Early-Cretaceous Syenites and Granites in the Northeastern Tengchong Block, SW China: Petrogenesis and Tectonic Implications

Whole-rock major and trace element and Sr-Nd isotopic data, together with zircon LA ICP- MS in-situ U-Pb and Hf isotopic data of the syenites and granites in the Tengchong Block are reported in order to understand their petrogenesis and tectonic implications. Zircon U-Pb data gives the emplacement ages of ca. 115.3±0.9 Ma for syenites and 115.7±0.8 Ma for granites, respectively. The syenites are characterized by low SiO2 content （62.01-63.03 wt%） and notably high Na20 content （7.04- 7.24 wt%） and Na20/K20 ratios （2.02-2.10）, low MgO, Fe2OaT and TiO2, enrichment of LILEs（large-ion lithophile element） such as Rb, Th, U, K, and Pb） and obvious depletion HFSE（high field strength element; e.g. Nb, Ta, P, and Ti） with clearly negative Eu anomalies （dEu=0.53-0.56）. They also display significant negative whole-rock eNd（t） values of-6.8 and zircon eHf（t） values（-9.11 to -0.27, but one is ＋5.30） and high initial S7Sr/86Sr=0.713013. Based on the data obtained in this study, we suggest that the ca. l15.3Ma syenites were possibly derived from a sodium-rich continental crustal source, and the fractionation of some ferro-magnesian mineral and plagioclase might occur during the evolution of magma. The granites have high SiO2 content （71.35-74.47 wt%）, metaluminous to peraluminous, low Rb/Ba, Rb/Sr, and AI2Oa/（MgO＋FeOT＋TiO2） ratios and moderate （AI2Oa＋MgO＋FeOT＋TiO2） content. They show low initial a7Sr/86Sr （0.703408 to 0.704241） and eNd（t） values （-3.8 to -3.5）, plotted into the evolutionary trend between basalts and lower crust. Hence, we suggest that the granites were derived from the melting of mixing sources in the ancient continental crust involving some metabasaltic materials and predominated metasedimentary greywackes. Together with data in the literatures, we infer that the Early Cretaceous magmatism in the Tengchong block was dominated by magmas generated by the partial melting of ancient crustal material, which represent the products that associated to the closure of Bangong-Nujiang Meso-Tethys.

Re-recognition of Tieshan “Syenite” and its Geological Significance in Zhenghe, Fujian Province

1 Introduction Tieshan Syenite crosses between Dongfeng and Zhangyuan’an in Zhenghe of Fujian province,occurs in the direction of 42°,Total length 8500m,width 600-800m and its Area of about 39km2.Outcrops of the mass are

LA-ICP-MS Zircon U-Pb Age of Longtou Syenite body in South Songxian County, Southern Margin of the North China Craton

Objective Indosinian magmatic rocks mainly locate in west Qinling Orogen, which are, however, extremely rare in east Qingling Orogen （Lu Xinxiang, 2000; Zhang Guowei et al., 2001; Guo Xianqing et al., 2017）. The Zhifang Huangzhuang （ZH） area in south Songxian County is located in the southern margin of the North China Craton （Fig. l a）, which is an important lndosinian alkaline magmatic occurrence including 32 syenite bodies and syenitic dykes in east Qinling Orogen. There are five syenite bodes in the ZH area, i.e., the Lang＇aogou, Mogou, Longtou, Jiaogou and Wusanggou from west to east （Fig. l b）.

