The Suzhou granitic pluton is the first identified Nb-Ta-rich granite in China.To reveal the genetic link between the sequence of magmatic and hydrothermal evolution and Nb-Ta mineralization in different intrusive pha...The Suzhou granitic pluton is the first identified Nb-Ta-rich granite in China.To reveal the genetic link between the sequence of magmatic and hydrothermal evolution and Nb-Ta mineralization in different intrusive phases of the Suzhou granite,whole-rock geochemistry,geochemistry and U-Th-Pb dating of monazite was analyzed.The unique geochemical characteristics show that the Suzhou pluton can be discriminated as an A-type granite.LA-ICP-MS U-Th-Pb dating of monazite in both the medium-and coarse-grained biotite granite(MBG)and the fine-grained biotite granite(FBG)indicates that the granite formed between 124 and 127 Ma.Based on geochemical characteristics and mineral textures,the MBG(Mnz-Ia)and FBG(Mnz-Ib)monazites are classified as magmatic monazites;another monazite(Mnz-II)from the MBG formed during a magmatic-hydrothermal transitional stage.Nb-Ta in the Suzhou pluton gradually concentrated during fractional crystallization and alteration of Ti-rich minerals and biotite.Ultimately,with the involvement of F-Li-rich fluid,Nb-Ta mineralization occurred during the magmatic-hydrothermal transition.The Suzhou pluton is considered part of a 600-km-and NE-SW-trending Nb-rich A-type granite belt together with other Early Cretaceous A-type granites in the Jiangnan Orogen that offers prospects of a new target for Nb-Ta prospecting.展开更多
To completely recover valuable elements and reduce the amount of waste,the impact of phosphoric acid on the decomposition of rare earth,fluorine and phosphorus during cyclic leaching was studied based on the character...To completely recover valuable elements and reduce the amount of waste,the impact of phosphoric acid on the decomposition of rare earth,fluorine and phosphorus during cyclic leaching was studied based on the characteristics of low-tempe rature sulfuric acid deco mposition.When a single monazite was leached using 75 wt% H_(2)SO_(4) solution with phosphoric acid,the size and number of monazite particles in the washing slag gradually decrease with the increase in phosphoric acid content in the leaching solution.The monazite phase can hardly be found in the slag when the phosphoric acid content reaches 70 g/L,which indicates that phosphoric acid is favorable for monazite decomposition.The mixed rare earth concentrate was leached by 75 wt% H_(2)SO_(4) containing 70 g/L phosphoric acid,the mineral compositions of the washing slag are only gypsum and unwashed rare earth sulfuric acid.After cyclic leaching of75 wt% H_(2)SO_(4),the mineral compositions of the primary leaching washing slag are mainly undecomposed monazite,rare earth sulfate and calcium sulfate.However,monazite is not found in the mineral phase of the second and third leaching washing slag.The leaching rates of rare earth and phosphorus gradually increase with the increase in cyclic leaching times.In addition,the phosphoric acid content in the leaching solution increases with the increase in the number of cyclic leaching time.However,the rising trend decreases when the phosphoric acid content reaches 50 g/L by adsorption and crystallization of phosphoric acid.A small amount of water can be used to clean the leaching residue before washing to recover the more soluble phosphorus acid according to the difference of dissolution between phosphoric acid and rare earth sulfuric acid.展开更多
The Tong’an-Baishuidong mining district(TBMD),located in the eastern section of the Jiangnan Orogen,is a newly discovered granite-type lithium mining district.Thisstudy presents new monazite U-Pb chronological,whole-...The Tong’an-Baishuidong mining district(TBMD),located in the eastern section of the Jiangnan Orogen,is a newly discovered granite-type lithium mining district.Thisstudy presents new monazite U-Pb chronological,whole-rock geochemical,and Nd-Pb isotopic data to reveal the petrogenesis and geodynamic setting of the Wutang granites in the TBMD.The monazite U-Pb age of 145.8±1.0 Ma indicates that the granites were emplaced at the end of the Late Jurassic.Whole-rock geochemical results demonstrate that the Wutang granites are enriched in SiO_(2)(72.80-73.40 wt%)but depleted in CaO(0.44-0.90 wt%)and MgO+TiO_(2)+TFeO(1.79-2.05 wt%).These granites exhibit negative Eu anomalies(δEu=0.3−0.4)and high aluminum saturation indexes(A/CNK=1.2−1.6),differentiation indexes(DI=90-92),and Rb/Sr ratios(4.7-8.1).They also have moderate Ba contents(239-278 ppm)and low Sr contents(52.7-82.0 ppm)as well as low Nb/Ta(2.2-5.3)and Zr/Hf(21.3-31.5)ratios.All these indicate that they are highly fractionated granites.Additionally,these granites contain 5-10 wt%muscovite but no hornblende,with calculated corundum contents of 2.3-5.5 wt%.They have low high-field strength element(HFSE)contents(Zr+Nb+Ce+Y=182-202 ppm)and zircon saturation temperatures(700-770℃),with Th and Y negatively linked with Rb.These petrographic and geochemi-cal features further reveal that the Wutang granites belong to highly fractionated S-type granites.TheεNd(t)values of these granites range from−9.03 to−8.23,corresponding to two-stage model ages(T DM2)of 1488-1553 Ma.The initial Pb isotope ratios are:(206 Pb/^(204)Pb)i=18.38-18.55,(^(207)Pb/^(204)Pb)i=15.67-15.68,and(^(208)Pb/^(204)Pb)i=38.62-38.67.These Nd-Pb isotopic results demonstrate that the parental magma originated from the partial melting of ancient crustal materials.In the meantime,the TBMD in the eastern section of the Jiangnan Orogen was in a compression-extension transitional setting associated with the episodic subduction of the Paleo-Pacific Plate.展开更多
Rare earth elements have been widely applied in various sectors.Bastnaesite and monazite are crucial rare earth minerals,and flotation is a vital technique for recovering fine-grained rare earth minerals and separatin...Rare earth elements have been widely applied in various sectors.Bastnaesite and monazite are crucial rare earth minerals,and flotation is a vital technique for recovering fine-grained rare earth minerals and separating them from associated gangue minerals such as fluorite and apatite.Flotation collectors play a key role in selectively adsorbing valuable minerals,enhancing their surface hydrophobicity,which has prompted considerable research interest.However,the interaction between minerals and reagents relies on the reactivity and selectivity of the reagent groups,as well as the reactive properties of the surface atoms of the minerals.This study proposes the use of H_(2)O_(2)oxidation to enhance the flotation process of rare earth minerals.The flotation experiments demonstrated that pre-adding H_(2)O_(2)before introducing the flotation collector significantly improved the grade and recovery of rare earth concentrates.The adsorption mechanisms of 2-hydroxy-3-naphthyl hydroxamic acid collector on rare earth mineral surfaces before and after H_(2)O_(2)pre-oxidation were studied.The 2-hydroxy-3-naphthyl hydroxamic acid interacts with Ce^(3+)on the surface of unoxidized rare earth minerals,forming chelate compounds with five-membered ring structures.The H_(2)O_(2)exhibited potent oxidizing properties and oxidized the Ce^(3+)on the bastnaesite and monazite surfaces to more stable Ce^(4+),which demonstrated stronger binding capability with hydroxamic acid.展开更多
