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This paper studies the mineralization process and the ore-forming setting of the Kantian fluorite deposit in South China through the zircon U-Pb chronology, quartz Rb-Sr dating, whole rock geochemistry, H-O isotope and fluid inclusions. A mineralization model for the Kantian fluorite deposit is proposed as follows: The subduction of the Pacific plate during the late mid-Jurassic and late Jurassic led to the formation of several fault zones. As the subduction gradually decelerated and eventually ceased, continental extension and lithosphere thinning occurred, accompanied by upwelling of the asthenosphere. This asthenosphere upwelling facilitated melting of the lithospheric mantle, resulting in the ascent of magma into the lower crust. Consequently, the intrusion of magma into the lower crust caused substantial heat, triggering partial melting of the lower crust. The molten material then ascended along faults, generating a significant quantity of granites. During the Early Cretaceous period, the Yanshan cycle witnessed another notable phase of magmatic activity. The residual magmatic hydrothermal fluid from this period served as a source of heating, while the pre-existing fault structures provided favorable pathways and storage space. Atmospheric precipitation infiltrated into the depth along these faults, and the deep-seated residual magmatic hydrothermal fluid heated the infiltrated atmospheric water, inducing cyclic upwelling. The upward migration of hydrothermal fluid continuously extracted Ca and F elements from the granites. Ongoing interaction between the fluid and the surrounding rocks led to changes in pH, coupled with alterations in temperature and pressure, ultimately resulting in the precipitation of fluorite with associated alteration zones in the surrounding rocks. [Display omitted] • Ca and F element in the fluorite were derived through the surrounding rocks. • The ore-forming fluids belong to the NaCl-H 2 O system and exhibit characteristics of medium–low temperature, low salinity, and low density, and were derived from meteoric water. • The intrusion age of surrounding rock in Kantian fluorite deposit was 159.4 ± 2.2 Ma, and the ore-forming of fluorite was 135.6 ± 0.7 Ma. • The tectonic setting responsible for the diagenesis and mineralization processes is believed to be an intracontinental stretching environment associated with the subduction of the Pacific plate. The Yanshanian events have led to the development of South China as a unique granite province globally. Within South Jiangxi, numerous metallic and non-metallic deposits have a close association with Mesozoic granite formations. The Kantian fluorite deposit, a newly discovered non-metallic deposit in southern Jiangxi Province, is one such deposit that is linked to Mesozoic granites. The orebody at the Kantian fluorite deposit is identified as occurring in veined structures within the silicification fracture zone of Mesozoic granites, with strict control exerted by fault systems. Fluorite ore can be classified into two categories based on the amount of quartz and fluorite. The first category is the fluorite quartz type, which has a higher amount of quartz than fluorite. The second category is quartz fluorite type, which has more fluorite than quartz. Among these two categories, the quartz fluorite type is precipitated during the primary mineralization stage. Through the analysis of fluid inclusions within the fluorite, it was determined that the homogenization temperature is relatively low, ranging from 133 to 236℃. The fluid inclusions also display low salinity (0.18–3.39 wt% NaCl eqv.) and low density (0.75–0.96 g/cm3). Laser Raman spectroscopy revealed that the primary components of the fluid inclusions are H 2 O, with minor C 3 H 6. Isotope analysis indicated δD VSMOW values of fluorite ranging from −61.9 ‰ to −54.8 ‰ (average −59.8 ‰), while δ18O VSMOW values varied from 1.3 ‰ to 3.1 ‰ (average 2.0 ‰). This study presents chronological, petrological and geochemical data that suggest several processes. The metallogenic age is 135.6 ± 0.7 Ma. The mineralizing fluids were identified to the NaCl-H 2 O system, with heated meteoric water identified as the primary source; The ore-forming materials originated from the granite, and water–rock interactions are proposed as the primary mechanism for fluorite precipitation. Based on a tectonic setting characterized by stretching, which is closely linked to the subduction of the Pacific plate, we proposed a model for the Kantian fluorite deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tainiolite, discovered in the Kaerqiaer F belt of China, implied the potential for F and Li exploration. • K-feldspar granite hosts F-tainiolite veins in an extensional fault. • The tainiolite yields an 40Ar-39Ar age of 421 ± 2 Ma. • The tainiolite formed from Li-F-P-rich magmatic-hydrothermal activity. The Kaerqiaer Fluorite Belt (KFB) contains the Kaerqiaer, Xiaobaihegou, Kumutashi, Northern Layidan, and Gaijike fluorite deposits in the western Altyn Tagh Terrane of NW China. An occurrence of Li-bearing mica tainiolite (KLiMg 2 (Si 4 O 10) F 2) has been recently discovered, associated with fluorite-bearing alkali feldspar granite. The tainiolite is hosted by fluorite-calcite veins that contain assemblages of tainiolite-fluorite-calcite and apatite-bastnaesite-tainiolite-fluorite-calcite along the contact zone with alkali feldspar granite. The tainiolite occurs as euhedral crystals and has high concentrations in the veins. 40Ar-39Ar dating of the tainiolite from Xiaobaihegou yields an age of 421 ± 2 Ma, and single-crystal X-ray diffraction confirms the tainiolite has a monoclinic 1 M−type with a C2/m (#12) space group. Minor structural variations in the mica are attributed to the substitution of Li for Mg. EPMA and LA-ICP-MS analyses show that the tainiolite has high Li, Rb, Cs, Sn and Nb concentrations, and low Ta, total REE concentrations. The average Li 2 O content of the fluorite-tainiolite veins reaches 0.36 %, surpassing the economic cut-off grade. We suggest that the fluorite deposits formed from highly fractionated Li-F-P-rich residual melt evolved from the parental magmas of alkali feldspar granite. The tainiolite mineralisation may result from subsequent hydrothermal activities caused by the reactivation of regional faults under the extensional regime between the Middle Altyn and Eastern Kunlun terranes. The discovery of tainiolite occurrences made KFB a potential area for not only F but also Li resources. [ABSTRACT FROM AUTHOR]

[Display omitted] • RGB information from televiewer logs are used to obtain fluorite ore grade. • White and ultraviolet illumination are employed in the logs. • Support vector machine with a salp swarm algorithm is applied. • Input for regression and classification are color intensity percentiles. • The method may be used to limit the amount of chemical analysis in ore grading. This paper describes a practical application of support vector machine (SVM) for ore grading in an underground fluorite mine. It covers all aspects from the inception of the experiments, data collection, input preparation, model description and results. Forty-eight drilling chips samples are collected while drilling six pseudo-horizontal boreholes at depth intervals of half a meter and their chemical composition determined through X-Ray fluorescence; the response of the drill rig is used to accurately define the depth of each sample along the blasthole. Images of the blasthole walls are collected with an optical televiewer with white and ultraviolet (UV) illumination. The color information of the images is characterized by the cumulative distribution of pixel color intensities of red, green and blue, used as inputs. A well-known metaheuristic algorithm is used to calibrate the SVM hyperparameters. Repeated k -fold cross validation is applied to increase the prediction performance due to the small-size of the dataset. An outlier inspection is made resulting in improved performance. The combination of pixel intensities from white and UV light scans leads to the best prediction of fluorite content (average R2 = 0.83 and RMSE = 3.32 %), while intensities from only white light procures the best classification results (average classification accuracies from 0.77 to 1). These metrics support the utility of the proposed methodology for reducing the amount of lab analysis in ore grade control. [ABSTRACT FROM AUTHOR]

