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Enrichment of the heavy rare earth elements (HREE) in carbonatites is rare as carbonatite petrogenesis favours the light (L)REE. We describe HREE enrichment in fenitized phonolite breccia, focusing on small satellite occurrences 1–2 km from the Songwe Hill carbonatite, Malawi. Within the breccia groundmass, a HREE-bearing mineral assemblage comprises xenotime, zircon, anatase/rutile and minor huttonite/thorite, as well as fluorite and apatite.A genetic link between HREE mineralization and carbonatite emplacement is indicated by the presence of Sr-bearing carbonate veins, carbonatite xenoliths and extensive fenitization. We propose that the HREE are retained in hydrothermal fluids which are residually derived from a carbonatite after precipitation of LREE minerals. Brecciation provides a focusing conduit for such fluids, enabling HREE transport and xenotime precipitation in the fenite. Continued fluid–rock interaction leads to dissolution of HREE-bearing minerals and further precipitation of xenotime and huttonite/thorite.At a maximum Y content of 3100 µg g−1, HREE concentrations in the presented example are not sufficient to constitute ore, but the similar composition and texture of these rocks to other cases of carbonatite-related HREE enrichment suggests that all form via a common mechanism linked to fenitization. Precipitation of HREE minerals only occurs where a pre-existing structure provides a focusing conduit for fenitizing fluids, reducing fluid – country-rock interaction. Enrichment of HREE and Th in fenite breccia serves as an indicator of fluid expulsion from a carbonatite, and may indicate the presence of LREE mineralization within the source carbonatite body at depth.

Актуальность и цель исследования. Изучением гранитоидов алейско-змеиногорского комплекса впервые установлено в единичной пробе лейкогранитов четвѐртой фазы внедрения присутствие редких акцессорных минералов иттрия (приорит, фергюсонит), генезис которых, по существующим данным, пегматитовый, пневматолито-гидротермально метасоматический, но формирование их на магматическом этапе становления интрузии считается наименее типичным. Цель работы состоит в выяснении условий генезиса приорита, фергюсонита в алейско-змеиногорских лейкогранитах. Кроме того, требует решения вопрос источника иттрия и сопутствующих редкоземельных элементов лишь на единственном участке внедрения пород. Методы исследования включают традиционные минералого-петрографические исследования, выделение акцессорных минералов и изучение их видового состава в искусственных протолочках, начальный вес которых составлял 5…8 кг; аналитические исследования минералов выполнены в Институте геологии и минералогии СО РАН (г. Новосибирск) на электронном сканирующем микроскопе JSM-6510LV (Jeol Ltd) с энергодисперсионным спектрометром INCA Energy 350+ (аналитик мл. науч. сотр. М. В. Хлестов) и на рентгено-флюоресцентном микроскопе (отделение геологии Инженерной школы природных ресурсов ТПУ, аналитик канд. геол.-минерерал. наук М. А. Рудмин). Результаты. Впервые в гранитоидах алейско-змеиногорского комплекса встречен комплекс редких акцессорных минералов иттрий-ниобиевого, иттрий-титанового состава наряду с ранее отмечавшимися минералами иттрия (ксенотим), редкоземельным монацитом, ниобатами (колумбит, ильменорутил). Выводы. Присутствие приорита и фергюсонита в единичном штоке лейкогранитов IV интрузивной фазы позволяет рассматривать данный шток как результат деятельности длительно существовавшего канала поступления вещества последовательных фаз внедрения интрузии. Вероятно, свободное поступление материала из первичного магматического очага стало благоприятным фактором для насыщения пород данного участка иттрием, РЗЭ, редкими металлами. Выделение акцессорных минералов соответствующего состава произошло на завершающей стадии формирования интрузива в результате автометасоматоза апикальной и краевых частей. The relevance and aim. The study of granitoids confined to the Aleysk Zmeinogorsk complex for the first time revealed the presence of rare accessory minerals of yttrium (priorite, fergusonite) in a sample spot of leucogranites of phase IV. According to the available data, these minerals are of pegmatitic, pneumatolith-hydrothermal and metasomatic origin, however their development at the magmatic stage is considered less common. The aim of the study is to reveal the origin of priorite and fergusonite in the Aleysk Zmeinogorsk leucogranites, as well as to explain the presence of yttrium and accessory rare-earth elements within the only intrusive zone. Research methods involve conventional mineralogical and petrographical methods, identification of accessory minerals and analysis of their composition using crashed samples; analytical studies were performed on an electronic scanning microscope JSM-6510LV (Jeol Ltd) fitted with an energy dispersive spectrometer INCA Energy 350+ in a laboratory of the Geology and Mineralogy Institute of the Siberian branch of the Russian Academy of Science (Novosibirsk) and X-ray fluorescence microscope (the Division for Geology, School of Earth Science and Engineering, TPU). Results. In line with earlier discovered yttrium (xenotime), rare-earth monazite, niobates (columbite, ilmenorutile), rare accessory minerals of yttrium-niobium and yttrium-titanium composition were identified in granitoids of the Aleysk Zmeinogorsk complex. Conclusions. The presence of priorite and fergusonite in a stock of leucogranites of IV intrusive phase allows the assumption that it was formed due to continuous inflow of melting rocks during successive intrusive phases. The inflow of intrusive material from the initial magma chamber served as a favorable condition for the rocks to be saturated with yttrium, rare-earth elements, and rare metals. The accessory minerals of corresponding composition occurred at the final stage of intrusion formation as a result of autometasomatism of its apical parts and selvages.

