Pegmatitic Rocks Research Articles

Mineralogical Study of Lithium -Caesium Tantalum (LCT) Pegmatite Rocks In Makarfi L.G.A, Kaduna State

This research focuses on the Mineralogical Study of Lithium-Caesium-Tantalum (LCT) Pegmatite Rocks in Makarfi Local Government Area (L.G.A), Kaduna State, Nigeria. The primary aim was to systematically characterize the mineralogical composition and assess the economic potential of LCT pegmatites in the region. Field surveys were conducted to identify pegmatite occurrences, and samples were collected for laboratory analysis using X-ray Diffraction (XRD), Atomic Absorption Spectroscopy (AAS), and X-ray Fluorescence (XRF)techniques. The XRD results revealed the presence of key lithium-bearing minerals such as Spodumene, Lepidolite, and Petalite, along with quartz, albite, and muscovite. AAS confirmed significant lithium concentrations ranging from 120 to 340 ppm, alongside notable caesium and tantalum values, indicating the potential for multielement mining. XRF analysis showed high silica content, consistent with the quartz-rich nature of the pegmatites. Petrographic thin section analysis identified Granoblastic, porphyritic, and interlocking textures, suggesting a complex history of crystallization and minimal alteration, enhancing the economic viability of the deposit. The findings suggest that the Makarfi pegmatites are promising for lithium extraction, with potential by-products of caesium and tantalum. The study recommends further geochemical mapping, exploratory drilling, and pilot metallurgical testing to fully assess the deposit's commercial potential.

Recovery of Niobium, Titanium and Yttrium from Poly-mineralized Concentrate of Gabal El- Aurf Pegmatitic Rocks, Central Eastern Desert, Egypt

Recovery of Niobium, Titanium and Yttrium from Poly-mineralized Concentrate of Gabal El- Aurf Pegmatitic Rocks, Central Eastern Desert, Egypt

Genetic model for the color anomalies at the termination of pegmatitic gem tourmaline crystals from the island of Elba, Italy

Abstract. Tourmaline crystals from the island of Elba commonly display a sharp transition to dark colors at the analogous termination due to the incorporation of Fe and/or Mn during the latest stages of crystallization in pegmatites. The formation of such color anomalies is related to a dramatic physicochemical change in the crystallization environment as a consequence of an opening of the geochemical system. However, mechanisms that may lead to the availability of Fe and/or Mn in the residual cavity fluids have been unclear. On the basis of chemical and spectroscopic investigations, combined with structural and paragenetic observations of the cavities, we propose a general genetic model in which, as a consequence of a pocket rupture event, chemical alteration of Fe- and Mn-rich minerals that formed early in the pegmatitic rock surrounding the cavities occurred through leaching processes, produced by the action of the highly reactive late-stage cavity fluids. Such processes were responsible for the release of Fe and Mn in the geochemical system, allowing the formation of the late-stage dark-colored terminations in the tourmaline crystals. In some cavities, a high availability of Mn and/or Fe determined the evolution of the crystals from an initial elbaite/fluor-elbaite composition to celleriite, foitite or schorl. This compositional evolution trend can be described by the following general chemical substitution: XNa+ + Y(Li1.5 + Al0.5)3+ + WF− ↔ X□ + 2Y(Fe,Mn)2+ + WOH−.

Origin, dynamics, and chemical evolution of garnet-bearing leucogranitic magma, Eastern Desert of Egypt: Controls on the rare-metal enrichment in the A-type magmatism