• Pennine Orefield hosts significant fluorite mineralization. • Northern Pennine Orefield consists of two structural blocks (Alston and Askrigg). • REY, FIA and Nd-Sr isotopes differ significantly between Alston and Askrigg fluorites. • Positive Eu SN anomalies in Alston; temperatures exceeding 250 °C. • Multiple fluids and REY sources, potential influence by basement granite and dykes. The Pennine Orefield is one of the most important ore fields for Pb-Zn-Ba-F mineralization in Great Britain. It is subdivided into the Northern Pennine Orefield (NPO), consisting of the Alston and Askrigg Blocks, and the Southern Pennine Orefield (SPO). The Alston Block is underlain by the early Devonian Weardale Granite and the Askrigg Block by the coeval Wensleydale Granite. The potential relationship between the batholiths and the mineralization is a matter of debate. We here studied the rare earth elements and Y (REY) geochemistry, Sr-Nd isotopes and fluid inclusion (FI) compositions of fluorites from the two structural blocks in the NPO and found that the fluorite mineralization in these blocks differ substantially. The REY in Askrigg fluorites show features that are characteristic for leaching of adjacent Lower Carboniferous limestones. In contrast, Alston fluorites have significantly higher REY concentrations, lack REY SN limestone signatures and show a decoupling of redox-sensitive Eu from its trivalent REY 'neighbours'. Neodymium isotopes indicate a similar crustal source of REY in both blocks, but higher REY concentrations and lower Y/Ho ratios suggest Lower Carboniferous shales as potential REY source in the Alston Block. The fluids that precipitated the Alston fluorites experienced temperatures > 250 °C prior to mineral formation, as evidenced by Eu geothermometry. Fluorite formation , however, occurred at much lower temperatures, as suggested by homogenization temperatures in FI, that fall within ranges of 105–159 °C in Alston and 99–160 °C in Askrigg fluorites. Mineralization of the Mississippi-Valley Type usually lack association with igneous activity. We show that some of the fluids responsible for the NPO mineralization were influenced by magmatic sources. The REY systematics in Alston fluorites may be linked to an interaction of the Permian-age Whin Sill dolerite with the basement granite, which heated fluids and focussed fluid flow into the overlying sedimentary rocks. In the Askrigg Block, where such a dolerite intrusion was not described, fluorites lack any positive Eu SN anomalies, indicating that these fluids had never been subjected to temperatures exceeding 200–250 °C. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Review and discussion of ore-forming processes in the North German Basin. • Comprehensive inventory and characterization of the mineralized zones in the North German Basin. • Post-Variscan hydrothermal mineralization occurs at depth in Permian strata. • Zn-Pb-Fe sulfide mineralization identified in the Lower Saxony Basin. • Fluorite-barite and quartz-calcite-hematite veins found in Altmark-Brandenburg Basin. Abstract Hydrothermal Zn-Pb-Fe sulfide and F-Ba mineralization occur as open space fillings, veins, and fracture coatings in various parts of the North German Basin in Paleozoic sedimentary rocks and volcanic units at depths of up to four kilometers. We present a petrographic and geochemical (fluid inclusion, mineral and formation water geochemistry) inventory of the mineralized zones and review the basin architecture, evolution, and stratigraphy in order to decipher the timing, extent, fluid pathways, and fluid-rock interactions associated with the ore formation. A particular focus lies on the sediment-hosted Zn-Fe-Pb sulfides in the western part of the North German Basin, the Lower Saxony Basin. Samples from hydrothermal veins from the Pre-Permian basement are also being investigated and compared to the North German Basin-style mineralization to uncover possible genetic links between them. The sediment-hosted sulfide mineralization in the Lower Saxony Basin in the Permian Stassfurt Carbonate unit (Ca2) shares many characteristics that are typical for carbonate-hosted base metal sulfide deposits such as MVT deposits. Petrographic observations, fluid inclusion and isotope data provide evidence that Zn-Fe-Pb sulfides were deposited by highly saline metal-rich basinal brines at temperatures of ∼160 °C. Carbon and oxygen isotope data point toward fluid mixing augmented by structurally-controlled fluid migration during the late Cretaceous basin inversion as the primary ore precipitation mechanism with no magmatic component. In the Altmark-Brandenburg Basin, steeply-dipping F-Ba (calcite, anhydrite, quartz) veinlets in Permo-Carboniferous sandstones and volcanic units are evidence for enhanced post-Variscan structurally-controlled fluid flow. Sulfides are, apart from rare occurrences of chalcopyrite, absent. This is interpreted to reflect the paleogeographic position of the Altmark-Brandenburg Basin (deeper paleogeographic basin position without carbonate aquifers), the lack of reductants, and the predominance of nitrogen-rich fluids as documented by fluid inclusions. Measurements on formation waters from the NGB show geochemical similarities to fluid inclusions in ore and gangue minerals and could represent a potential future exploration tool for hydrothermal ore deposits. This has the potential to aid future research and exploration of deeply covered sediment-hosted deposits and to meet future mineral resources demands. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Nb + Ta vs TREE diagram seems to differentiate the deposits from high to low temperature. • REE-bearing fluorite deposits of Turkey are different than MVT deposits. • Correlation coefficient values between Sr and Eu indicates that fluorite formed under both reducing and oxidizing conditions. Abstract Rare Earth Element (REE)-bearing fluorite deposits in Turkey occur in association with Cenozoic post-collisional alkaline-carbonatite systems and can be divided into three groups: (1) carbonatite-associated; (2) those associated with subalkaline to alkaline magmatic rocks of Cretaceous to Cenozoic age; and (3) those in sedimentary successions, typically in areas dominated by limestone. Some of these deposits show significant enrichment in the REE, especially the Kızılcaören deposit which has average REE grades of almost 30,000 ppm; others have very low REE contents but have potential fluorite resources. The homogenization temperature and salinity values of fluid inclusions in these deposits vary between 600 °C and 150 °C, and 10–65 wt% NaCl eq., respectively. The carbonatite-associated deposits have the highest bulk REE contents and are LREE-enriched. As a general feature, the REE contents of the fluorite deposits decrease with decreasing homogenization temperatures and salinity of the fluorite fluid inclusions. Fluorite ore chemistry indicates that a plot of Nb + Ta versus total REE differentiates the carbonatite- hosted from the alkali intrusive- hosted and carbonate- hosted deposits. Beyond the cooling and/or dilution of the fluids, REE and fluorite deposition was driven by changes in pH, instead of change in Eh, according to our geostatistical treatment. The chondrite-normalized rare earth element patterns of each group of deposits show some similar features, indicating that the REE in the fluorite are independent of their host lithology, but reflect the magmatic systems from which they were derived. Overall, the F-REE deposits of the Anatolides-Taurides in Turkey are considered to be largely related to the post-collisional magmatic systems, but with variable contributions of fluids from other sources. [ABSTRACT FROM AUTHOR]

[Display omitted] • The seven deposits of the Bou-Izourane district show similar characteristics in terms of paragenesis, geochemistry and emplacement temperature, except for the site of Bou-Imetssene. • Both late magmatic fluids and meteoric waters are identified as mineralizing fluids. • The fluids have interacted with the rocks of the Tamazeght complex, which also acts as a heat source and a driving mechanism for fluid flows. • F is provided from the partial leaching of various minerals from the Tamazeght complex, while Ca is sourced mainly from the host sedimentary rocks. Fluorite deposits in the Bou-Izourane district of the High Atlas in Morocco are distributed over seven known mineralized sites near the Middle Eocene Tamazeght magmatic complex and hosted in sedimentary rocks (limestones and marls) of the Lower Jurassic (Bou-Izourane, Takkat, Bou-Kharouba and Tabja deposits), magmatic rocks (Bou-Imetssene and Meghsan deposits) and skarns (Tamazeght and Bou-Imetssene deposits). This paper examines the origin of the mineralizing fluids and the relationship between the Tamazegth complex and fluorite deposits. Fluorspar occurs in veins oriented according to three families (N20, N50-80 and N120), in karst cavities and as stratabound deposits. Three stages are identified in the mineralization: (1) fluorite emplacement associated with the dissolution of the host rocks; (2) fracturing and sealing by calcite and finally (3) silicification associated with the partial dissolution of fluorite and calcite. Fluid inclusions in fluorite hosted in marls and carbonates of the Lower Jurassic have low salinities (1.5 to 3 wt% equiv. NaCl) and homogenization temperatures between 91 °C and 159 °C. Fluid inclusions in the Tabja, Tamazeght and Meghsan fluorites exhibit the same salinity range, but with increased homogenization temperatures, ranging from 99 °C to 241 °C, with a vapour phase containing CO 2. Secondary solid daughter phases, such as nahcolite, calcite and strontianite are identified. Only Bou-Imtessene fluorite has high salinity fluid inclusions (∼18 wt% equiv. NaCl) and intermediate homogenization temperatures between 126 °C and 187 °C. These high local salinities and the presence of nahcolite and secondary carbonates in the fluid inclusions of the Tabja, Tamazeght and Meghsan fluorites may reflect the involvement of late-magmatic fluids. The δ18O isotopic composition of the fluid that precipitated calcites from Tabja (highest Th) and Bou-Izourane (lowest Th) indicates a meteoric origin. Fluorite has a broadly similar REE distribution to that of the Tamazeght carbonatites, suggesting that REE are derived from: i) carbonatites by hydrothermal alteration (e.g., Bou-Izourane, Bou-Kharouba and Takkat), and ii) carbonatitic (late-magmatic) fluids (e.g., Tabja, Tamazeght, Meghsan and Bou-Imtessene). Our data shows that fluorite mineralization in the Bou-Izourane district and the spatially associated middle Eocene Tamazeght magmatism have a direct genetic relationship through the contribution of late-magmatic F-rich fluids in close proximity to the complex. Fluorite mineralization farther from the complex is formed by per descensum circulation of meteoric waters along fractures resulting in fluorine leaching. The Tamazeght complex acts as a heat source and driving mechanism for fluid flows. The dissolution and recrystallization reactions are made possible by a strong geothermal gradient persisting after the complex was emplaced. The upwelling of these hydrothermal fluids into the calcium-rich host rocks (limestone and marl) leads to the precipitation of fluorite. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Fluorite mineralization occurred in exo-contact zone of Krivograd-Novoukrainan granite massif. • The fluorites had 5–10% salinity values and high (240–280 °C) and low (100–150 °C) homogenization temperatures. • REE contents indicate the decrease in temperature or increases in ƒO 2 and pH, high oxygen fugacity in the source. • Low Sr and high Sc values of fluorites point out similar rift and skarn type fluorite deposits. • The mean ∑REE concentrations of green, violet and yellow fluorites range 258.02, 97.39 and 80.2 ppm, respectively. Abstract The Bobrynets fluorite mineralization in the exo-contact zone of Krivograd-Novoukrainian granite intrusion is found in the southern part of the Kirovograd-Cherkassy fault zone between the Novoukrainian anticlinoria and the Ingulo-Ingulets synclinoria. The fluorite mineralization appears as vein and disseminat, as well as in the form of a cement in the tectonic breccia among the metasomatically altered granites. Fluorite mineralization is observed for 5 km along this fault zone, down to a depth of 300 m with the thickness of the individual mineralized zones ranging from a few meters to 75 m, with average fluorite contents ranging from 1–2% to 28%. The estimated reserve of Bobrynets fluorites is approximately 1.56 million tonnes. Fluid inclusion data in the studied fluorites indicate that the study area has two types of fluorites: high temperature fluorites (240–280 °C) and low temperature fluorites (100–150 °C). The total rare earth element (REE) contents of the fluorites range from 62.4 ppm to 527.9 ppm, with a mean of 218 ppm. The mean ∑REE concentrations of different colored massive fluorites range from 80.2 ppm for yellow fluorites to 258 ppm for green fluorites, 97.4 ppm for violet fluorites and 526.5 ppm for granite samples. The mean Y concentrations of the studied fluorites are 86.2 ppm for violet fluorites, 104.5 ppm for yellow fluorites, 242.5 ppm for green fluorites and 39.9 ppm for granite samples. The chondrite-normalized REE patterns of the Bobrynets fluorites exhibit trends similar to each other and show a decrease from light REEs (LREE) to heavy REEs (HREEs). All fluorites in the study area have positive Ce anomalies between 1.06 and 1.16 (with mean of 1.12), negative Eu anomalies (with a range of 0.35 to 0.58; mean: 0.46), and positive Y anomalies between 1.38 and 2.67 (with mean of 2.12). The Y/Ho values change from 48.3 to 92.2 with mean of 71.1. The Tb/Ca and Tb/La ratios of the Bobrynets fluorites are between 0.00000249 and 0.0000404 and between 0.098 and 0.30, respectively, and these ratios also indicate a formation from fractionated ore-bearing fluids at an early stage of mineralization, mainly a hydrothermal and less pegmatitic stage. The (Tb/Yb) n –(La/Yb) n ratios are low because these fluorites are not LREE rich when compared to other fluorite deposits. The (La/Yb) n –(Eu/Eu∗) n values also indicate low negative Eu anomalies and low LREE enrichments for the Bobrynets fluorites. The Sc/Eu vs Sr diagram and Sc vs ∑REE diagram show that the Bobrynets fluorites have low Sr contents and high Sc/Eu values and that they cover the same areas as the Rift Deposits of New Mexico and the skarn fluorite deposits of Akdagmadeni. The 208Pb/204Pb isotope values of fluorites vary between 53.5 and 62.6 and the 206Pb/204Pb isotope values of fluorites vary between 23.3 and 26.8. The 208Pb/204Pb vs 206Pb/204Pb ratios indicate that fluorites originated from upper crust materials. All these findings indicate that REE contents of the Bobrynets fluorites have different physicochemical parameters such as decrease in temperature or increases in ƒO 2 and pH, high oxygen fugacity in the source of the hydrothermal fluids, and low Sr and high Sc values similar to rift and skarn deposits. [ABSTRACT FROM AUTHOR]