Abundant porphyritic granites, including Grt-bearing and Bt-bearing porphyritic granites, and porphyritic potash-feldspar granite (trondhjemite-granitic composition) are widely distributed within the Kovela granitic c...Abundant porphyritic granites, including Grt-bearing and Bt-bearing porphyritic granites, and porphyritic potash-feldspar granite (trondhjemite-granitic composition) are widely distributed within the Kovela granitic complex Southern Finland, which associated with monazite-bearing dikes (strong trondhjemite composition). The investigated monazite-bearing dikes are dominated by a quartz + K-feldspar + plagioclase + biotite + garnet + monazite assemblage. The monazite forms complexly zoned subhedral to euhedral crystals variable in size (100 - 1500 μm in diameter) characterized by high Th content. The chemical zoning characterised as: 1) concentric, 2) patchy, and 3) intergrowth-like. Textural evidence suggests that these accessory minerals crystallized at an early magmatic stage, as they are commonly associated with clusters of the observed variations in their chemical composition are largely explained by the huttonite exchange , and subordinately by the cheralite exchange with proportions of huttonite (ThSiO4) and cheralite [CaTh(PO4)2] up to 20.4% and 9.8%, respectively. Textural evidence suggests that these monazites and associated Th-rich minerals (huttonite/thorite) crystallized at an early magmatic stage, rather than metamorphic origin. The total lanthanide and actinide contents in monazite and host dikes are strongly correlated. Mineral compositions applied to calculate P-T crystallization conditions using different approaches reveal a temperature range of 700°C - 820°C and pressure 3 - 6 kbars for the garnet-biotite geothermometry. P-T pseudo-section analyses calculated using THERMOCALC software for the bulk compositions of suitable rock types, constrain the PT conditions of garnet growth equilibration within the range of 5 - 6 kbars and 760°C - 770°C respectively. Empirical calculations and pseudo-section approaches indicate a clockwise P-T path for the rocks of the studied area. 207Pb/206Pb dating of monazite by LA-MC-ICPMS revealed a recrystallization period at around 1860 - 1840 Ma. These ages are related to the tectonic-thermal event associated with the intense crustal melting and intra-orogenic intrusions, constraining the youngest time limit for metamorphic processes in the Kovela granitic complex.展开更多
New monazite U\|Pb geochronological data from the Everest region suggest that 20～25Ma elapsed between the initial India—Asia collision and kyanite\|sillimanite grade metamorphism. Our results indicate a two\|phase m...New monazite U\|Pb geochronological data from the Everest region suggest that 20～25Ma elapsed between the initial India—Asia collision and kyanite\|sillimanite grade metamorphism. Our results indicate a two\|phase metamorphic history, with peak Barrovian metamorphism at (32 2±0 4)Ma and a later high\|temperature, low\|pressure event (620℃, 400MPa) at (22 7±0 2)Ma.. Emplacement and crystallization of the Everest granite subsequently occurred at 20 5～21 3Ma. The monazite crystallization ages that differ by 10Ma are recorded in two structurally adjacent rocks of different lithology, which have the same post collisional p—T history.. Scanning electron microscopy reveals that the younger monazite is elaborately shaped and grew in close association with apatite at grain boundaries and triple junctions, suggesting that growth was stimulated by a change in the fluid regime. The older monazite is euhedral, is not associated with apatite, and is commonly armoured within silicate minerals. During the low\|pressure metamorphic event, the armouring protected the older monazites, and a lack of excess apatite in this sample prevented new growth. Textural relationships suggest that apatite is one of the necessary monazite\|producing reactants, and spots within monazite that are rich in Ca, Fe, Al and Si suggest that allanite acted as a preexisting rare earth element host. We propose a simplified reaction for monazite crystallization based on this evidence.展开更多
Electron probe microanalysis(EPMA) dating of monazite has been developed over decades. However, limited by the detectability and analytical sensitivity of dating-related elements(Th, Pb, U and Y), the EPMA dating has ...Electron probe microanalysis(EPMA) dating of monazite has been developed over decades. However, limited by the detectability and analytical sensitivity of dating-related elements(Th, Pb, U and Y), the EPMA dating has been restricted to geological research. In this study, various probe currents, beam diameters and counting times have been utilized on a JEOL JXA-8230 electron microprobe to determine the optimal experimental conditions for measuring Th, Pb, U and Y in monazite. The optimal conditions are:(1) accelerating voltage is 15 k V;(2) probe current is 100 n A;(3) beam diameter is 1 μm;(4) the peak and background counting time of U and Pb are 200 and 100 s;and(5) the peak and background counting time of Th and Y are 100 and 50 s. We apply this method to monazite from garnet-bearing biotite gneiss in the Zanhuang area of the Central Orogenic Belt of the North China Craton. The Pb O-Th O2* isochron age calculated by EPMA data is 1 812±17 Ma(MSWD=2.06), which is similar to the weighted mean 207 Pb/206 Pb age(1 805±12 Ma, MSWD=1.07) obtained by LA-ICP-MS. This study suggests that EPMA dating of monazite as a powerful dating technique can be widely used in geochronological study.展开更多
The process of decomposion of the bastnasite and monazite rare earth concentrates by alkali solutions was investigated. The mixed slurries of the rare earth concentrates and the alkali solutions were calcined at diffe...The process of decomposion of the bastnasite and monazite rare earth concentrates by alkali solutions was investigated. The mixed slurries of the rare earth concentrates and the alkali solutions were calcined at different temperatures in a rotary tubular electric furnace. The effects of calcination temperature on the decomposing ratio of rare earth, the oxidation ratio of cerium, the stripping of fluorine and phospho-rous after calcinations, and the adaptability of the process to the mixed rare earth concentrates of different grade were studied. The results showed that the decomposition ratio of rare earth and the oxidation ratio of cerium could reach 95.8% and 93.7%, respectively, while the cal-cinating temperature was above 300℃.展开更多
High-temperature magma generation process and granulite-facies metamorphism can provide important information about mantle-crustal interaction and tectonic evolution. The strongly peralu- minous monzonite pluton, the ...High-temperature magma generation process and granulite-facies metamorphism can provide important information about mantle-crustal interaction and tectonic evolution. The strongly peralu- minous monzonite pluton, the Jinshuikou cordierite granite on the southern margin of the Qaidam Block, can provide important information about the mantle-crustal interaction and constraints on tectonic tran- sition from Proto-Tethys to Paleo-Tethys. This pluton develops enclaves of mafic granulite, amphibolite and quartzofeldspathic rocks, and is cut by massive monzonitic leuco-granite veins. Zircon and monazite U-Pb dating for the cordierite granite, the granulite enclaves and a massive monzonitic leuco-granite vein reveal that the cordierite granitic magma was generated from Mesoproterozoic continental crust with protolith derived from a provenanee that was composed of 〉2.8 Ga old recycled crustal materials and re- corded a -1.7 Ga magmatic event. The continental crust underwent low-pressure granulite-facies metamorphism at -380 Ma ago, whereas the cordierite granite magmas was generated and emplaced during 380 Ma, followed by intrusion of the massive monzonitic leuco-granite vein at circa 370-330 Ma. These data suggest that after the final closure of Proto-Tethys Ocean spreading along the southern Qaidam Block at -420 Ma, break-off of the subducted slab or delamination of the lower crustal base and upwelling of the asthenospheric mantle beneath the southern Qaidam Block occurred before the Mid-Devonian, and that the initiation of the Paleo-Tethys tectonics might initiate near the end of Early-Carboniferous in the East Kunlun-Qaidam region, East Asia.展开更多
Low thermal conductivity, matched thermal expansion coefficient and good compatibility are general requirements for the environmental/thermal barrier coatings(EBCs/TBCs) and interphases for Al2O3 f/Al2O3 composites. I...Low thermal conductivity, matched thermal expansion coefficient and good compatibility are general requirements for the environmental/thermal barrier coatings(EBCs/TBCs) and interphases for Al2O3 f/Al2O3 composites. In this work, a novel high-entropy(HE) rare-earth phosphate monazite ceramic (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 is designed and successfully synthesized. This new type of HE rare-earth phosphate monazite exhibits good chemical compatibility with Al2O3, without reaction with Al2O3 as high as 1600℃ in air. Moreover, the thermal expansion coefficient(TEC) of HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4(8.9 × 10^-6/℃ at 300–1000℃) is close to that of Al2O3. The thermal conductivity of HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 at room temperature is as low as 2.08 W·m^-1·K^-1, which is about 42% lower than that of La PO4. Good chemical compatibility, close TEC to that of Al2O3, and low thermal conductivity indicate that HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 is suitable as a candidate EBC/TBC material and an interphase for Al2O3 f/Al2O3 composites.展开更多