Mineralogical and geochemical characteristics of stream sediments collected from 30 stations in the Dahab-Wadi Kid area (southeastern Sinai, Egypt) are presented. The studied sediments contain considerable amounts of heavy minerals, including abundant Fe–Ti oxides, with up to 25.94% index figure that measures the relative abundance of heavy minerals to light minerals. Immaturity of the sediments and nature of Fe–Ti oxide intergrowths, in addition to some non-opaque heavy minerals, indicate multiple provenances with contributions from a variety of Neoproterozoic mafic to felsic intrusions. Appreciable amounts of heavy minerals are derived from schists that belong to the so-called Wadi Kid volcano-sedimentary group. Owing to the considerable contribution of the felsic intrusions represented by within-plate granites, the sediments are enriched in REE-bearing minerals (e.g., monazite, cerianite, La-cerianite and allanite), V-bearing thorite, zircon, and a ZrO2 phase. The majority of Fe–Ti oxides are derived from the mafic intrusions, and they show evidence of pre-, syn- and post-depositional phases of alteration and formation of intergrowths. As to the geochemical signature of the bulk silt fraction, there is remarkable enrichment of LREEs with distinct negative Eu anomaly, and this supports dominance of a provenance dominated by felsic intrusions (i.e., the A-type within-plate granite and associated pegmatites). Also, the felsic provenance is responsible for slight abnormality of ∑U + Th content (up to ~ 37 ppm) and few anomalous samples bear uraniferous zircon and Ce-type monazite. The present paper sheds light on the fertility of the Dahab stream sediments in some economic minerals for possible future exploitation, not for gold only, but for potential REE-bearing minerals that are needed for a wide spectrum of modern technological industries.

The natural radiometric data revealed that eU and eTh-contents of mylonite rocks reach up to 464 and 1283 ppm, respectively. The studied mineralised mylonites are enriched in thorite, ishikawite and zircon as well as other accessories (ferrocolumbite, xenotime, fergusonite, synchysite, cassetrite, apatite, fluorite, galena and barite). Ishikawaite is considered as the almost enriched mineral in uranium contents, whereas UO2 ranges from 31.02 to 50.78 wt%. The higher concentrations of UO2 reached up to 15.88 wt% and ThO2 up to 4.32 wt% related to metamictization of columbite. Some zircon crystals possess higher values of HfO2 reached up to 6.38 wt% could be affected by hydrothermal activity. Both xenotime and fergusonite are enriched in HREE (average ∑HRE2O3 31.19 and 14.1 wt%, respectively) whereas synchysite is main LREE bearing mineral (average ∑LRE2O3 55.78 wt%).

The present study deals with the detailed field geology, mineralogy, geochemistry, and spectrometric prospection of rare metals and radioactive minerals associated with granitic pegmatites in the Gabal Um Lassaf- Abu Dob- Um Atelia- Kadabora- Kab El Rakeb area (LDAKK), which are situated in the central Eastern Desert of Egypt. The study area is composed of granodiorites and monzogranites. The latter is dissected by granitic pegmatites with a discriminatory distribution of economically important mineralization (rare-metals and U–Th minerals). The granitic pegmatites display a zoning structure composed of feldspar-rich zones enveloping pockets of mica (mostly muscovite) and all zoning internal quartz core. Microscopically, the monzogranite and granitic pegmatites are composed of potash-feldspar, albite, and quartz with a small amount of biotite and muscovite. The mineralogical investigation of the highly radioactive zones in the granitic pegmatite shows enrichment in kasolite, uranothorite, thorite, xenotime, columbite, zircon, bismuth, and galena. Geochemically, the granitic pegmatites are enriched with high field strength elements (HFSE; Zr, Nb, Th, and U) and ion lithophilic elements (LILE; Rb, and Pb) and depleted in Ba, Sr, and Eu. They are strongly peralkaline to metalumainous except for two samples, which are peraluminous. They are formed by partial melting of metagreywackes at depth. The studied granitic pegmatites could belong to the NYF family (Niobium–Yttrium–Fluorine family) according to the geochemistry of the trace elements. The studied granitic pegmatites show deep negative Eu anomaly and display a strong M-type tetrad effect of rare earth elements. The field spectroscopy measurements showed the localization of the radiometric anomalous associated with the granitic pegmatites, which are intruded in the granitic host rocks. Their eU and eTh contents reached up to 316 and 1367 ppm, respectively. Uranium and thorium occurrences in the investigated granitic pegmatites are related to magmatic (syngenetic) origin with hydrothermal (epigenetic) input. The magmatic mineralization is evidenced by the occurrence of thorite and zircon, whilst the hydrothermal activity is represented by alteration of feldspars and formation of pyrite and iron oxides associated with the radioactive minerals. The high concentrations of uranium and rare metals mineralization in the investigated granitic pegmatites make them a target to exploration and to enlarge the potentiality of the highly mineralized zones.