[Display omitted] • Textural features, in situ trace elements and fluid inclusion of fluorite are studied. • A coupled dissolution-reprecipitation replacement process is proposed. • Fluorite acts as an indicator of carbonatite-related REE deposit. • Multiple pulses of fluids during formation of the Muluozhai deposit were recorded in fluorite. Formation of carbonatite-related REE deposits generally associated with hydrothermal fluids exsolved from carbonatite melts. Deciphering the nature and evolution of the fluids is critical for establishing ore-formation models, and was mostly benefited from multi-analytical investigation of specific minerals presenting in multi-generation veins. However, there is a risk that the minerals in specific-generation veins not always precipitated solely from the single-stage fluids particularly for a dynamic mineralizing system. In order to evaluate this potential risk, this study conducted a combined textural, in situ trace elemental and fluid inclusion investigation of fluorite from multiple generations of veins in the Muluozhai carbonatite-related REE deposit, SW China. The veins dominate the mineralization system of the deposit, and include four generations/stages: fenitization (Stage I), pre-REE (Stage II), early REE (Stage III) and late REE (Stage IV) stages in which the ore minerals are all dominated by bastnäsite. Fluorite grains are widely present in these generations of veins, but high-resolution CL imaging reveal that most of them display complex internal textures composed commonly of core, mantle and rim domains from center outward. These domains exhibit different CL-intensities that are well correlated with chemical compositions and even types of fluid inclusions they hosted. This study confirmed that the "core-mantle-rim" textures of fluorite are essentially responses to interaction of early grains (i.e., represented by cores) with multi-stage fluids through dissolution-reprecipitation processes. Trace elemental and fluid-inclusion microthermometric results show that the cores (also for mantles or rims) in fluorite from Stages I to III veins have comparable REE concentrations and patterns and homogenization temperatures of fluid inclusions, strongly suggesting that the core-mantle-rim fluorite grains in these veins are originally formed at Stage I, and were variably captured or metasomatized by fluids of Stage II or III during development of these generations of veins. Similar core-mantle-rim fluorite grains are also present in Stage IV veins, and thus are constrained to be also "xenocrysts" formed in a similar manner. They are surrounded or even locally disturbed by a number of euhedral and/or slightly oscillatory fluorite grains which are supposed to be formed from a different manner. On the basis of their close association with bastnäsite and relatively high homogenization temperatures of fluid inclusions they host, we proposed that these euhedral fluorite grains are products of Stage IV fluids. Clear understanding of the internal textures and paragenesis of fluorite allows us to propose a genetic model for the Muluozhai deposit that the REE mineralization in Stages III and IV involves likely different pulses of carbonatite-related REE-rich fluids, and REE deposition was possibly mainly triggered by incursions of external fluids (e.g., meteoric water). This study also highlights that the phenomenon regarding presences of early-stage "xenocrysts" in late-generation veins of carbonatite-related vein systems may be more common than previously thought, and thus investigation in a textural context is critical for deciphering ore genesis. [ABSTRACT FROM AUTHOR]

The Central Eastern Desert (CED) of Egypt, a part of Neoproterozoic Arabian Nubian Shield (ANS), embraces a multiplicity of rare metal bearing granitoids. Gabal El-Ineigi represents one of these granitic plutons and is a good example of the fluorite-bearing rare metal granites in the ANS. It is a composite pluton consisting of a porphyritic syenogranite (SG; normal granite) and coarse- to medium-grained highly evolved alkali-feldspar granite (AFG; fluorite and rare metal bearing granite) intruded into older granodiorite and metagabbro-diorite rocks. The rock-forming minerals are quartz, K-feldspar (Or 94-99 ), plagioclase (An 0-6 ) and biotite (protolithonite-siderophyllite) in both granitic types, with subordinate muscovite (Li-phengite) and fluorite in the AFG. Columbite-(Fe), fergusonite-(Y), rutile, zircon and thorite are the main accessory phases in the AFG while allanite-(Ce) and epidote are exclusively encountered in the SG. Texture and chemistry of minerals, especially fluorite, columbite and fergusonite, support their magmatic origin. Both granitic types are metaluminous to weakly peraluminous (A/CNK = 0.95–1.01) and belong to the post-collisional A2-type granites, indicating melting of underplated mafic lower crust. The late phase AFG has distinctive geochemical features typical of rare metal bearing granites; it is highly fractionated calc-alkaline characterized by high Rb, Nb, Y, U and many other HFSE and HREE contents, and by extremely low Sr and Ba. Moreover, the REE patterns show pronounced negative Eu anomalies (Eu/Eu ∗ = 0.03 and 0.06) and tetrad effect (TE 1,3 = 1.13 and 1.27), implying extensive open system fractionation via fluid–rock interactions that characterize the late magmatic stage differentiation. The SG is remarkably enriched in Sr, Ba and invariably shows a relative enrichment in light rare-earth elements (LREEs). The SG rocks (569 ± 15 Ma) are characterized by relatively low initial 87 Sr/ 86 Sr ratios (0.7034–0.7035) that suggest their derivation from the mantle, with little contamination from the older continental crust. By contrast, the AFG has very high 87 Rb/ 86 Sr and 87 Sr/ 86 Sr ratios that reflect the disturbance of the Rb-Sr isotopic system and may give an indication for the high temperature magma-fluid interaction. The positive εNd(t) values of AFG (+7.40) and SG (+5.17), corresponding to young Nd-T DM2 ages ranging from 707 to 893 Ma, clearly reflect the juvenile crustal nature of Gabal El-Ineigi granitoids and preclude the occurrence of pre-Neoproterozoic continental crust in the ANS. The field relationships, chemical, petrological and isotopic characteristics of El-Ineigi SG and AFG prove that they are genetically not associated to each other and indicate a complex origin involving two compositionally distinct parental magmas that were both modified during magmatic fractionation processes. We argue that the SG was formed by partial melting of a mid-crustal source with subsequent fractional crystallization. In contrast, the AFG was generated by partial melting and fractionation of Nb- and Ta-rich amphibole (or biotite) of the lower crust. The appreciable amounts of fluorine in the magma appears to be responsible for the formation of rare metal element complexes (e.g., Nb, Ta, Sn and REEs), and could account for the rare metal mineralization in the El-Ineigi AFG. [ABSTRACT FROM AUTHOR]

The Ashram Zone, which is host to the Ashram Rare Earth Element (REE) Deposit, occurs within the Eldor Carbonatite Complex, Québec, Canada. The complex is located within the Paleoproterozoic New Québec Orogen (Labrador Trough), and has been subjected to greenschist metamorphism and folding during the Hudsonian Orogeny at 1.75 Ga. To date, consanguineous undersaturated alkaline rocks have not been recognized within or adjacent to the complex. It is evident that the bulk compositions of the rocks, essentially magnesiocarbonatites and ferrocarbonatites, do not represent those of liquid compositions, as many are complex breccias which have been subjected to later hydrothermal activity. The Ashram Zone is dominated by diverse textural varieties of carbonatite which include: fluorite-rich schlieren carbonatites; coarse-to-medium grained granular carbonatites; fine grained, commonly mosaic-textured, quartz-bearing carbonatites; and colloform carbonatites. Compositional and textural data are provided for the minerals present in the carbonatites. The major rock-forming minerals are diverse Ca-Mg-Fe carbonates, fluorite, and quartz. The carbonates range in their compositional evolution from rare dolomite through ferrodolomite and magnesian siderite to siderite. The principal REE-bearing minerals of the Ashram Deposit are monazite-(Ce) and monazite-(Nd), with lesser amounts of bastnaesite-(Ce) and bastnaesite-(Nd). The minor and accessory mineral suite is characterized by the presence of apatite, phlogopite, xenotime, diverse Sc- and sn-bearing Nb-Ti-minerals (niobian rutile, nioboaeschynite, samarskite), barite, sphalerite, several uncommon, but here relatively abundant, Ba- and Ba-Be minerals (bafertisite, magbasite, barylite, betrandite, sanbornite, cebaite), yangzhumingite, cassiterite, galena, pyrite, and rare magnetite and potassium feldspar. Pyrochlore is absent and the Nb-Ti oxide assemblage is similar to that found in NYF-pegmatites associated with F-rich, A-type granitoids. The mineralogy of the Ashram Deposit, compared to that of other carbonatites associated with undersaturated silicate rocks is unique, especially with respect to the abundance of fluorite and monazite (commonly with Nd-enrichment), Ba-Be-enrichment, the NYF-type Nb-Ti oxide assemblage (especially xenotime, Y-Nb-aeschynite, samarskite), phlogopite-potassium feldspar quartz-rich residua with granitoid characteristics, paucity of magnetite, pyrochlore, and Sr-bearing carbonates. The Ashram Deposit is considered to be a late-magmatic-to-hydrothermal F-REE magnesio-to-ferrocarbonatite derived from as yet unknown consanguineous antecedents. [ABSTRACT FROM AUTHOR]