Alkali feldspar syenites with shoshonitic affinities from Chhotaudepur area: Implication for mantle metasomatism in the Deccan large igneous province

Two petrologically distinct alkali feldspar syenite bodies （AFS-1 and AFS-2） from Chhotaudepur area, Deccan Large Igneous Province are reported in the present work. AFS-1 is characterized by hypidio-morphic texture and consists of feldspar （Or55Ab43 to Or25Ab71）, ferro-pargasite/ferro-pargasite horn-blende, hastingsite, pyroxene （Wo47, En5, Fs46）, magnetite and biotite. AFS-2 exhibits panidiomorphic texture with euhedral pyroxene （Wo47-50, En22-39, Fs12e31） set in a groundmass matrix of alkali feldspar （Or99Ab0.77 to Or1.33Ab98）, titanite and magnetite. In comparison to AFS-1, higher elemental concentra-tions of Ba, Sr and PREE are observed in AFS-2. The average peralkaline index of the alkali feldspar syenites is w1 indicating their alkaline nature. Variation discrimination diagrams involving major and trace elements and their ratios demonstrate that these alkali feldspar syenites have a shoshonite affinity but emplaced in a within-plate and rifting environment. No evidence of crustal contamination is perceptible in the multi-element primitive mantle normalized diagram as well as in terms of trace elemental ratios. The enrichment of incompatible elements in the alkali feldspar syenites suggests the involvement of mantle metasomatism in their genesis.

Whole-rock geochemical, U-Pb and Sm-Nd isotope characteristics of the Dongueni Mont nepheline syenite intrusion, Mozambique

The Dongueni Mont nepheline syenite intrudes migmatitic paragneisses and siliciclastic metasediments of the Barue Complex, Mozambique. This study reports the whole-rock geochemical, U-Pb and Nd isotopic data of the nepheline syenite. The ferroan and alkalic geochemical characteristics are typical of alkaline rocks formed in a within-plate setting. The strong depletion in high field strength elements(HFSEs)(e.g. Ba, Nb, P,and Ti) and enrichment in large ion lithophile elements(LILEs)(e.g. Rb, Th, K, and Pb) are consistent with magmatism in a continental alkaline magmatic province associated with intracontinental rifting. Zircon U-Pb data yielded crystallization ages from 498 ± 19 to 562± 14 Ma,consistent with the Pan-African Orogeny and the inherited zircons yield an age of 1040 Ma, which supports the presence of a Mesoproterozoic crust. Theε_(Nd)(t) values from the nepheline syenite samples range from-15.1 to-16.1 and the T_(DM)values from 1.77 to 1.67 Ga, which indicate that the initial nepheline syenite magma formed from a tholeiitic or mantle source in a within-plate setting with crustal assimilation.

Late Carboniferous Vertical Crustal Growth in Northern North China Craton: Evidence from Zircon U-Pb Age and Depleted Hf Isotope of the Dongwanzi Syenite

Objective Though the Central Asian Orogenic Belt (CAOB) is characterized by widespread Phanerozoic crustal growth,there is little juvenile crust documented in its southeastern segment,northern margin of the North China Craton(NCC)(Zhang et al,2007,2009).Late Carboniferous Dongwanzi ultramafic-mafic cumulate complex occurs in northern margin of the NCC and is intruded by a syenite with depleted Sr-Nd isotopes (Ma et al.,2014).However,the age and petrogenesis of this syenite is poorly constrained.In this study,we present new petrological,zircon U-Pb and Hf isotopic data of the Dongwanzi syenite,in order to put insights on its formation age and petrogenetic relationship with cumulates.

Zircon micro-texture and chemistry:an investigation of magmatic history and crystallization temperature of quartz potassic syenite from Iwo area,Southwestern Nigeria