Egypt hosts numerous rare-metal granites, i.e., highly evolved granites enriched in rare metals (Ta, Nb, Be, Sn, Zr, Th, and REE). However, the processes involved in the rare-metal enrichment are not fully understood. We present new data on the textural characteristics and chemical composition of rare-metal mineralization associated with microgranite dikes in the Ras Abdah area of the Egyptian Eastern Desert. These dikes are garnet-bearing leucogranites (GLG) composed of perthitic alkali-feldspars and quartz. When compared to other Egyptian A-type granites, microgranite dikes are alkaline rocks with particularly higher HREE contents. Zircon, huttonite, fergusonite (Y), and Fe-Ti-Zn oxides (magnetite, Zn-bearing ilmenite and pyrophanite) are largely associated with the altered domains, which are also enriched in Nb, Zr, Y, Ta, Th, and REE. However, similarities between the chondrite-normalized REE patterns of the altered and unaltered domains of the GLG dikes favor the hypothesis of a unique magmatic signature. Moreover, the chemical and textural features of rare-metal minerals indicate that the alteration of primary minerals was caused by deuteric fluids or aqueous residual melt exsolved from the parental granitic magma (autometasomatism). Garnet compositions are rich in the spessartine component (up to 84 %), which is typical of garnet in highly evolved pegmatitic rocks. Furthermore, garnet exhibits no major element zoning but shows chemical fluctuations in trace element concentrations, suggesting correspondingly abrupt changes in melt composition due to sequential magma pulsing. This magma emplacement may cause crystal nucleation and oscillatory crystallization followed by magmatic segregation. Overall, parental magma type, dike injection, and magmatic-hydrothermal processes all play a role in the unusual enrichments of rare metals.

Characteristics of early Paleozoic granite-pegmatite and associated lithium-beryllium mineralization in the Tugeman area, Altun orogenic system, northwestern China

The Altun Orogenic Belt (AOB) is located on the northern margin of the Tibetan Plateau. We report the petrography, zircon U-Pb ages, Hf isotopic compositions, and whole-rock geochemistry of the Tugeman pegmatitic and granitic rocks from the AOB to constrain their petrogenesis and tectonic setting. Zircon U-Pb dating of the pegmatitic and granitic rocks yielded ages of 500–440 Ma, which we interpret as the emplacement ages of the granites and formation age of pegmatite. The granites are weakly peraluminous to peraluminous (A/CNK = 1.01–1.26), and they have high SiO2 (63.9–74.2 wt%) and Al2O3 (13.7–17.6 wt%) and low CaO (0.72–3.80 wt%) and P2O5 (0.06–0.44 wt%) contents. They show marked depletion in HREEs, enrichment in LREEs, and pronounced negative Eu anomalies, and they are enriched in Th, U, K, Pb, Nd, and Sm and depleted in Ba, Nb, Ce, Sr, P, and Ti. Zircon εHf(t) values vary from − 12.0 to + 3.3, with two-stage Hf model ages of 2.2–1.2 Ga, implying that the granites were derived mainly from ancient crust with a minor contribution from juvenile crust. Weakly peraluminous pegmatitic rocks have geochemistry characters of SiO2 (74.4–79.9 wt%) and Al2O3 (12.3–14.9 wt%) and low CaO (0.08–0.69 wt%) and P2O5 (0.05–0.33 wt%), depletion in HREEs, enrichment in LREEs, depletion in Ba, La, Ce and Ti, enriched in U, K, Pb and P. Granitic pegmatite can be formed at different stages of crystallization differentiation of granitic magma, but the pegmatite associated with highly differentiated granites is favorable to the Li and/or Be mineralization, while the pegmatite associated with low differentiated granites (such as biotite granites) is unfavorable to the Li and/or Be mineralization. Based on our findings, we propose that the Tugeman granitic magmas originated from partial melting of crustal metagreywacke and metabasalt. Furthermore, we suggest that the early Paleozoic magmatism in the Central Altun Block (CAB) can be categorized into three groups, which correspond to different tectonic events. These events include the northward subduction of the Central Altun Ocean (CAO) beneath the CAB around 520 Ma, the closure of CAO at 490–480 Ma, and post-collisional extension at 480–440 Ma induced by slab breakoff and delamination of the subducted CAO.

