Highly evolved granite associated with pegmatite shells exhibits significant potential for rare metal mineralization;however,the mechanisms through which these pegmatite shells contribute to magmatic evolution and rar...Highly evolved granite associated with pegmatite shells exhibits significant potential for rare metal mineralization;however,the mechanisms through which these pegmatite shells contribute to magmatic evolution and rare metal enrichment remain poorly understood.The Late Jurassic Shihuiyao Nb-Ta-(Rb-Be-Li)deposit is one of the largest rare-metal deposits in the Southern Great Xing’an Range(SGXR),Northeast China.Exploratory trenches expose distinct layered zones from top to bottom:alternating microcline pegmatite and aplite layers(zone I),topaz lepidolite albite granite and lepidolite amazonite pegmatite(zone II),and muscovite albite granite(zoneⅢ).We conducted U-Pb dating of cassiterite,monazite,and Nb-Ta oxide,monazite Nd isotopes,and whole-rock and mineral geochemistry for the three zones.Multi-mineral U-Pb ages indicate that the three zones formed during the Late Jurassic-Early Cretaceous(147-142 Ma).Geochemical analyses of whole-rock,mica,and microcline suggest an evolutionary sequence from zone I to zoneⅢ,and finally to zone II.The Zr/Hf,Nb/Ta,Y/Ho,and K/Rb ratios combined with the rare earth element(REE)tetrad effects suggest higher degree of differentiation and fluid-melt interaction of the Shihuiyao leucogranite without a pegmatite shell compared to coeval barren granites from both Shihuiyao and the SGXR.A progressive increase in the degree of evolution is evident from the leucogranite without a pegmatite shell to the leucogranite with a discontinuous shell,and ultimately to the leucogranite with a continuous shell.The pegmatite shell acted as a geochemical barrier that facilitated the accumulation of Li and F in the underlying magma,which played a crucial role in lowering the solidus temperature of the granitic magma.This process prolonged the crystallization duration while reducing melt viscosity and density,thereby creating favorable conditions for magma differentiation and fluid-melt interaction.Rapid crystallization of the earlier water-and Be-rich melt led to the Be mineralization in the pegmatite shell.Moreover,the formation of this shell served as a barrier for Li mineralization in the underlying topaz lepidolite albite granite.This study enhances our understanding of the critical contribution of pegmatite shells to magmatic evolution and rare-metal mineralization.展开更多
The Duanfengshan deposit is a newly discovered large pegmatitic-type Nb-Ta deposit in the central section of the Jiangnan orogenic belt,South China.There are three types of pegmatite in the Duanfengshan area:microclin...The Duanfengshan deposit is a newly discovered large pegmatitic-type Nb-Ta deposit in the central section of the Jiangnan orogenic belt,South China.There are three types of pegmatite in the Duanfengshan area:microcline pegmatite,microcline-albite pegmatite and albite pegmatite.Although several geological,geochronological and geochemical studies of this deposit have been carried out,the relationships between the evolution degree of different types of pegmatites and mineralization are still unclear.We address this problem through systematic petrographic and geochemical studies of muscovite and feldspars from two representative pegmatite veins,the No.328 microcline-albite pegmatite vein,and the No.610 albite pegmatite vein.The results of electron probe microanalysis(EPMA)and laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)analyses of muscovite and K-feldspar reveal that K/Rb ratios decrease with increasing Rb,Cs,Ga,Nb and Ta contents alongside decreasing Ba and Sr contents,suggesting that magmatic differentiation played a dominant role in rare metal mineralization.A comparison of the analytical results of this study with those from rare metal pegmatites globally suggests that the No.610 vein has a high mineralization potential,whereas the No.328 vein has relatively low mineralization potential.The results from this study may be applied to the evaluation of mineralization potential for other pegmatite veins in the Duanfengshan area and other rare metal pegmatite fields with similar geological settings.展开更多
The Gabo lithium deposit represents a newly discovered pegmatite-type lithium deposit within the Himalayan metallogenic belt.The tourmaline-muscovite granite,the largest leucogranite in the mining area,displays a clos...The Gabo lithium deposit represents a newly discovered pegmatite-type lithium deposit within the Himalayan metallogenic belt.The tourmaline-muscovite granite,the largest leucogranite in the mining area,displays a close spatial correlation with the Li-pegmatite veins.This study aims to examine the genesis of tourmaline and evaluate the significance and potential of pegmatite lithium deposits.Tourmaline is extensively distributed in tourmaline-muscovite granite at Gabo deposit in Luozha county(Xizang).Investigation of the compositional and in situ boron isotopes of the tourmaline revealed that the tourmalines mainly belong to the schorl group and exhibit uniform elevated Li-Sn contents andδ^(11)B values(-11.6‰to-10.5‰).This indicates that the tourmaline mainly crystallized from a boron-rich granitic magma undergoing enrichment in elemental lithium during the tourmaline crystallization process.Compared with the principal rare metal leucogranite-pegmatites in the Himalayan orogen,it is proposed that the elevated lithium(Li)content of tourmaline serves as an eff ective mineral indicator for the highly evolved pegmatite-type rare metal deposits.展开更多
The Guanpo pegmatite field in the North Qinling orogenic belt(NQB),China,hosts the most abundant LCT pegmatites.However,their emplacement conditions and structural control remain unexplored.In this contribution,we inv...The Guanpo pegmatite field in the North Qinling orogenic belt(NQB),China,hosts the most abundant LCT pegmatites.However,their emplacement conditions and structural control remain unexplored.In this contribution,we investigated it combining pegmatite orientation measurement with oxygen isotope geothermometry and fluid inclusion study.The orientations of type A1 pegmatites(P_(f)<σ_(2))are predominantly influenced by P-and T-fractures due to simple shearing in Shiziping dextral thrust shear zone during D_(2)deformation,whereas type A2 pegmatites(contemporaneous with D_(4))are governed by hydraulic fractures aligned with S_(0)and S_(0+1)stemming from fluid pressure(P_(f)<σ_(2)).Additionally,type B pegmatites(P_(f)≤σ_(2))exhibit orientations shaped by en echelon extensional fractures in local ductile shear zones(contemporaneous with D_(3)).The albite-quartz oxygen isotope geothermometry and microthermometric analysis of fluid inclusions in elbaites from the latest pegmatites(including types B and A2)suggest that the crystallization P-T for late magmatic and hydrothermal stages are 527.5-559.2℃,320℃,3.1-3.6 kbar and 2.0 kbar,respectively.Our observations along with previous studies suggest that the genesis of the LCT pegmatites was a long-term,multi-stage event during early Paleozoic orogeny(including the collision stage)of the NQB,and was facilitated by various local fractures.展开更多
Lack of information regarding lithium(Li)crystal chemistry in numerous minerals,especially those containing trace amounts of Li(ranging from a few to tens of ppm),limits our understanding of Li isotopic fractionation ...Lack of information regarding lithium(Li)crystal chemistry in numerous minerals,especially those containing trace amounts of Li(ranging from a few to tens of ppm),limits our understanding of Li isotopic fractionation in pegmatites.In this study,we examined the Li isotopic composition and Li content in various Li-poor(e.g.,quartz or feldspar)together with Li-rich(sopdumene or lepidolite)mineral phases within granitic pegmatites.We compiled a comprehensive dataset,encompassing a broad spectrum of Li contents(ranging from a few to tens of thousands of ppm)and Li isotopic values(-8‰to 41‰).The minerals exhibit distinct Li isotopic signatures.Specifically,elbaite and beryl show the highest values,while biotite displays a negative average.Compared to individual minerals,whole rocks demonstrate lower Li isotopic values,with pegmatites exhibiting the highest and non-granitic pegmatite wall rocks showing the lowest.Our study also uncovers a clear“V”shape relationship between Li isotopic values and logarithm of Li contents,with different mineral groups occupying specific regions within this shape.Furthermore,a significant correlation was observed between average Li isotopic values and Li-O(OH,F)bond lengths in various minerals.These discoveries underscore the crucial role of crystal chemistry in shaping the Li isotopic behavior in pegmatites from a statistical perspective.展开更多