• Multiple isotope dating methods for dating fluorite mineralization and its surrounding rocks. • Characterization and analysis of geological information of typical super-large fluorite deposits in Southeast China. • The medium-low temperature hydrothermal filling fluorite deposit is related to the late hydrothermal extraction from surrounding rocks, but has little relationship with the time of rock emplacement in South China. • The formation of the Nanzhou fluorite deposit supported well subduction and extension of the Pacific plate to Southeast China during the Late Cretaceous. In SE China, there are numerous Mesozoic igneous rocks and a tectonically active area known as the Wuyi Fluorite Mineralization Belt. The Nanzhou fluorite deposit can effectively represent most hydrothermally filled fluorite deposits strictly controlled by the fault zones. These were mainly trending NE, NNE, followed by NW, and nearly EW. It is the epitome of fluorite mineralization in the Wuyi fluorite metallogenic belt, which can provide clues for the subduction of the Mesozoic Pacific plate to the Eurasian plate. As the surrounding rocks of the Nanzhou fluorite ore bodies, the zircon U-Pb isotopic age of the Anjiang syenogranite is 147±1 Ma, while the biotite plagioclase granulite of the Xiafeng Formation in the Wanquan group is 817±3 Ma and 811±3 Ma. However, fluorite is of hydrothermal origin. It yields an Sm-Nd isochron age of 103.8±5.0 Ma and an Rb-Sr isochron age of 106±15.0 Ma, more than c.a. 40 Ma younger than the Anjiang Syenogranite, indicating fluorite is a product of late hydrothermal mineralization. The right-leaning REE distribution curves of most fluorite samples are similar to those of Yanshanian Anjiang syenogranite and biotite plagioclase granulite of the Xiafeng Formation, which indicates that fluorite is closely related to the surrounding rocks. Most fluid inclusions in fluorite have salinities of 0.5–2.24 wt% NaCl eqv and low homogenization temperatures of 140–200 °C. The inclusions include a NaCl-H 2 O system with δD V-SMOW between −79.7 to −77.6‰ and δ18O V-SMOW values range from 0.4 to 2.1‰. The (87Sr/86Sr) i ratios of the fluorite, which are between 0.717427 and 0.719482, are characteristic of a crustal contribution. Based on the above description, the mineralized fluid of Nanzhou fluorite deposit belongs to the NaCl-H 2 O system with medium-low temperature and low salinity, which is obviously different from the magmatic hydrothermal fluid. In addition, the age of fluorite mineralization is younger than that of igneous rocks by ca. 40 Ma, so they are not correlated. It is proposed that the ore-forming fluid may be involved in atmospheric precipitation and circulate within the northeastward fault with increasing geothermal gradient to form Nanzhou-fluorite deposit. The Nanzhou-fluorite deposit was formed in 103.8±5.0 Ma and 106±15.0 Ma, which corresponds to the plate subduction and rollback period of the Late Cretaceous (in ca. 110–70 Ma). The formation of the Nanzhou deposit has important implications for the subduction of the Pacific plate to the Eurasian plate. [ABSTRACT FROM AUTHOR]

The Silius vein system, located in SE Sardinia (Italy) is analogous to other late- to post-Hercynian mineral systems of this type in Europe. The Silius system consists of two main veins, characterized by several generations of fluorite, calcite and quartz, with initial ribbon-like geometries, followed by breccias and cockade-like textures. In this study, aimed at investigating the REE concentrations in the Silius vein system, a REE average of ~ 800 ppm (locally ΣREE > 1500 ppm) has been observed in the carbonate gangue of the fluorite orebody. These amounts are related to the presence of the REE-bearing minerals synchysite-(Ce) and xenotime-(Y). The chemical composition of synchysite-(Ce) has been obtained by wavelength dispersive spectrometry (WDS). The average synchysite-(Ce) formula, built on the basis of (CO 3 ) 2 F and 5 negative charges, is Ca 1.07 (La 0.19 ,Ce 0.36 ,Pr 0.04 ,Nd 0.15 ,Sm 0.03 ,Gd 0.03 ,Y 0.13 )(CO 3 ) 2 F. From their geochemical characteristics, and their textural relationships with other gangue phases, it is likely that synchysite-(Ce) and xenotime-(Y) formed at the same P-T- X conditions as the other minerals of the Silius fluorite mineralization. Synchysite-(Ce) and xenotime-(Y) at Silius could be related to a local circulation phenomenon, where the REE are derived from a REE-bearing source rock in the basement of southeastern Sardinia, which has been leached by the same fluids precipitating the fluorite/calcite mineralization. REE concentrations contained in the carbonate gangue of still unexploited parts of the Silius vein deposit, as well as in dumps and tailings accumulated during past fluorite processing, could possibly represent a sub-economic by-product of the fluorite exploitation. [ABSTRACT FROM AUTHOR]

Stratabound fluorite deposits occur at the unconformity between the Variscan crystalline basement and the Mesozoic sandstone, conglomerate, limestone, and dolomite rocks of the Morvan Massif in central Burgundy. This study describes their petrographic characteristics in an attempt to determine the nature and temperature of mineralizing fluids in order to better understand the fluid migrations that led to massive stratabound fluorite deposition. The general paragenesis encompasses two major mineralizing events causing a succession of fluorite, barite, and quartz in all deposits. The two mineralizing events were preceded by two corrosion (dissolution or karstification) events affecting both the dolomite host rock at Pierre-Perthuis and Marigny-sur-Yonne and the limestone host rock at Courcelles-Frémoy with the creation of 1–10 m cavities and microscopic vugs. At Antully, the blocky calcite initially cementing the sandstone was partially dissolved. Microthermometric data on aqueous two-phase inclusions attest to CaCl 2 -rich fluids giving rise to fluorite deposition in the Pierre-Perthuis, Courcelles-Frémoy, and Antully deposits. Homogenization temperatures range from 80 to 100 °C at Pierre-Perthuis and Courcelles-Frémoy, with sporadically higher temperatures. The range of CaCl 2 contents is 6.5–15 wt.% at Pierre-Perthuis, 1.7–9.4 wt.% at Courcelles-Frémoy, and 1.6–16.3 wt.% at Antully. The thermal history of the northwestern Morvan, compiled from organic matter, clay minerals and apatite fission track data indicates that the temperatures in fluorite and barite are higher than the maximum temperature recorded in sediments. This implies deep ascendant hydrothermal brine circulation during the Early Cretaceous. The impermeable cap rock retained the ascendant hydrothermal brine and allowed the deposition of massive fluorite stratabound mineralizations. [ABSTRACT FROM AUTHOR]

Vein fluorite deposits (Tebarray, Lanuza, Bielsa-Parzán, Bizielle and Yenefrito) as well as one MVT-style fluorite mineralization (Portalet) in the Central Pyrenees are the focus in this contribution. These deposits are made up of fluorite, barite, base metal sulphides, calcite, and quartz and are hosted in sedimentary rocks and granites of Palaeozoic age. Generally, these mineral occurrences, typically associated with Late Palaeozoic steeply dipping faults are similar with respect to geologic setting, mineralogy and geochemical trends to other fluorite and base metal veins located in the Central Pyrenees. Veins occurring along such faults most likely represent channelways used by mineralizing solutions that were expelled from the basement. Previous work argued for genetic processes involving circulation of mineralising fluids during the Triassic–Lower Cretaceous period, which is often considered to represent a period of heat, fluid, and mass transfers related to rifting events in the western European basins, which is related to the opening of the Atlantic. A major goal of this study was to decipher the timing of fluid flow and ore formation on the basis of Nd–Sm dating of fluorite sampled from a number of deposits sharing a similar geological framework. No precise age(s) could be obtained due to a scatter in data, but results from the Portalet MVT-style deposit point to a mid-Triassic age (around 220 Ma) for this mineralization. The model that best explains the diagenetic stratabound mineralization at Portalet is gravity-driven fluid flow involving basinal brines during a rifting stage. Indeed, the formation of horst and graben structures during Early Alpine extensional tectonics favoured the infiltration of meteoric water into uplifted blocks, followed by fluid migration through the deeper parts of the basins whereby heat and dissolved components were acquired. This model also explains diagenetic changes recorded in the host limestone at Portalet. Also, overall Pb, Sr and Nd isotopic ratios measured in galena and fluorite suggest that differences in host rock and in the lithology of the basement seem to have exerted control on the chemistry of mineralizing fluids providing each deposit with distinctive characteristics. [ABSTRACT FROM AUTHOR]