Petrography and Geochemical Signatures of Pegmatites from the Southeastern Part Comoé Basin (South-East Côte d'Ivoire, North Alépé)

The pegmatitic rocks located in the south-east of Côte d'Ivoire between the Comoé basin and the Sefwi belt are the subject of this study. The geology of this region consists of gneisses, granites, microgranites, amphibolites, mylonites and metasediments. All these rocks are generally crosscut by quartz and pegmatite lodes. The petrographic studies allow us to discriminate four groups of pegmatites on the basis of mineralogy: (i) beryl-muscovite bearing pegmatite (Aboisso-Comoé), (ii) albite-tourmaline bearing pegmatite (Aboisso-Comoé), (iii) micas-tourmaline bearing pegmatite (Alosso) and (iv) muscovite-garnet bearing pegmatite (Songan forest). XRD analyzes on 4 samples revealed the presence of lepidolite (lithium ore) in the muscovite-garnet bearing pegmatite (Songan forest) and phengite in beryl-muscovite bearing pegmatite (Aboisso-Comoé). The pegmatite diffractograms of Aboisso-Comoé (beryl-muscovite bearing pegmatite) and Songan forest (muscovite-garnet bearing pegmatite) show almost same signatures and would suggest that those pegmatites come from the same source. Geochemical analyzes by portable XRF carried out on muscovite and feldspar minerals indicate that the samples from Aboisso-Comoé and Songan forest have the characteristics of Lithium-Cesium-Tantale type (LCT) pegmatites. The geochemical diagrams indicated the probable presence of beryl and spodumene type mineralization in the muscovite-garnet bearing pegmatite.

AN OVERVIEW ON THE MINERALOGY AND CRISTALLOGRAPHY FIELD COURSE GUIDE AT THE SERIDÓ PEGMATITIC PROVINCE: A CONTRIBUTION FOR UNDERGRADUATE GEOLOGY STUDENTS OF THE FEDERAL UNIVERSITY OF PERNAMBUCO, BRAZIL

This report presents basic guidelines to help undergraduate first year geology students at the Federal University of Pernambuco Brazil. It reviews general aspects of the Mineralogy field trip presenting a comprehensive review on pegmatite classification, regional geology of the Seridó Pegmatitic Province (Rio Grande do Norte and Paraíba states) as well as local geological aspects of three mines that are visited and locally mapped. During the field trip, the Dedego, Pendanga and Sítio Mulungu mines are visited, offering the opportunity to describe pegmatites and host rocks in one of the most famous regions that produce industrial minerals and gemstones for commercial purposes. During the visit, crystallographic and physical aspects of granitic pegmatite-related minerals are discussed, including didactical varieties of quartz, feldspars, mica, tourmaline, garnet and beryl crystals. Mining aspects on pegmatitic rocks in the region are also accessed, allowing the first-year student to have an early contact with mineral exploration and mining companies and their professionals, which will be of great importance for their development during the geology undergraduate course.

Measurement of Radioactivity Concentration in Pegmatite Rock Samples and Dose Assessment from Wamba in North Central Nigeria

Aims: To evaluate the radiological impact parameters on mine workers.
 Study Design: The research work was carried out by using a gamma–ray spectrometer with a NaI (TI) detector.
 Place and Duration of Study: Centre for Energy and Research Development (CERD), Obafemi Awolowo University, Ile- Ife, Osun State, Nigeria between September 2016 and June 2017.
 Methodology: The activity concentrations of 226Ra, 232Th, and 40K were determined in ten samples which were used to evaluate the absorbed dose rate, radium equivalent activity, external and internal hazard indices, representative level index, and annual effective dose equivalent.
 Results: The average activity concentrations of 226Ra (24068.11, 232Th (387.72 , 40K (9509.24) and absorbed dose rate (11720.77) were higher than their respective recommended world mean values of 35 , 45 , 420 and 59 by UNSCEAR. The mean values of radium equivalent activity, external hazard index (Hex), internal hazard index (Hin), representative level index, and annual effective dose equivalent of the area under study were determined as 25346.82, 68.52, 135.43, 357.95, and 14374.36 respectively. This study revealed that all the radiological parameters were higher than their respective recommended world average values.
 Conclusion: With the high concentrations obtained in this study, it is therefore concluded that this may pose a serious health risk to the miners and the general public. It is therefore advised that necessary guidelines should be provided for the exploration of minerals in this mining site.