The detailed description of two granite complexes in the Olkhon subterrane is given.The Early Paleozoic Sharanur complex was formed by granitization of gneisses of the Olkhon series.It includes migmatites,granite-gnei...The detailed description of two granite complexes in the Olkhon subterrane is given.The Early Paleozoic Sharanur complex was formed by granitization of gneisses of the Olkhon series.It includes migmatites,granite-gneisses,granites and pegmatites of normal alkalinity;they belong to the type of syncollisional granites.The Middle Paleozoic Aya granite complex includes mother Aya massif of amazonite-bearing granites and several types of rare-metal pegmatites.They have elevated alkalinity,low of Ba,Sr,and high LILE and HFSE elements contents.The Aya pegmatites lie in northwest cracks of stretching and associated with the rise of the territory under the influence of the North Asian plume.These cracks and pegmatites mark the beginning of a new intraplate geodynamic setting.Two geochemical types are distinguished among the pegmatites of this complex.These are amazonite pegmatites of Li-F type with Ta mineralization and complex type pegmatite with Be-Rb-Nb-Ta and Li-F mineralization(the Ilixin vein).The Tashkiney pegmatite vein is similar to Ilixin,but lies in the gneisses of the Olkhon series.It shows high concentrations of Be,Nb,Ta,as well as W,Sn,but lacks Li and F,due to a greater depth and higher temperature of the melt crystallization of this pegmatite.展开更多
The lithium potential in the Aïr massif is represented by mineral index of spodumene pegmatites and, lepidolite pegmatites. The mineral deposits of lithium occur in cluster or veins that cut the host rock or are ...The lithium potential in the Aïr massif is represented by mineral index of spodumene pegmatites and, lepidolite pegmatites. The mineral deposits of lithium occur in cluster or veins that cut the host rock or are located near the contact between the greenstone belt and granitic massif. The evidence of lithium is in the form of clusters or disseminated and stockwerk. Mineralogical characteristics show similarities between the Air Massif pegmatites and indicate the same homogenous source during the magma-generation process. The pegmatite rocks attracted the attention due to their wide exposure and composition, well appearance, and economically hosting of significant rare earth metals such as Sn and W. The mineralogical and petrographical investigations on the eight pegmatites rocks samples observed have a relative similarity, while a little difference in the shapes attributed to the ratio in the pegmatite rocks of the minerals. The occurrence of the kink band indicates the influence of the tectonic processes which affected the Aïr massif after the emplacement of late magmatic or post-magmatic pegmatites by injection into fractured rocks in the upper part of the crust. The Air Massif pegmatite has higher concentrations Li and of all trace elements except Hf and occasionally Zr, Ti, Sn and Mg of for the economic exploration.展开更多
Granitic pegmatites are commonly thought to form by fractional crystallization or by liquid immiscibility of granitic magma; however, these proposals are based mainly on analyses of fluid and melt inclusions. Here, we...Granitic pegmatites are commonly thought to form by fractional crystallization or by liquid immiscibility of granitic magma; however, these proposals are based mainly on analyses of fluid and melt inclusions. Here, we use the Jiajika pegmatite deposit, the largest spodumene deposit in Asia, as a case study to investigate ore forming processes using isotope dating. Dating of a single granite sample from the Jiajika deposit using multiple methods gave a zircon U-Pb SHRIMP age of 208.4 ~ 3.9 Ma, an 4~Ar/39Ar age for muscovite of 182.9 ~ 1.7 Ma, and an 4~Ar/39Ar age for biotite of 169.9 ＋ 1.6 Ma. Based on these dating results and the 4~Ar/39Ar age of muscovite from the Jiajika pegmatite, a temperature-time cooling track for the Jiajika granite was constructed using closure temperatures of the different isotope systems. This track indicates that the granite cooled over ^-40 m. y., with segregation of the pegmatite fluid from the granitic magma at a temperature of ~700~C. This result suggests that the Jiajika pegmatite formed not by fractional crystallization, but by segregation of an immiscible liquid from the granitic magma. When compared with fractional crystallization, the relatively early timing of segregation of an immiscible liquid from a granitic magma can prevent the precipitation of ore-forming elements during crystallization, and suggests that liquid immiscibility could be an important ore-forming process for rare metal pegmatities. We also conclude that isotope dating is a method that can potentially be used to determine the dominant ore-forming processes that occurred during the formation of granite-related ore deposits, and suggest that this method can be employed to determine the formation history of the W-Sn ore deposits found elsewhere within the Nanling Metallogenic Belt.展开更多
The Zhawulong granitic pegmatite lithium deposit is located in the Ganzi-Songpan orogenic belt.Fluid inclusions in spodumene and coexisting quartz were studied to understand the cooling path and evolution of fluid wit...The Zhawulong granitic pegmatite lithium deposit is located in the Ganzi-Songpan orogenic belt.Fluid inclusions in spodumene and coexisting quartz were studied to understand the cooling path and evolution of fluid within albite–spodumene pegmatite.There are three distinguishable types of fluid inclusions:crystal-rich,CO2–NaCl–H2 O,and NaCl–H2 O.At more than 500°C and 350~480 MPa,crystal-rich fluid inclusions were captured during the pegmatitic magma-hydrothermal transition stage,characterized by a dense hydrous alkali borosilicate fluid with a carbonate component.Between 412°C and 278°C,CO2–Na Cl–H2 Ofluid inclusions developed in spodumene(I)and quartz(II)with a low salinity(3.3–11.9 wt%NaCl equivalent)and a high volatile content,which represent the boundary between the transition stage and the hydrothermal stage.The subsequentNaCl–H2 Ofluid inclusions from the hydrothermal stage,between 189°C and 302°C,have a low salinity(1.1–13.9 wt%NaCl equivalent).The various types of fluid inclusions reveal the P–T conditions of pegmatite formation,which marks the transition process from magmatic to hydrothermal.The oreforming fluids from the Zhawulong deposit have many of the same characteristics as those from the Jiajika lithium deposit.The ore-forming fluid provided not only materials for crystallization of rare metal minerals,such as spodumene and beryl,but also the ideal conditions forthe growth of ore minerals.Therefore,this area has favorable conditions for lithium enrichment and excellent prospecting potential.展开更多