The Longquanguan shear zone is an important structural belt in the North China Craton, separating the underlying Fuping complex from the overlying Wutai complex. This shear zone has experienced three episodes of defor...The Longquanguan shear zone is an important structural belt in the North China Craton, separating the underlying Fuping complex from the overlying Wutai complex. This shear zone has experienced three episodes of deformation: the first and main episode is a ductile top-to-ESE shear along the gently northwest-west dipping foliations, while the other two episodes are later collapse sliding. Prolonged granites parallel to the shear foliations make one of the main compositions of the Longquanguan shear zone. These granites experienced deformation to form mylonitic rocks when they emplaced during the first episode of deformation. Structural characters of the granites and their contacts to the country rocks indicate that these granites possibly resulted from in-situ partial remelting by shearing, i.e., they are syn-deformational granites. Monazites in these mylonitic granites are magmatic minerals and their crystallization ages may represent ages of the magmatic events, and also the ages for the main deformation of the Longquanguan shear zone. Monazite electronic microprobe dating were carried on two samples of granite, which gives multiple peak ages, among which 1,846 Ma and 1,877 Ma are the main peak ages for the two samples. These ages represent the main deformation of the Longquanguan shear zone, which is consistent with the main regional geological event at about 1,850 Ma caused by the collision between the Eastern and Western Blocks in North China. The good match between the monazite ages and the corresponding regional tectono-thermal events shows the feasibility and reliability of monazite electronic microprobe dating.展开更多
Five lengthy periods involving multiple phases of cordierite and andalusite growth were revealed by detailed studies of foliation inflection/intersection axes （FIA） preserved in porphyroblasts in schists from the Ar...Five lengthy periods involving multiple phases of cordierite and andalusite growth were revealed by detailed studies of foliation inflection/intersection axes （FIA） preserved in porphyroblasts in schists from the Arkansas River region in Colorado, USA. The regionally consistent character of the succession of five different FIA trends enabled the relative timing of each FIA with respect to the next to be determined. The FIA succession from first to last is： FIA 1 trending W-E, FIA 2 trending SSW- NNE, FIA 3 trending NNW-SSE, FIA 4 trending NW-SE and FIA 5 trending SW-NE. For four of the FIA sets, samples were found containing monazite grains preserved as inclusions. These were dated on an electron microprobe. The ages obtained concur exactly with the FIA succession, with FIA 1 at 1506±15 Ma, FIA 2 at 1467±23 Ma, FIA 3 at 1425±18 Ma, FIA 4 not dated and FIA 5 at 1366±20 Ma. These ages are directly reflected in a succession of plutons in the surrounding region dated by other isotopic approaches, suggesting that deformation, metamorphism and pluton emplacement occurred together episodically, but effectively continuously, for some 140 Ma.展开更多
Understanding the mechanisms of parent-daughter isotopic mobility at the nanoscale is key to rigorous interpretation of Ue The Pb data and associated dating. Until now, all nanoscale geochronological studies on geolog...Understanding the mechanisms of parent-daughter isotopic mobility at the nanoscale is key to rigorous interpretation of Ue The Pb data and associated dating. Until now, all nanoscale geochronological studies on geological samples have relied on either Transmission Electron Microscope(TEM) or Atom Probe Microscopy(APM) characterizations alone, thus suffering from the respective weaknesses of each technique. Here we focus on monazite crystals from a ~1 Ga, ultrahigh temperature granulite from Rogaland(Norway). This sample has recorded concordant UeP b dates(measured by LA-ICP-MS) that range over 100 My, with the three domains yielding distinct isotopic Ue Pb ages of 1034 ± 6 Ma(D1; Srich core), 1005 ± 7 Ma(D2), and 935 ± 7 Ma(D3), respectively. Combined APM and TEM characterization of these monazite crystals reveal phase separation that led to the isolation of two different radiogenic Pb(Pb*) reservoirs at the nanoscale. The S-rich core of these monazite crystals contains Cae Srich clusters, 5 -10 nm in size, homogenously distributed within the monazite matrix with a mean interparticle distance of 40 -60 nm. The clusters acted as a sink for radiogenic Pb(Pb*) produced in the monazite matrix, which was reset at the nanoscale via Pb diffusion while the grain remained closed at the micro-scale. Compared to the concordant ages given by conventional micro-scale dating of the grain,the apparent nano-scale age of the monazite matrix in between clusters is about 100 Myr younger, which compares remarkably well to the duration of the metamorphic event. This study highlights the capabilities of combined APM-TEM nano-structural and nano-isotopic characterizations in dating and timing of geological events, allowing the detection of processes untraceable with conventional dating methods.展开更多
Monazite((Ce,La)PO_(4))is one of the major types of light rare earth minerals from which the light rare earth elements cerium(Ce)and lanthanum(La)are economically extracted.Flotation is extensively used to recover fin...Monazite((Ce,La)PO_(4))is one of the major types of light rare earth minerals from which the light rare earth elements cerium(Ce)and lanthanum(La)are economically extracted.Flotation is extensively used to recover fine-grained monazite.Sodium oleate(NaOL)is considered as the collector with strong collecting ability for monazite flotation.However,this study shows that its collecting ability is still limited.In this paper,a phosphonic acid,nonane-1,1-bisphosphonic acid(C9-BPA),was employed as the novel collector in place of NaOL.Flotation experiments show that even when the C9-BPA dosage is less than one-fifth of the NaOL dosage,the monazite recove ry using C9-BPA as the collector is approximately 22 wt%higher than that using NaOL.The mechanism by which C9-BPA adsorbs on monazite was investigated using zeta potential,infrared(IR)spectroscopy and X-ray photoelectron spectroscopy(XPS)measurements as well as first-principles calculations.Zeta potential measurements show a more significant decrease in the zeta potentials of monazite after the addition of C9-BPA compared to those after the addition of NaOL.For C9-BPA-treated monazite,the characteristic peaks of C9-BPA are observed in the IR and C 1 s XPS spectrum,whereas for monazite treated by NaOL,no characteristic peak of NaOL was observed.Experimental results show that C9-BPA has a stronger affinity towards the monazite surface than NaOL as confirmed by the higher adsorption energy of CP-BPA on the monazite surface(-204.22 kJ/mol)than NaOL(-48.48 kJ/mol).This study demonstrates an extensive application value and prospect of C9-BPA in monazite flotation and helps design novel collectors with strong collecting ability for monazite flotation.展开更多
New metamorphic petrology and geochronology from the Loe Sar dome in the Swat region of northern Pakistan place refined constraints on the pressure, temperature and timing of metamorphism and deformation in that part ...New metamorphic petrology and geochronology from the Loe Sar dome in the Swat region of northern Pakistan place refined constraints on the pressure, temperature and timing of metamorphism and deformation in that part of the Himalayan orogen. Thermodynamic modelling and monazite petrochronology indicate that metamorphism in the area followed a prograde evolution from ～525 ± 25 ℃and 6 士 0.5 kbar to ～610 ± 25 ℃ and 9 士 0.5 kbar, between ca. 39 Ma and 28 Ma. Partitioning of heavy rare earth elements between garnet rims and 30-28 Ma monazite are interpreted to indicate coeval crystallization at peak conditions. Microtextural relationships indicate that garnet rim growth post-dated the development of the main foliation in the area. The regional foliation is folded about large-scale N-S trending fold axes and overprinting E-W trending folds to form km-scale domal culminations. The textural relationships observed indicate that final dome development must be younger than the 30-28 Ma monazite that grew with garnet rims post-regional foliation development, but pre-doming-related deformation. This new timing constraint helps resolve discrepancy between previous interpretations,which have alternately suggested that N-S trending regional folds must be either pre-or post-early Oligocene. Finally, when combined with existing hornblende and white mica cooling ages, these new data indicate that the study area was exhumed rapidly following peak metamorphism.展开更多