The petrogenesis and metallogenesis of the Chakabeishan Li-Be pegmatitic deposit in Qinghai, NW China: Evidence from Geochronology, Geochemistry, and mineral geochemistry

In recent years, a newly rare metal metallogenic belt has been discovered in the North Qaidam Terrane (NQT), NW China, of which the Chakabeishan (CKBS) Li-Be pegmatitic deposit is an important part. In this study, CMS (chemical composition-mineral assemblage-structural geology) classification is applied on CKBS pegmatitic rocks, based on their CMS features, the rocks are identified as pegmatite type. The CKBS pegmatites exhibit unique internal vertical zonation characteristics, and six zones are identified: biotite-muscovite-albite zone, graphic zone, layered tourmaline-albite zone, beryl-albite zone, spodumene-beryl-albite zone, and spodumene-albite zone. In this article, we present U-Pb zircon ages, Hf isotope dating, whole-rock geochemistry, and mineral geochemistry to elucidate pegmatite evolution. The zircon U-Pb ages of the spodumene-bearing pegmatite are 258.1 ± 1.4 Ma and 219.6 ± 6.3 Ma, indicate that the magma experienced two stage crystallization. The negative εHf(t) values range from −14.55 to −9.4 with T2DM model ages of 1845–2173 Ma, indicate that the magma originated from ancient rocks anatexis. The first anatectic event occurred during the Paleo-Tethys Ocean subduction process, as the magma originated from the anatexis of ancient metasedimentary rocks, provided enough rare elements (Li, Be, Nb, Ta). However, the second anatectic event occurred during post-orogenic stage and intruded in the host rocks forming pegmatite veins in the Late Triassic. Subsequently, intruded magma experienced mild fractionated crystallization, melt-fluid immiscibility and subsequent metasomatism, forming the vertical zonings.

Mineralogy of Recent Sediments of AL-Teeb River Basin East Missan Governorate Southeastern Iraq

The main aim of this research is to define the mineralogical composition of recent sediments deposited around the Al-Teeb river basin in eastern Missan, trying to determine the provenance or the source of these sediments. The study area represents the southeastern edge of the Mesopotamian Plain and is part of it. Quaternary deposits cover most of the area. It is clayey with old sea and river deposits and part of aeolian deposits. These sediments cover 95% of the study area, while the older rocks, which date back to the Tertiary (Late Miocene – Pliocene), exposed in the area east and northeast of the Al-Teeb area, made up hills which back to the undifferentiated Pliocene Mukdadiya and Bai-Hassan formations. The light components of these sediments consist mainly of quartz, feldspars (potash and plagioclase feldspar), sedimentary rock fragments (carbonate rock fragments, chert rock fragments, evaporates fragments), igneous rock fragments, and metamorphic rock fragments The heaviest minerals are opaque, amphiboles, pyroxenes, chlorite, epidotes, biotite, garnet, muscovite, zircon, kyanite, staurolite, and rutile. These sediments are typically formed by sedimentary rocks (single or many cycles), low and high-rank metamorphic rocks, acidic and basic igneous rocks, and pegmatite rocks. The high percentage of opaque heavy minerals in clastic sediment refers to unstable clastic sediments. The stability issue to the areas during the study shows that there are significant variances over the several places, indicating dissimilar sources and types of source rocks

Identifying xenocrystic tourmaline in Himalayan leucogranites

Abstract Tourmaline is a common autocrystic mineral in granitic and pegmatitic rocks that records valuable information on the physicochemical evolution of magmas. However, xenocrystic tourmaline that does not crystallize from host magmas is also common but seldom reported and notoriously difficult to identify. Here, autocrystic (Tur G) and xenocrystic (Tur P) tourmalines are identified in two-mica granites and granitic pegmatites from the Cuonadong leucogranites, eastern Himalaya. Electron backscatter diffraction (EBSD), coupled with electron-probe micro-analysis (EPMA) and laser ablation ICP-MS analyses (LA-ICP-MS), is used to discriminate xenocrystic from autocrystic tourmaline. Although both tourmalines have slightly different chemical compositions, the differences are insufficient to permit unambiguous discrimination. However, EBSD systematically shows complex intra-crystalline orientations and deformation xenocrystic grains, and undeformed crystal lattices are predominant in autocrystic grains. EBSD could be a useful tool to identify the origin of tourmaline in granitic rocks, particularly when geochemical analyses and/or geochronological measurements are inconclusive.