Fully-coupled thermo-mechanical simulations are implemented in COMSOL Multiphysics to investigate micro-scale stress-strain variability in pegmatite specimens subjected to thermal loading using microwaves. Thermally-i...Fully-coupled thermo-mechanical simulations are implemented in COMSOL Multiphysics to investigate micro-scale stress-strain variability in pegmatite specimens subjected to thermal loading using microwaves. Thermally-induced compressive and tensile stresses increase as the microwave irradiation duration increases. The dielectric constant, coefficient of expansion, and type and size of mineralogical boundary have significant impacts on the responses of the rock to microwave irradiation. The maximum principal stress of the chlorite is the smallest, indicating that the chlorite experiences the most damage under microwave irradiation, followed by the quartz. The maximum principal stress values of plagioclase and orthoclase are larger, indicating that they are likely to incur the least damage. Where quartz or chlorite is dominant, the resulting von Mises stresses are consistently higher after 120 s of microwave irradiation. The rate of generation of von Mises stresses increases most rapidly along the interface between quartz and plagioclase, and the interface between quartz and orthoclase, followed by the interface between quartz and chlorite, and finally the interface between plagioclase and orthoclase. The presented modeling approach provides a practical method to investigate stress-strain relationships within mineralogical boundaries inside a rock thin section.展开更多
In this paper, we show that supercritical fluids have a greater significance in the generation of pegmatites,and for ore-forming processes related to granites than is usually assumed. We show that the supercritical me...In this paper, we show that supercritical fluids have a greater significance in the generation of pegmatites,and for ore-forming processes related to granites than is usually assumed. We show that the supercritical melt or fluid is a silicate phase in which volatiles; principally H_2O are completely miscible in all proportions at magmatic temperatures and pressures. This phase evolves from felsic melts and changes into hydrothermal fluids, and its unique properties are particularly important in sequestering and concentrating low abundance elements, such as metals. In our past research, we have focused on processes observed at upper crustal levels, however extensive work by us and other researchers have demonstrated that supercritical melt/fluids should be abundant in melting zones at deep-crustal levels too. We propose that these fluids may provide a connecting link between lower and upper crustal magmas,and a highly efficient transport mechanism for usually melt incompatible elements. In this paper, we explore the unique features of this fluid which allow the partitioning of variouselements and compounds, potentially up to extreme levels,and may explain various features both of mineralization and the magmas that produced them.展开更多
In this study, we carried out petrography, zircon U-Pb geochronology and Hf isotopic analyses on a granitic pegmatite dyke in the Xiaoqinling area in southern margin of the North China Craton（NCC）. Our study suggest...In this study, we carried out petrography, zircon U-Pb geochronology and Hf isotopic analyses on a granitic pegmatite dyke in the Xiaoqinling area in southern margin of the North China Craton（NCC）. Our study suggests that the pegmatite dyke likely crystallized from a volatile-rich pegmatitic magma. Different from most other pegmatite elsewhere, zircon from this pegmatite dyke does not contain unusually high U and Th concentrations and suffered no evident radioactive damage, therefore we successfully obtained a zircon U-Pb dating using laser ablation-inductively coupled plasma-mass spectrometry（LA-ICP-MS）, which yields an average 207Pb/206 Pb age of 1 814±6 Ma, representing the intrusive age of the granitic pegmatite dyke. Zircon εHf（t） values are between-8.3 and-3.0, corresponding to Hf depleted mantle model ages from 2 649 to 2 991 Ma with an average of 2 881 Ma. These data indicate that this granitic pegmatite dyke may have been derived from partial melting of Meso-Neoarchean metamorphic rocks from the Xiaoqinling basement. Granitic pegmatite magma may have emplaced within the Taihua Group wall rocks during the last stage of the middle to high grade metamorphism. Furthermore, according to the petrographic observation, the 1.81 Ga pegmatite dyke and the 1 800–1 750 Ma Xiong’er Group rocks were not undergone middle to high grade metamorphism, indicating 1.81 Ga as the termination of the latest regional metamorphism in the southern margin of the NCC.展开更多
The Zhaxikang Pb-Zn-Sb polymetallic deposit is one of the most important deposits in the newly recognized southern Tibet antimony-gold metallogenic belt.Compared to the porphyry deposits in the Gangdese belt,much less...The Zhaxikang Pb-Zn-Sb polymetallic deposit is one of the most important deposits in the newly recognized southern Tibet antimony-gold metallogenic belt.Compared to the porphyry deposits in the Gangdese belt,much less researches have addressed these deposits,and the genesis of the Zhaxikang deposit is still controversial.Based on field investigation,petrographic,microthermometric,Laser Raman Microprobe（LRM） and SEM/EDS analyses of fluid,melt-fluid,melt and solid inclusions in quartz and beryl from pegmatite,this paper documents the characteristics and the evolution of primary magmatic fluid which was genetically related to greisenization,pegmatitization,and silification in the area.The results show that the primary magmatic fluids were derived from unmixing between melt and fluid and underwent a phase separation process soon after the exsolution.The primary magmatic fluids are of low salinity,high temperature,and can be approximated by the H_2O-NaCl-CO_2 system.The presence of Mn-Fe carbonate in melt-fluid inclusions and a Zn-bearing mineral（gahnite） trapped in beryl and in inclusions from pegmatite indicates high Mn,Fe,and Zn concentrations in the parent magma and magmatic fluids,and implies a genetic link between pegmatite and Pb-Zn-Sb mineralization.High B and F concentrations in the parent magma largely lower the solidus of the magma and lead to late fluid exsolution,thus the primary magmatic fluids related to pegmatite have much lower temperature than those in most porphyry systems.Boiling of the primary magmatic fluids leads to high-salinity and high-temperature fluids which have high capacity to transport Pb,Zn and Sb.The decrease in temperature and mixing with fluids from other sources may have caused the precipitation of Pb-Zn-Sn（Au） minerals in the distal fault systems surrounding the causative intrusion.展开更多
Western Altun in Xinjiang is an important area,where lithium(Li)-bearing pegmatites have been found in recent years.However,the complex terrain and harsh environment of western Altun exacerbates in prospecting for Li-...Western Altun in Xinjiang is an important area,where lithium(Li)-bearing pegmatites have been found in recent years.However,the complex terrain and harsh environment of western Altun exacerbates in prospecting for Li-bearing pegmatites.Therefore,remote-sensing techniques can be an effective means for prospecting Li-bearing pegmatites.In this study,the fault information and lithologyical information in the region were obtained using the median-resolution remotesensing image Landsat-8,the radar image Sentinel-1 and hyperspectral data GF-5.Using Landsat-8 data,the hydroxyl alteration information closely related to pegmatite in the region was extracted by principal component analysis,pseudoanomaly processing and other methods.The high spatial resolution remote-sensing data WorldView-2 and WorldView-3 short-wave infrared images were used and analyzed by principal component analysis(PCA),the band ratio method and multi-class machine learning(ML),combined with conventional thresholds specified the algorithms used to automatically extract Li-bearing pegmatite information.Finally,the Li-bearing pegmatite exploration area was determined,based on a comprehensive analysis of the faults,hydroxyl alteration lithology and Li-bearing pegmatite information.Field investigations have verified that the distribution of pegmatites in the central part of the study area is consistent with that of Li-bearing pegmatites extracted in this study.This study provides a new technique for prospecting Li-bearing pegmatites,which shows that remote-sensing technology possesses great potential for identifying lithium-bearing pegmatites,especially in areas that are not readily accessible.展开更多