The Guilaizhuang deposit is the largest gold producer in the southwestern Shandong Province with a unique Au–Te mineralization feature different from the other gold deposits in the adjacent Jiaodong Peninsula. The Tongshi alkaline intrusive complex, which is composed of syenites and monzonites with a crystallization age of ~ 180 Ma, is the main magmatic unit in this area, and considered to represent post-collisional magmatism. The syenite intruded into the sedimentary carbonate sequence in the Guilaizhuang district, cryptoexploded and was altered by fluorine-rich fluid. The intensely mineralized cryptoexplosive breccias along the EW-trending fault are extensively cemented by fluorite and calcite minerals. The intrusive age of the syenite should mark the lower limit of the gold mineralization age, whereas the formation age of the fluorite and calcite would represent the upper limit. In this study, we analyzed zircons from the altered syenite in the open-pit, and the results show U–Pb ages of 179–180 Ma consistent with those of the Tongshi intrusive complex. We also present a Sm–Nd isochron age from the fluorite–calcite mineral pair that shows 181 Ma. Based on those results, we infer the timing of gold mineralization to be approximately 180 Ma, coeval with the intrusion of the Tongshi complex. A correlation with the regional tectonic milieu shows that the Guilaizhuang gold deposit was located in a post-collision setting at this time, following the amalgamation between the North China Craton and the Yangtze Craton. Thus, the Guilaizhuang deposit should mark an important alkaline rock-related gold-forming event within the eastern margin of the North China Craton in a post-collisional setting associated with the collision of the North China Craton and Yangtze Craton during late Triassic to Early Jurassic, and is obviously different from the Early Cretaceous intensive gold mineralization in the adjacent Jiaodong Peninsula. [ABSTRACT FROM AUTHOR]

The Baiyanghe Be–U–Mo deposit is located in the Late Paleozoic Xuemisitan–Kulankazi island arc of the northwestern margin of the Junggar plate, Northwest China. It is the largest Be deposit (2.2 M tons of ore with grades ranging from 0.2% to 1.4%) in Asia. Orebodies in the deposit occur as fractures along contact zones between the Yangzhuang granite porphyry intrusion and Devonian pyroclastic country rocks and within the porphyry itself. Muscovite–fluorite veins are closely associated with the Be–U–Mo mineralization. A new Ar–Ar dating of the muscovite in this study yields a plateau age of 303.0 ± 1.6 Ma, which constrains the timing of the Be–U–Mo mineralization of the deposit. Three stages of fluorite of different colors have been identified at the deposit, with the earliest dark-purple fluorite more closely associated with the mineralization. Microthermometry of fluid inclusions obtained from the three stages of fluorite suggests that the fluorites were precipitated as veins from low temperature (120–150 °C) hydrothermal fluids with salinity ranging from 4.7 to 19.7 wt.% NaCl eqv. Based on the trace elemental concentrations and REE patterns of the fluorite, the style of veining, and the low salinity and low temperature characters of the fluid inclusions, it is suggested that Be and U were most likely transported as fluoride complexes and Mo as hydroxyl complexes. Pb isotopic compositions of the ores and country rocks, as well as O and H isotopic characters of the ore-related muscovite, indicate mixing between magmatic and meteoric waters; both contributed to formation of the ore-forming fluids. Metallic Be, U, and Mo were most likely leached out from the granite porphyry by the fluids. The fluid mixing led to the reduction of U, Mo, and Be and their precipitation at the deposit. [ABSTRACT FROM AUTHOR]

The Monakoff iron oxide–Cu–Au (IOCG) deposit, located to the north east of Cloncurry within the Eastern Succession of the Mount Isa Inlier, Queensland, Australia, is characterised by high concentrations of F and Ba, with a host of other enriched elements including Co, Ag, Mn, REE, U, Pb, Zn and Sr. This gives the deposit a characteristic gangue assemblage dominated by fluorite, barite and calcite. The nearby E1 deposit, located 25 km to the NNE of Monakoff, and the large Ernest Henry deposit, 3 km to the west of E1, also contain abundant fluorite, barite and calcite in late stage assemblages. The three deposits, therefore, constitute a distinct group of IOCG deposits within the district, based on their F-rich geochemical and mineralogical affinities. The Monakoff ore zone is hosted in dilational openings along a shear zone developed within metasediments and metavolcanic rocks at the boundary between competent hangingwall rocks of the Toole Creek Volcanics and footwall rocks of the Mount Norna Quartzites. Four stages of alteration and mineralisation are recognised: Stage 1 garnet–biotite alteration; Stage 2 biotite–magnetite alteration; Stage 3 main F–Ba-ore mineralisation; and a Stage 4 pyrite–alloclasite Au–Co–As overprint. The E1 deposit has a more complex history, but Stage 5 has veins of fluorite–barite–carbonate that are comparable to Monakoff's main stage. The Stage 3 assemblage at Monakoff comprises a sheared groundmass of fluorite, barite, manganoan calcite, magnetite, chalcopyrite, pyrite, galena and sphalerite, with coarser grained pods of the same mineralogy interpreted to be dilational structures infilled during syn-ore deformation. Accessory minerals include U–Pb-oxides, REE–F-carbonates and Ag–Pb–Bi-sulfosalts, with no discrete Au minerals. The sulfosalts are interpreted to have formed from an immiscible Bi-melt within the mineralising fluid at temperatures higher than the melting point of Bi. The Stage 4 overprint at Monakoff contains pyrite and alloclasite. Laser ablation analyses of the sulphide minerals at Monakoff reveal that Stage 3 sulphides contain only trace amounts of Au (0.04 ppm in pyrite), although galena and chalcopyrite contain significant concentrations of Ag. Stage 4 pyrite and alloclasite, however, contain ~ 1 ppm Au in solid solution and mass balance calculations indicate the majority of bulk rock Au to be present in these minerals, although the majority of bulk Ag is present in Stage 3 sulphides. The Stage 5 veins at E1 have an identical gangue and accessory mineralogy to Stage 3 at Monakoff and differ in the sulphide mineralogy only in the lack of galena and sphalerite. Four fluid inclusion populations are identified within the fluorite at Monakoff: Group 1 is CO 2 rich; Group 2 is complex solid–liquid–vapour inclusions, with two groups based on homogenisation temperature (> 450 °C and 300–375 °C). Laser ablation-ICP-MS analyses indicate that these inclusions contain Cu, Pb, Zn, Fe, Mn, Mg, Ag, REE, U and Ba, but significantly no S, Se or Au; Group 3 are solid–liquid–vapour inclusions with a T h of 200–275 °C, and contain Ba, Na, Mg, K and Br; and Group 4 are low salinity liquid–vapour inclusions. Group 1, 2 and 4 inclusions are also present in fluorite at E1. The REE geochemistry of fluorite from Monakoff and E1 is comparable and is characterised by a distinct positive Eu anomalies in all analyses, interpreted to indicate oxidising conditions at the time of high temperature ore deposition. The presence of abundant fluorite and barite is indicative of fluid mixing due to the insolubility of barite and fluorite and thus Ba and S, and Ca and F must have been introduced via different fluids. We propose that the oxidised fluid represented by the Group 2 inclusions and containing F, Ba, REE, U and base metals, mixed with a reduced, S-bearing fluid in [ABSTRACT FROM AUTHOR]

The Vergenoeg fluorite deposit in the Bushveld Complex in South Africa is hosted by a volcanic pipe-like body. The distribution characteristics, composition and formation conditions of high-field-strength element (HFSE)-rich minerals in different lithological units of the deposit were investigated by optical and cathodoluminescence microscopy, scanning electron microscopy, X-ray fluorescence, inductively-coupled plasma mass-spectrometry and electron-probe microanalysis. The Vergenoeg host rocks comprise a diverse silica-undersaturated assemblage of fayalite–magnetite–fluorite with variably subordinate apatite and mineral phases enriched in rare-earth elements (REEs). The Sm–Nd isotope systematics of the fluorite from the various lithological units of the pipe support the model that the HFSE budget of the Vergenoeg pipe was likely derived from a Lebowa-type granitic magma. Isotopically, there is no evidence for other REE sources. Formation of the pipe, including development of the fluorite mineralization, occurred within the same time frame as the emplacement of other magmatic rock units of the Bushveld Complex (Sm–Nd isochron age for fluorite separates: 2040 ± 46 Ma). Hydrothermal alteration is manifested in strongly disturbed Rb–Sr isotope systematics of the Vergenoeg deposit, but did not affect its HFSE and REE budget. Whole-rock chondrite-normalized REE + Y distribution patterns of two types were observed: (i) flat patterns characteristic of magnetite–fluorite unit, gossan, metallurgical-grade fluorite (“metspar”) plugs and siderite lenses, and (ii) U-shaped patterns showing enrichment towards the heaviest REE (Tm–Lu) observed in the fayalite-rich units. Common HFSE minerals are complex Nb-rich oxides (samarskite, fergusonite), REE phosphates and fluorocarbonates. Additionally, fluocerite and REE silicates, whose identification requires further work, were found. Most of the HFSE-rich minerals are spatially associated with Fe-rich phases (e.g., pyrite, magnetite, greenalite and hematite). To a smaller extent, they are found finely disseminated or healing micro-fractures in fluorite. The whole-rock REE + Y distribution patterns of the individual lithological units are mainly controlled by the distribution of Yb-rich and Y-rich xenotime in these rocks. The common occurrence of bastnäsite-(Ce) in the gossan, “metspar” plugs and especially in the rhyolitic carapace at the pipe–wall-rock contact, controls the REE + Y distribution patterns of these rocks. HFSE minerals in the Vergenoeg pipe rocks have formed in several stages. Samarskite and coarse fluorapatite belong to the primary mineral assemblage. Fergusonite and Yb-rich xenotime formed during high- to moderate-temperature hydrothermal activity. Significant remobilization of the HFSE from the early-crystallized minerals (breakdown of fluorapatite and possibly allanite with release of REE + Y) and subsequent partial redistribution of these elements into near surface rocks are inferred. The late-stage assemblages are characterized by the presence of fine-grained REE fluorocarbonates, monazite-(Ce), monazite-(La) and xenotime-(Y). [ABSTRACT FROM AUTHOR]