Significance of viscous coalescence in migmatites of the Assam-Meghalaya Gneissic Complex, eastern India

ABSTRACT The magnetite ocelli preserved in the Chandrapur area of the Assam-Meghalaya Gneissic Complex, eastern India, display viscous coalescence. The viscous coalescence phenomenon generally occurs below a critical capillary number, which is governed by the size of the coalescing droplets. The smaller the size of the coalescing droplets, the greater the possibility that they will exhibit viscous coalescing. From our results we infer that intrusion of younger pegmatitic magma into the much older polyphase deformed quartzofeldspathic gneiss of Chandrapur initiated localized partial melting in the gneissic rocks surrounding the intrusions. This localized partial melting produced small magma pools or leucocratic neosome, which was followed by intermingling between the in situ melt (leucocratic neosome) and external melt (pegmatite), leading to chaotic mixing between the two magmatic phases. Chaotic mixing produced thin veins or filaments of the pegmatitic magma as a result of stretching and folding dynamics. Gradually, the thin filaments underwent capillary instability to produce discrete viscous swirls or ocelli. The ocelli consist of leucocratic minerals like K-feldspar, plagioclase, and quartz, with crystals of magnetite at the center representing magnetite ocelli. The mineralogical assemblage of the ocelli matches that of the pegmatitic rocks. After their formation, some of the smaller magnetite ocelli underwent very gentle collisions due to the effect of capillary and viscous forces. Such collisions produced pairs, clusters, or linear structures that are now preserved in the migmatites of the study area.

Geology and Radioactivity of the Pegmatitic Rocks of Gabal El Urf, Northern Eastern Desert, Egypt

Geology and Radioactivity of the Pegmatitic Rocks of Gabal El Urf, Northern Eastern Desert, Egypt

Paleothermometric fluctuations and ornamentation pattern of Ostracoda species from a short core, off Ongole, Bay of Bengal, South-east Indian coast

An investigation on the elemental chemistry and its fluctuation in Ostracoda carapace to render the environmental traits from off Ongole, Andhra Pradesh is outlined in the paper. Paleothermometric elucidation of the environment using elements Ca, Mg, As, Nb, Sb, Al, Si, Cl, K and Na and the ornamentation pattern exhibited by Ostracoda are identified and ventilated. A short core of length 20 cm was collected from the study area using a multicorer during the ORV Sagar Kanya cruise (SK-308 Leg 1) fieldwork, at a water depth of 47 m. Ostracoda separated from the sediment matrix were subjected to standard micro-paleontological procedures. The elemental weight percentages reveal that the distribution of the elements in the carapace for different species is not the same and fluctuates along the downcore. The occurrence of Niobium in the offshore sediments is observed to be of terrestrial influence, which is derived from granitic and pegmatite rocks of the adjoining coastal terrain. A traceable quantity of Antimony and Arsenic is identified in the carapace of the certain Ostracoda. Mg/Ca ratio in carapace indicates that an endurance of mild temperature fluctuation to the downcore. Smooth, spinose, pitted, punctate and reticulate ornamentation are found occurring in Ostracoda carapace which reflects on the depositional environment and granulometry.