The Neoproterozoic quartz potassic syenite of the Iwo area,Southwestern Nigeria has been investigated for its magmatic history and zircon saturation temperature.The zircon morphology showed irregular shapes with sectoral and oscillatory micro zoning.The majority of the zircon grains have embayment,which corresponds to magmatic resorption.The syenite crystallized from probably multiple recharge of less evolved magma.Both the magma injection and subsequent crystallization of the rock occurred over a length of time giving the rock some degree of protracted thermal history and slight fluctuation in chemistry,which are manifested as zonation in the analyzed zircon grains.The initial stage of zircon crystallization was marked by a lower cerium anomaly than the final stage,which indicates changes from lower oxidizing to higher oxidizing conditions.The protracted history does not affect the europium anomalies at any stage of crystallization.An average zircon saturation temperature of 865℃estimated from titanium in zircon(T_(Tiz)℃)thermometer using titanium activity of 0.7(^(a)TiO_(2)~0.7)is taken as reasonable crystallization temperature of the rock.This is fairly consistent with 877℃deduced from the zircon solubility model.The titanium in zircon temperature of 910℃at aTiO_(2)~1 is rather too high to be a useful estimate.Both the temperatures 865 and 877℃are however consistent with those of intermediate rocks.The size of the syenite and protracted crystallization history would have made the temperature to have impacted the metamorphic envelope around the syenite.

Luku Alkali Syenite in the Hongge Ore District,SW China:Geochemistry,Geochronology and Metallogenic Significance

Luku alkali syenite is distributed throughout the southern end of the Hongge basic-ultrabasic intrusion in Panzhihua,Sichuan,SW China.Using LA-ICP-MS,the alkali syenite intrusion yielded a zircon U-Pb age of_(2)64.5±1.6 Ma,concordant with the ages of the E’meishan large igneous province(260 Ma).The intrusion displayed silica-saturated,Al-adequate and alkali-rich signatures,with SiO_(2)62.07%-64.04%,Al_(2)O_(3)16.26%-16.79%and Na_(2)O+K_(2)O 9.17%-9.91%(averaging 9.31%).The rock falls into the alkaline zone on the SiO_(2)-A.R.diagram,as well as in the potassium zone on the K_(2)O-Na_(2)O diagram,indicating a potassium alkaline rock.The rock has a low total REE concentration and showed enrichment in LREE(LREE/HREE=7.06-7.95),typical negative Eu anomalies(δEu=0.73-0.80),trace element deficiencies in LILEs(Ba,K,Sr,Zr)and enrichment in HFSEs(Th,U,Nd,Sm,Ta and Nb),displaying crust and mantle element information.Zircons show a strong positive Ce anomaly and negative Eu anomaly,similar to the characteristics of crustal source magmatic zircon,however the(Lu/Gd)N ratio ranges from 1.48 to 3.17,and the(Yb/Sm)N ratio ranges from 38.49 to 77.15,which are similar to the characteristics of mantle-derived magmatic zircon.In the La/Yb-δEu correlation diagram,the data plots near the boundary between crust type and crust-mantle type.From the combined‘trinity’spatiotemporal relationship of Indosinian intermediate-acid alkali intrusive rocks in the Panxi area with E’meishan basalt and basic-ultrabasic intrusive rocks,the regional tectonic evolution and the partial melting model of the most intraplate magma sources,we believe that the Luku alkali syenite in Sichuan was formed from the partial melting of a crust-mantle source material,due to underplating of the mantle plume basic magma.

Extraction of Rare Earth from K-rich Syenite Tailings

The application of K-rich nephline syenite ores would produce some tailings, which will cause many disadvantages such as more land occupation. In this research, an process was obtained to extract rare earth from the K-rich nephline syenite tailings of Gejiu, Yunnan province, China. This tailings mainly composed of K-feldspar, biotite, magnetite, andradite, nepheline and 0.1% rare earth. The chemical compositions are shown in Table 1.

Nepheline Syenite Decomposition Using NaOH by Hydrothermal Reaction

Nepheline syenite is an important potassium-rich rock resource. Nepheline syenite powder was decomposed successfully by hydrothermal reaction using NaOH additive. Hydroxycancrinite (Na8(Al6Si6O24)(OH)2·2H2O ) solid and (K,Na)2SiO3 solution was obtained as a result of the hydrothermal reaction.