The Tumen molybdenite-fluorite vein system is hosted by carbonate rocks of the Neoproterozoic Luanchuan Group, located on the southern margin of the North China Craton (NCC) in central China. Previous studies divided the mineralization into four stages according to the crosscutting relationships between veinlets and their mineral assemblages. In this contribution, two distinctive types of fluorite mineralization are recognized: 1) the first type (Type 1) includes colourless, white or green fluorite grains present in Stage 1 veins; and 2) the second type includes Type 2a purple fluorite present in Stage 2 veins and does not coexist with sulfides, and Type 2b purple fluorite crystals associated with sulfides in Stage 2 veins. The rare earth element (REE) content in the fluorite ranges between 13.8 and 27.9 ppm in Type 1, 16.9 and 27.2 ppm in Type 2a, and 42.5 and 75.1 ppm in Type 2b, which suggests that the fluorite was precipitated from acidic fluids (given that REEs are mobile in saline HCl-bearing fluids at high temperature (~ 400 °C)). Comparing the REE chemistry of the Stage 1 against Stage 2 fluorite, the LREE/HREE ratios decrease from 9.8 to 4.0, La/Yb ratios decrease from 16.0 to 6.9 and La/Ho ratios decrease from 10.2 to 3.0, indicating that the hydrothermal process was at high-T and low-pH conditions. The Eu/Eu* ratios in the fluorite decrease from 1.11 ± 0.35 for Type 1 through 0.89 ± 0.19 for Type 2a to 0.75 ± 0.17 for Type 2b, suggesting a gradual increase in oxygen fugacity (fO2) and pH of the mineralising fluid. The Tb/Ca, Tb/La and Y/Ho ratios of the fluorite types indicate that they were formed from the interaction between magmatic fluids and carbonate wallrocks. The fluorite samples show similar REE + Y (REY) patterns to those of dolostone units in the Luanchuan Group and the nearby Neoproterozoic syenite, suggesting that the REY in the fluorite was mainly sourced from the host-rocks, although the syenite could be an additional minor source. [ABSTRACT FROM AUTHOR]

[Display omitted] • Textural features and in situ trace elements of fluorite are studied. • Water-rock reaction plays a dominant role for fluorite mineralization. • Variation in pH and temperature caused the precipitation of fluorite. • A dissolution-reprecipitation-recrystallization process is proposed. The Wujianfang fluorite deposit shows a four-stage mineralization history: (1) pre-ore stage of disseminated fluorites, (2) early-ore stage of fluorite-muscovite-pyrophyllite, (3) main-ore stage of fluorite-pyrophyllite, and (4) late-ore stage of fluorite-albite-quartz. Detailed cathodoluminescence imaging, fluid inclusion study, and in-situ LA-ICP-MS trace element analysis of fluorite in different stages or mineral assemblages were applied to reveal the fluorite mineralization and metasomatic history of this deposit. These data show that water-rock reaction between hydrothermal fluids and wall rocks not only provides the dominant ore-forming materials for fluorite mineralization, but also promotes the precipitation of fluorite by changing the pH of ore-forming fluids. Temperature change also plays an important role in fluorite precipitation. Fluorite grains from the pre-, early-, and main-ore stages have been variably metasomatized by a coupled dissolution-reprecipitation-recrystallization mechanism, which is characterized by complex petrographic and chemical zones. During this process, many trace elements were leached from the primary fluorite grains or other accompanied minerals, and parts of these elements were immediately reprecipitated into the new phases. Then, the recrystallized phases were formed from the leachate solutions of primary minerals. Our study highlights that fluorite generally has a complex growth history due to metasomatic alteration by hydrothermal fluids during the ore-forming process. Thus, in-situ microanalysis is essential and necessary to obtain effective and accurate constraints on hydrothermal evolution, and most of the interpretations based on bulk analysis of fluorites crystals should be cautioned. [ABSTRACT FROM AUTHOR]

[Display omitted] • The fluorite Sm-Nd isotopic data which yielded an isochron age of 152.0 ± 3.7 Ma. • C–H–O isotopes indicate the derivation of ore-forming fluids mixed with basinal water and meteoric water. • Origin of the ore-forming components from carbonate rocks in the deep crust. • The F-Li deposit was related to the flat-slab subduction and delamination of the Paleo-Pacific plate. Fluorite and lithium have become extremely important minerals globally. The newly discovered medium-to-large-scale Pingqiao fluorite-lithium deposit in the southwest Yangtze Block contains a rare mineral system with fluorite and lithium associations. This unique deposit provides an excellent example for the study of the origin and formation processes of the fluorite-lithium mineral system. The fluorite ore bodies in the Pingqiao mining area are hosted in the silicified limestone of the late Carboniferous Nandan Formation, and the lithium-bearing ore bodies occur in the claystone and micrite of the early Permian Longyin Formation. Fluorite and lithium clay show different REE patterns, but both have negative Eu and Ce anomalies. The isochron age yielded by the fluorite Sm-Nd isotope data was 152.0 ± 3.7 Ma. The δD V-SMOW values ranged between −63.1‰ and −56.8‰, and the δ18O V-SMOW values ranged from −5.7‰ to −4.9‰. The δ13C V-PDB values were between 1.3 and 2.7‰ for calcite. The 87Sr/86Sr ratios ranged between 0.708489 and 0.708810 for Li-clay and 0.708584 to 0.709180 for fluorite. The field geological, petrological, and geochemical data reported in this study indicate the following salient findings: (1) the ore-forming fluid was formed by mixing basinal water and meteoric water; (2) the ore-forming materials originated from the Cambrian, Ordovician, and Devonian carbonate rocks, and Carboniferous limestone; and (3) the deposit was formed in an extensional setting within the Yangtze Block and is closely associated with the late Jurassic to early Cretaceous polymetallic events and is related to the flat-slab subduction and delamination of the Paleo-Pacific plate. We propose a model of fluorite-lithium mineralisation that explains the fluid composition, transport, and precipitation mechanisms involved in the mineral system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorite deposits in Linxi district share similar and relatable geological features. • Fluorite mineralization in the Linxi district occurred approximately at 137–132 Ma. • Ore-forming fluids are dominantly of meteoric water origin. • Fluorite vein system may link to the regional Late Mesozoic metallogenic events. The Linxi fluorite district is located in the southern Great Xing'an Range and tectonically belongs to the eastern segment of the Central Asian Orogenic Belt. Previous studies mainly focus on the metal deposits in this region, but relatively little attention has been paid to the fluorite mineralization. The Linxi district contains more than 60 fluorite deposits while the formation age, nature of mineralized fluids, and ore-forming processes are poorly understood. This study focuses on geology, geochronology and geochemistry of the fluorite deposits in the Linxi district which share similar and relatable geological features. Fluorite veins are strictly controlled by ∼S-N-, NNE-SSW- and NE-SW-striking fault zones. Ore mineral assemblages are quite simple and mainly include fluorite, quartz and calcite. Geochronological data indicate that the main-stage fluorite vein mineralization in the Linxi district occurred approximately at 137–132 Ma. Fluid inclusions hosted in fluorite, quartz and calcite mainly homogenize at 140–220 °C, corresponding to low salinities (mainly 0.3–1.2 wt% NaCl equivalent). Ore-forming fluids are characterized by low temperatures, low salinities and low densities of the H 2 O–NaCl system. The carbon, hydrogen and oxygen isotopic compositions of samples obtained from the Linxi fluorite district indicate an origin of meteoric water. Combined with trace element geochemistry, fluorite, quartz and calcite in this area share a common hydrothermal origin. The large-scale fluorite mineralization in this region may link to the Late Mesozoic metal metallogenic events in the southern Great Xing'an Range associated with the extensional tectonic setting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Field-portable exploration methods were systematically described in shallow overburden areas for vein-type fluorite deposits. • The advantages and disadvantages of field-portable fluorite exploration methods have been analyzed. • The Effectiveness of RS + VLF-EM + PRXF for exploration has been validated by trenching and drilling. Fluorite deposits are widespread throughout eastern China and commonly occur in vein systems. These vein-type fluorite deposits are the primary source of fluorine worldwide and were predominantly formed during the Mesozoic or Cenozoic periods. In the absence of ore outcrops, fluorite exploration is necessarily concentrated within the shallow overburden area. The Wuliji'Oboo fluorite deposit is an example of a medium–low temperature vein-type subsurface orebody in eastern Inner Mongolia. Five portable technology methods have been implemented within the study area, including multispectral remote sensing (RS) technology, very low-frequency electromagnetic measurement (VLF-EM), portable X-ray fluorescence analyses (PXRF), portable gamma-ray spectroscopy, and partial extraction geochemistry. This paper describes the application principles, influencing factors, and technical solutions for each method. By investigating various examples, the applications of portable technology methods and their associated limitations were evaluated. Combining geological research with multi-spectral RS techniques is essential for optimum fluorite ore body prediction, thus narrowing prospecting targets. First, the target area was scanned using VLF-EM to identify the distribution of potential anomalies. Second, PXRF was used to distinguish the mineralised anomaly. Finally, trenching and drilling were performed to verify the effectiveness of the combination of methods. This study establishes a geology-geophysics-geochemistry-remote sensing integrated exploration model that may provide theoretical and technical support for the prediction of fluorite ore bodies in large Quaternary shallow overburden areas. [ABSTRACT FROM AUTHOR]