Mineralogical and physical studies of low-grade tantalum-tin ores from selected areas of Rwanda

In this work, mineralogical and physical characterization of low-grade tantalum-tin ore-samples from Ntunga and Kamonyi of Rwanda were carried out using various techniques. The ore-samples were classified as low-grade and non-radioactive ores as they contained less than 0.1% Ta2O5 and Nb2O5, and the percentage of radioactive oxides were below the critical value of 0.5%. The characteristic elements associated with tantalum as detected and quantified by Inductively Coupled Plasma-Optical Emission Spectroscopy and expressed as oxides for their natural occurrence included Ta2O5, Nb2O5, Fe2O3, MnO, SnO2, MgO, TiO2, U3O8, and ThO2, among others. Analysis of samples in raw form showed presence of valuable minerals of cassiterite (0.067%–0.469%), and columbite-(Fe) with Nb2O5 (0.050%–0.062%) and Fe2O3 (0.194%–0.769%), and tantalite-(Mn) with Ta2O5 (0.039%–0.063%) and MnO (0.080%–0.186%). Upon a rough gravity concentration, the ore-samples resulted in concentrate with compositions of 66.14%SnO2, 7.66%Ta2O5 and 7.70%Nb2O5. These minerals with most particle sizes of 125 μm were disseminated within the alumino-silicate matrix of the pegmatite rock. All samples showed nearly similar mineralogical compositions, and the XRD results strongly supported this observation, with diffractograms showing identical characteristic peaks which matched mainly with kaolinite, muscovite, and quartz minerals. Peaks of cassiterite, columbite and tantalite were not strong and visible but upon concentration, they became clear, sharp, and strong. These results will serve as a baseline for selecting and designing appropriate processing technique to effectively harness this mineral resource.

Rare element minerals\u2019 assemblage in El Quemado pegmatites (Argentina): insights for pegmatite melt evolution from gahnite, columbite-group minerals and tourmaline chemistry and implications for minerogenesis

The pegmatite district of El Quemado (NW Pampean Ranges, NW Argentina) hosts several Ordovician pegmatite bodies of the LCT (Li, Cs, Ta) type. We present paragenetic assemblages for a set of samples from two of the El Quemado pegmatite groups, Santa Elena and Tres Tetas, and mineral chemistry analyses for gahnite, columbite-group minerals, tourmaline, micas, albite, microcline, and discuss the relation between their major element composition and the degree of evolution of pegmatite melts. The chemical composition of rare element minerals allows recognizing an evolutive trend reaching highly differentiated compositions, with complex paragenetic assemblages including Li-, Zr-, U-, Zn-, P-, Mn- and Ta-bearing minerals. The temperature of crystallization during the magmatic phase was below 400 °C. Non-pervasive hydrothermal alteration, testified by a moderate presence of phyllosilicates, affected the pegmatite bodies. Chlorite geothermometry indicates that the circulation of post-magmatic hydrothermal fluids occurred at a temperature ranging between 200 °C and 250 °C. The mineralogical features recognized in the El Quemado pegmatite rocks have implications for the metallogenesis of the region, suggesting that the pegmatites potentially contributed to the genesis of Ta-Nb oxide placer mineralizations.

The Mg/(Fe + Mg) ratio and the Ti and A site contents of tourmaline as promising indicators of granitic magma evolution

In the recent past, important research has shown how tourmaline can be used as a petrogenetic indicator in pegmatite rocks and related mineralization. Previous studies have demonstrated that tourmaline composition may be a useful guide to ascertain the degree of evolution and oxygen fugacity of host granitic rocks from the Variscan orogen in the Central Iberian Zone (CIZ). Following those promising preliminary conclusions, we have investigated whether these results hold for tourmaline-bearing granitic rocks from other geotectonic contexts, enlarging our scope to include whole-rock stable isotope analyses. The data collected so far has shown that, whereas most tourmaline components and component ratios seem essentially impervious to granitic magma composition and oxygen fugacity, there are a few exceptions, such as the Mg/(Mg + Fe) ratio and Ti contents of tourmaline that show clear variation with the degree of evolution and oxygen fugacity of the host granitic rocks. From both mineralogical and petrological points of view, it seems that these compositional features in tourmaline may be used as indicators of the degree of evolution and of specific characteristics of the granitic magmas that produced them.