—Metasomatic alterations in cataclased granites of the Primorsky Complex PR1 in the Southern Siberian Craton are represented by albitization and riebeckitization, accompanied by microclinization, dolomitization and completed by the formation of hydrothermal quartz–carbonate veins. Albitization, epidotization, and carbonatization are occurred in the host metavolcanics. Mineral parageneses and mineral thermometry data indicate the occurrence of hydrothermal–metasomatic processes in the temperature range from 400–500 to 200‒250°С. Calcite deposited at an early stage has values of δ13С –(3.2–3.3)‰ and δ18O +(8.3–9.4)‰, ferruginous dolomite δ13С –(1.6–1.9)‰ and δ18O +(10.6–11.1)‰. The calculated values of δ13C in CO2 contained in the fluid from which calcite was deposited at 450°C (about –0.7 to 0.8‰) indicate marine carbonates as the source of CO2; the calculated values of δ18O in a fluid in equilibrium with calcite (from +5.4 to +6.5‰) show that the fluid underwent isotopic exchange with magmatic silicate rocks at elevated temperatures and a low fluid-rock ratio. The initial (87Sr/86Sr)t ratio in newly formed calcite (0.718087) and dolomite (0.712033) and eNdT = –(7.3–8.2) indicate the leading role of an upper crustal source of material. The maximum U concentration (52 ppm on average) contains albite–biotite–magnetite schists at the contact with altered granites. The U concentrators in metasomatically altered rocks are the crichtonite group minerals, zircon, and thorite.

A new mineral species of the pyrochlore supergroup, hydroxyplumbopyrochlore (IMA2018-145), (Pb1.5,□0.5)Nb2O6(OH), has been discovered in the Jabal Sayid peralkaline granitic complex of the Arabian Shield, Saudi Arabia. It is associated with quartz, microcline, ‘biotite’, rutile, zircon, calcite, rhodochrosite, columbite-(Fe), goethite, thorite, bastnäsite-(Ce), xenotime-(Y), samarskite-(Y), euxenite-(Y), hydropyrochlore and fluornatropyrochlore. Hydroxyplumbopyrochlore usually shows euhedral octahedra, slightly rhombic dodecahedra and cubes or their combination (0.01–0.06 mm). The mineral is pale yellow to pale brown, transparent with white streak, and has adamantine to transparent lustre. It is brittle with conchoidal fracture. No cleavage or parting are observed. It is isotropic and non-fluorescent. The average microhardness is 463.4 kg mm–2. The calculated density is 6.474 g cm–3.Hydroxyplumbopyrochlore belongs to the cubic crystal system and exhibits the space group Fd$\bar{3}$m with unit-cell parameters a = 10.5456(6) Å, V = 1172.8(2) Å3 and Z = 8. Electron microprobe analysis gave (6-point average composition, wt.%): CaO 0.32, SrO 0.16, FeO 0.17, Ce2O3 0.07, Pr2O3 0.02, PbO 51.69, Nb2O5 40.06, SiO2 0.05, TiO2 1.68, Ta2O5 4.74, H2Ocalc 0.95, total 99.90, yielding the empirical formula (Pb1.34Ca0.03Fe0.01Sr0.01□0.61)Σ2(Nb1.75Ti0.12Ta0.12Si0.01)Σ2O6(OH0.53O0.08□0.39)Σ1, where □ = vacancy. The Raman spectrum of hydroxyplumbopyrochlore contains the characteristic bands of O–H vibrations and no bands for H2O vibrations.

Gabal El Fereyid area, represents a promising area for monzogranite and pegmatites hosted rare-metal mineralization. Microscopically, monzogranite and pegmatites consist of K-feldspar, albite, and quartz with few biotite +/– hornblende. The radiometric studies of anomalous pegmatite samples show that their eU-contents reached up to 149 ppm while their eTh-contents reached up to 375 ppm, in contrast the eU and eTh contents of monzogranite range from 1 to 5.7 ppm and from 4.2 to 29.1 ppm, respectively. This indicates strong post-magmatic U-enrichment in the pegmatitic melt, due to the presence of radioactive minerals as thorite, uranothorite, fergusonite, samarskite and ishikawit. U and Th mineralization in pegmatites are discriminated as hydrothermal and magmatic types. Pegmatites show enrichment of large ion lithophile elements (LILE; Pb and Rb,), high field strength elements (HFSE; Y, Zr, Th, U, Nb and Ta) and rare earth elements but depleted in K, P, Sr, Cs, Ba and Ti. Pegmatites indicate moderate to large negative Eu anomaly and show clear W-type tetrad effect of the REE.