Abstract: Fluorite vein-type deposits occur along the western edge of the Bohemian Massif in SE Germany, from Bayerischer Wald to Frankenwald. They are emplaced in various host rock lithologies, as old as Late Variscan granites and low-grade metasediments of late Paleozoic age. The Nabburg-Wölsendorf mining district in NE Bavaria, Germany, used to be the largest in Germany and one of the most important in the world. A minor proportion of fluorite is also concentrated in the Permo-Mesozoic siliciclastic sediments resting unconformably upon the basement rocks near Pingarten. Fluorite is investigated in the present study for its REE variation, the REE minerals associated with it and its Sm/Nd isotope ratios. The primary blue-black fluorites precipitated from aqueous hydrothermal solutions during early stages without noticeable interaction with wall rocks and were poor in REE and Y. The secondary green, white and yellow fluorites formed from remobilization of older fluorite and through the interaction of more viscous fluids with the wall rocks and they are abundant in REE plus Y. Monazite–(Ce) is the major source for the REE re-deposited into fluorite. In a double cross plot, designed during this study and using the Ce-, Eu anomalies and the skewness (fractionation) of the REE pattern, the geological and hydrological evolution of fluorite vein mineralizations are related to the granite and the unconformity, which is the hydraulic reference plane for the fluorite mineralization. First, blue fluorite formed at considerable depth below the unconformity. Fetid fluorite is exclusive to the deep-seated vein mineralization with abundant uranium minerals. These uranium minerals caused some radiation damage to the lattice of the blue fluorite and turned into black. Based upon the variation of REE in fluorite and the Sm/Nd dating (fluorite age: ca. 270Ma) the Permian paleogeography can be reconstructed. It is suggested that in the Nabburg-Wölsendorf District a NW–SE oriented swell stood out from a vast peneplain. Second, fluorite vein mineralization composed of green, white and yellow fluorite along the western edge of the Bohemian Massif resulted from remobilization associated with an increase in REE and Y relative to the blue and black fluorites and a strong fractionation of LREE vs. HREE. The REE signature of the latter fluorites got increasingly more “unconformity-related” (Eh>0), notwithstanding the fluid source which the mineralizing fluids originated from. The REE patterns, Sr- and Sm/Nd isotopes suggest that mineralizing fluids mainly derived from a granitic source rock with little impact from metasedimentary rocks. Cerite–(Ce) formed during the initial stages of fluorite mineralization when little REE were accommodated in the lattice of blue fluorite. During precipitation of green, white and yellow fluorite, REE minerals failed to continue developing on their own, because REE were increasingly accommodated in the structure of fluorite changing its color from blue via green into white. REE minerals were again formed during supergene alteration of fluorite mineral assemblages, terminating the entire F-REE cycle. Rhabdophane is of supergene origin and indicative of meteoric conditions that are neutral to slightly alkaline. Subsequently, florencite evolved under a more acidic regime of chemical weathering. The distinct data arrays in the cross plots of the Sm-, Nd- and Sr isotopes, likewise, indicate this subdivision into fluorite originating from fluids that interacted with granitic and gneissic rocks at depth and those being formed proximal and distal to the unconformity. [Copyright &y& Elsevier]

Abstract: Fluorite deposits in Asturias (Iberian Peninsula, N Spain) are hosted in Permo-Triassic and Paleozoic rocks. The three main districts of Berbes, La Collada and Villabona preferentially occur along the margins of a Mesozoic basin and comprise veins and stratabound mineralization composed of fluorite, barite, calcite, dolomite, quartz and sulphides. Although the geological framework is similar and fluorite dominates in all deposits, variability in sources and processes has led to each area having its own distinctive characteristics. Sr isotope data of fluorite, calcite and barite (87Sr/86Sr=0.7080 to 0.7105) are compatible with a mixing between seawater and an evolved groundwater that interacted with basement rocks. Sm/Nd ratios in fluorites from Villabona district provide an isochron age of 185±28Ma (Late Triassic–Late Jurassic), consistent with other hydrothermal events in the Iberian Peninsula and Europe. The total REE content of fluorite increases from Berbes to Villabona by an order of magnitude (0.4 to 9.3). The La/Lu ratio in fluorites decreases from a mean value of 0.36 in Berbes, 0.17 in La Collada to 0.09 in Villabona indicating a strong fractionation between LREE and HREE. Calculated δ 18O of fluids ranges from 0.3 to +7.4‰ during barite precipitation, from +0.8 to +4‰ during quartz formation and around +3‰ during carbonate deposition. The δ 34S of barite (+17 to +56‰), is explained by sulphate reduction processes (either thermochemically or bacterially mediated) in a system closed with respect to sulphate. The δ 34S of sulphide (+0.6 to −32‰) is compatible with these processes although bacterial processes must have dominated at Villabona. Organic matter was an important source of C in the fluids especially in Villabona (δ 13C=−14.8 to −2.5‰ in calcites and from −7.9 to −2.2‰ in dolomites). Differences in host rock and position within the basin, and the lithology of the basement, seem to have exerted a strong control on the chemistry of mineralizing fluids providing each district with distinctive characteristics. [Copyright &y& Elsevier]

Abstract: The Nabburg–Wölsendorf vein-type fluorites in SE Germany which are characterized by a pronounced timebound variation in mineral color (blue→black→green→white/colorless→yellow→brown) were investigated for their accessory minerals included in or associated with these different fluorite types. Nabburg–Wölsendorf is not a unidirectional fluorite mineralization but a polyphase mineralizing process with several repetitions of the various color types during the vein mineralization event. Accessory minerals of the fluorite mineralization include silicates, sulfates, oxide/hydroxides, phosphates, sulfides and carbonates. These minerals are intimately intergrown with fluorite in the vein-type mineralization and are efficient tools to broaden knowledge on the depositional environment of fluorite that is otherwise poor in marker minerals for redox conditions, temperature, alkalinity/acidity and fluid viscosity. Pyrite, galena and cinnabar, are indicative of hypogene processes, while uranyl phosphates and APS minerals furnish evidence for supergene mineralizing processes. Some minor constituents may be used as marker minerals of redox conditions (hematite, galena, and goethite) or held to be characteristic for the changing pH regime (kaolinite and smectite). Oxidizing conditions prevailed during fluorite mineralization, excluding some phases when fetid and white fluorite precipitation ran through a maximum. Yellow-brown honey spar marks the oxidizing physical–chemical conditions by its brown mineral color at the end of fluorite mineralization. Oxidizing conditions prevailed also during supergene mineralization. The pH of the mineralizing fluids of the hypogene stages was greater than pH 7. During the supergene stage, Eh fluctuated, but was mainly >0; the pH of fluids ranged between 7 and 4. The black color of fetid fluorite and its pungent odor resulted from the U present primarily in its tetravalent state. Incomplete haloes recognized in some fetid fluorites reflect “frozen” uranium disequilibria and an early phase of supergene alteration. In this respect, the fetid fluorite (“Stinkspat”) plays an important part and held to be a marker for the radioactive “hot spot” as well as “ghost” uranium mineralization. Fetid fluorite is defined as to its mineral color, morphology and characteristic spectral features so as to allow for a precise distinction from other dark blue or green fluorite varieties by its outward appearance and easy-to-handle methods. The accessory minerals under study are indicative of the depocentre of the fluids which lies close to an unconformity but does not, however, deliver information on the source of the mineralizing fluids. The nearness to the potential source rock of the fluids can only concluded from the presence of cerite-(Ce) which formed prior to fluorite. This REE silicate is cast as a marker of the root zone of the fluorite veins which fade out into late Variscan granites. Cerium is assumed to have been derived from monazite an accessory mineral largely found outside the fluorite veins, proper, in the late Variscan granites. In the waning stages of fluorite mineralization different types of REE-bearing phosphates, belonging to the rhabdophane solid solution series, and some APS minerals (aluminum–phosphate–sulfate solid solution series) evolved. [Copyright &y& Elsevier]

Abstract: The fluorite district of Zaghouan, north-eastern Tunisia, is characterized by F-(Ba–Pb–Zn) ore deposits. Mineralization occurs within stratabound to stratiform bodies, either within Jurassic back-reef limestone uplifted blocks, or along unconformity surfaces that separate them from the overlying sequence. Fluorite mineralization also occurs within fractures crosscutting the uplifted limestone blocks and their overburden. Despite the similarity of the Liassic series throughout the major part of the district, stratabound fluorite deposits formed subsequent to a strong epigenetic dolomitization (Souissi et al., 1998), and occurring along the Lower–Middle Liassic unconformity, are known only at Jebel Stah and at the adjacent Jebel Kohol. Four petrographic types of fluorite are recognized: the finely-laminated karst deposits (Fl1a), the macrogranular fluorite (Fl1b), resulting from the recrystallization of Fl1a, and the megacrystalline fluorite (Fl2) associated to calcite in lodes, and fluorite in geodes (Fl3). This study gives new arguments in terms of the genetic model of the fluorite ore of Jebel Stah and by using trace metal elements (MTE), rare earth elements (REE) and Sr isotope geochemistry. The MTE geochemistry shows, that the epigenetic dolomites and the fluorite Fl1a bear higher concentrations in Mn and Zn, with respect to the fluorites Fl1b, Fl2 and Fl3, while the latter are depleted in all MTE, but enriched in Co. The similarity of their REE patterns indicates that the latter are coeval, and that Fl1a fluorite may be considered as the early ore generation. The same argument confirms that this geochemical imprint has been inherited from a hydrothermal fluid that had remained in equilibrium with shales at depth. Fluorite deposition appears related to an oxidized fluid derived from a sedimentary basin. Fluid circulation may have been triggered in response to hydraulic fracturing within a high geothermal gradient setting, especially along the major structural trends. Fl1b, Fl2 and Fl3 fluorites have been generated from the residual fraction of the ore fluid at later stages of mineralization and in a closed system. Both mineralization and the epigenetic dolomites are characterized by Sr isotope ratios that are higher than the barren Lower–Middle Liassic rocks, indicating that the Sr cannot be derived from the wallrocks. However, these ratios are higher than the Triassic seawater; yet consistent with those of the Paleozoic period. Thus, the fluorite ore of Jebel Stah, is believed to be remobilized from primary ore deposits which are suspected to be hosted in the late series within this period. [Copyright &y& Elsevier]