Li-Be-Nb-Ta mineralogy of the Kuqu leucogranite and pegmatite in the Eastern Himalaya, Tibet, and its implication

稀有金属矿物记录了花岗伟晶岩成岩成矿的重要信息。喜马拉雅是全球著名的淡色花岗岩带，库曲岩体位于喜马拉雅东段的特提斯喜马拉雅岩系中。本文调查了库曲岩体的二云母花岗岩、白云母花岗岩、电气石花岗岩和花岗伟晶岩，其中，花岗伟晶岩涉及花岗岩的伟晶岩相和独立伟晶岩脉。库曲岩体产出的稀有金属矿物包括锂辉石、锂绿泥石、绿柱石、铌铁矿-钽铁矿、钇铀钽烧绿石和细晶石，它们主要赋存于似文象伟晶岩、石英-钠长石-白云母伟晶岩、块体长石-钠质细晶岩、块体长石-电气石钠质细晶岩、锂辉石-块体长石-细晶岩、白云母花岗岩的伟晶岩相以及电气石花岗岩内。显微镜观察、电子探针和LA-ICP-MS测试结果显示锂辉石具有四种产状，包括粗粒锂辉石自形-半自形晶、细粒锂辉石-石英镶嵌晶、中细粒锂辉石-钾长石-钠长石-云母镶嵌晶以及发育锂绿泥石的粗粒锂辉石，揭示了其形成时复杂的熔流体动荡结晶环境。绿柱石背散射电子图像（BSE）下呈均一结构和不均一结构（蚀变边、不规则分带和补丁分带），元素替代机制包括通道-八面体替代、通道-四面体替代以及通道中碱金属阳离子间的置换。铌铁矿族矿物包括原生、蚀变边和不规则分带结构，部分被钇铀钽烧绿石和细晶石交代。与原生铌铁矿相比，蚀变边和不规则分带铌铁矿族矿物总体上富钽贫锰，显示了结晶分异、过冷却引起的过饱和以及流体作用。根据稀有金属矿物揭示的成因信息，独立伟晶岩脉（似文象伟晶岩）、白云母花岗岩的伟晶岩相和电气石花岗岩在岩浆分异程度、经历的演化过程、以及流体活动方面存在差异，很可能是不同期次岩浆活动的产物。库曲岩体绿柱石的Rb和Zn含量、以及铌铁矿族矿物的Sc₂O₃、SiO₂和PbO含量，与已有指示标志存在相关性，作为潜在指示标志仍需开展更多的研究工作。综合含锂辉石伟晶岩的产出、岩浆分异演化程度、多期花岗质岩浆活动、复杂的流体作用以及所属锂丰度高值区等因素，库曲岩体是喜马拉雅东段找锂的有利地段。;The rare-element minerals record important information of rock-forming process and metallogenesis. Himalaya is a famous leucogranite belt. The Kuqu intrusion is located in the Tethys Himalayan sedimentary sequence in the Eastern Himalaya. This study investigated two-mica granite, muscovite granite, tourmaline granite and granitic pegmatites in the Kuqu intrusion. The granitic pegmatites refer to either the pegmatite rocks that are included in and related to granite or the pegmatite zones that make up a single pegmatite dyke. The rare-element minerals identified in the Kuqu intrusion include spodumene, cookeite, beryl, columbite-tantalite, Y-hatchettolite and microlite. They are distributed in quartz-feldspar-muscovite pegmatite, quartz-albite-muscovite pegmatite, blocky feldspar-aplite, block feldspar-tourmaline aplite, spodumene-blocky feldspar-aplite, pegmatite rock in muscovite granite, and tourmaline granite. The EMPA and LA-ICP-MS analytical results indicate that spodumenes show four occurrences which consists of coarse-grained subhedral to euhedral spodumene, fine-grained symplectitic reaction border composed of spodumene and quartz, middle to fine-grained mosaic structure of spodumene, K-feldspar, albite and muscovite, and coarse-grained spodumene filled by cookeite veins. These occurrences of spodumene reveal a complex and fluid-rich unstable crystallization environment. There are homogeneous and heterogeneous beryl crystals in the intrusion. The internal zonation patterns for heterogeneous beryls are alteration border, patches and complex irregular zoning in BSE images. The substitution mechanisms of beryl in the Kuqu intrusion are channel-octahedral, channel-tetrahedral and alkali cations in channel. The columbite-group mineral crystals are composed of primary part and alteration border or display irregular zoning pattern, some of which are altered by Y-hatchettolite and microlite. Compared with primary parts, the alteration border and irregular zoned crystals have higher Ta/(Nb+Ta) values and lower Mn/(Fe+Mn) values, indicating fractional crystallization, supersaturation caused by strong undercooling, and fluid activities. Based on the studies of rare-element minerals, the single pegmatite dyke (quartz-feldspar-muscovite pegmatite), pegmatite rock in muscovite granite and tourmaline granite display differences on the degree of fractionation of magma, evolution processes and fluid activities and they might be magma products of different stages. The Rb and Zn contents of beryl, and Sc₂O₃, SiO₂ and PbO contents of columbite-group minerals show correlation with the existed indicators for evolution degree of magma, but more studies are needed to carry out for them to be possible indicators. Considering the spodumene-bearing pegmatite indentified in the intrusion, the high degree of magma evolution, multistage of magmatism, complex fluid activities and being in a high lithium abundance value area, the Kuqu intrusion is an important potential area for future lithium prospecting in the Eastern Himalaya.

