), ranging from 0.05 to 0.39; some crystals are homogenous, and others present normal, oscillatory, mottled and reverse-zoning patterns. The Okhmylk CGMs are irregular normal, patchy and homogeneous columbite-(Fe) and columbite-(Mn), with Ta/(Ta + Nb) = 0.09–0.24 and Mn/(Mn + Fe) = 0.29–0.92, indicating the suppressed magmatic fractionation and iron drop due to precipitation of Fe minerals. Columbite-(Fe) and columbite-(Mn) from the Be-Ta Shongui deposit are less evolved, with Ta/(Ta + Nb) = 0.07–0.23 and Mn/(Mn + Fe) = 0.31–0.55. The minerals are characterized by progressive normal, oscillatory, homogeneous and irregular reverse patterns. Associated pyrochlore minerals occur both as early magmatic (Kolmozero) and late hydrothermal (Polmostundra, Okhmylk). Cassiterite is found only in the Okhmylk dykes, and is apparently of hydrothermal origin. CGM from Li pegmatites have impurities of Ti (0.01–0.05 apfu) and W (up to 0.02 apfu), whereas CGM from Be pegmatites contains elevated Ti (up to 0.09 apfu). The mineral system analysis presented here is relevant for exploration. [ABSTRACT FROM AUTHOR]

The global need for lithium (Li) is increasing due to its use in batteries which are used to make electric vehicles, wind turbines and fuel cells to facilitate the world’s ‘green transition’ to low carbon economies. The mining of Li, like that of other Earth materials, produces large volumes of waste such as tailings and processing chemicals. A growing body of research is addressing the resource potential and environmental impacts of wastes from mining of Li-bearing granites and pegmatites that produce around 40% of the world’s Li. The wastes are dominated by SiO2 and Al2O3, with lesser Na2O, K2O and Fe2O3, that are hosted in quartz, feldspar and micas. They can contain around 1 wt% Li2O that is found in residual spodumene, lepidolite and zinnwaldite, and trace (

Abstract In the county of Pedra Lavrada - PB, various mineral occurrences of pegmatite are observed with prominence at Alto Dois Irmãos - PB, where quartz, feldspar and mica are mined. The understanding of mineral constituents is fundamental to define their industrial employment and to implement improvements in the beneficiation process. The proposal of this research is the detailed characterization and proof of that part of the ore (quartz) considered waste, presenting low poisoning (Fe2O3) and high silica (SiO2) content, to enable its industrial use. Besides that, to minimize the environmental impact through the reuse of this waste, and to determine the correct utilization of the milling equipment. For the pegmatite characterization, done were density determination tests, mineralogical identification by X-ray diffraction (XRD), chemical analysis by fluorescents X-rays and morphological analysis by scanning electron microscopy (SEM/EDS). Then tests were done for the Work Index (WI) calculous and consequently the empirical determination of the dimensions (LxD) of the pebble mill. The sterile presented a medium density of 2.66g/cm³, majority chemical composition of silicon and oxygen and quartz as the main mineralogical stage, indicating that this material has high purity. The. The Work Index (WI) was 15.9 kwh/t showing that this material can be considered resistant to breaking in the grinding process. The necessary energy to the milling was defined in 11.52 kwh/st, that corresponds to 57.28 HP. This power allowed the mill selection with diammeter and length of 1.83m, that provides the production maximization and the energy saving.

Pegmatite (sample 13/10) exposed in the valley of the Berezivka River (Krynychuvatka village) was studied and its isotopic age was determined by monazite. Granitoids of the Krynichuvatsky massif differ from other granitoids of the Kirovohrad complex in their petrographic composition (mainly plagioclase, plagioclase-microcline), structural (aplitoid, pegmatoid inclusions) and texture (in some areas, aplitoid granites are characterized by linearly oriented grains of lamellar (lenticular) quartz, elongated feldspar crystals) and the composition of xenoliths (amphibolites, amphibole-biotite, biotite, pyroxene-biotite gneisses). To find out the time and duration of the formation of granites of the massif using the uranium-lead isotope method, we determined the age of the monazite of the apilito-pegmatoid granite (sample 12/10) — 2039.9±1.4 Ma. The age of the vein body of the pegmatite (sample 13/10) has now been determined that is widespread above the dam on the right side of the stream, the left tributary of the Berezivka River, village Krynychuvatka. Monazite occurs mainly as large (> 0.1 mm) diskshaped crystals with well-developed pinacoid facets and, in individual grains, several other facets and even ribs. The crystals are yellow, honey yellow to honey transparent and translucent. Light-yellow, water-transparent crystals with an even, smooth, shiny surface and rounded contours are present singly. Considering the fact that the main mass of granites (aplito-pegmatoid granites) exposed in the valley of the Berezivka River (Krynychuvatka village) are 2039.9±1.4 Ma, and the vein body of peg9 matite that dissects the granite was formed in 2029.1± 3.4 Ma, it can be assumed with a high probability that the Krynichuvatsky massif was formed for at least 10 million years, in the age interval of 2040—2030 Ma ago.