Petrography and geochemistry of the altered and unaltered host rocks surrounding the Koktokay No.3 pegmatite revealed that the unaltered amphibolite is mainly composed of hornblende, plagioclase, and ilmenite.Beyond t...Petrography and geochemistry of the altered and unaltered host rocks surrounding the Koktokay No.3 pegmatite revealed that the unaltered amphibolite is mainly composed of hornblende, plagioclase, and ilmenite.Beyond these primary components, the altered host rocks contain a few newly formed minerals, including biotite,tourmaline, chlorine, and muscovite. The alteration zone surrounding the Koktokay No.3 pegmatite is limited to 2.0 m, characterized by biotitization, tourmalization, and chloritization. In the altered host rocks, the contents of SiO2, MgO, MnO, Na2O, and TiO2 did not vary greatly.However, Al2O3 showed a weak decreasing trend with the increasing distance from the pegmatite contact zone, while Fe2O3 and CaO showed an increasing trend. The contents of Li, Rb, and Cs in the altered host rocks were much higher than those in the unaltered host rocks, decreasing with distance from the contact. The chondrite-normalized rare earth element（REE） pattern of the altered and unaltered host rock was right-inclined from La to Lu, but enriched in light REEs over heavy REEs after hydrothermal alteration. An isocon plot shows that some oxides migrated in with an order of P2O5〉K2O 〉TiO2〉Al2O3〉SiO2〉MnO≥MgO, while others migrated out with an order of Na2O 〉CaO 〉Fe2O3. For REEs, the migration ratios are positive values withCs 〉Rb 〉Li 〉Nb 〉Ta 〉Be, signifying that all REEs migrated from the exsolved magmatic fluid into the altered host rocks. It was concluded that diffusion was the only mechanism for migration of ore-forming elements in the alteration zone. The effective diffusion coefficients（Deff）of LiF, RbF, and CsF were estimated under a fluid temperature of 500–550℃. Using a function of concentration（C（x,t）） and distance（x）, the order of migration distance was determined to be LiF 〉CsF 〉RbF, with diffusion times of （3.39 ± 0.35）× 10^6,（3.19 ± 0.28） × 10^5 and（6.33 ± 0.05） × 10^5 years, respectively.展开更多
Remote sensing technique plays an important role in geological prospecting in Altay because of the remote location and steep terrain with mountains. Pegmatite has important implications for metallogenic prospecting as...Remote sensing technique plays an important role in geological prospecting in Altay because of the remote location and steep terrain with mountains. Pegmatite has important implications for metallogenic prospecting as most of rare metals occurs in it. Pegmatite information from optical and radar images was extracted, and the spatial distribution and scale of pegmatite were generalized in Azubai, Altay. Three mining targets, that is, Halon-Azubai, Kuermutu-Tuyibaguo and Zhuolute-Akuoyige, were delineated based on the analysis of pegmatite information, structure interpretation and other geological data.展开更多
1.Objectives Keeryin rare metal ore district is located at the intersection of Markam,Jinchuan and Rangtang counties.More than 1000 pegmatite dykes are associated with the Keeryin granite pluton.These pegmafite dykes ...1.Objectives Keeryin rare metal ore district is located at the intersection of Markam,Jinchuan and Rangtang counties.More than 1000 pegmatite dykes are associated with the Keeryin granite pluton.These pegmafite dykes are the major source of industrial spodumene ore bodies.Based on the previous studies,we chose Keeryin rare metal ore district as the key target area for geology survey.In this study,we discovered six pegmatite lithium veins in the Sizemuzu district of the Keeryin.Moreover,we study the distribution of regional ore deposits and metallogeny,delineate prospecting target and evaluate the mineralization potential of Lithium.展开更多
This article is investigating analysis and chemical composition of ceramic pegmatite minerals obtained from the Terek deposit in Toktogul district of Kyrgyzstan. Several methods such as mineralogical studies, magnetic...This article is investigating analysis and chemical composition of ceramic pegmatite minerals obtained from the Terek deposit in Toktogul district of Kyrgyzstan. Several methods such as mineralogical studies, magnetic and gravitational enrichments, silicate and chemical analyses of ceramic pegmatite minerals, quartz-feldspathic concentrate and sludge removal have been performed for determination of pegmatite mineral applicability for production of porcelain and earthenware.展开更多
In the Kenticha area,a series of barren to rare metal-bearing pegmatites intruded into the Neoproterozoic Adola Belt.The pegmatites host world-class Nb and Ta deposits and significant Li and Be reserves.In this contri...In the Kenticha area,a series of barren to rare metal-bearing pegmatites intruded into the Neoproterozoic Adola Belt.The pegmatites host world-class Nb and Ta deposits and significant Li and Be reserves.In this contribution,fluid inclusion data and feldspar geothermometry have been combined to define the crystallization condition of the Kenticha rare-metal pegmatite.Primary and complex assemblages of secondary fluid inclusions representing episodic fluid circulations have been identified in quartz and spodumene.A primary aqueous-carbonic fluid of low salinity aqueous solution with liquid and vapour CO_(2) phases,secondary carbonic fluid rich and carboniconly fluids,and multiple generations of secondary aqueous inclusions that represent sub-solidus hydrothermal circulation have been identified.All aqueous inclusions were homogenized into the liquid phase between 100 and 290℃.Aqueous-carbonic inclusions were homogenized,usually via a critical transition[T_(h)(LV→SCF)]between 241 and 397℃,or less commonly,via a dew-point transition[T_(h)(LV→V)]between 213 and 264℃.Crystallization of the rare-element pegmatite is certainly associated with the late-stage magmatic or early hydrothermal low-salinity aqueous-carbonic fluid that homogenizes to critical conditions.A combination of microthermometric data and existing experimentally determined solidus from flux and volatile bearing haplogranite suggests exsolution of fluids from hydrous silicate melt,perhaps during crystallization of the aplitic layer.The fluids were then trapped and isobarically cooled along a reasonable geothermal gradient within the pegmatite unit down to a temperature of around 397℃.展开更多
The Wadi Ibib area is situated in the northern part of the Neoproterozoic Hamisana Shear Zone(HSZ), which is a high strain zone evolved during the late stages of the Pan-African orogeny, likely as a tectonic escape st...The Wadi Ibib area is situated in the northern part of the Neoproterozoic Hamisana Shear Zone(HSZ), which is a high strain zone evolved during the late stages of the Pan-African orogeny, likely as a tectonic escape structure. Amphibolite facies pelitic metasedimentary windows crop out in the axial parts of the HSZ and are noticeably associated with numerous N-trending pegmatite dikes. Whole-rock geochemistry of the pegmatites reveals a peraluminous(S-type) affinity, with low K/Rb ratios and elevated concentrations of U, Th, REE, Rb, Li, Cs, Y, Nb and Ta. Structurally, the pegmatite sets intrude along the shear plane of the HSZ, corresponding to the regional N-trending tectonic fabrics, such as axial planar foliation and dextral-shearing in the metasedimentary host rock. Field relationships, including structural context, coupled with geochemical characteristics of the Wadi Ibib pegmatites, do not support their formation as a complementary part of evolved granitic magmas. Space-localized decompression-induced partial melting of peraluminous garnet-bearing metapelites was alternatively the underlying process for formation of these pegmatites. Such decompression was associated with regional escape tectonics and stress axes permutations during the late deformation stage(D3) in the evolution of the south Eastern Desert terrane, due to end-orogeny system pressure-release.展开更多
基金supported by the Key Research Program of the Institute of Geology&Geophysics,CAS(IGGCAS-202205)the National Natural Science Foundation of China(Grant No.92062216 and 42102046)+1 种基金Doctoral Students'Scientific Research and Innovation Capability Enhancement Program of Jilin Province(JJKH20250074BS)Graduate Innovation Fund of Jilin University(2024CX231).