Preparation of K_2CO_3 Using Potassic Syenite from East Qinling Mountains

1 Introduction Songxian at East Qinling mountains in China possesses more than 100 million tons potassic syenite with the average K2O content of 13%and the main mineral phase of K-feldspar which is a kind of potential potassium

Mineralogy, Petrography and Geochemistry of the Ina Syenite (Linté, Central Cameroon) as a Source of Industrial Feldspars

The syenite from Ina (Central region of Cameroon) constitutes a 1000 km2 syntectonic batholith intruded in the Paleoproterozoic granitic basement. The aim of this work is to assess the potential of the Ina batholith syenite as a feldspar minerals resource for industrial use through petrographic and geochemical characterization. Most of the rocks are grey coloured and consist of shimmering feldspar phenocrysts in a fine-grained ferromagnesian matrix. Petrography reveals the presence of two major syenite facies: a widely distributed porphyritic syenite and a less-abundant massive syenite. These facies are dominated by phenocrysts of sub-automorphic perthitic orthoclase. Its malgachite face is due to the presence of numerous inclusions of opaque minerals observed by scanning electron microscopy (ESEM-EDX). Plagioclase phenocrysts have a zonal texture characterised microscopically by an oscillatory compositional zonation. Biotite, hornblende and augite, identified by X-ray powder diffraction, are finely disseminated in the feldspar matrix. Quartz appears as small automorphic crystals with maximum abundance of about 4 wt%. The XRF chemical composition reveals, alongside silica (59.29 wt% to 63.27 wt%), significant proportion of alumina (15.82 wt% to 19.80 wt%), potassium and sodium oxides considered as fluxing elements (K2O + Na2O ≥ 10 wt%). The K2O/Na2O ratio varies between 1.65 and 5.51 (average 2.58). Iron and titanium oxides (1 ≥ wt% Fe2O3 + TiO2 ≥ 5), harmful in ceramic industry, are high as in most other feldspathic sources. The characteristics of the Ina syenite are close to most of the syenite ores used worldwide for ceramics and glass raw materials and necessitates purification and beneficiation treatments. Others rock types have been identified at the study site (granite, monzonite, granodiorite) and are considered as inappropriate as a source of industrial feldspars.

Mineralogy and Beneficiation of Lamujärvi Syenites

The Lamujärvi syenites intrusions occur within Svecofennian (ca. 1.92 Ga) gneisses, ca. 70 km west of the Otanmaki alkaline area in central Finland. Previous studies have revealed zones in the syenites that display strong enrichment in Zr (1587 ppm), Nb (up to 685 ppm), Ta (up to 82 ppm), and REE (up to 5350 ppm). The major REE-bearing minerals in the Lamujarvi syenites are allanite and monazite. A sample of the Lamujärvi syenites with the REE content of 4700 ppm was studied on the mineralogy and beneficiation at GTK Mintec. The mineralogical analysis was conducted by MLA. The REE-bearing minerals allanite, parisite, zircon, and apatite were identified at significant concentrations and high contents of titanite (15.4%), biotite (30.9%) and magnetite (8.2%) were displayed in the sample. The beneficiation experiments by flotation, wet low and high gradient magnetic separations and gravity separation with a shaking table were carried out. A composite REE-Ti concentrate with REE 23,000 ppm, Zr 5000 ppm, Nb 3400 ppm and TiO2 25.5% at REE and Ti recoveries of 57% and 54% was obtained. In addition, biotite and magnetite concentrates were gained as by-products.

Petrogenesis and Tectonic Implications of Peralkaline A-Type Granites and Syenites from the Suizhou-Zaoyang Region,Central China