The Barroso–Alvão region is an excellent setting for studying Li mineralization associated with granitic pegmatites and developing Li exploration techniques. Among the distinguished pegmatite types in this pegmatite field, the spodumene-bearing dyke from Alijó is a representative example of an Iberian Li–Cs–Ta (LCT) pegmatite currently under exploitation. In this work, we examine the internal evolution of the Alijó dyke and its external metasomatic effect on the surrounding metasediments, contributing to lithium exploration techniques. Electron microprobe analyses provided clues about the crystallization conditions and the degree of differentiation of the pegmatitic melt, whereas the external metasomatism induced by the spodumene-bearing pegmatite was studied through whole-rock geochemistry. The obtained results indicate that the primary crystallization of the studied dyke likely occurred at temperatures between 450–500 °C, with emplacement at shallow crustal levels of about 2–3 kbar. The high concentrations of trace elements such as Li, Cs, Rb, Be, Sn, Nb, Ta, Ge, U, and Tl in the pegmatitic melt suggests high availability of these elements, allowing their partitioning into an early exsolved fluid phase. The exsolution of this fluid phase, subtracting components such as F and B, from the pegmatitic melt would cause a significant undercooling of the melt. Moreover, the interaction of this expelled fluid with the country rock generated a metasomatic overprint in the surrounding metasedimentary host rocks. The metasomatic effect in Alijó is strongly influenced by the nature of the host metasediments, with a significantly higher grade of metasomatism observed in pelitic (mica-rich) samples compared to psammitic (mica-poor) samples collected at same distances from the dyke. The greisen developed close to the pegmatite contact reflects this metasomatic signature, characterized by the mobilization of at least B, F, Li, Rb, Cs, Sn, Be, Nb, Ta, and Tl. We cautiously suggest that whole rock Li concentrations greater than 300 ppm, combined with a minimum value of 1000 ppm for the sum of B, F, Li, Rb, Cs, and Sn in pelitic metasediments of Barroso–Alvão, may be indicative of a mineralized pegmatite in this region.

This paper examines the potential use of pegmatite and marble as additives in amalgamation with Meiganga kaolin to produce stoneware products capable to resist high temperatures as well as enhancement the mechanical characteristics. Two series of ceramic products were formulated by partly replacing kaolin with 0, 3, 5 and 7 wt% of both pegmatite and marble wastes. The specimens were sintered at 1000°C, 1050°C and 1100°C. Fired ceramic samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and the microstructure of the products was determined using an environmental scanning electron microscope and energy-dispersive X-ray spectroscopy. Also, the physico-mechanical properties were evaluated. Results divulged that, the addition of pegmatite or marble to kaolin enhances the strength of the ceramic body and act as a fluxing agent by promoting vitrification and glassy phase in clay after firing. The highest flexural strength results were observed with 7 wt% of pegmatite added at 1100 °C, with an increase - 35% compared to the control sample. High silica and alumina contents in pegmatite fill in voids, providing densification matrices. The incorporation of pegmatite allows to obtain a ceramic with better mechanical properties and energy saving as compared by the conventional ceramic. [ABSTRACT FROM AUTHOR]

The Kenticha pegmatite field comprises suites of barren to fertile pegmatite swarms. It shows textural, mineralogical, and geochemical variations. The pegmatites are structurally controlled and emplaced in mafic–ultramafic belts during the Neoproterozoic. This study aims to constrain the genetic and tectonic setting of the Kenticha rare-metal (RM) pegmatite and the associated granite. The presence of minerals such as biotite, muscovite, spodumene, spessartine-almandine garnet, gahnite, beryl, tourmaline, cordierite, and topaz indicate the peraluminous nature of the granite and associated pegmatites. The Kenticha rare-metal granite-pegmatite shows ASI > 1.1, low V, Y, very low Sr, Ba, Th, Zr and REE, very high Be, Li, Rb, Cs, Ga, Nb, and Ta than the upper continental crust. The parental two-mica granite has higher Co, Rb, Ba, and Ce and lower V, Zr, Y, Nb, Ni, La, Pb, Sr, and Th than the upper continental crust. The Ta/Nb value in the two-mica granite is nearly equal to the average upper crustal value. In both parental granite and pegmatites, the normative corundum (C) is greater than 1%. The P2O5 content is low in the assumed parental granite. However, in the main ore body, the P2O5 content increases towards the more fractionated pegmatite. Due to its peraluminous character and high content of Be, Cs, Li, Ta, and Rb, we can categorise the granite-pegmatite under the LCT subclass of the rare-element pegmatite. It's associated with S-type granite. HFSE and LIL elements show characteristics of bulk continental crust composition and syn-collisional felsic magmatism. Biotite composition suggests partial melting of the metasedimentary protolith as the source of the two-mica granite. The plots of Y vs. SO2, P2O5 vs. SiO2, % normative C vs. Rb, Y vs. Rb, and Th vs. Rb support the S-type magma source. Geochemical and mineralogical data show a nearly vertical evolutional trend of the granite-pegmatite. It varies from the basal granitic unit to the pegmatite core unit. The mineralization of rare metals in the granite-pegmatite was mainly controlled by genetic (processes). [ABSTRACT FROM AUTHOR]

Background. One of the directions for recycling industrial waste is the use of ironcontaining dust from gas purification for the preparation of ceramic masses in order to obtain facing slabs. Purpose. Study of the properties of iron-containing waste - gas purification dust in metallurgy, development of ceramic compositions for facing slabs. Methodology. Methods of chemical and x-ray phase analysis were used. The physical and mechanical indicator is determined according to GOST 6141-91 and O'zSt 823-97. Originality. The possibility of introducing 5-25% iron-containing waste into the composition of the ceramic mass of facing slabs - dust from gas purification of metallurgical industries, due to sintering and recrystallization, with the formation of minerals -hematite--Fe2O3, α-hematite α-Fe2O3, partially wustite FeO, fayalite Fe2SiO4, quartz SiO2 and pyrite FeS2. Findings. The chemical and mineralogical composition of gas purification dust has been determined. It was revealed that the introduction of 5-25% of it has a positive effect on the intensification of sintering and the physical and mechanical properties of ceramics. [ABSTRACT FROM AUTHOR]