The Madi rare metal granite is a complex massif,which contains a variety of rare metals,such as Nb,Ta,Li,and Be.In this paper,the geochemical characteristics of the granite were obtained by multi-collector inductively...The Madi rare metal granite is a complex massif,which contains a variety of rare metals,such as Nb,Ta,Li,and Be.In this paper,the geochemical characteristics of the granite were obtained by multi-collector inductively coupled mass spectrometry(MC-ICP-MS).The precise crystalline age of the granite was obtained from monazite U-Pb dating,and the source of the granite was determined using Li-Nd isotopes.The Madi rare metal granite is a high-K(calc-alkaline),peraluminous,S-type granite.The U-Pb monazite age indicates that the crystalline age of the granite is 175.6 Ma,which is Early Jurassic.The granite is characterized by a relatively wide range ofδ7 Li values(+2.99‰to+5.83‰)and high lithium concentrations(181 ppm to 1022 ppm).The lithium isotopic composition of the granite does not significantly correlate with the degree of magmatic differentiation.An insignificant amount of lithium isotope fractionation occurred during the granitic differentiation.The lithium isotopic composition of the granite significantly differs from that of the wall rock,but it is very similar to that of a primitive mantle peridotite xenolith(meanδ7 Li value+3.5‰).The plot of Li concentration versusδ7 Li indicates that the Li isotopic composition of the granite is similar to that of island arc lavas.Based on the above-described evidence,the granite was mainly derived from the crust,but it was contaminated by a deep granitic magma.展开更多
This study presents a re-examination of historical specimens(DG136 and DG167)from the Monashee complex in the southeastern Canadian Cordillera that are critical to the current understanding of rare earth element(REE)d...This study presents a re-examination of historical specimens(DG136 and DG167)from the Monashee complex in the southeastern Canadian Cordillera that are critical to the current understanding of rare earth element(REE)distribution between garnet and monazite(and other accessory minerals)during metamorphism.Nine-hundred and fifty-one new monazite petrochronology spot analyses on 29 different grains across two specimens outline detailed(re)crystallization histories.Trace element data collected from the same ablated volume,interpreted in the context of new phase equilibria modelling that includes monazite,xenotime and apatite,link ages to specific portions of the pressure-temperature(P-T)paths followed by the specimens.These linkages are further informed by garnet Lu-Hf geochronology and xenotime petrochronology.The clockwise P-T paths indicate prograde metamorphism was ongoing by ca.80 Ma in both specimens.The structurally deeper specimen,DG136,records peak P-T conditions of~755-770℃and 8.8-10.4 kbar,interpreted to coincide with(re-)crystallization of low Y monazite at~75-70 Ma.Near-rim garnet isopleths from DG167 cross in the observed peak assemblage field at~680℃ and 9.3 kbar.These conditions are interpreted to correspond with low Y monazite(re-)crystallisation at~65 Ma.Both specimens record decompression along their retrograde path coincident with high Y 70-55 Ma and 65-55 Ma monazite populations in DG136 and DG167,respectively.These findings broadly agree with those initially reported~20 years ago and confirm early interpretations using trace elements in monazite as generally reliable markers of metamorphic reactions.Modern phase equilibria modelling and in situ petrochronological analysis,however,provide additional insight into monazite behaviour during anatexis and the effects of potential trace element buffering by REE-bearing phases such as apatite.展开更多
The present work dealt with the preconcentration of rare earth elements in Saghand ore(Yazd province,Iran)which was achieved by Humphrey spiral using orthogonal optimization method after scrubbing the sample at 45%sol...The present work dealt with the preconcentration of rare earth elements in Saghand ore(Yazd province,Iran)which was achieved by Humphrey spiral using orthogonal optimization method after scrubbing the sample at 45%solid pulp density for 30 min.The pulp was diluted and was fed to a Humphrey spiral for upgrading.The process parameters considered were feed size,feed solids and feed rate,and Taguchi’s L9(34)orthogonal array(OA)was selected for optimization of the process.The results show that the feed rate and feed size were more significant than the other operation parameters of the process.It was also found that under optimal conditions,the concentrate grade of rare earth elements increased from2860 10 6to 6050 10 6and recovery reached to 58%.展开更多
The Grove Mountains, 400 km south of the Chinese Antarctic Zhongshan Station, are an inland continuation of the Pan-African-aged （i.e., Late Neoproterozoic/Cambrian） Prydz Belt, East Antarctica. In this paper we car...The Grove Mountains, 400 km south of the Chinese Antarctic Zhongshan Station, are an inland continuation of the Pan-African-aged （i.e., Late Neoproterozoic/Cambrian） Prydz Belt, East Antarctica. In this paper we carried out a combined U-Th-Pb monazite and Sm-Nd mineral-whole-rock dating on para- and orthogneisses from bedrock in the Grove Mountains. U-Th-Pb monazite dating of a cordierite-bearing pelitic paragneiss yields ages of 523 ？ 4 Ma for the cores and 508 ？ 6 Ma for the rims. Sm-Nd mineral-whole-rock isotopic analyses yield isochron ages of 536 ？ 3 Ma for a coarse-grained felsic orthogneiss and 507 ？ 30 Ma for a fine-grained quartzofeldspathic paragneiss. Combined with previously published age data in the Grove Mountains and adjacent areas, the older age of ~530 Ma is interpreted as the time of regional medium- to low-pressure granulite-facies metamorphism, and the younger age of ~510 Ma as the cooling age of the granulite terrane. The absence of evidence for a Grenville-aged （i.e., Late Mesoproterozoic/Early Neoproterozoic） metamorphic event indicates that the Grove Mountains have experienced only a single metamorphic cycle, i.e., Pan-African-aged, which distinguishes them from other polymetamorphic terranes in the Prydz Belt. This will provide important constraints on the controversial nature of the Prydz Belt.展开更多
Gravity, magnetic and electrostatic separation methods allowed to obtain different titanium oxide concentrates (ilmenite, leucoxene, rutile) and different varieties of zircon concentrates (premium zircon, standard zir...Gravity, magnetic and electrostatic separation methods allowed to obtain different titanium oxide concentrates (ilmenite, leucoxene, rutile) and different varieties of zircon concentrates (premium zircon, standard zircon, medium grade zircon standard) from Senegal’s heavy mineral sands. During mining separation, monazite, which is a paramagnetic mineral, was found in a non-negligible concentration of 0.57 wt% on average in the medium grade zircon standard which also contains 37.96 wt% zircon and 44.46 wt% titanium oxides. Magnetic and gravity separation tests were carried out on the Medium grade zircon standard (MGZS) to produce a monazite concentrate at Eramet Ideas laboratory. Magnetic separation at 1.5 teslas intensity resulted in the recovery of 94.8% of the monazite from the MGZS. Gravity separation also recovered 76.6% of the monazite from the MGZS. The combination of these two treatment methods can thus produce three concentrates from MGZS (a monazite concentrate, a zircon concentrate, and a titanium oxide concentrate).展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41903025 and 41803048)the National Nonprofit Institute Research Grant of IGGE(Grant Nos.AS2024J03,JY202106 and AS2022P03)+2 种基金the Hebei Key Science and Technology Program(Grant No.19057411Z)the National Science and Technology Major Project(Grant No.2024ZD1002402)the China Geological Survey Project(Grant No.DD20221807).