In this study, we present systematic petrological, geochemical, LA-ICP-MS zircon U-Pb ages and Nd isotopic data for the A-type granites and syenites from Suizhou-Zaoyang region. The results show that the peralkaline A-type granites and syenites were episodically emplaced in Suizhou-Zaoyang region between 450±3 and 441±7 Ma which corresponds to Late Ordovician and Early Silurian periods, respectively. Petrologically, the syenite-peralkaline granite association comprises of nephefine normative-syenite and alkaline granite in Guanzishan and quartz normative syenite and alkafine granite in Huangyangshan. The syenite-granite associations are ferroan to alkali in composition. They depict characteristics of typical OIB （oceanic island basalts） derived A-type granites in multi-elements primitive normalized diagram and Ybffa vs. Y/Nb as well as Ce/Nb vs. Y/Nb binary plots. Significant depletion in Ba, Sr, P, Ti and Eu indicates fractionation of feldspars, biotite, amphiboles and Ti-rich augite. The values of eNd（t） in Guanzishan nepheline syenite and alkaline granite are ＋1.81 and ＋2.26, respectively and the calculated two-stage model age for these rocks are 1 040 and 1 003 Ma, respectively. On the other hand, the Huangyangshan alkaline granite has eNd（t） values ranging from ＋2.61 to ＋3.46 and a relatively younger two-stage Nd model age values ranging from 906 to 975 Ma, respectively. Based on these data, we inferred that the Guanzishan nepheline syenites and granites were formed from fractional crystallization of OIB-like basic magmas derived from upweliing of metasomatized lithospheric mantle. The Huangyangshan quartz syenite and granite on the other hand, were formed from similar magmas through fractional crystallization with low input from the ancient crustal rocks. Typically, the rocks exhibit Al-type granite affinity and classified as within plate granites associated with the Ordovician crustal extension and the Silurian rifting.

Origin of Baotoudong syenites in North China Craton:Petrological, mineralogical and geochemical evidence

Baotoudong syenite pluton is located to the east of Baotou City, Inner Mongolia, the westernmost part of the Trias- sic alkaline magmatic belt along the northern margin of the North China Craton （NCC）. Zircon U-Pb age, petrological, miner- alogical and geochemical data of the pluton were obtained in this paper, to constrain its origin and mantle source characteris- tics. The pluton is composed of nepheline-clinopyroxene syenite and alkali-feldspar syenite, with zircon U-Pb age of 214.7±1.1 Ma. Diopside （cores）-aegirine-augite （rims）, biotite, orthoclase and nepheline are the major minerals. The Bao- toudong syenites have high contents of rare earth elements （REE）, and are characterized by enrichment in light rare earth ele- ments （LREE） and large ion lithophile elements （LILE; e.g., Rb, Ba, Sr）, depletion in heavy rare earth elements （HREE） and high field strength elements （HFSE）. They show enriched Sr-Nd isotopic compositions with initial 87Sr/86Sr ranging from 0.7061 to 0.7067 and eNd（t） values from -9.0 to -11.2. Mineralogy, petrology and geochemical studies show that the parental magma of the syenites is SiO2-undersaturated potassic-ultrapotassic, and is characterized by high contents of CaO, Fe2O3, K2O, Na2O and fluid compositions （H2O）, and by high temperature and high oxygen fugacity. The syenites were originated from a phlogopite-rich, enriched lithospheric mantle source in garnet-stable area （〉80 km）. The occurrence of the Baotoudong sye- nites, together with many other ultrapotassic, alkaline complexes of similar ages on the northern margin of the NCC in Late Triassic implies that the lithospheric mantle beneath the northern margin of the NCC was previously metasomatized by melts/fluids from the subducted, altered paleo-Mongolian oceanic crust, and the northern margin of the craton has entered into an extensively extensional regime as a destructive continental margin in Late Triassic.