Drilled cores of Macusani green obsidian pebbles from Peru were hydrated and melted above their liquidus temperatures at 200 MPa to a single column ~4 cm in length and then undercooled in a thermal gradient >150 °C along the length of the cores. Despite thousands of hours at subliquidus temperatures, the crystallinity of the products ranged from ~30 to ~5 vol%. Mineral assemblages varied along the length of the cores but not in relation to the thermal gradients in all cases. Oscillations in the abundances of plagioclase, K-feldspar, and quartz were observed across the crystallization fronts and along the lengths of the cores. The originally homogeneous melts became heterogeneous in response to crystallization and to thermal gradients. Chemical gradients in the glasses included sharp boundary layer pile-up of F and B adjacent to the crystallization fronts, as well as linear gradients among several of the elements spanning the entire lengths of the melt columns. Values of molar K/(K+Na) in the glasses, plotted as K*, varied positively with Si, inversely with Al and F, and positively with the domains of K-feldspar that formed at maximum distance from the plagioclase-rich regions. Overall, the results are marked by sharply bounded textural domains, by the spatial segregation of mineral assemblages, by oscillations in mineral assemblages at multiple scales, and by monomineralic crystal aggregates that are hallmarks of pegmatite bodies. Temperatures recorded by feldspars closely approached the actual temperature gradient down to ~500 °C, and the solvus on the alkali feldspar join has been delineated for the first time by the simultaneous crystallization of feldspars from an undercooled melt. [ABSTRACT FROM AUTHOR]

Most recent studies consider the formation of individual pegmatite bodies to be a fast process with estimated crystal growth rates reaching a walloping 10 m/day. This opinion is presumably underpinned by the traditional way of thinking of them as the end products of magmatic fractionation. Indeed, modelling has shown that if a pegmatite-forming substance with a temperature near granitic solidus intrudes into a much colder host rock, as recorded in some outcrops, it must cool rapidly. From here, a conclusion is made that the crystallisation must likewise be rapid. However, this view is challenged by several studies that published isotopic dates supported by petrological characterisation of the analysed materials, which suggested or can be used to suggest that some minerals in pegmatites grew over millions of years. Surprisingly, such in-depth work on the geochronology of individual pegmatite bodies is relatively uncommon, so it is early to make generalisations. Here, I highlight some of the existing evidence with the aim to stimulate further research into the timescales of pegmatite crystallisation, including the use of petrologically constrained isotopic dating. [ABSTRACT FROM AUTHOR]

We developed new methodologies for the quantitative determination of lithium in lithium-bearing silicate minerals and clays. This research describes direct analysis of Li in powder using an atomic-emission complex for spectrum analysis "PGS-DDP-BAES" and sintering as a sample preparation technique followed by ICP-OES analysis. A new atomicemission complex for spectrum analysis could be used to efficiently overcome the complex matrix effects, and thus allows for the direct quantitative determination of lithium in solid samples (ores, clays). The relative standard deviation is up to 7.0%. For the extraction of Li from silicate ores and clays by sintering various parameters including sintering temperature, reaction time and additives were studied. The results indicate that the optimal temperature for sintering with NH4 Cl and CaCO3 is at around 900°C. Optimum conditions for lithium extraction were found to be 300 °C (30 min) and 900 °C (60 min), at mass ratios of an ore : NH4Cl :CaCO3 of 1 : 1 : 8. In these conditions a lithium extraction degree of 92% is reached. Relative standard deviations for the method with sintering and ICP-OES analysis vary in the interval from 1.7 to 2.2%. [ABSTRACT FROM AUTHOR]

A modified model based on classical nucleation theory was applied to a natural hydrous peraluminous pegmatite composition and tested against crystallization experiments in order to further investigate the quantification of nucleation delay in felsic melts. Crystallization experiments were performed in a piston-cylinder apparatus at 630 MPa and temperatures between 650 and 1000 °C for durations ranging from 0.3 to 211 h. Experimental run products were investigated by scanning electron microscopy paired with energy dispersive spectroscopy analyses of both crystalline and quenched liquid phases, the results of which were compared to an established theoretical nucleation delay model from the literature. The experiments showed good agreement (within a factor of 5) with the model for quartz, while it showed moderate agreement (within a factor of 10) with the model for sodic feldspar. Other crystals also nucleated, demonstrating abundant features of disequilibrium. Our research further demonstrates the potential of the model to predict nucleation delay, showing promising results for the quantification of the nucleation delay of quartz and feldspar in natural felsic melts, thus adding to previously published studies on hydrous, metaluminous, felsic melts and dry basaltic melts.

Pegmatites and granitic intrusives from eastern Colombia, belonging to the Guainía department, were studied to determine the generating magma type, as well as to assess the degree of magmatic fractionation and its relationship with the presence of Nb-Ta-bearing minerals (strategic minerals). To that end, 31 rock samples were studied; EPMA electronic microprobe analyses were conducted on apatite, biotite, garnet, microcline, muscovite, and tourmaline. The results from biotite, garnet, and tourmaline suggest that these rocks originated from a Fe-rich peraluminous melt. Moreover, content variation of Ba in microcline, Na in muscovite, Fe-Mg in biotite, and Mn-Sr in apatite, allowed the proposal of a magmatic evolutionary line for these rocks. Nb-Ta-bearing samples were present in the most fractionated rocks where tourmaline and garnet occurred, and thus, were proposed as possible indicators of strategic minerals. [ABSTRACT FROM AUTHOR]