文摘The Suzhou granitic pluton is the first identified Nb-Ta-rich granite in China.To reveal the genetic link between the sequence of magmatic and hydrothermal evolution and Nb-Ta mineralization in different intrusive phases of the Suzhou granite,whole-rock geochemistry,geochemistry and U-Th-Pb dating of monazite was analyzed.The unique geochemical characteristics show that the Suzhou pluton can be discriminated as an A-type granite.LA-ICP-MS U-Th-Pb dating of monazite in both the medium-and coarse-grained biotite granite(MBG)and the fine-grained biotite granite(FBG)indicates that the granite formed between 124 and 127 Ma.Based on geochemical characteristics and mineral textures,the MBG(Mnz-Ia)and FBG(Mnz-Ib)monazites are classified as magmatic monazites;another monazite(Mnz-II)from the MBG formed during a magmatic-hydrothermal transitional stage.Nb-Ta in the Suzhou pluton gradually concentrated during fractional crystallization and alteration of Ti-rich minerals and biotite.Ultimately,with the involvement of F-Li-rich fluid,Nb-Ta mineralization occurred during the magmatic-hydrothermal transition.The Suzhou pluton is considered part of a 600-km-and NE-SW-trending Nb-rich A-type granite belt together with other Early Cretaceous A-type granites in the Jiangnan Orogen that offers prospects of a new target for Nb-Ta prospecting.
基金support by the National Natural Science Foundation of Inner Mongolia (2022SHZR1885)Natural Science Foundation of Hebei province (E2022402101,E2022402105)。
文摘To completely recover valuable elements and reduce the amount of waste,the impact of phosphoric acid on the decomposition of rare earth,fluorine and phosphorus during cyclic leaching was studied based on the characteristics of low-tempe rature sulfuric acid deco mposition.When a single monazite was leached using 75 wt% H_(2)SO_(4) solution with phosphoric acid,the size and number of monazite particles in the washing slag gradually decrease with the increase in phosphoric acid content in the leaching solution.The monazite phase can hardly be found in the slag when the phosphoric acid content reaches 70 g/L,which indicates that phosphoric acid is favorable for monazite decomposition.The mixed rare earth concentrate was leached by 75 wt% H_(2)SO_(4) containing 70 g/L phosphoric acid,the mineral compositions of the washing slag are only gypsum and unwashed rare earth sulfuric acid.After cyclic leaching of75 wt% H_(2)SO_(4),the mineral compositions of the primary leaching washing slag are mainly undecomposed monazite,rare earth sulfate and calcium sulfate.However,monazite is not found in the mineral phase of the second and third leaching washing slag.The leaching rates of rare earth and phosphorus gradually increase with the increase in cyclic leaching times.In addition,the phosphoric acid content in the leaching solution increases with the increase in the number of cyclic leaching time.However,the rising trend decreases when the phosphoric acid content reaches 50 g/L by adsorption and crystallization of phosphoric acid.A small amount of water can be used to clean the leaching residue before washing to recover the more soluble phosphorus acid according to the difference of dissolution between phosphoric acid and rare earth sulfuric acid.
基金funded by the Program of Science and Technology Department of Jiangxi Province(2023KDG01002 and 2023KDG01003)the National Natural Science Foundation of China(42062006 and 41962007)+1 种基金the Key Research and Development Program of Jiangxi Province(20223BBG71015)the Personnel Training Project of Jiangxi Bureau of Geology(2023JXDZKJRC02,2022JXDZKJRC04,and 2024JXDZKJRC05).
文摘The Tong’an-Baishuidong mining district(TBMD),located in the eastern section of the Jiangnan Orogen,is a newly discovered granite-type lithium mining district.Thisstudy presents new monazite U-Pb chronological,whole-rock geochemical,and Nd-Pb isotopic data to reveal the petrogenesis and geodynamic setting of the Wutang granites in the TBMD.The monazite U-Pb age of 145.8±1.0 Ma indicates that the granites were emplaced at the end of the Late Jurassic.Whole-rock geochemical results demonstrate that the Wutang granites are enriched in SiO_(2)(72.80-73.40 wt%)but depleted in CaO(0.44-0.90 wt%)and MgO+TiO_(2)+TFeO(1.79-2.05 wt%).These granites exhibit negative Eu anomalies(δEu=0.3−0.4)and high aluminum saturation indexes(A/CNK=1.2−1.6),differentiation indexes(DI=90-92),and Rb/Sr ratios(4.7-8.1).They also have moderate Ba contents(239-278 ppm)and low Sr contents(52.7-82.0 ppm)as well as low Nb/Ta(2.2-5.3)and Zr/Hf(21.3-31.5)ratios.All these indicate that they are highly fractionated granites.Additionally,these granites contain 5-10 wt%muscovite but no hornblende,with calculated corundum contents of 2.3-5.5 wt%.They have low high-field strength element(HFSE)contents(Zr+Nb+Ce+Y=182-202 ppm)and zircon saturation temperatures(700-770℃),with Th and Y negatively linked with Rb.These petrographic and geochemi-cal features further reveal that the Wutang granites belong to highly fractionated S-type granites.TheεNd(t)values of these granites range from−9.03 to−8.23,corresponding to two-stage model ages(T DM2)of 1488-1553 Ma.The initial Pb isotope ratios are:(206 Pb/^(204)Pb)i=18.38-18.55,(^(207)Pb/^(204)Pb)i=15.67-15.68,and(^(208)Pb/^(204)Pb)i=38.62-38.67.These Nd-Pb isotopic results demonstrate that the parental magma originated from the partial melting of ancient crustal materials.In the meantime,the TBMD in the eastern section of the Jiangnan Orogen was in a compression-extension transitional setting associated with the episodic subduction of the Paleo-Pacific Plate.
基金financially supported by the National Natural Science Foundation of China(No.52174236)Fundamental Research Funds for the Central Universities(No.FRF-DF-23-001)the Natural Science Foundation of Inner Mongolia of China(Nos.2024MS05061 and 2023LHMS05050)。
文摘Rare earth elements have been widely applied in various sectors.Bastnaesite and monazite are crucial rare earth minerals,and flotation is a vital technique for recovering fine-grained rare earth minerals and separating them from associated gangue minerals such as fluorite and apatite.Flotation collectors play a key role in selectively adsorbing valuable minerals,enhancing their surface hydrophobicity,which has prompted considerable research interest.However,the interaction between minerals and reagents relies on the reactivity and selectivity of the reagent groups,as well as the reactive properties of the surface atoms of the minerals.This study proposes the use of H_(2)O_(2)oxidation to enhance the flotation process of rare earth minerals.The flotation experiments demonstrated that pre-adding H_(2)O_(2)before introducing the flotation collector significantly improved the grade and recovery of rare earth concentrates.The adsorption mechanisms of 2-hydroxy-3-naphthyl hydroxamic acid collector on rare earth mineral surfaces before and after H_(2)O_(2)pre-oxidation were studied.The 2-hydroxy-3-naphthyl hydroxamic acid interacts with Ce^(3+)on the surface of unoxidized rare earth minerals,forming chelate compounds with five-membered ring structures.The H_(2)O_(2)exhibited potent oxidizing properties and oxidized the Ce^(3+)on the bastnaesite and monazite surfaces to more stable Ce^(4+),which demonstrated stronger binding capability with hydroxamic acid.