Detailed electron probe microanalyses (EPMA) of accessory minerals from Wadi Rod Elsayalla granitoids (SE Desert, Egypt) furnished insights into U, Th, Zr, and REE mineralization. Thorite and uranothorite are the main radioactive minerals, in addition to zircon and monazite. Thorite occurs in syenogranite and quartz syenite rocks with marked enrichment in UO2 up to 6.89 wt% in the former rock type. High Y and Zr elements content in thorite indicates marked replacement of Th by Y and Zr. Uranothorite in syenogranite contains up to 51.68 wt% ThO2, 19.12 wt% SiO2, and 20.62 wt% UO2, in addition to minor amount of Y2O3 up to 1.94 wt%. Zoned zircon shows thorium-rich core, with marked fluctuation in UO2 content, owing to extensive hydrothermal alterations. Total REE content as REE2O3 reaches to about 6 wt% in zircon rims from the syenogranite. Zircon from quartz syenite shows U, Th, and REEs below the detection limit of the electron microprobe. Identified REE prospects in the study area contain (i) REE fluorocarbonates and fluoride (bastnasite, synchysite, and flocerite), (ii) REE phosphates (monazite-Ce, xenotime, and florencite), and (iii) REE silicates (allanite-Ce and zircon), with a clear predominance of LREE minerals, in which Ce is the main REE. The average REE contents of bastnasite-Ce, flocerite, synchysite-Ce, and synchysite-Y are 77.28, 74.01, 52.89, and 49.09 wt%, respectively. Xenotime from syenogranite and quartz syenite has average HREE contents (Gd2O3–Lu2O3) of 20.45 and 23.72 wt%, respectively.

Critical and rare earth elements are in high demand for their increasing incorporation in modern technological devices for applications in the military, industrial, commercial, and consumer sectors. Round Top Mountain, a rhyolite laccolith in Sierra Blanca, west Texas, U.S.A. is a unique mineral deposit that offers opportunity for development of rare earth elements, especially the heavy rare earths, as well as associated critical elements. The main objective here is to evaluate the distances between accessory minerals of potential economic value (yttrofluorite, cryolite, uraninite, thorite, cassiterite, and columbite), and to major (potassium feldspar, albite, and quartz) and minor minerals (annite mi-ca, magnetite, and zircon). In this study we explore the proximity and clustering of these minor and accessory minerals, at the mi-cron-to-millimeter scale, from mineral maps constructed in a previous application of ArcGISTM tools to electron probe microanal-ysis (EPMA) element maps. Our goal is to determine whether specific minerals cluster spatially and, if so, at what distances. We noted that the high-value target yttrofluorite grains often neighbor potassium feldspar and quartz grains, but less commonly magnetite and mica grains. With regard to cluster analysis, most minor and accessory minerals were found to group together at small scales (low micrometer) and were dis-persed or random at larger (up to 1 mm) distances.

The chemical weathering of rocks and minerals on the Earth’s surface leads to the mobilization and redistribution of elements and has (a) significant control on the chemistry of the soil-hydrosphere-atmosphere system, (b) a profound effect on the bioavailability and toxic effects of elements, and (c) applications in mineral exploration among others. In this study, we describe the sequential weathering of spessartine- and pyrope-bearing almandine garnet in metamorphosed banded magnetite quartzite from the Khetri Copper Belt, western India. Based on detailed microtextural relations the following sequence of garnet weathering is proposed: garnet → alumo-goethite1 → alumo-goethite2 → kaolinite ± (monazite + xenotime ± thorite) → haematite. Our study thus reports for the first time the presence of alumo-goethite, kaolinite, monazite, xenotime, and thorite in weathering assemblage of garnet. The sequential chemical weathering of garnet was both grain boundary-controlled and fracture-controlled. Tectonic fractures (developed during exhumation), reaction-induced fractures (developed due to volume expansion), and secondary porosity (developed due to volume reduction) collectively controlled the propagation of weathering. Integrating multiple lines of evidence, e.g., corrugated contact between the weathering phases, presence of pores, relative molar volume changes, and high mobility of most elements it is argued that the weathering progressed through an interface-coupled dissolution-precipitation process. In situ major and trace element measurements and mass balance calculations show that several major (Fe, Na, K, P) and trace elements (Cl, F, alkalis, alkaline earth elements, and first series transition and base metals) were added while Si, Al, Ca, Mg and Mn were lost during the garnet to alumo-goethite transformation. During kaolinitization, all the major elements except Si and Al were lost to the weathering fluid. The alkali and alkaline earth, first series transition elements, base metals excepting Cr were lost during this weathering stage. Phosphorous, REEs, and Th were locally immobilized as monazite, xenotime, and thorite. In the more advanced stages of weathering, kaolinite was replaced by haematite. This stage involved re-addition of several major (except Al and Si) and trace elements. It is seen that although alumo-goethite, kaolinite, and haematite can host significant quantities of several trace elements, alumo-goethite and haematite have a much better potential of immobilizing most trace elements including toxic ones compared to kaolinite in the weathering profile.