文摘Highly evolved granite associated with pegmatite shells exhibits significant potential for rare metal mineralization;however,the mechanisms through which these pegmatite shells contribute to magmatic evolution and rare metal enrichment remain poorly understood.The Late Jurassic Shihuiyao Nb-Ta-(Rb-Be-Li)deposit is one of the largest rare-metal deposits in the Southern Great Xing’an Range(SGXR),Northeast China.Exploratory trenches expose distinct layered zones from top to bottom:alternating microcline pegmatite and aplite layers(zone I),topaz lepidolite albite granite and lepidolite amazonite pegmatite(zone II),and muscovite albite granite(zoneⅢ).We conducted U-Pb dating of cassiterite,monazite,and Nb-Ta oxide,monazite Nd isotopes,and whole-rock and mineral geochemistry for the three zones.Multi-mineral U-Pb ages indicate that the three zones formed during the Late Jurassic-Early Cretaceous(147-142 Ma).Geochemical analyses of whole-rock,mica,and microcline suggest an evolutionary sequence from zone I to zoneⅢ,and finally to zone II.The Zr/Hf,Nb/Ta,Y/Ho,and K/Rb ratios combined with the rare earth element(REE)tetrad effects suggest higher degree of differentiation and fluid-melt interaction of the Shihuiyao leucogranite without a pegmatite shell compared to coeval barren granites from both Shihuiyao and the SGXR.A progressive increase in the degree of evolution is evident from the leucogranite without a pegmatite shell to the leucogranite with a discontinuous shell,and ultimately to the leucogranite with a continuous shell.The pegmatite shell acted as a geochemical barrier that facilitated the accumulation of Li and F in the underlying magma,which played a crucial role in lowering the solidus temperature of the granitic magma.This process prolonged the crystallization duration while reducing melt viscosity and density,thereby creating favorable conditions for magma differentiation and fluid-melt interaction.Rapid crystallization of the earlier water-and Be-rich melt led to the Be mineralization in the pegmatite shell.Moreover,the formation of this shell served as a barrier for Li mineralization in the underlying topaz lepidolite albite granite.This study enhances our understanding of the critical contribution of pegmatite shells to magmatic evolution and rare-metal mineralization.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.42102110,U2444204,42472111 and U2344220).
文摘The Duanfengshan deposit is a newly discovered large pegmatitic-type Nb-Ta deposit in the central section of the Jiangnan orogenic belt,South China.There are three types of pegmatite in the Duanfengshan area:microcline pegmatite,microcline-albite pegmatite and albite pegmatite.Although several geological,geochronological and geochemical studies of this deposit have been carried out,the relationships between the evolution degree of different types of pegmatites and mineralization are still unclear.We address this problem through systematic petrographic and geochemical studies of muscovite and feldspars from two representative pegmatite veins,the No.328 microcline-albite pegmatite vein,and the No.610 albite pegmatite vein.The results of electron probe microanalysis(EPMA)and laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)analyses of muscovite and K-feldspar reveal that K/Rb ratios decrease with increasing Rb,Cs,Ga,Nb and Ta contents alongside decreasing Ba and Sr contents,suggesting that magmatic differentiation played a dominant role in rare metal mineralization.A comparison of the analytical results of this study with those from rare metal pegmatites globally suggests that the No.610 vein has a high mineralization potential,whereas the No.328 vein has relatively low mineralization potential.The results from this study may be applied to the evaluation of mineralization potential for other pegmatite veins in the Duanfengshan area and other rare metal pegmatite fields with similar geological settings.
基金The National Key Research and Development Program of China(No.2021YFC2901903)the National Key Research and Development Program of China(No.2023YFC2906805)+1 种基金the Second Comprehensive Scientific Expedition to the Qinghai-Tibet Plateau(No.2019QZKK0806)the Geological Survey Project of China Geological Survey,(Nos.DD20240071,DD20240014,DD20211690,DD20240069)。
文摘The Gabo lithium deposit represents a newly discovered pegmatite-type lithium deposit within the Himalayan metallogenic belt.The tourmaline-muscovite granite,the largest leucogranite in the mining area,displays a close spatial correlation with the Li-pegmatite veins.This study aims to examine the genesis of tourmaline and evaluate the significance and potential of pegmatite lithium deposits.Tourmaline is extensively distributed in tourmaline-muscovite granite at Gabo deposit in Luozha county(Xizang).Investigation of the compositional and in situ boron isotopes of the tourmaline revealed that the tourmalines mainly belong to the schorl group and exhibit uniform elevated Li-Sn contents andδ^(11)B values(-11.6‰to-10.5‰).This indicates that the tourmaline mainly crystallized from a boron-rich granitic magma undergoing enrichment in elemental lithium during the tourmaline crystallization process.Compared with the principal rare metal leucogranite-pegmatites in the Himalayan orogen,it is proposed that the elevated lithium(Li)content of tourmaline serves as an eff ective mineral indicator for the highly evolved pegmatite-type rare metal deposits.
基金supported by the National Key R&D Program of China(Grant Nos.2021YFC2901902 and 2019YFC0605202)。
文摘The Guanpo pegmatite field in the North Qinling orogenic belt(NQB),China,hosts the most abundant LCT pegmatites.However,their emplacement conditions and structural control remain unexplored.In this contribution,we investigated it combining pegmatite orientation measurement with oxygen isotope geothermometry and fluid inclusion study.The orientations of type A1 pegmatites(P_(f)<σ_(2))are predominantly influenced by P-and T-fractures due to simple shearing in Shiziping dextral thrust shear zone during D_(2)deformation,whereas type A2 pegmatites(contemporaneous with D_(4))are governed by hydraulic fractures aligned with S_(0)and S_(0+1)stemming from fluid pressure(P_(f)<σ_(2)).Additionally,type B pegmatites(P_(f)≤σ_(2))exhibit orientations shaped by en echelon extensional fractures in local ductile shear zones(contemporaneous with D_(3)).The albite-quartz oxygen isotope geothermometry and microthermometric analysis of fluid inclusions in elbaites from the latest pegmatites(including types B and A2)suggest that the crystallization P-T for late magmatic and hydrothermal stages are 527.5-559.2℃,320℃,3.1-3.6 kbar and 2.0 kbar,respectively.Our observations along with previous studies suggest that the genesis of the LCT pegmatites was a long-term,multi-stage event during early Paleozoic orogeny(including the collision stage)of the NQB,and was facilitated by various local fractures.