文摘Abundant porphyritic granites, including Grt-bearing and Bt-bearing porphyritic granites, and porphyritic potash-feldspar granite (trondhjemite-granitic composition) are widely distributed within the Kovela granitic complex Southern Finland, which associated with monazite-bearing dikes (strong trondhjemite composition). The investigated monazite-bearing dikes are dominated by a quartz + K-feldspar + plagioclase + biotite + garnet + monazite assemblage. The monazite forms complexly zoned subhedral to euhedral crystals variable in size (100 - 1500 μm in diameter) characterized by high Th content. The chemical zoning characterised as: 1) concentric, 2) patchy, and 3) intergrowth-like. Textural evidence suggests that these accessory minerals crystallized at an early magmatic stage, as they are commonly associated with clusters of the observed variations in their chemical composition are largely explained by the huttonite exchange , and subordinately by the cheralite exchange with proportions of huttonite (ThSiO4) and cheralite [CaTh(PO4)2] up to 20.4% and 9.8%, respectively. Textural evidence suggests that these monazites and associated Th-rich minerals (huttonite/thorite) crystallized at an early magmatic stage, rather than metamorphic origin. The total lanthanide and actinide contents in monazite and host dikes are strongly correlated. Mineral compositions applied to calculate P-T crystallization conditions using different approaches reveal a temperature range of 700°C - 820°C and pressure 3 - 6 kbars for the garnet-biotite geothermometry. P-T pseudo-section analyses calculated using THERMOCALC software for the bulk compositions of suitable rock types, constrain the PT conditions of garnet growth equilibration within the range of 5 - 6 kbars and 760°C - 770°C respectively. Empirical calculations and pseudo-section approaches indicate a clockwise P-T path for the rocks of the studied area. 207Pb/206Pb dating of monazite by LA-MC-ICPMS revealed a recrystallization period at around 1860 - 1840 Ma. These ages are related to the tectonic-thermal event associated with the intense crustal melting and intra-orogenic intrusions, constraining the youngest time limit for metamorphic processes in the Kovela granitic complex.
文摘New monazite U\|Pb geochronological data from the Everest region suggest that 20～25Ma elapsed between the initial India—Asia collision and kyanite\|sillimanite grade metamorphism. Our results indicate a two\|phase metamorphic history, with peak Barrovian metamorphism at (32 2±0 4)Ma and a later high\|temperature, low\|pressure event (620℃, 400MPa) at (22 7±0 2)Ma.. Emplacement and crystallization of the Everest granite subsequently occurred at 20 5～21 3Ma. The monazite crystallization ages that differ by 10Ma are recorded in two structurally adjacent rocks of different lithology, which have the same post collisional p—T history.. Scanning electron microscopy reveals that the younger monazite is elaborately shaped and grew in close association with apatite at grain boundaries and triple junctions, suggesting that growth was stimulated by a change in the fluid regime. The older monazite is euhedral, is not associated with apatite, and is commonly armoured within silicate minerals. During the low\|pressure metamorphic event, the armouring protected the older monazites, and a lack of excess apatite in this sample prevented new growth. Textural relationships suggest that apatite is one of the necessary monazite\|producing reactants, and spots within monazite that are rich in Ca, Fe, Al and Si suggest that allanite acted as a preexisting rare earth element host. We propose a simplified reaction for monazite crystallization based on this evidence.
基金supported by the National Natural Science Foundation of China(No.41602234)the Fundamental Research Funds for the Central Universities,China University of Geosciences,Wuhan,China(Nos.CUGL180406,CUGCJ1707)Open Fund(No.GRMR201901)from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan
文摘Electron probe microanalysis(EPMA) dating of monazite has been developed over decades. However, limited by the detectability and analytical sensitivity of dating-related elements(Th, Pb, U and Y), the EPMA dating has been restricted to geological research. In this study, various probe currents, beam diameters and counting times have been utilized on a JEOL JXA-8230 electron microprobe to determine the optimal experimental conditions for measuring Th, Pb, U and Y in monazite. The optimal conditions are:(1) accelerating voltage is 15 k V;(2) probe current is 100 n A;(3) beam diameter is 1 μm;(4) the peak and background counting time of U and Pb are 200 and 100 s;and(5) the peak and background counting time of Th and Y are 100 and 50 s. We apply this method to monazite from garnet-bearing biotite gneiss in the Zanhuang area of the Central Orogenic Belt of the North China Craton. The Pb O-Th O2* isochron age calculated by EPMA data is 1 812±17 Ma(MSWD=2.06), which is similar to the weighted mean 207 Pb/206 Pb age(1 805±12 Ma, MSWD=1.07) obtained by LA-ICP-MS. This study suggests that EPMA dating of monazite as a powerful dating technique can be widely used in geochronological study.
基金Project supported by Key Scientific Projects of Baotou Science and Technology Bureau Intellectual Property (2010Z2003)
文摘The process of decomposion of the bastnasite and monazite rare earth concentrates by alkali solutions was investigated. The mixed slurries of the rare earth concentrates and the alkali solutions were calcined at different temperatures in a rotary tubular electric furnace. The effects of calcination temperature on the decomposing ratio of rare earth, the oxidation ratio of cerium, the stripping of fluorine and phospho-rous after calcinations, and the adaptability of the process to the mixed rare earth concentrates of different grade were studied. The results showed that the decomposition ratio of rare earth and the oxidation ratio of cerium could reach 95.8% and 93.7%, respectively, while the cal-cinating temperature was above 300℃.
基金supported by the National Natural Science Foundation of China(Nos.40972042,40772041,42072030)the Open Research Program of the Key Laboratory of Continental Dynamics,Northwest University
文摘High-temperature magma generation process and granulite-facies metamorphism can provide important information about mantle-crustal interaction and tectonic evolution. The strongly peralu- minous monzonite pluton, the Jinshuikou cordierite granite on the southern margin of the Qaidam Block, can provide important information about the mantle-crustal interaction and constraints on tectonic tran- sition from Proto-Tethys to Paleo-Tethys. This pluton develops enclaves of mafic granulite, amphibolite and quartzofeldspathic rocks, and is cut by massive monzonitic leuco-granite veins. Zircon and monazite U-Pb dating for the cordierite granite, the granulite enclaves and a massive monzonitic leuco-granite vein reveal that the cordierite granitic magma was generated from Mesoproterozoic continental crust with protolith derived from a provenanee that was composed of 〉2.8 Ga old recycled crustal materials and re- corded a -1.7 Ga magmatic event. The continental crust underwent low-pressure granulite-facies metamorphism at -380 Ma ago, whereas the cordierite granite magmas was generated and emplaced during 380 Ma, followed by intrusion of the massive monzonitic leuco-granite vein at circa 370-330 Ma. These data suggest that after the final closure of Proto-Tethys Ocean spreading along the southern Qaidam Block at -420 Ma, break-off of the subducted slab or delamination of the lower crustal base and upwelling of the asthenospheric mantle beneath the southern Qaidam Block occurred before the Mid-Devonian, and that the initiation of the Paleo-Tethys tectonics might initiate near the end of Early-Carboniferous in the East Kunlun-Qaidam region, East Asia.