Research subject. The article presents results of mineralogical and geochemical investigation of albite-bearing granites with high concentrations of trace elements located in the Western Trans-Baikal region. Methods. The composition of rocks was determined by the methods of classical silicate analysis, X-ray fluorescence and ICP-MS analysis. Microstructural features, relationships and homogeneity of minerals were studied using an electron microscope LEO-1430 equipped with an energy dispersive spectrometer Inca Energy-300. Isotopic compositions of oxygen were carried out using a mass spectrometer Finigan MAT 253 in the mode of a constant helium flow. Results. Ore mineralization is specified by the presence of Nb-bearing and less REE-bearing minerals. The studied rocks were divided into two groups: albitized granites, and deep albitized granites and albitites. These groups differ in terms of the presence of accessory minerals. The deep albitized granites and albitites belong to alkaline riebeckite-albite granites containing Nb-, Zr-, Y- and REE-bearing minerals. These rocks contain Y-bearing minerals - thalenite and yttrialite, with an up to 4 wt % inclusion of Y 2 O 3 in titanite, chevkinite, thorite and monazite. In contrast, the albitized granites contain fewer amounts of Y and HREE along with LREE-bearing minerals (monazite, allanite, fluocerite, samarskit). Conclusion. The selected groups of rocks have been analyzed in terms of their mineral and geochemical characteristics. The main Nb-bearing mineral in albitized granites is columbite. Minerals from albitites are rich in Y and HREE. The isotopic investigation has shown involvement of a magmatic-derived fluid in the rock formation process.

Nowadays zircon is the most common mineral of the geological U-Pb dating method. One of the main barriers of getting properly time-resolved and reliable zircon age data is just the internal heterogeneity of the zircon crystals themselves. For overcoming that limitation we defined a four-step pre-examination protocol to be followed before LA-ICP-MS based local geochronology aimed data collection on zircon. Our studied zircon crystals (Table 1) came from Variscan K-Mg-rich granitoids in southern Hungary (Moragy) and northern Austria (Rastenberg). In previous geochronology-aimed publications (KLOTZLI & PARRISH 1996; KLOTZLI et al. 2004; GERDES 2006; KOROKNAI et al. 2010) the Variscan age of the two magmatic complexes is already determined. Nevertheless, these investigations left open basic questions with respect to the whole history of the intrusions (origin of the different rock types and age of the secondary overprinting effect), mainly because of the ambiguity caused by the overlooked textural heterogeneity of the studied zircon crystals. In order to answer the open questions, we clarified and identified the different geological processes on the basis of their preserved traces in zircon textures from two intrusions using a four-step pre-examination process:1. Zircon crystals of different morphology were hosted by different rock-forming minerals at both localities based on light microscopy: “normal” (S24, S25), “flat” (re-defined from S4 to AB5) and “long” (P5) prismatic zircon crystals. The basis of separation is the position of the c-axis in the crystals (Figure 2). Zircon grains occur with the same frequency in all the rock types of both locations (Moragy, Rastenberg). By morphology, “normal” prismatic zircon crystals are dominant in different granitoid rocks, “flat” prismatic zircon crystals are less frequent, while “long” prismatic zircon crystals occur rarely (Figure 3). Analysis of a limited number of zircon crystals in their undisturbed petrographic position in thin sections showed that the “normal” and “flat” prismatic zircon crystals were present in all rock-forming minerals of granitoid rocks, while the few, “long” prismatic zircon crystals occurred only in quartz and feldspar (Figure 4). 2. Determination of mineral inclusions in zircon based on electron probe microanalyses (EPMA). Multiphase (K-feldspar, albite, quartz) and single-phase inclusions (apatite, feldspar, biotite, quartz, thorite/uranothorite) were found in zircon crystals at both localities (Table 2). From a genetic viewpoint, multiphase inclusions are the most relevant. This inclusion type, consisting of Na-free K-feldspar, albite and quartz and occurring most commonly in “long” prismatic zircon crystals, indicates lower temperature crystallization from Si-rich granite melt, confirming that zircon was crystallizing continuously during the solidification of the rest granitoid magma (Figure 5). 3. Primary and secondary textural patterns of zircon crystals were identified in details on by comparison of the cathodoluminescence (CL) and back-scattered electron (BSE) contrasts using scanning electron microscope (SEM). Four internal texture types of zircon could be distinguished (Figure 6a, b). Primary internal textures are growth zoning ± xenocrystic core and sector zoning. The observed secondary textural feature is convolute zoning. Primary texture types occur in all rock types at both localities, but secondary texture is observable only in zircon crystals from Moragy Complex. 4. Structural state of zircon zones was determined by Raman spectroscopy. We classified three groups of structural state of the individual zircon zones based on the full width at half maximum (FWHM) of the ν3(SiO4) Raman band: I. well crystallized ( 15 cm-1 FWHM). Accordingly, the strongly radiation-damaged zones could be excluded from the LA-dating, because these zircon zones are not too resistant toward to the fluid-driven replacement processes (PUTNIS 2009). In the case of the alteration of previously radiation-damaged zircon zones we have to take into account the possibility of Pb loss during the replacement reaction, which can modify and disturb the precise U-Pb age determination (NASDALA et al. 1998). Our samples are generally characterized by moderate radiation damage, FWHM values were mainly between 5 cm-1 and 15 cm-1 (Figure 7). Having regard to four-step pre-examination of zircon crystals from all rock types (Figure 1) we can conclude, that the areas of the primary textures (growth zoning ± xenocrystic core and sector zoning) represent the effect of the main magmatic event. The age difference between the core and rim of zircon gives the time interval of the main magmatic crystallization. The xenocrystic core can inform us about the crustal origin. The secondary texture (convolute zoning, fluid-mediated reactions) reflects the imprint of any post-magmatic event in zircon crystals (Figure 8).Having collected these pieces of information one can mark the promising spots (areas of some ten micrometer in diameter) in zircon crystals from both localities for reliable and geologically well interpretable age data determination (Table 3). With the help of the four-step pre-examination of zircon crystals the yield of the age data was: zircon core 80%, growth and sector zoning 94%-os, convolute zoning 100%.