Rare-element pegmatites are the crystallization product of melts strongly enriched in incompatible elements. Some of these elements, e.g., Li, B, P, F, and H 2 O, function as melt structure modifiers, allowing such melts to reach unusually low crystallization temperatures and regulating the saturation of aqueous-carbonic fluids from the melt. However, the timing of fluid saturation is highly debated, and the processes that mark the magmatic-hydrothermal transition in rare-element pegmatites are still elusive. The crystallization sequence of phosphate minerals can be used to assess the timing and nature of fluid-related processes in pegmatitic systems. In the Buranga pegmatite, western Rwanda, magmatic phosphates are replaced by (hydrous) alkali-rich phosphates and later by strongly hydrated phosphates as the dike cools. This reaction series indicates a disequilibrium in the crystal-melt-fluid system and records complex fluid-rock interactions during dike consolidation. This contribution compares these interactions with the fluid record preserved in fluid inclusions in the main phosphates of the crystallization sequence. Three major fluid inclusion types are observed, aqueous-carbonic (mostly-two-phase, L-V), carbonic-aqueous (two-phase, V-L, or three-phase, L-L-V), and crystal-rich inclusions (multiphase, L-V-Solids). Crystal-rich fluid inclusions in trolleite [Al 4 (PO 4) 3 (OH) 3 ], the last primary phosphate to precipitate from the melt, show a paragenesis of solid phases similar to the secondary phosphates observed in the dike. LA-ICPMS analyses of individual fluid inclusions show high concentrations of Na and K, with some content of Li, Rb, Cs, B, Fe, and Mn in the fluid. A similar composition is present in all inclusion types within the same mineral. Crystal-rich fluid inclusions demonstrate that during the magmatic-hydrothermal transition, primary phosphates react with the fluid in the presence of melt to generate secondary phosphates. No evidence of external fluid sources has been observed during the magmatic-hydrothermal transition. The fluid inclusion record shows that the fluid salinity is kept constant due to fluid-mineral interactions and corroborates the hypothesis that fluid-soluble elements are internally remobilized in the melt-crystal-fluid system during the magmatic-hydrothermal stage. These interpretations have implications for the general evolution of P-rich pegmatitic melts and the mineralization of Nb and Ta in these systems. [ABSTRACT FROM AUTHOR]

Large pegmatite body/bodies are outcropping in the "Suhata Reka" quarry, near the town of Rakitovo. Their bulk mineral composition with dominant K-feldspar (40%), plagioclase (30%), quartz (25%) and mica (≤ 5%) is complemented by (REE+Y)-bearing association of primary and secondary accessories. Zircon, monazite, xenotime, scarce apatite and noticeable amount of garnet are among the pegmatite primary minerals. The cm-sized almandinespessartine crystals contain numerous fractures which host secondary (REE+Y)-bearing phosphate (xenotime, cheralite) and silicate minerals (e.g. REE-epidote). Formation of the late-stage REE-mineralization in garnet is due to its hydrothermal alteration and redistribution of REE+Y in the secondary phases. [ABSTRACT FROM AUTHOR]

Lithium (Li) has grown to be a strategic key metal due to the enormous demand for the development of new energy industries over the world. As one of the most significant sources of Li resources, pegmatite-type Li deposits hold a large share of the mining market. In recent years, several large and super-large spodumene (Spd)-rich pegmatite deposits have been discovered successively in the Hoh-Xil–Songpan-Garzê (HXSG) orogenic belt of the northern Tibetan Plateau, indicative of the great Li prospecting potential of this belt. Hyperspectral remote sensing (HRS), as a rapidly developing exploration technology, is especially sensitive to the identification of alteration minerals, and has made important breakthroughs in porphyry copper deposit exploration. However, due to the small width of the pegmatite dykes and the lack of typical alteration zones, the ability of HRS in the exploration of Li-rich pegmatite deposits remains to be explored. In this study, Li-rich pegmatite anomalies were directly extracted from ZY1-02D hyperspectral imagery in the Zhawulong (ZWL) area of western Sichuan, China, using target detection techniques including Adaptive Cosine Estimator (ACE), Constrained Energy Minimization (CEM), Spectral Angle Mapper (SAM), and SAM with BandMax (SAMBM). Further, the Li-rich anomalies were superimposed with the distribution of pegmatite dykes delineated based on GF-2 high-resolution imagery. Our final results accurately identified the known range of Spd pegmatite dykes and further predicted two new exploration target areas. The approaches used in this study could be easily extended to other potential mineralization areas to discover new rare metal pegmatite deposits on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The Dorchap Dyke Swarm hosts the first recorded occurrence of lithium–caesium–tantalum (LCT) pegmatites in Victoria, Australia. Syn-orogenic emplacement of pegmatite dykes occurred along a northwest-trending shear system during the Benambran Orogeny. Pegmatites are derived from fractionated melt associated with the Mount Wills Granite, which is an S-type, peraluminous granite originating from supracrustal melting of Ordovician sedimentary sequences. A distinct, eastward-oriented fractionation trend across the Dorchap Dyke Swarm has highlighted a 20 × 8 km highly fractionated zone in the northeastern Dorchap Range, which includes spodumene- and petalite-bearing pegmatites. A distinct pattern of elemental enrichment (P > Cs > Be > Nb ≥ Ta > Li > Sn) is observed across the strongly fractionated zone of the Dorchap Dyke Swarm. Subsequent metasomatic fluid movements and hydrothermal overprinting have resulted in redistribution of mobile elements in the Dorchap Range, either as hydrothermal alteration species or in some instances as the development of exomorphic halos. Additionally, a regional alteration overprint, likely associated with subsequent metamorphism of pegmatite dykes has resulted in alteration of primary petalite to spodumene plus quartz, and primary spodumene to cookeite. Bulk rock geochemical data from the Dorchap Dyke Swarm suggest a syn-collisional setting for dyke intrusion, consistent with the inferred tectonic setting of the central Lachlan Fold Belt at the time of pegmatite emplacement. Pegmatite dykes locally contain an overprinted structural foliation, which is consistent with the primary structural trend of deformed metasediments and may indicate that dyke emplacement was syngenetic with regional folding and compression of the surrounding Omeo Metamorphic Complex during the Benambran Orogeny. Subsequent hydrothermal alteration of some dykes likely occurred immediately following the Bindian Orogeny. Dorchap Dyke Swarm are the first recorded Li–Cs–Ta pegmatites in Victoria, Australia. Pegmatites were emplaced synchronous with or immediately following the Benambran Orogeny. Dorchap Dyke Swarm pegmatites are geochemically correlated with the Mount Wills Granite. [ABSTRACT FROM AUTHOR]