基金financially supported by the National Natural Science Foundation of China (Nos. 51672064 and U1435206)
文摘Low thermal conductivity, matched thermal expansion coefficient and good compatibility are general requirements for the environmental/thermal barrier coatings(EBCs/TBCs) and interphases for Al2O3 f/Al2O3 composites. In this work, a novel high-entropy(HE) rare-earth phosphate monazite ceramic (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 is designed and successfully synthesized. This new type of HE rare-earth phosphate monazite exhibits good chemical compatibility with Al2O3, without reaction with Al2O3 as high as 1600℃ in air. Moreover, the thermal expansion coefficient(TEC) of HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4(8.9 × 10^-6/℃ at 300–1000℃) is close to that of Al2O3. The thermal conductivity of HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 at room temperature is as low as 2.08 W·m^-1·K^-1, which is about 42% lower than that of La PO4. Good chemical compatibility, close TEC to that of Al2O3, and low thermal conductivity indicate that HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 is suitable as a candidate EBC/TBC material and an interphase for Al2O3 f/Al2O3 composites.
基金This work was financially supported by the key project for international collaboration, the National Natural Science Foundation of China (Project No. 40420120135).
文摘The Longquanguan shear zone is an important structural belt in the North China Craton, separating the underlying Fuping complex from the overlying Wutai complex. This shear zone has experienced three episodes of deformation: the first and main episode is a ductile top-to-ESE shear along the gently northwest-west dipping foliations, while the other two episodes are later collapse sliding. Prolonged granites parallel to the shear foliations make one of the main compositions of the Longquanguan shear zone. These granites experienced deformation to form mylonitic rocks when they emplaced during the first episode of deformation. Structural characters of the granites and their contacts to the country rocks indicate that these granites possibly resulted from in-situ partial remelting by shearing, i.e., they are syn-deformational granites. Monazites in these mylonitic granites are magmatic minerals and their crystallization ages may represent ages of the magmatic events, and also the ages for the main deformation of the Longquanguan shear zone. Monazite electronic microprobe dating were carried on two samples of granite, which gives multiple peak ages, among which 1,846 Ma and 1,877 Ma are the main peak ages for the two samples. These ages represent the main deformation of the Longquanguan shear zone, which is consistent with the main regional geological event at about 1,850 Ma caused by the collision between the Eastern and Western Blocks in North China. The good match between the monazite ages and the corresponding regional tectono-thermal events shows the feasibility and reliability of monazite electronic microprobe dating.
文摘Five lengthy periods involving multiple phases of cordierite and andalusite growth were revealed by detailed studies of foliation inflection/intersection axes （FIA） preserved in porphyroblasts in schists from the Arkansas River region in Colorado, USA. The regionally consistent character of the succession of five different FIA trends enabled the relative timing of each FIA with respect to the next to be determined. The FIA succession from first to last is： FIA 1 trending W-E, FIA 2 trending SSW- NNE, FIA 3 trending NNW-SSE, FIA 4 trending NW-SE and FIA 5 trending SW-NE. For four of the FIA sets, samples were found containing monazite grains preserved as inclusions. These were dated on an electron microprobe. The ages obtained concur exactly with the FIA succession, with FIA 1 at 1506±15 Ma, FIA 2 at 1467±23 Ma, FIA 3 at 1425±18 Ma, FIA 4 not dated and FIA 5 at 1366±20 Ma. These ages are directly reflected in a succession of plutons in the surrounding region dated by other isotopic approaches, suggesting that deformation, metamorphism and pluton emplacement occurred together episodically, but effectively continuously, for some 140 Ma.
基金Both UJM and CNRS (INSU TelluS-SYSTER) are thanked for financial support for AMSG and ATL. The Australian Resource Characterisation Facility (ARCF), under the auspices of the National Resource Sciences Precinct (NRSP) - a collaboration between CSIRO, Curtin University and The University of Western Australia e is supported by the Science and Industry Endowment Fund (SIEF RI13-01)
文摘Understanding the mechanisms of parent-daughter isotopic mobility at the nanoscale is key to rigorous interpretation of Ue The Pb data and associated dating. Until now, all nanoscale geochronological studies on geological samples have relied on either Transmission Electron Microscope(TEM) or Atom Probe Microscopy(APM) characterizations alone, thus suffering from the respective weaknesses of each technique. Here we focus on monazite crystals from a ~1 Ga, ultrahigh temperature granulite from Rogaland(Norway). This sample has recorded concordant UeP b dates(measured by LA-ICP-MS) that range over 100 My, with the three domains yielding distinct isotopic Ue Pb ages of 1034 ± 6 Ma(D1; Srich core), 1005 ± 7 Ma(D2), and 935 ± 7 Ma(D3), respectively. Combined APM and TEM characterization of these monazite crystals reveal phase separation that led to the isolation of two different radiogenic Pb(Pb*) reservoirs at the nanoscale. The S-rich core of these monazite crystals contains Cae Srich clusters, 5 -10 nm in size, homogenously distributed within the monazite matrix with a mean interparticle distance of 40 -60 nm. The clusters acted as a sink for radiogenic Pb(Pb*) produced in the monazite matrix, which was reset at the nanoscale via Pb diffusion while the grain remained closed at the micro-scale. Compared to the concordant ages given by conventional micro-scale dating of the grain,the apparent nano-scale age of the monazite matrix in between clusters is about 100 Myr younger, which compares remarkably well to the duration of the metamorphic event. This study highlights the capabilities of combined APM-TEM nano-structural and nano-isotopic characterizations in dating and timing of geological events, allowing the detection of processes untraceable with conventional dating methods.
基金Project supported by the National Key Research and Development Program of China(2019YFC0408300)the Excellent Youth Foundation of IMUST(2017YQL05)+7 种基金the Key Program for International S&T Cooperation Projects of China(2019YFE012999)the Science Fund for Distinguished Young Scholars of Hunan Province(2020JJ2044)the Young Elite Scientists Sponsorship Program of Hunan Province,China(2018RS_(3) 011)Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resourcesthe National Natural Science Foundation of China(U2067201,51774328,51674045,51404300)the National 111Project of China(B14034)Inner Mongolia Natural Science Foundation(2020LH05027,2019MS05039)。
文摘Monazite((Ce,La)PO_(4))is one of the major types of light rare earth minerals from which the light rare earth elements cerium(Ce)and lanthanum(La)are economically extracted.Flotation is extensively used to recover fine-grained monazite.Sodium oleate(NaOL)is considered as the collector with strong collecting ability for monazite flotation.However,this study shows that its collecting ability is still limited.In this paper,a phosphonic acid,nonane-1,1-bisphosphonic acid(C9-BPA),was employed as the novel collector in place of NaOL.Flotation experiments show that even when the C9-BPA dosage is less than one-fifth of the NaOL dosage,the monazite recove ry using C9-BPA as the collector is approximately 22 wt%higher than that using NaOL.The mechanism by which C9-BPA adsorbs on monazite was investigated using zeta potential,infrared(IR)spectroscopy and X-ray photoelectron spectroscopy(XPS)measurements as well as first-principles calculations.Zeta potential measurements show a more significant decrease in the zeta potentials of monazite after the addition of C9-BPA compared to those after the addition of NaOL.For C9-BPA-treated monazite,the characteristic peaks of C9-BPA are observed in the IR and C 1 s XPS spectrum,whereas for monazite treated by NaOL,no characteristic peak of NaOL was observed.Experimental results show that C9-BPA has a stronger affinity towards the monazite surface than NaOL as confirmed by the higher adsorption energy of CP-BPA on the monazite surface(-204.22 kJ/mol)than NaOL(-48.48 kJ/mol).This study demonstrates an extensive application value and prospect of C9-BPA in monazite flotation and helps design novel collectors with strong collecting ability for monazite flotation.