Petrographic and mineralisation Potentials of Precambrian Pegmatities and associated rock units of Olode area, Southwestern Nigeria

The geology of the Olode area, south-western Nigeria was investigated petrographically and geochemically in order to elucidate the mineralisation potential of the rock units in the area. The area under study is generally underlain by granite gneiss, mica schist and pegmatites. Petrographical studies indicated prevalence of anhedral quartz (30 – 50%), plagioclase (14 – 20%), orthoclase (12 – 15%), muscovite (11 – 15%), tourmaline (6 – 10) and other minerals (8 – 11%) for the pegmatite. The high value of SiO2 and Al2O3 is consistent with the petrographical study. High values and wide range in Ba (34 – 737 ppm) and Zr (3.8 – 132.6 ppm) strongly support a mixture of igneous and sedimentaryThe bivariant plots of Rb vs K/Rb, Zn vs K/Rb and Th vs K/Rb indicated a partial series of fractionation, suggesting that the pegmatites are of rare element classes while granite gneiss and mica schist belong to the barren muscovite and rare element classes. This was supported by high ratios of K/Cs and K/Ba but low Th/U values indicating distinctively low rare metal mineralization. The plot of Na2O/Al2O3 vs K2O/Al2O3 revealed an igneous precursor for all the rock units. The negative Eu anomalies especially in the pegmatitic rock unit indicates fractionation and point toward a late metasomatic effect and their relatively weak negative Ce anomalies, also suggest their rare metal mineralization. The pegmatites, granite gneiss and mica schist of Olode area considered as barren as all the samples plotted below the Gordiyenkos and Beus’ line of mineralization.

A Polyamide 6/Muscovite Composites with Thermal Insulation Properties

AbstractThe production of garments with strong thermal control is of paramount importance to improve the working conditions of people who engage in activities under hot sun. From this perspective, bearing in mind the reuse of ornamental stone tailings, the present project aimed at developing a fabric made of polyamide 6 and muscovite, which is a mineral tailing from the cutting and processing of pegmatite rocks and has thermal insulation characteristics. Tensile specimens containing 50%, 70%, 80%, 90% and 95% muscovite by mass are generated in the polyamide matrix, which are submitted to physical index and temperature absorption tests. The addition of 95% mineral filler does not significantly alter the physical characteristics of the samples, since the density increased only from 1.30 to 1.60 g.cm−3. In addition, specimens containing 90% mineral filler in the polyamide matrix reduced the temperature by more than 50%.