The Huayangchuan uranium deposit, located in the west of the Xiaoqinling belt on the southern margin of the North China Craton, is a large U–Nb–Pb deposit accompanied with rare–earth elements. The Huayangchuan uranium deposit, discovered in the 1950s, has long been known as a carbonatite–type uranium deposit. Recently, new geological work has found uranium mineralization in many granitic pegmatite veins in the Huayangchuan deposit and adjacent areas. Here, we report a systematic investigation of the petrography, whole–rock geochemistry, zircon U–Pb ages, and in situ Lu–Hf isotopic characteristics of newly discovered U–rich granitic pegmatite veins in the west of Huayangchuan deposit. The petrological results showed that the lithology of the samples is granite pegmatite. The U–Pb ages of zircon were 1826.3 ± 7.9 and 1829 ± 11 Ma. Microscopically, the paragenetic characteristics of zircon, betafite, and uraninite exist in the intergranular fissures of K–feldspar and quartz, reflecting metallogenic phenomena in the rock formation process. Almost all whole–rock samples were rich in SiO2 (64.37−70.69 wt.%), total alkalis (K2O + Na2O = 8.50–10.30 wt.%), and Al2O3 (12.20–14.41 wt.%) but poor in TiO2 (0.23–0.73 wt.%), MgO (0.38–0.90 wt.%), CaO (1.23–2.22 wt.%), P2O5 (0.14–0.83 wt.%), and MnO (0.04–0.57 wt.%). Additionally, they showed enrichment of LILEs (such as Rb, Ba, Th, U, and K), depletion of HFSEs (such as Ta, P, Ti, and Hf), and no alkaline dark minerals, and the characteristics are intraplate A1–type granite. The A1–type granite displayed low zircon εHf(t) values (−19.42–−15.02) with zircon two–stage Hf model aged 3.10–2.76 Ga, indicating that the U–rich granitic pegmatite was derived predominantly from partial melting of the ancient continental crust (such as the early Taihua group formed in Archean–Neoarchean). Combined with the above results and regional geological data, the U–rich granitic pegmatite discovered in the Huayangchuan deposit was formed in a post–collisional regime after the Luliang movement in the late Paleoproterozoic. This study suggests that future uranium prospecting work in this area should focus on late Paleoproterozoic U–rich granitic pegmatites. [ABSTRACT FROM AUTHOR]

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The petrogenesis of regionally zoned granitic pegmatite veins remains debated. Because of the economic significance, we carried out a study on the Chakabeishan (CKBS) pegmatite-type Li-Be deposit, eastern North Qaidam Tectonic Belt, Northern Tibetan Plateau, by means of in-situ major element and B isotope compositions of tourmalines in the beryl-bearing and spodumene-bearing pegmatite veins. Tourmalines (Tur-Be) from the beryl-bearing pegmatite are homogeneous schorl with low Mg/(Mg + Fe), high Na/(Na + Ca) and YAl, suggesting that they are of magmatic origin. Two generations of tourmalines (Tur-Li) from the spodumene-bearing pegmatite are identified: (i) the crystal cores (mostly elbaite and Li-rich schorl with subordinate schorl) are consistent with being of magmatic origin crystallized at the magmatic stage; (ii) the crystal rims (schorl) are best understood as the overgrowth at the later hydrothermal stage. Tur-Be and Tur-Li show an obvious difference in core-to-rim B isotopic variation trend with δ11B decrease in Tur-Be and increase in Tur-Li. The core-to-rim δ11B decrease in Tur-Be results from degassing during its host pegmatitic melt evolution, whereas the core-to-rim δ11B increase in Tur-Li is related to fluid exsolution. The estimated δ11B values for the initial melts of the beryl-bearing and spodumene-bearing pegmatites are −10.46‰ and −10.78‰, respectively, indicating that they most likely originate from protracted fractional crystallization/differentiation of granitic intrusions rather than partial melting of metapelite. Both Mg/(Mg + Fe) ratios and Li abundances in the cores of Tur-Be are lower than those of Tur-Li, suggesting that Tur-Li crystallizes from chemically more evolved melts.