基金supported by a Higher Education Commission of Pakistan Post-Doctoral Scholarship to A. Ali, NSERC Discovery Grant and Canada Foundation for Innovation grants to K. Larson, and NSF grant NSF-EAR-1119380 to J. Cottle. D. Arkinstall is thanked for his assistance in the FiLTER
文摘New metamorphic petrology and geochronology from the Loe Sar dome in the Swat region of northern Pakistan place refined constraints on the pressure, temperature and timing of metamorphism and deformation in that part of the Himalayan orogen. Thermodynamic modelling and monazite petrochronology indicate that metamorphism in the area followed a prograde evolution from ～525 ± 25 ℃and 6 士 0.5 kbar to ～610 ± 25 ℃ and 9 士 0.5 kbar, between ca. 39 Ma and 28 Ma. Partitioning of heavy rare earth elements between garnet rims and 30-28 Ma monazite are interpreted to indicate coeval crystallization at peak conditions. Microtextural relationships indicate that garnet rim growth post-dated the development of the main foliation in the area. The regional foliation is folded about large-scale N-S trending fold axes and overprinting E-W trending folds to form km-scale domal culminations. The textural relationships observed indicate that final dome development must be younger than the 30-28 Ma monazite that grew with garnet rims post-regional foliation development, but pre-doming-related deformation. This new timing constraint helps resolve discrepancy between previous interpretations,which have alternately suggested that N-S trending regional folds must be either pre-or post-early Oligocene. Finally, when combined with existing hornblende and white mica cooling ages, these new data indicate that the study area was exhumed rapidly following peak metamorphism.
基金the project of“Comprehensive integration and service of mineral geology and its metallogenic regularity in China”from China Geological Survey(Grant No.DD20160346)
文摘The Madi rare metal granite is a complex massif,which contains a variety of rare metals,such as Nb,Ta,Li,and Be.In this paper,the geochemical characteristics of the granite were obtained by multi-collector inductively coupled mass spectrometry(MC-ICP-MS).The precise crystalline age of the granite was obtained from monazite U-Pb dating,and the source of the granite was determined using Li-Nd isotopes.The Madi rare metal granite is a high-K(calc-alkaline),peraluminous,S-type granite.The U-Pb monazite age indicates that the crystalline age of the granite is 175.6 Ma,which is Early Jurassic.The granite is characterized by a relatively wide range ofδ7 Li values(+2.99‰to+5.83‰)and high lithium concentrations(181 ppm to 1022 ppm).The lithium isotopic composition of the granite does not significantly correlate with the degree of magmatic differentiation.An insignificant amount of lithium isotope fractionation occurred during the granitic differentiation.The lithium isotopic composition of the granite significantly differs from that of the wall rock,but it is very similar to that of a primitive mantle peridotite xenolith(meanδ7 Li value+3.5‰).The plot of Li concentration versusδ7 Li indicates that the Li isotopic composition of the granite is similar to that of island arc lavas.Based on the above-described evidence,the granite was mainly derived from the crust,but it was contaminated by a deep granitic magma.
文摘This study presents a re-examination of historical specimens(DG136 and DG167)from the Monashee complex in the southeastern Canadian Cordillera that are critical to the current understanding of rare earth element(REE)distribution between garnet and monazite(and other accessory minerals)during metamorphism.Nine-hundred and fifty-one new monazite petrochronology spot analyses on 29 different grains across two specimens outline detailed(re)crystallization histories.Trace element data collected from the same ablated volume,interpreted in the context of new phase equilibria modelling that includes monazite,xenotime and apatite,link ages to specific portions of the pressure-temperature(P-T)paths followed by the specimens.These linkages are further informed by garnet Lu-Hf geochronology and xenotime petrochronology.The clockwise P-T paths indicate prograde metamorphism was ongoing by ca.80 Ma in both specimens.The structurally deeper specimen,DG136,records peak P-T conditions of~755-770℃and 8.8-10.4 kbar,interpreted to coincide with(re-)crystallization of low Y monazite at~75-70 Ma.Near-rim garnet isopleths from DG167 cross in the observed peak assemblage field at~680℃ and 9.3 kbar.These conditions are interpreted to correspond with low Y monazite(re-)crystallisation at~65 Ma.Both specimens record decompression along their retrograde path coincident with high Y 70-55 Ma and 65-55 Ma monazite populations in DG136 and DG167,respectively.These findings broadly agree with those initially reported~20 years ago and confirm early interpretations using trace elements in monazite as generally reliable markers of metamorphic reactions.Modern phase equilibria modelling and in situ petrochronological analysis,however,provide additional insight into monazite behaviour during anatexis and the effects of potential trace element buffering by REE-bearing phases such as apatite.
基金the deputy director of Research and Development in Atomic Energy of Iran for financial support as well as Nuclear Science and Technology Research Institute for technical support
文摘The present work dealt with the preconcentration of rare earth elements in Saghand ore(Yazd province,Iran)which was achieved by Humphrey spiral using orthogonal optimization method after scrubbing the sample at 45%solid pulp density for 30 min.The pulp was diluted and was fed to a Humphrey spiral for upgrading.The process parameters considered were feed size,feed solids and feed rate,and Taguchi’s L9(34)orthogonal array(OA)was selected for optimization of the process.The results show that the feed rate and feed size were more significant than the other operation parameters of the process.It was also found that under optimal conditions,the concentrate grade of rare earth elements increased from2860 10 6to 6050 10 6and recovery reached to 58%.
基金financial support from the National Natural Science Foundation of China (Grant no.41530209)the Central Public-Interest Scientific Institution Basal Research Fund (Grant no.JYYWF201819)
文摘The Grove Mountains, 400 km south of the Chinese Antarctic Zhongshan Station, are an inland continuation of the Pan-African-aged （i.e., Late Neoproterozoic/Cambrian） Prydz Belt, East Antarctica. In this paper we carried out a combined U-Th-Pb monazite and Sm-Nd mineral-whole-rock dating on para- and orthogneisses from bedrock in the Grove Mountains. U-Th-Pb monazite dating of a cordierite-bearing pelitic paragneiss yields ages of 523 ？ 4 Ma for the cores and 508 ？ 6 Ma for the rims. Sm-Nd mineral-whole-rock isotopic analyses yield isochron ages of 536 ？ 3 Ma for a coarse-grained felsic orthogneiss and 507 ？ 30 Ma for a fine-grained quartzofeldspathic paragneiss. Combined with previously published age data in the Grove Mountains and adjacent areas, the older age of ~530 Ma is interpreted as the time of regional medium- to low-pressure granulite-facies metamorphism, and the younger age of ~510 Ma as the cooling age of the granulite terrane. The absence of evidence for a Grenville-aged （i.e., Late Mesoproterozoic/Early Neoproterozoic） metamorphic event indicates that the Grove Mountains have experienced only a single metamorphic cycle, i.e., Pan-African-aged, which distinguishes them from other polymetamorphic terranes in the Prydz Belt. This will provide important constraints on the controversial nature of the Prydz Belt.
文摘Gravity, magnetic and electrostatic separation methods allowed to obtain different titanium oxide concentrates (ilmenite, leucoxene, rutile) and different varieties of zircon concentrates (premium zircon, standard zircon, medium grade zircon standard) from Senegal’s heavy mineral sands. During mining separation, monazite, which is a paramagnetic mineral, was found in a non-negligible concentration of 0.57 wt% on average in the medium grade zircon standard which also contains 37.96 wt% zircon and 44.46 wt% titanium oxides. Magnetic and gravity separation tests were carried out on the Medium grade zircon standard (MGZS) to produce a monazite concentrate at Eramet Ideas laboratory. Magnetic separation at 1.5 teslas intensity resulted in the recovery of 94.8% of the monazite from the MGZS. Gravity separation also recovered 76.6% of the monazite from the MGZS. The combination of these two treatment methods can thus produce three concentrates from MGZS (a monazite concentrate, a zircon concentrate, and a titanium oxide concentrate).