基金financially supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0802)。
文摘Lack of information regarding lithium(Li)crystal chemistry in numerous minerals,especially those containing trace amounts of Li(ranging from a few to tens of ppm),limits our understanding of Li isotopic fractionation in pegmatites.In this study,we examined the Li isotopic composition and Li content in various Li-poor(e.g.,quartz or feldspar)together with Li-rich(sopdumene or lepidolite)mineral phases within granitic pegmatites.We compiled a comprehensive dataset,encompassing a broad spectrum of Li contents(ranging from a few to tens of thousands of ppm)and Li isotopic values(-8‰to 41‰).The minerals exhibit distinct Li isotopic signatures.Specifically,elbaite and beryl show the highest values,while biotite displays a negative average.Compared to individual minerals,whole rocks demonstrate lower Li isotopic values,with pegmatites exhibiting the highest and non-granitic pegmatite wall rocks showing the lowest.Our study also uncovers a clear“V”shape relationship between Li isotopic values and logarithm of Li contents,with different mineral groups occupying specific regions within this shape.Furthermore,a significant correlation was observed between average Li isotopic values and Li-O(OH,F)bond lengths in various minerals.These discoveries underscore the crucial role of crystal chemistry in shaping the Li isotopic behavior in pegmatites from a statistical perspective.
基金The study was conducted within the framework of the state task(topic ID 0350-2019-0007)and supported by grant 20-55-44002-Mong_a of the Russian Foundation for Basic Research.
文摘The detailed description of two granite complexes in the Olkhon subterrane is given.The Early Paleozoic Sharanur complex was formed by granitization of gneisses of the Olkhon series.It includes migmatites,granite-gneisses,granites and pegmatites of normal alkalinity;they belong to the type of syncollisional granites.The Middle Paleozoic Aya granite complex includes mother Aya massif of amazonite-bearing granites and several types of rare-metal pegmatites.They have elevated alkalinity,low of Ba,Sr,and high LILE and HFSE elements contents.The Aya pegmatites lie in northwest cracks of stretching and associated with the rise of the territory under the influence of the North Asian plume.These cracks and pegmatites mark the beginning of a new intraplate geodynamic setting.Two geochemical types are distinguished among the pegmatites of this complex.These are amazonite pegmatites of Li-F type with Ta mineralization and complex type pegmatite with Be-Rb-Nb-Ta and Li-F mineralization(the Ilixin vein).The Tashkiney pegmatite vein is similar to Ilixin,but lies in the gneisses of the Olkhon series.It shows high concentrations of Be,Nb,Ta,as well as W,Sn,but lacks Li and F,due to a greater depth and higher temperature of the melt crystallization of this pegmatite.
文摘The lithium potential in the Aïr massif is represented by mineral index of spodumene pegmatites and, lepidolite pegmatites. The mineral deposits of lithium occur in cluster or veins that cut the host rock or are located near the contact between the greenstone belt and granitic massif. The evidence of lithium is in the form of clusters or disseminated and stockwerk. Mineralogical characteristics show similarities between the Air Massif pegmatites and indicate the same homogenous source during the magma-generation process. The pegmatite rocks attracted the attention due to their wide exposure and composition, well appearance, and economically hosting of significant rare earth metals such as Sn and W. The mineralogical and petrographical investigations on the eight pegmatites rocks samples observed have a relative similarity, while a little difference in the shapes attributed to the ratio in the pegmatite rocks of the minerals. The occurrence of the kink band indicates the influence of the tectonic processes which affected the Aïr massif after the emplacement of late magmatic or post-magmatic pegmatites by injection into fractured rocks in the upper part of the crust. The Air Massif pegmatite has higher concentrations Li and of all trace elements except Hf and occasionally Zr, Ti, Sn and Mg of for the economic exploration.
基金supported by grants from the National Natural Science Foundation of China (40702014)the China Postdoctoral Science Foundation (2008044018,200902580)+1 种基金the Chinese SinoProbe Project (SinoProbe-03-01)the National Nonprofit Institute Research Grant of IMR,GAGS(K1001)
文摘Granitic pegmatites are commonly thought to form by fractional crystallization or by liquid immiscibility of granitic magma; however, these proposals are based mainly on analyses of fluid and melt inclusions. Here, we use the Jiajika pegmatite deposit, the largest spodumene deposit in Asia, as a case study to investigate ore forming processes using isotope dating. Dating of a single granite sample from the Jiajika deposit using multiple methods gave a zircon U-Pb SHRIMP age of 208.4 ~ 3.9 Ma, an 4~Ar/39Ar age for muscovite of 182.9 ~ 1.7 Ma, and an 4~Ar/39Ar age for biotite of 169.9 ＋ 1.6 Ma. Based on these dating results and the 4~Ar/39Ar age of muscovite from the Jiajika pegmatite, a temperature-time cooling track for the Jiajika granite was constructed using closure temperatures of the different isotope systems. This track indicates that the granite cooled over ^-40 m. y., with segregation of the pegmatite fluid from the granitic magma at a temperature of ~700~C. This result suggests that the Jiajika pegmatite formed not by fractional crystallization, but by segregation of an immiscible liquid from the granitic magma. When compared with fractional crystallization, the relatively early timing of segregation of an immiscible liquid from a granitic magma can prevent the precipitation of ore-forming elements during crystallization, and suggests that liquid immiscibility could be an important ore-forming process for rare metal pegmatities. We also conclude that isotope dating is a method that can potentially be used to determine the dominant ore-forming processes that occurred during the formation of granite-related ore deposits, and suggest that this method can be employed to determine the formation history of the W-Sn ore deposits found elsewhere within the Nanling Metallogenic Belt.
基金funded by the National Natural Science Foundation of China(No.41703048,41872096)the Chinese National Nonprofit Institute Research Grant of CAGS,CGS(YYWF201520,JYYWF201814)the China Geological Survey(DD20160055,DD20190173)
文摘The Zhawulong granitic pegmatite lithium deposit is located in the Ganzi-Songpan orogenic belt.Fluid inclusions in spodumene and coexisting quartz were studied to understand the cooling path and evolution of fluid within albite–spodumene pegmatite.There are three distinguishable types of fluid inclusions:crystal-rich,CO2–NaCl–H2 O,and NaCl–H2 O.At more than 500°C and 350~480 MPa,crystal-rich fluid inclusions were captured during the pegmatitic magma-hydrothermal transition stage,characterized by a dense hydrous alkali borosilicate fluid with a carbonate component.Between 412°C and 278°C,CO2–Na Cl–H2 Ofluid inclusions developed in spodumene(I)and quartz(II)with a low salinity(3.3–11.9 wt%NaCl equivalent)and a high volatile content,which represent the boundary between the transition stage and the hydrothermal stage.The subsequentNaCl–H2 Ofluid inclusions from the hydrothermal stage,between 189°C and 302°C,have a low salinity(1.1–13.9 wt%NaCl equivalent).The various types of fluid inclusions reveal the P–T conditions of pegmatite formation,which marks the transition process from magmatic to hydrothermal.The oreforming fluids from the Zhawulong deposit have many of the same characteristics as those from the Jiajika lithium deposit.The ore-forming fluid provided not only materials for crystallization of rare metal minerals,such as spodumene and beryl,but also the ideal conditions forthe growth of ore minerals.Therefore,this area has favorable conditions for lithium enrichment and excellent prospecting potential.