The mineral and geochemical features of soils with increased natural radioactivity in the southern China province of Guangdong have been studied. The distribution patterns of uranium (U), thorium (Th), lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), ytterbium (Yb), and lutetium (Lu) in the profile of ferrallitic soils (Ferralsols) have been examined for the first time, using a wide range of research methods. The method of neutron activation analysis has revealed increased concentrations of radioactive and some rare earth elements. Electron microscopy, fragmentation radiography, and X-ray phase analysis have been applied to study the forms of the elements. The correlation between the particle-size distribution of soils and element concentrations in particular particle-size fractions has been revealed. The mineralogical composition of soils has been studied, and minerals-concentrators of radioactive and rare-earth elements—monazite, zircon, xenotime, thorite, and a rare-earth cerium phase with thorium—have been determined. A high Th concentration in the soil has been pointed out. Its significant part migrates with the destroyed material of alkaline thorium granites represented by fine solid particles with an admixture of accessory minerals. The anomalous levels of U, Th, Ce, and La in the studied soils are mainly related to the high content of these elements in the soil-forming rocks. The dependence of the increase in radon activity due to the uranium release from structural lattices of minerals and transition to other forms (adsorbed in particular) has been revealed. A possible effect of high concentration of radionuclides in rocks, soils, and groundwater and of the increased radon activity on the development of malignant tumors in people has been pointed out. According to the World Health Organization, the Guangdong province is characterized by the highest rate of nasopharyngeal cancer in the world.

The N-S trending Central-Aldan magnesiocarbonatite province is located in the Aldan-Stanovoy shield (South Yakutia, Russia). Several apatite-dolomitic carbonatite occurrences were studied: Seligdar, Muostalaah, Ust-Chulman and Birikeen. Mineralogical and petrographic investigations indicate intense hydrothermal-metasomatic alteration and metamorphism, which are reflected in the evolution of the mineral parageneses. The primary minerals are fluorapatite, magnetite, ilmenite, dolomite, K-feldspar, phlogopite and accessory zircon, titanite, baddeleyite and thorite. The hydrothermal-metasomatic minerals are quartz, calcite and siderite aggregates with haematite, monazite-(Ce), xenotime-(Y), rutile-(Nb), barite-(Sr), anhydrite, ancylite-(Ce) and rare sulphide mineral phases. Alkaline rocks associated with the Muostalaah complex, were also studied. The following U-Pb ages have been obtained (Ma): 1930 ± 7 for Muostalaah alkaline basic rocks, 1906 ± 6 for Muostalaah carbonatites, and 1880 ± 13 and 1878 ± 17 for Seligdar and Ust-Chulman carbonatites, respectively.

The quartz vein cutting the granodiorite of Ras Abda, along the western shear zone, exhibits highradioactive potentiality (up to 3000 ppm for Th and 1600 ppm for U. The microscopic investigation ofthe quartz vein revealed that it is composed mainly of quartz and iron oxides enclosing squadrons ofthe accessory minerals. Granitic fragments are corroded and digested from the wall-rock affecting thechemical composition of the studied rock. Chemically, it is characterized by low alumina and mediumpotassium contents with peralkaline affinity. It is also characterized by high concentrations of the traceelements (Zr >10000, Nb 3481, Y 8621, U 903 and Th 2340 ppm) and the total rare earth elements (up to24246 ppm) specially the HREEs with very low degree of fractionation in the melt (0.014) and in turn,high degree of fractionation in the accessory minerals.The mineralogical investigation using ESEM and XRD techniques revealed the minerals areresponsible for the radioactivity in the anomalous rock such as zircon, thorite, uranothorite and Nb-Taminerals (columbite, euxenite and uranopolycrase).Experimental work in this study agreed with the previous experiments and concluded that metamictizationis attributed to the heat of self-annealing that responsible for transformation of U-euxenite to metamictizedeuxenite and transformation of Ti-U-euxenite to metamictized uranopolycrase.The present study concluded that the studied quartz vein originated from silicic magma rich in the traceand rare earth elements; hence it is considered as good hostile for the radioelements and possesses highradioactive potentiality.

Gabal (G.) El-Mueilha Granitic rocks are represented by an oval shaped stock that intruding thesurrounding older rock units including ophiolitic melange, metavolcanics, older granitoids and youngergabbros and sending several offshoots into them. The study area is affected by several fault systems inNW-SE, NE-SW and N-S directions. Petrographically, these younger granites are mainly represented bymuscovite granite (syenogranite) that shows different degrees of albitization especially at the peripheralparts of the stock beside the ferrugination and silicification. The main accessory minerals are cassiterite,fluorite, zircon, beryl, monazite, thorite and uranothorite which are responsible for the radioactiveanomalies in G. El-Mueilha syenogranitic mass. The airborne gamma ray spectrometry shows highradioactive anomaly restricted to the younger granitic mass relative to the other surrounding rocks that havelow to moderate radioactivity. The eTh/eU ratio of G. El-Mueilha syenogranite indicates U-enrichmentespecially during albitization processes.