Geochronology and Geochemistry of Wangjiadashan Quartz Syenite Porphyry in Suizao Area of Hubei Province in the Tongbai-Dabie Orogenic Belt

The Wangjiadashan area in Suizhou-Zaoyang region of Hubei Province in the Tongbai-Dabie orogenic belt hosts important copper-gold deposits and contains a large number of quartz syenite porphyry dykes,occurring mostly along the NEE-trend faults.In this study,we used LA-ICP-MS zircon U-Pb dating method and obtained an age of 143.6±1.4 Ma,which represents the emplacement of these quartz syenite porphyry dykes was at the Yanshanian,but it was slightly earlier than the previously reported ages(139-135 Ma)for granites widespreading in Suizao area.The geochemical data of the Wangjiadashan quartz syenite porphyry show high K_(2)O,CaO,Na_(2)O and Al_(2)O_(3)contents but extremely low MgO contents(0.01 wt.%-0.46 wt.%).The geochemical characteristics indicate that these quartz syenite porphyry dykes belong to the typical C-type adakite and were possibly formed in the post-collisional environment.Multi-isotopic(Sr-Nd-Pb-Hf)analyses indicate that these quartz syenite porphyry dykes were originated from crust without distinct mantle materials involved.It is suggested that the Wangjiadashan quartz syenite porphyry was generated from partial melting of the thickened lower continental crust,and garnet but no plagioclase was left as residual phase.Compared with the widespread granites of the Tongbai area,the Wangjiadashan quartz syenite porphyry formed earlier and derived from more juvenile and K-rich lower crust,while they all belong to intensive magmatism concentrated during the Early Cretaceous epoch in the Tongbai area.

From mantle to critical zone:A review of large and giant sized deposits of the rare earth elements

The rare earth elements are unusual when defining giant-sized ore deposits,as resources are often quoted as total rare earth oxide,but the importance of a deposit may be related to the grade for individual,or a limited group of the elements.Taking the total REE resource,only one currently known deposit（Bayan Obo） would class as giant（〉1.7×10^7 tonnes contained metal）,but a range of others classify as large（〉1.7×10^6 tonnes）.With the exception of unclassified resource estimates from the Olympic Dam 10 CG deposit,all of these deposits are related to alkaline igneous activity- either carbonatites or agpaitic nepheline syenites.The total resource in these deposits must relate to the scale of the primary igneous source,but the grade is a complex function of igneous source,magmatic crystallisation,hydrothermal modification and supergene enrichment during weathering.Isotopic data suggest that the sources conducive to the formation of large REE deposits are developed in subcontinental lithospheric mantle,enriched in trace elements either by plume activity,or by previous subduction.The reactivation of such enriched mantle domains in relatively restricted geographical areas may have played a role in the formation of some of the largest deposits（e.g.Bayan Obo）.Hydrothermal activity involving fluids from magmatic to meteoric sources may result in the redistribution of the REE and increases in grade,depending on primary mineralogy and the availability of ligands.Weathering and supergene enrichment of carbonatite has played a role in the formation of the highest grade deposits at Mount Weld（Australia） and Tomtor（Russia）.For the individual REE with the current highest economic value（Nd and the HREE）,the boundaries for the large and giant size classes are two orders of magnitude lower,and deposits enriched in these metals（agpaitic systems,ion absorption deposits） may have significant economic impact in the near future.

The Thermal History of the Huangmeijian Granite Intrusion in Anhui and Its Relation to Mineralization: Isotopic Evidence

Whole-rock Rb-Sr, zircon U-Pb and hornblende, biotite and K-feldspar K-Ar ages areused to reconstruct the cooling history of the Huangmeijian intrusion in the Anqing-Lujiangquartz-syenite belt in Anhui. Oxygen isotope geothermometry of mineral pairs demonstrates thatdiffusion is a dominant factor controlling the closure of isotopic systems. Assuming the coolingof the intrusion is synchronous with a dicrease in local geothermal gradients, an emplacementdepth of about 8 km and the magma crystallization temperature of 800±50℃ are estimated. TheHuangmeijian intrusion experienced a rapid cooling process and uplifted after its emplacementand crystallization at 133 Ma B.P. with a cooling rate of 34.5℃/Ma and an uplifting rate of 0.35mm/a. The intrusion was rising until it rested at a depth of 3km at a temperature of 300±50℃about 14 Ma later. Then the intrusion was in slow cooling and uplifting with a cooling rate of4.4℃/Ma and an uplifting rate of 0.04 mm/a. U-Pb dating of pitchblende is done for the hydrothermal uranium deposit formed in thecontact zone of the Huangmeijian intrusion. The result shows that the mineralization age is closeto the closing time of the K-Ar system in biotite. The fluid inclusion thermometry indicates thatthe mineralization temperature is in agreement with the closure temperature of the biotite K-Arsystem. This suggests a close relationship between the slow cooling of the intrusion and thehydrothermal uranium mineralization process.