基金supported by the US National Science Foundation (CMMI award 1550307)the China Scholarship Council for financial support as a visiting scholar at the Colorado School of Mines (Grant No. 201706375077)
文摘Fully-coupled thermo-mechanical simulations are implemented in COMSOL Multiphysics to investigate micro-scale stress-strain variability in pegmatite specimens subjected to thermal loading using microwaves. Thermally-induced compressive and tensile stresses increase as the microwave irradiation duration increases. The dielectric constant, coefficient of expansion, and type and size of mineralogical boundary have significant impacts on the responses of the rock to microwave irradiation. The maximum principal stress of the chlorite is the smallest, indicating that the chlorite experiences the most damage under microwave irradiation, followed by the quartz. The maximum principal stress values of plagioclase and orthoclase are larger, indicating that they are likely to incur the least damage. Where quartz or chlorite is dominant, the resulting von Mises stresses are consistently higher after 120 s of microwave irradiation. The rate of generation of von Mises stresses increases most rapidly along the interface between quartz and plagioclase, and the interface between quartz and orthoclase, followed by the interface between quartz and chlorite, and finally the interface between plagioclase and orthoclase. The presented modeling approach provides a practical method to investigate stress-strain relationships within mineralogical boundaries inside a rock thin section.
文摘In this paper, we show that supercritical fluids have a greater significance in the generation of pegmatites,and for ore-forming processes related to granites than is usually assumed. We show that the supercritical melt or fluid is a silicate phase in which volatiles; principally H_2O are completely miscible in all proportions at magmatic temperatures and pressures. This phase evolves from felsic melts and changes into hydrothermal fluids, and its unique properties are particularly important in sequestering and concentrating low abundance elements, such as metals. In our past research, we have focused on processes observed at upper crustal levels, however extensive work by us and other researchers have demonstrated that supercritical melt/fluids should be abundant in melting zones at deep-crustal levels too. We propose that these fluids may provide a connecting link between lower and upper crustal magmas,and a highly efficient transport mechanism for usually melt incompatible elements. In this paper, we explore the unique features of this fluid which allow the partitioning of variouselements and compounds, potentially up to extreme levels,and may explain various features both of mineralization and the magmas that produced them.
基金financially supported by the National Key Basic Research Program of China (No. 2006CB403506)the National Natural Science Foundation of China (No. 41203011)the Fundamental Research Funds for the Central Universities (No. 2013B03014)
文摘In this study, we carried out petrography, zircon U-Pb geochronology and Hf isotopic analyses on a granitic pegmatite dyke in the Xiaoqinling area in southern margin of the North China Craton（NCC）. Our study suggests that the pegmatite dyke likely crystallized from a volatile-rich pegmatitic magma. Different from most other pegmatite elsewhere, zircon from this pegmatite dyke does not contain unusually high U and Th concentrations and suffered no evident radioactive damage, therefore we successfully obtained a zircon U-Pb dating using laser ablation-inductively coupled plasma-mass spectrometry（LA-ICP-MS）, which yields an average 207Pb/206 Pb age of 1 814±6 Ma, representing the intrusive age of the granitic pegmatite dyke. Zircon εHf（t） values are between-8.3 and-3.0, corresponding to Hf depleted mantle model ages from 2 649 to 2 991 Ma with an average of 2 881 Ma. These data indicate that this granitic pegmatite dyke may have been derived from partial melting of Meso-Neoarchean metamorphic rocks from the Xiaoqinling basement. Granitic pegmatite magma may have emplaced within the Taihua Group wall rocks during the last stage of the middle to high grade metamorphism. Furthermore, according to the petrographic observation, the 1.81 Ga pegmatite dyke and the 1 800–1 750 Ma Xiong’er Group rocks were not undergone middle to high grade metamorphism, indicating 1.81 Ga as the termination of the latest regional metamorphism in the southern margin of the NCC.
基金financially supported by the State Basic Research Plan(973 project)(No.2011CB403100)IGCP/SIDA-600 project
文摘The Zhaxikang Pb-Zn-Sb polymetallic deposit is one of the most important deposits in the newly recognized southern Tibet antimony-gold metallogenic belt.Compared to the porphyry deposits in the Gangdese belt,much less researches have addressed these deposits,and the genesis of the Zhaxikang deposit is still controversial.Based on field investigation,petrographic,microthermometric,Laser Raman Microprobe（LRM） and SEM/EDS analyses of fluid,melt-fluid,melt and solid inclusions in quartz and beryl from pegmatite,this paper documents the characteristics and the evolution of primary magmatic fluid which was genetically related to greisenization,pegmatitization,and silification in the area.The results show that the primary magmatic fluids were derived from unmixing between melt and fluid and underwent a phase separation process soon after the exsolution.The primary magmatic fluids are of low salinity,high temperature,and can be approximated by the H_2O-NaCl-CO_2 system.The presence of Mn-Fe carbonate in melt-fluid inclusions and a Zn-bearing mineral（gahnite） trapped in beryl and in inclusions from pegmatite indicates high Mn,Fe,and Zn concentrations in the parent magma and magmatic fluids,and implies a genetic link between pegmatite and Pb-Zn-Sb mineralization.High B and F concentrations in the parent magma largely lower the solidus of the magma and lead to late fluid exsolution,thus the primary magmatic fluids related to pegmatite have much lower temperature than those in most porphyry systems.Boiling of the primary magmatic fluids leads to high-salinity and high-temperature fluids which have high capacity to transport Pb,Zn and Sb.The decrease in temperature and mixing with fluids from other sources may have caused the precipitation of Pb-Zn-Sn（Au） minerals in the distal fault systems surrounding the causative intrusion.
基金supported by the National Key Research and Development Program of the China Geological Survey(DD20190173)the Fundamental Research Funds for the Institute of Mineral Resources,the Chinese Academy of Geological Sciences(KK2102)+1 种基金the National Natural Science Foundation of China(42172332)the Chinese Geological Survey Project(DD20190379)。
文摘Western Altun in Xinjiang is an important area,where lithium(Li)-bearing pegmatites have been found in recent years.However,the complex terrain and harsh environment of western Altun exacerbates in prospecting for Li-bearing pegmatites.Therefore,remote-sensing techniques can be an effective means for prospecting Li-bearing pegmatites.In this study,the fault information and lithologyical information in the region were obtained using the median-resolution remotesensing image Landsat-8,the radar image Sentinel-1 and hyperspectral data GF-5.Using Landsat-8 data,the hydroxyl alteration information closely related to pegmatite in the region was extracted by principal component analysis,pseudoanomaly processing and other methods.The high spatial resolution remote-sensing data WorldView-2 and WorldView-3 short-wave infrared images were used and analyzed by principal component analysis(PCA),the band ratio method and multi-class machine learning(ML),combined with conventional thresholds specified the algorithms used to automatically extract Li-bearing pegmatite information.Finally,the Li-bearing pegmatite exploration area was determined,based on a comprehensive analysis of the faults,hydroxyl alteration lithology and Li-bearing pegmatite information.Field investigations have verified that the distribution of pegmatites in the central part of the study area is consistent with that of Li-bearing pegmatites extracted in this study.This study provides a new technique for prospecting Li-bearing pegmatites,which shows that remote-sensing technology possesses great potential for identifying lithium-bearing pegmatites,especially in areas that are not readily accessible.