A well‐preserved remnant of the middle crust of the former Adriatic passive margin is exposed in the Southern Alps (Italy). The Dervio–Olgiasca Zone is located south of the Insubric Line along the northern part of Como Lake and, because of the lack of Alpine overprint, provides favourable conditions to investigate the pre‐Alpine (rift‐related) history. We reconstruct the P–T–t–d evolution of the Adria middle crust through petrological (petrography, mineral chemistry, thermobarometry and thermodynamic modelling) and geochronological (Lu/Hf in garnet and U–Pb in monazite) data from pegmatites and host micaschists. These data allow reconstruction of a complex tectono‐thermal evolution of the future proximal Adriatic margin at the onset of Alpine rifting. The amphibolite‐facies Carboniferous metamorphic basement (7.6–10 kbar and 610–660°C at 318–312 Ma) was affected by pervasive extensional deformation (5.1–7.6 kbar and 580–660°C) in the Middle‐ to Late‐Permian (257.5 ± 3.8 Ma). Pegmatite intruded at 249.8 ± 1.1 Ma in an extensional phase that re‐equilibrated rocks of the basement at 3.5–4.5 kbar and 560–600°C. During the Middle‐ to Late‐Triassic (241–235 Ma), the basement experienced static thermal recrystallization (T = 689 ± 41°C and ~5.0 kbar). This Late‐Anisian to Early‐Carnian thermal event was simultaneous with the emersion of carbonate platforms, volcanism and ore deposition in the future proximal Adriatic margin. The subsequent cooling of the middle crust was synchronous with large‐scale extensional detachments developed in the upper crust (e.g., the Lugano‐Val Grande Fault), which controlled the formation of the Monte Generoso Basin. This study reveals that the local post‐Carboniferous thinning and heating events recorded in the Adriatic middle crust were interconnected to other processes occurring at different crustal levels that were, in turn, induced by crustal stretching in the early stages of the Alpine rifting. [ABSTRACT FROM AUTHOR]

The pegmatite in the Dagbala area, southwestern Nigeria occurs as a dyke trending in a NW-SE direction which intrudes the Hornblende-Biotite-Granite. Geochemical, petrological, and mineralogical analyses were carried out on four (4) pegmatite samples obtained from the study area to determine the feldspar quality and the results were compared with commercial ceramic and glass grade to determine its suitability in ceramics and glass production. From the results, SiO2 ranges from 74.97% to 72.06%, Al2O3 ranges from 15.16% to 15.05%, Fe2O3 ranges from 0.45% to 0.31%, Na2O ranges from 5.56% to 2.76%, K2O ranges from 8.42% to 3.53% and CaO ranges from 0.72% to 0.09% respectively. After comparing the results with the commercial ceramic grade and glass grade, it shows that they can be used as raw materials in the ceramic and glass industry. However, minor pre-treatment processes are required, such as magnetic separation, to reduce the w content and froth floatation to reduce the K2O content in ceramic production. In glass production, magnetic separation should also be carried out to reduce the Fe2O3 content and froth floatation should be carried out to reduce the K2O content. Additives should be added to increase the amount of CaO, Al2O3, and Na2O present. [ABSTRACT FROM AUTHOR]