Geological Characteristics and Ore-controlling Factors of the Beiya Gold–Polymetallic Ore Deposit, Northwestern Yunnan Province

Based on comprehensive petrological, geochronological, and geochemical studies, this study analyzed the relationships between the Beiya gold-polymetallic skarn deposit and quartz syenite porphyries, and discussed the source（s） and evolution of magmas. Our results suggest that syenite porphyries（i.e. the Wandongshan, the Dashadi, and the Hongnitang porphyries）, which formed between the Eocene and the early Oligocene epochs, are the sources for the gold-polymetallic ores at the Beiya deposit. Carbonate rocks（T2 b） of the Triassic Beiya Formation in the ore district provide favorable host space for deposit formation. Fold and fault structures collectively play an important role in ore formation. The contact zone between the porphyries and carbonates, the structurally fractured zone of carbonate and clastic rocks, and the zone with well-developed fractures are the ideal locations for ore bodies. Four types of mineralization have been recognized： 1） porphyry-style stockwork gold–iron（copper） ore, 2） skarn-style gold-iron（copper and lead） ore in the near contact zone, 3） strata-bound, lense-type lead–silver–gold ore in the outer contact zone, and 4） distal vein-type gold–lead–silver ore. Supergene processes led to the formation of oxide ore, such as the weathered and accumulated gold–iron ore, the strata-bound fracture oxide ore, and the structure-controlled vein-type ore. Most of these ore deposits are distributed along the axis of the depressed basin, with the hypogene ore controlling the shape and characteristics of the oxide ore. This study provides critical geology understanding for mineral prospecting scenarios.

The role of carbonate-fluoride melt immiscibility in shallow REE deposit evolution

The Lugiin Gol nepheline syenite intrusion, Mongolia, hosts a range of carbonatite dikes mineralized in rare-earth elements(REE). Both carbonatites and nepheline syenite-fluorite-calcite veinlets are host to a previously unreported macroscale texture involving pseudo-graphic intergrowths of fluorite and calcite. The inclusions within calcite occur as either pure fluorite, with associated REE minerals within the surrounding calcite, or as mixed calcite-fluorite inclusions, with associated zirconosilicate minerals. Consideration of the nature of the texture, and the proportions of fluorite and calcite present(～29 and 71 mol%,respectively), indicates that these textures most likely formed either through the immiscible separation of carbonate and fluoride melts, or from cotectic crystallization of a carbonatefluoride melt. Laser ablation ICP-MS analyses show the pure fluorite inclusions to be depleted in REE relative to the calcite. A model is proposed, in which a carbonate-fluoride melt phase enriched in Zr and the REE, separated from a phonolitic melt, and then either unmixed or underwent cotectic crystallization to generate an REE-rich carbonate melt and an REE-poor fluoride phase. The separation of the fluoride phase(either solid or melt) may have contributed to the enrichment of the carbonate melt in REE, and ultimately its saturation with REE minerals. Previous data have suggested that carbonate melts separated from silicate melts are relatively depleted in the REE, and thus melt immiscibility cannot result in the formation of REE-enriched carbonatites. The observations presented here provide a mechanism by which this could occur, as under either model the textures imply initial separation of a mixed carbonate-fluoride melt from a silicate magma. The separation of an REEenriched carbonate-fluoride melt from phonolitic magma is a hitherto unrecognized mechanism for REE-enrichment in carbonatites, and may play an important role in the formation of shallow magmatic REE deposits.