The stream sediments of Wadi El Reddah (North Eastern Desert, Egypt) are geochemically and mineralogically investigated. Their content of radioactive and other heavy minerals is mainly represented by thorite, uranothorite, zircon, monazite, xenotime, columbite, fergusonite, and unknown rare earth elements (REEs) bearing minerals as well as cassiterite. Special emphasis on REE content of thorite, uranothorite, zircon and xenotime has been done to correlate them with the increase of uranium contents in these sediments. The key evidence for the presence low-temperature alteration processes includes the presence of some zircon crystals as remnants after complete dissolution of the overgrowth zircon in severe acidic environment, the sulphur content, biogenic minerals, occurrence of unusual minerals as cassiterite pore filling in zircon, variation in the REEs content from the surrounding granites to the stream sediments and the abundance of monazite in the surrounding granites. Most minerals are partially and/or completely altered, which indicated by the pseudomorphism of zircon by xenotime, thorite, and uranothorite.

The main deposits of the Bafq district (Choghart, Se Chahun and Chadormalou deposits) are magnetite-apatite ore bodies with Early Cambrian age, hosted by Early Cambrian volcano-sedimentary rocks, showing lava flow structure with miarolitic cavities and occasional brecciation. The texture and geochemistry (trace elements and O-isotope) of the studied magnetite crystals show three types of magnetite with different proportions in different parts of the district and the deposits. These are primary ignious magnetite and high-temperature hydrothermal magnetite in the massive parts of the deposits and foam-like magnetite in the veins or in the fractures of the massive part. The lack of zonation, high Ti/Fe ratios and δ18O values (2‰ ) than the massive magnetites. The magmatic origin for the main part of the ores in the Bafq is more plausible. Contamination of the primary magmas of the Bafq magmatic rocks with crustal phosphorus and evaporate units was the major agent for triggering iron-rich melt immiscibility from the original magma. Concentration of volatiles in the iron-rich melt involving in crystallization of the primary magnetite and nucleation of the aqueous fluid bubbles on magnetite surfaces led to ascending the buoyant fluid bubble-magnetite aggregates. This caused continuation of the magmatic magnetite microlites growth from the iron-rich magmatic-hydrothermal fluid and formed high-temperature hydrothermal magnetite. Formation of hypersaline fluid due to crystallization of iron-rich melt at shallow depth led to crystallization of titanite (and Th-U-REE-bearing minerals) and sodic-calcic alteration related to magnetite mineralization. Microscopic evidence (replacement of magnetite by hematite and filling of fractures of thorite by magnetite) show that degassing continued at shallow depth, which led to re-crystallization of the primary magnetites and formation of the foam-like magnetites.

The Mocambo Granitic Massif is an A-type granite located in the northeastern part of Goias State, near the city of Monte Alegre de Goias. It belongs to the Pedra Branca Suite, which is itself part of the Goias Tin Province, a group of stanniferous granites that exhibit similar geochemical features, including to a greater or lesser degree of rare earth elements enrichment. The parent rock in the Mocambo Granitic Massif is a coarse porphyritic pink biotite granite. Thin section observations coupled with electron microprobe analyses reveal the presence of several REE-bearing minerals: allanite, fergusonite (Ce), fergusonite-(Y), zircon and apatite as accessory minerals, and xenotime-(Y), bastnasite-(Ce), thorite, monazite-(Ce) and hingganite-(Y) as secondary (hydrothermal) minerals. Fergusonite and hingganite are identified in this massif for the first time. This work investigates the forms of occurrence and enrichment of rare earth elements in the Mocambo Granitic Massif, in the parent rock, as well as in greisen, saprolite and soil, with emphasis placed on the rare earth elements adsorbed on clay minerals, and the entire process of transport and fractionation of these elements from the fresh rock until adsorption. The results show enrichment of rare earth elements (with the exception of Ce) in soils in comparison to rock, especially in the clay fraction. Moreover they suggest that these elements are mostly adsorbed on clay minerals, mostly kaolinite and illite, which are identified in the X-ray patterns. The surface oxidation of Ce3+ to Ce4+ on surfaces and the probable formation of Ce oxides cause this element to present a smaller quantity of exchangeable ions. The presence of cerianite grains in one superficial soil sample shows that Ce is mostly found in the Ce4+ state in the soil profile. The Mocambo Granitic Massif displays substantial enrichment in REEY, 555–1229 ppm for the parental granite and 569 ppm for the greisen, and the exchangeable REEY concentrations in the soils horizons, more than 600 ppm, in particular, representing a potential target for an ion-adsorption-type rare earth elements deposit.