基金supported jointly by the Natural Science Foundation of China (Grant No.41372104)Research Project of Xinjiang Nonferrous Metals Industry (Group) Co.,Ltd.(Grant No.YSKY2011-02)
文摘Petrography and geochemistry of the altered and unaltered host rocks surrounding the Koktokay No.3 pegmatite revealed that the unaltered amphibolite is mainly composed of hornblende, plagioclase, and ilmenite.Beyond these primary components, the altered host rocks contain a few newly formed minerals, including biotite,tourmaline, chlorine, and muscovite. The alteration zone surrounding the Koktokay No.3 pegmatite is limited to 2.0 m, characterized by biotitization, tourmalization, and chloritization. In the altered host rocks, the contents of SiO2, MgO, MnO, Na2O, and TiO2 did not vary greatly.However, Al2O3 showed a weak decreasing trend with the increasing distance from the pegmatite contact zone, while Fe2O3 and CaO showed an increasing trend. The contents of Li, Rb, and Cs in the altered host rocks were much higher than those in the unaltered host rocks, decreasing with distance from the contact. The chondrite-normalized rare earth element（REE） pattern of the altered and unaltered host rock was right-inclined from La to Lu, but enriched in light REEs over heavy REEs after hydrothermal alteration. An isocon plot shows that some oxides migrated in with an order of P2O5〉K2O 〉TiO2〉Al2O3〉SiO2〉MnO≥MgO, while others migrated out with an order of Na2O 〉CaO 〉Fe2O3. For REEs, the migration ratios are positive values withCs 〉Rb 〉Li 〉Nb 〉Ta 〉Be, signifying that all REEs migrated from the exsolved magmatic fluid into the altered host rocks. It was concluded that diffusion was the only mechanism for migration of ore-forming elements in the alteration zone. The effective diffusion coefficients（Deff）of LiF, RbF, and CsF were estimated under a fluid temperature of 500–550℃. Using a function of concentration（C（x,t）） and distance（x）, the order of migration distance was determined to be LiF 〉CsF 〉RbF, with diffusion times of （3.39 ± 0.35）× 10^6,（3.19 ± 0.28） × 10^5 and（6.33 ± 0.05） × 10^5 years, respectively.
基金Project(11JJ6029)supported by Natural Science Foundation of Hunan Province,ChinaProject(2011QNZT006)supported by Fundamental Research Funds for the Central Universities,China
文摘Remote sensing technique plays an important role in geological prospecting in Altay because of the remote location and steep terrain with mountains. Pegmatite has important implications for metallogenic prospecting as most of rare metals occurs in it. Pegmatite information from optical and radar images was extracted, and the spatial distribution and scale of pegmatite were generalized in Azubai, Altay. Three mining targets, that is, Halon-Azubai, Kuermutu-Tuyibaguo and Zhuolute-Akuoyige, were delineated based on the analysis of pegmatite information, structure interpretation and other geological data.
文摘1.Objectives Keeryin rare metal ore district is located at the intersection of Markam,Jinchuan and Rangtang counties.More than 1000 pegmatite dykes are associated with the Keeryin granite pluton.These pegmafite dykes are the major source of industrial spodumene ore bodies.Based on the previous studies,we chose Keeryin rare metal ore district as the key target area for geology survey.In this study,we discovered six pegmatite lithium veins in the Sizemuzu district of the Keeryin.Moreover,we study the distribution of regional ore deposits and metallogeny,delineate prospecting target and evaluate the mineralization potential of Lithium.
文摘This article is investigating analysis and chemical composition of ceramic pegmatite minerals obtained from the Terek deposit in Toktogul district of Kyrgyzstan. Several methods such as mineralogical studies, magnetic and gravitational enrichments, silicate and chemical analyses of ceramic pegmatite minerals, quartz-feldspathic concentrate and sludge removal have been performed for determination of pegmatite mineral applicability for production of porcelain and earthenware.
文摘In the Kenticha area,a series of barren to rare metal-bearing pegmatites intruded into the Neoproterozoic Adola Belt.The pegmatites host world-class Nb and Ta deposits and significant Li and Be reserves.In this contribution,fluid inclusion data and feldspar geothermometry have been combined to define the crystallization condition of the Kenticha rare-metal pegmatite.Primary and complex assemblages of secondary fluid inclusions representing episodic fluid circulations have been identified in quartz and spodumene.A primary aqueous-carbonic fluid of low salinity aqueous solution with liquid and vapour CO_(2) phases,secondary carbonic fluid rich and carboniconly fluids,and multiple generations of secondary aqueous inclusions that represent sub-solidus hydrothermal circulation have been identified.All aqueous inclusions were homogenized into the liquid phase between 100 and 290℃.Aqueous-carbonic inclusions were homogenized,usually via a critical transition[T_(h)(LV→SCF)]between 241 and 397℃,or less commonly,via a dew-point transition[T_(h)(LV→V)]between 213 and 264℃.Crystallization of the rare-element pegmatite is certainly associated with the late-stage magmatic or early hydrothermal low-salinity aqueous-carbonic fluid that homogenizes to critical conditions.A combination of microthermometric data and existing experimentally determined solidus from flux and volatile bearing haplogranite suggests exsolution of fluids from hydrous silicate melt,perhaps during crystallization of the aplitic layer.The fluids were then trapped and isobarically cooled along a reasonable geothermal gradient within the pegmatite unit down to a temperature of around 397℃.
基金supported by a research cooperation(Grant No.3TE1107T)between Kyushu University,Japan and the Egyptian Nuclear Materials Authority(NMA)。
文摘The Wadi Ibib area is situated in the northern part of the Neoproterozoic Hamisana Shear Zone(HSZ), which is a high strain zone evolved during the late stages of the Pan-African orogeny, likely as a tectonic escape structure. Amphibolite facies pelitic metasedimentary windows crop out in the axial parts of the HSZ and are noticeably associated with numerous N-trending pegmatite dikes. Whole-rock geochemistry of the pegmatites reveals a peraluminous(S-type) affinity, with low K/Rb ratios and elevated concentrations of U, Th, REE, Rb, Li, Cs, Y, Nb and Ta. Structurally, the pegmatite sets intrude along the shear plane of the HSZ, corresponding to the regional N-trending tectonic fabrics, such as axial planar foliation and dextral-shearing in the metasedimentary host rock. Field relationships, including structural context, coupled with geochemical characteristics of the Wadi Ibib pegmatites, do not support their formation as a complementary part of evolved granitic magmas. Space-localized decompression-induced partial melting of peraluminous garnet-bearing metapelites was alternatively the underlying process for formation of these pegmatites. Such decompression was associated with regional escape tectonics and stress axes permutations during the late deformation stage(D3) in the evolution of the south Eastern Desert terrane, due to end-orogeny system pressure-release.