Blue-colored corundum (sapphire) is found in syenitic pegmatites in Alvand igneous complex in the Khako area. From the petrographic point of view, the host rock is composed of feldspar and small amounts of quartz, which includes corundum crystals of transparent to translucent blue color, 1 to 6 cm long, covered with a sheath of mica with a composition of muscovite to phengite. It seems that the core of corundum crystals crystallized in the magmatic stage in equilibrium with mica + aluminosilicate + feldspar ± perthite, and in the next metasomatic stage, corundum crystals grew from the reaction of plagioclase and mica. The chemical composition of the main minerals in pegmatite rocks indicates the magmatic origin of these rocks, which were formed during the magmatic differentiation process. In the continuation of the metasomatic cycle, the geochemical conditions for formation of new corundum crystals and regrowth of primary corundum have been prepared by reducing the silica content (de-silicification) and increasing the Al/Si ratio. These processes during post-magmatic cycles in granite masses, are known as Plumasite processes. The classifications done in pegmatites, based on abundance of rare elements and phosphorus content in feldspar crystals, indicate fertility of these rocks from rare elements. These pegmatites are included in the group rich in lithium and beryllium. Moreover, comparison of the chemical composition of corundum crystals with famous corundum deposits in other parts of the world shows that these rocks have a special similarity with magmatic corundum deposits in connection with synthetic intrusive masses. In addition, these rocks show a composition similar to magmatic deposits created by metasomatic processes. Introduction The corundum crystals found in the southern part of Alvand's intrusive mass have been introduced as the most important sapphire gem potential in Iran (Sadeghi et al., 2022; Sajjadi Alehashem et al., 2021). The corundum crystals in this area have been reported in preliminary studies conducted by different researchers (Beharifar, 2012). Although it is not possible to determine certain criteria for the gem value of a mineral., characteristics such as transparency, color, hardness, refractive index, reflection, and absorption of light are among the most important factors in determining the quality of colored gems. The crystallized oxide of pure corundum is colorless However, corundum has five main coloring elements, including Cr3+, Fe3+, Fe2+, Ti4+ and V3+. Geochemical factors in the formation of corundum are usually magmatic or high-grade metamorphic processes that cause formation of aluminum oxide crystals from a magma with a low silica content (Černý, 1991; Černý and Ercit, 2005) or a differentiated pegmatite magma (Sánchez-Muñoz et al., 2017). These rocks can provide special conditions to produce corundum with the help of fluids originating from magmatic fractionation and metamorphic processes (Zwaan et al., 2015; Peucat et al., 2007). Many studies have been done on classification and genesis of corundum deposits (Sutherland et al., 2009, Schmetzer and Peretti, 1999; Simonet et al., 2004). Classification of corundum reserves is essential in choosing detailed prospecting and exploration methods and prospecting for new reserves in similar structural zones. Materials and methods 25 thin sections were prepared from the collected samples. 5 thin polished sections have been used in electron microscope studies and electron probe microanalysis (EPMA). 5 samples of pegmatites containing corundum crystals found in the Khaku deposit Index and 10 single crystals of separated corundum crystals, have been chemically analyzed by XRF and ICP-MS methods in Zarazma Company of Tehran under standard conditions for major elements and trace elements. Also, EPMA analysis of accompanying minerals and corundum crystals was performed by a Cameca-SX-100 device with a beam diameter of 5 microns and accelerating voltage of 2400 mA at the Iranian Mineral Materials Processing Research Center in Karaj. Results In the newest pegmatite classification (Černý, 1991; Černý and Ercit, 2005), which is most widely used by researchers nowadays, a combination of factors, including depth of establishment, metamorphic degree, and rare element contents are considered. This classification has 4 main categories or classes including 2 Abyssal classes (high grade, high pressure to low), Muscovite (high pressure, low temperature), and Miarolitic (shallow level of rare element with low temperature and pressure). The class of pegmatites with rare elements is divided into LCT and NYF types based on abundance of rare elements: LCT Type is rich in lithium, cesium, and NYF type tantalum and rich in niobium, yttrium, and fluorine. Descriptions of sub-groups by Pezzotta Corundum-bearing pegmatites are included in the Abyssal sub-group. This group is of high pressure and temperature type and is formed at a temperature between 700 and 800 degrees Celsius and a pressure of 4 to 6 kbar (Černý and Ercit, 2005). The mineral abundance of muscovite and biotite shows that Alvand pegmatite shows few characteristics of the muscovite subgroup (high pressure, low temperature). This indicates formation of these rocks at temperatures lower than 700 degrees Celsius. A mineralogical classification is based on the latest classification done in pegmatites (Müller et al., 2022). The pegmatites of the Khaku area are in the corundum pegmatites, a product of magmatism, and are affected by the processes of subsolidus fluids. This group of pegmatites are mostly rich in rare elements and aluminum. Chlorite is the most abundant secondary mineral in corundum-bearing rocks. The chemical composition shows that chlorites of the region are rich in iron and poor in titanium and calcium, their XMg varies from 0.23 to 0.37 (Table 3), and in the classification of chlorites, they are in the range of pycnochlorite to diabenitite (Fig 4-A). The 8 samples of biotite and muscovite from the Khaku region were analyzed by EPMA (Tab 4). There were four biotite crystals in sample SH-1, and four other muscovite crystals in sample SH-3. The structural formula of micas has been calculated based on 11 oxygen atoms and 8 cations (Deer et al., 2013). The lowest amount of XMg in sample SH-1 is equal to 0.46, and the highest amount of XMg in sample SH-3 is equal to 0.56. According to Al versus Fe/Fe+Mg variations (Deer et al., 2013). These biotites are a compositional variety between polar siderophyllite and anite (Fig 3-B). The chemical composition of feldspars in the Khaku region shows a relatively uniform chemical composition rich in albite and a major part that is rich in an orthosis in pegmatites such that XAb is equal to 0.90 to 0.95. Most of the feldspars have a composition of orthosis type XOr 85 % to 90% (Tab 5). In the ternary diagram of albite-anorthite-orthoses (Deer et al., 2013), feldspars in pegmatites are located in the orthosis zone and in the zone of pure albite and oligoclase (Fig 3-C). The results obtained from chemical analysis of corundum crystals show that they all contain 86% to 97% aluminum oxide (Al2O3). In all the samples analyzed by theSiO2 method as the second main oxide, there is more than one percent in the crystal., and it varies in the range 1.01%-1.46% to. Discussion The geochemical and geotectonic characteristics of pegmatites in the Khaku area are like those of group II and III pegmatites of the classification of Sánchez-Muñoz et al., (2017), indicating that they are the result of primary crystallization from magmatic melts After those subsolidus reactions during exhumation and cooling rock mass has caused crystallization of corundum and condensation of rare elements (Fig 5). The samples of Khaku are in the range of corundums of magmatic origin and along the dividing line of the magmatic and metamorphic region. These crystals have significant similarities with blue sapphires from the Bo Phloi mine in Thailand (Bo Phloi/Thailand), which are magmatic-metasomatic corundums rich in titanium and magnesium (Fig 6-A). Chromium is also an important tracer in corundum with metamorphic genesis, especially corundum crystallized in alumina-rich marbles and under severe metasomatism. From this point of view, the corundums of the Hamedan Khaku deposit have relatively low amounts of chromium and vanadium and are among the metasomatic magmatic deposits. They are comparable to the sapphires of the Mogok mine in Myanmar (Mogok/Myanmar) (Fig 6-B). This mine is of the metamorphic magmatic type containing ruby in alumina-rich marbles with intense metasomatism (Peucat et al., 2007).

The Ke'eryin area in Sichuan province is one of the large rare metal ore concentration areas in the Songpan–Garze metallogenic belt. Numerous granite pegmatite dikes spread around the Ke'eryin mass. However, locating rare metal dikes in such a large pegmatite field has always been one of the challenges in this region. This paper summarized the geochemical element distribution in the Ke'eryin pegmatite and put forward geochemical indexes, e.g., characteristic element indexes, indicator indexes and grade indexes, to locate rare metal ore in the Ke'eryin area based on a systematic petrogeochemical analysis of two-mica granite, pegmatite microcline albite granite, different pegmatite types and typical deposits. Characteristic element indexes include Li, B, Sn, Rb, Be, Nb and Ta, etc. Indicator indexes for lateral variation are Cs, Tl, F, Zr, Y and ΣREE elements as well as values, e.g., TiO2/Ta, Zr/Hf, Ta/Zr, Nb/Ta, K/Na, etc., while indicator indexes for vertical variation include B, U, Zr, Be, Sn, Rb, Sr, Ba, Tl and In, etc. The variation in these indexes can be used to locate rare-metal-mineralized pegmatite, indicating ore bodies in a deep basin. Grade indexes are aluminum saturation index（A/CNK, A/NK）and rittmann index(σ), etc. Li ore grade is positively correlated with aluminum saturation but is negatively correlated with alkalinity. Grade index variation is a good indicator of lithium enrichment in ore bodies.