The world-class Sn-Nb-Ta Madeira deposit is located in the Pitinga mine (northern Brazil). The deposit is associated with the albite-enriched granite facies of the A-type Madeira Granite (∼1820 Ma). The mine commercially extracts tin (cassiterite), Nb and Ta (U-Pb-pyrochlore and columbite). Fluorine (cryolite), Y, REE (xenotime), Zr (zircon), U (U-Pb-pyrochlore and zircon) and Th (thorite) are potential byproducts. This work presents a detailed study of thorite mineralization in the albite-enriched granite subfacies: the albite-enriched granite core, the albite-enriched granite border and associated pegmatites. The Madeira deposit is revealed in this work to be among the largest Th deposits in the world, with 164 Mt of homogeneously dispersed ore, average grade of 759 ppm ThO2 in the rock, and higher concentrations (up to 1.8 wt% ThO2) in small pegmatites (average of ∼0.51 wt% ThO2). Thorite compositions are either close to the thorite pole or correspond to relatively limited substitutions in the thorite-zircon-xenotime-coffinite solid solution system. The concentration of Fe in thorite ranges from 0.11 wt% to 29.56 wt% Fe2O3, and in many cases is considered to be of structural nature, as well as part of the content of F (up to 6.02 wt% F). Thorites of all subfacies were strongly affected by hydrothermal alteration related to F-rich, low-temperature aqueous fluids. The hydration of thorite allowed the introduction of M3+ cations (Y, REE, Fe, and Al) and F, and caused losses in Si and Th contents (average of ∼48 wt% ThO2). The alteration also created a Fe-rich halo in thorite, with associated secondary minerals, likely Th-Fe-hydroxyfluorides and Y-Th-Fe-fluorcarbonates. The Th/U average ratios in bulk-rock are 1.85 in the albite-enriched granite border, 3.82 in the albite-enriched granite core, and 19.85 in the associated pegmatites. This variation reflects a pattern of magmatic evolution, with higher availability of U in earlier stages and U depletion in later stages. In Pitinga, the Th and U mineralization are divided into different minerals formed at distinct stages of magma evolution. This feature is related to fluorine enrichment and high alkalinity of the magma that strongly inhibited the early crystallization of zircon, as well as columbite, and favored the early appearance of U-Pb-pyrochlore. When crystallization of hydrous silicates reduced alkalinity, crystallization of zircon (from a magma depleted in U, Nb, Ta and LREE) became intense, accompanied by thorite and xenotime.

The first data on the discovery of Th–Sc mineralization in the pyritic complexes of the Southern Urals are presented. The minerals of Th (thorite) and Sc-containing thorium minerals are described. The conclusion is made that the Th–Sc mineralization formed due to crystallization of a residual melt in the local volume.

El-Regeita shear zone occurs at south central Sinai massif attains the interest of many authors due the occurrence and mining of copper mineralization. The highest radiometric measurements of eU up to 130 ppm and eTh 34.5 ppm are recorded in diorite dikes, whereas eU and eTh reached up to 15 and 54.2 ppm in monzogranite, respectively. On the other hand, quartz monzonite and granodiorite as well as andesite dikes are generally possess the lowest eU, eTh-contents. The studied monzogranite and diorite dikes are enriched in U and Th minerals (thorite and uranothorite) as well as zircon and monazite in addition to wakefieldite that enclosed fine inclusion of uranothorite and thorite, respectively. These minerals give rise to anomalous radioactive zones. The investigated copper mineralization is chalcocite, covellite, bornite, and chalcopyrite as well as barite and titanite were restricted to the monzogranite intrusion and diorite dikes having NW–SE trend.

A comprehensive study of monazite–cheralite–huttonite solid solutions (s.s.) and xenotime from the highly evolved, strongly peraluminous P–F–Li-rich Podlesí granite stock in the Krušné Hory Mts., Czech Republic, indicates that, with the increasing degree of magmatic and high-T early post-magmatic evolution, the content of the cheralite component in monazite increases and the relative dominance of middle rare earth elements (MREE) in xenotime becomes larger. Considering the overall compositional signatures of these two accessory minerals in the late Variscan granites of the Erzgebirge/Krušné Hory Mts., three types of granites can be distinguished: (i) chemically less evolved F-poor S(I)- and A-type granites contain monazite with a smooth, mostly symmetric chondrite-normalized (CN) rare-earth elements (REE) pattern gradually declining from La to Gd, associated xenotime is Y-rich (˃0.8 apfu Y) with a flat MREE–HREE (heavy rare earth elements) pattern, (ii) fractionated A-type granites typically contain La-depleted monazite with Th accommodated as the huttonite component, combined with usually Y-poor (0.4–0.6 apfu Y) xenotime characterized by a smoothly inclining, Yb–Lu-dominant CN-REE pattern, (iii) fractionated peraluminous Li-mica granites host monazite with a flat, asymmetric (kinked at La and Nd) CN-LREE pattern, with associated xenotime distinctly MREE (Gd–Tb–Dy)-dominant. Monazite and xenotime account for the bulk of the REE budgets in all types of granite. In peraluminous S(I)-type granites, which do not bear thorite, almost all Th is accommodated in monazite–cheralite s.s. In contrast, Th budgets in A-type granites are accounted for by monazite–huttonite s.s. together with thorite. The largest portion of U is accommodated in uraninite, if present.