The fluorite deposit of the Chumathang area of south‐eastern Ladakh, India, is hosted in pegmatite which cross‐cuts the Paleogene Chumathang granite. The rare earth element and yttrium (REE‐Y) and the trace element's composition of different colored (green, purple, and white) fluorite were investigated to understand its genesis. The green fluorite core is surrounded by purple fluorite, indicating that green fluorite crystallized earlier than the purple one. The white fluorite is mineralized with green fluorite, it does not exhibit any zoning like the other fluorite. The REE pattern of green and white fluorites is similar to those in the host pegmatite and associated Chumathang granite. ƩREE content in fluorite increases from green, white to purple. Fluorites in the study area are characterized by negative Ce suggesting partial reducing conditions during its formation. The Y/Y*, Ce/Ce*, and Eu/Eu* ratios show that fluorite records the compositional evolution of the hydrothermal solutions that transported the trace and REE from the host granite during the fluid–wall rocks interactions. The fluorite exhibits a positive Y anomaly which is suggestive of strong Y‐Ho fractionation in the fluid system. Chumathang fluorite show significant degrees of differentiation between terbium (Tb) and lanthanum (La) in all the purple, green, and white colored fluorite. The Tb/La and Tb/Ca ratios of the fluorites confirm the role of pegmatitic melt and hydrothermal fluid in the genesis of Chumathang fluorite. [ABSTRACT FROM AUTHOR]

In order to consistently highlight the distribution and forms of finding lithium in the subsoil of Ukraine, its geochemistry and mineralogy, genetic types of deposits and ore occurrences, mineralogical criteria and methods of their search and evaluation, the authors have planned a series of articles. The first part quantitatively and qualitatively analyzed the distribution and forms of Li occurrence in existing and prospective objects — the Volyn deposit, the Perzhansky ore district, rare-metal granites of the Azov region and the Korosten pluton, rare-metal pegmatites of the Azov region and the Shpolyansk-Tashlytsky ore region (Inguletsky megablock), hydrothermal of the Nagolny ridge (Donbas). The lithium-concentrating minerals in these objects, according to our data, are the following: spodumene, petalite, evcryptite, tourmaline, holmquistite, Li-Al micas of the isomorfic series (muscovite-lepidolite), Li-Fe micas of the isomorphic series (anite (lepidomelane) or siderophyllite, protolithionite, zinnwaldite, cryophyllite, lepidolite), margarite, donbasite, kukeite, polylithionite (?), tainiolite, tryphyllite, amblygonite, simferite. [ABSTRACT FROM AUTHOR]

Lithium (Li) can be found in many minerals, including lepidolite. Lepidolite is found in pegmatite-related tin deposits in the Phang Nga area in southern Thailand. According to their field occurrence, petrography, mineral chemistry, and whole-rock geochemistry, the Li-bearing pegmatites and the granitic rocks in the study area can be linked to tin deposits in southern Thailand as part of the SE Asian tin belt. The Li-bearing pegmatites are characterized by an abundance of lepidolite, K-feldspar, plagioclase, and quartz with some accessory minerals of fluorite, cassiterite, apatite, monazite, and beryl. The granitic rocks show various compositions, including porphyritic biotite–muscovite granite, biotite granite, and muscovite—tourmaline granite with different proportions of K-feldspar, plagioclase, quartz, biotite, muscovite, and tourmaline. Whole-rock geochemistry indicates that both the Li-bearing pegmatites and granitic rocks have a close relationship rooted in their peraluminous S-type granite affinity. The Li-bearing pegmatites evolved from highly fractionated S-type granitic rocks comparable with the Western Belt Granite of Thailand. The enrichment of large-ion lithophile elements (e.g., Rb and K) and the depletion of Ba, Nb, and Ti together with similar rare Earth element patterns reflect the collisional setting indicating the Sibumasu–West Burma and West Burma—Indo-Burma collisions during the Cretaceous to the Eocene. The crystallization pressure—temperature conditions of these rocks were 3.49–4.25 kbar and 622°C–675°C, respectively, with an emplacement depth of 13–15 km. The Li-bearing pegmatites had a relatively high average Li grade compared with those of other Li-bearing pegmatites in the world.

The pegmatite in the Dagbala area, southwestern Nigeria occurs as a dyke trending in a NW-SE direction which intrudes the Hornblende-Biotite-Granite. Geochemical, petrological, and mineralogical analyses were carried out on four (4) pegmatite samples obtained from the study area to determine the feldspar quality and the results were compared with commercial ceramic and glass grade to determine its suitability in ceramics and glass production. From the results, SiO2 ranges from 74.97% to 72.06%, Al2O3 ranges from 15.16% to 15.05%, Fe2O3 ranges from 0.45% to 0.31%, Na2O ranges from 5.56% to 2.76%, K2O ranges from 8.42% to 3.53% and CaO ranges from 0.72% to 0.09% respectively. After comparing the results with the commercial ceramic grade and glass grade, it shows that they can be used as raw materials in the ceramic and glass industry. However, minor pre-treatment processes are required, such as magnetic separation, to reduce the Fe2O3 content and froth floatation to reduce the K2O content in ceramic production. In glass production, magnetic separation should also be carried out to reduce the Fe2O3 content and froth floatation should be carried out to reduce the K2O content. Additives should be added to increase the amount of CaO, Al2O3, and Na2O present.