[Display omitted] • REE and metals were transported predominantly as chloride complexes. • H 2 S was sourced from TSR of the evaporite sulfate in ore-hosting strata. • Metals were derived from a mixed source of basement and country rocks. • Fluid mixing between two fluids lead to sulfides precipitation. • The Pb-Zn deposits at Huayuan belong to MVT formed in a foreland basin. The Xiangxi-Qiandong metallogenic belt (>300 Mt sulfide ores @∼4.0 wt% Pb + Zn), located at the southeastern margin of the Yangtze Block, is one of the important Pb-Zn producers in China. Although carbonate-hosted Pb-Zn deposits in this district have attracted great attention during past decades, many issues, particularly the ore genesis and geodynamic setting, remain unclear. In this study, we take the Limei and Yutang deposits as typical case studies, using detailed geology, rare earth elements and yttrium (REY) geochemistry of fluorite and sulfides in situ S-Pb isotopes, to propose a new model for early Cambrian reef limestone-hosted Pb-Zn deposits in the district. REY contents (0.47 to 8.67 ppm; mean = 3.99 ppm) in fluorite from Limei and Yutang slightly deplete in LREE and HREE relative to MREE, indicating that the REEs and metals were transported predominantly as chloride complexes in a low-temperature (<200 °C) hydrothermal fluid with high saline. New δ 34S values of sulfides (+27.66 to + 35.46‰ in Limei and + 24.80 to + 36.07‰ in Yutang) imply that S2- was originated from evaporite sulfate within ore-hosting strata via thermo-chemical reduction (TSR) as the presence of reducing agents (bioclastic limestone and organic matter). In situ δ 34S values show a slightly large range (variation up to 11.27‰) and vary significantly within single grain (up to 4.60‰), which may be inherited from the S composition of H 2 S in the original fluid. In situ Pb isotopic ratios of sulfides from Limei (206Pb/204Pb = 18.001–18.269, 207Pb/204Pb = 15.645–15.796 and 208Pb/204Pb = 38.243–38.597) and Yutang (206Pb/204Pb = 18.135–18.384, 207Pb/204Pb = 15.714–15.924 and 208Pb/204Pb = 38.347–38.874) positively correlates in Pb-Pb diagrams, indicating the mineralizing metals are mainly derived from Proterozoic basement rocks with an amount of contribution from early Cambrian sedimentary rocks. Mineralogy, fluorite REY geochemistry and sulfides in situ S-Pb isotopes together with previously reported mineralization ages suggest that the mixing of metal-rich fluid from basement rocks and the H 2 S-rich fluid originated from ore-hosting strata plays an important role in forming the Pb-Zn deposits of Limei and Yutang. This study provides a typical example for better understanding the genesis and geodynamic setting of MVT deposits in the foreland basin, South China. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chalukou porphyry Mo deposit is characterized by high fluorine. • The fluorites have CL-heterogeneity in A vein and CL- homogeneous in B and D veins. • Temperature decreasing and fluid mixing are the main mechanisms for variation of REE contents in fluorites. • Fluorine mainly affects mineral enrichment and has no obvious influence on the main mineralization period. The Chalukou deposit is a world-class porphyry Mo deposit in the Great Hingan Range, northeast China. Fluorites were analyzed by scanning electron microscope-cathodoluminescence (SEM-CL), microthermometry, and laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS) to characterize the composition and temperature of mineralizing fluids. There are four types of veins in Chalukou deposit that can be categorised as A vein (quartz – fluorite – magnetite – K-feldspar vein), B vein (quartz – fluorite – molybdenite vein), D vein (quartz – fluorite – sphalerite – galena – pyrite vein) and post-mineralization vein. The CL images of fluorites are characterized by heterogeneous texture in A vein, but homogeneous texture in B and D veins. Fluorites in A vein have total rare earth elements (REE) contents of 10 – 4963 ppm and temperatures of 370 – 410 °C, which show similar geochemical features with ore-bearing porphyry. In contrast, fluorites in B and D veins exhibit total REE contents of 4.6 – 41.3 ppm and temperatures between 257 and 300 °C, showing the decreasing trends of total REE contents and temperatures from early to late stage. Fluid inclusions of four types of veins are composed of one-phase, two-phase and daughter mineral-bearing multiphase with decreasing trend of temperatures from 450 °C to 120 °C and salinities from 53.0% to 0.7 wt% NaCl equiv. during the evolution. It is proposed that high-fluorine fugacity has a considerable influence on metal solubility and migration in the early stage of the Chalukou deposit. Temperature decreasing and fluid mixing may be the key factors of metal precipitation during the Mo mineralization stage, but the effect of fluorine is not obvious. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pyrite with hydrothermal origin and δ34S values from −1.15‰ to 3.88 ‰ suggest a homogeneous magmatic sulfur source. • The ore-forming fluid was mainly derived from post-magmatic hydrothermal fluid, mixing with meteoric water in stage IV. • The purple fluorites with enriched REEs and positive Eu anomaly can be used as a proxy for prospecting Ag-Pb-Zn deposits. • The high Sn contents of pyrite indicate potential Sn mineralization might exist in the deeper level of the Baiyine'lebu deposit. The recently discovered Baiyine'lebu Ag-Pb-Zn-F deposit in the southern Great Xing'an Range is hosted by NNE-trending transgressional fractures within Late Permian granodiorite. The fluorite ore veins in the periphery of the mining area show close spatial association with the Ag-Pb-Zn ore bodies. A total of four mineralization stages are recognized based on the cross-cutting relationships and mineral assemblages, among which three types of pyrite are identified, including: i) coarse-grained pyrite (Py1) from stage I quartz-pyrite vein, ii) fine-grained cubic pyrite (Py2) from stage II quartz sulfide-rich vein, showing association with metallic sulfide minerals, and iii) anhedral, irregular pyrite (Py3) disseminated in Ag-bearing sulfide ore vein from stage III. The stage IV is quartz-fluorite-calcite vein with very rare distribution of pyrite. Here we investigate the texture, trace element and sulfur isotopic composition of pyrite and rare earth elements (REEs) of fluorite to gain insights into the genesis and mineralization process of the Baiyine'lebu Ag-Pb-Zn-F deposit. Systematic trace element analyses indicate that the compatible and some other elements (Co, Ni, Cr and As) were incorporated in the pyrite structure via isomorphism in all pyrite types, whereas ore metals such as Cu, Pb, Zn, and Sn entered pyrite as structurally bound elements or micro/nanosized mineral inclusions. The Ag concentrations significantly increase from Py1 to Py3 in the form of invisible nanoparticles of sulfides or micro- to nano-sized mineral inclusions during the decrease of temperature. The narrow range of sulfur isotopic compositions from −0.80 to 3.88 ‰ (average in 1.17‰) indicates a relatively homogeneous sulfur source. In combination with REE patterns of fluorite, we propose that the ore-forming fluids originated mainly from post-magmatic hydrothermal fluid mixed with meteoric water in stage IV. The hydrothermal fluorite veins in the periphery of the Baiyine'lebu deposit could be genetically linked to the Ag-Pb-Zn veins. The purple fluorites with enriched REEs and positive Eu anomaly can be used as a proxy for prospecting Ag-Pb-Zn deposits. In addition, the high Sn content of pyrite in hydrothermal Ag-Pb-Zn deposit indicates the potential of Sn mineralization in the surrounding area or deeper level of the ore field in the South Great Xing'an Range. [ABSTRACT FROM AUTHOR]

[Display omitted] • Younusisayi Th deposit is an alkali-feldspar granite-type magmatic-hydrothermal deposit. • It formed in a post collisional extensional environment during the early Paleozoic. • Apatite U-Pb geochronology limits Th mineralization age at 442–439 Ma. • Four population fluorites effectively trace the process of Th mineralization. Thorium deposit related to alkaline/peralkaline magmatism is the dominant thorium source. Its ore-forming thorium mechanism has long been fascinating. The Younusisayi Th deposit, hosted in early Paleozoic alkali-feldspar granite in the South Altyn Complex, NW China, is an example to explore the Th mineralization processes in magmatic-hydrothermal systems. Zircon U-Pb dating shows that the ore-hosting alkali-feldspar granites are emplaced at 445.7–439.0 ± 1.3 Ma. The apatite that occurs concomitantly with thorite in the mineralized alkali-feldspar granites formed at are 442.0–438.0 ± 14 Ma, indicating Th mineralization temporally related to the magmatism. Four populations of fluorite exhibit distinct occurrences, the fluorite Ia and Ib are in intergrowth with thorite, but the fluorite IIa and IIb are not. Notably, four populations of fluorite are differentiated by their Th + U and HREE concentrations, fluorite Ia and Ib show higher Th + U contents and lower HREE contents than fluorite IIa and IIb. Th was extracted by magma during emplacement. As a strong incompatible element, thorium will not be enriched in rock-forming minerals. In the process of magmatic evolution, thorium is gradually enriched in the post-magmatic fluids which contains abundant volatile components. Thorium can be transported as F-Th complexes in F-rich fluids. As temperature decreased, thorium precipitated in the form of thorite, and fluorite Ia and Ib crystallized with a low HREE content. Fluorine from the decomposition of F-Th complexes, reacts with HREE in the fluids to form F-HREE complexes, which increases the HREE content in the fluid. Therefore, the fluorite IIa and IIb which formed in the late stage of mineralization have obviously higher contents of HREE. We propose that the Younusisayi deposit, with an average grade of 0.4 wt% ThO 2 , formed in a post-collisional extensional environment during the early Paleozoic. The Younusisayi deposit is best classified as a magmatic-hydrothermal deposit. Our results demonstrate the usefulness of geochemistry of fluorite for tracing the ore-forming process, thus establishing the ore formation model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorite Sm–Nd age of 148 Ma demonstrate the timing of Mo mineralisation. • Ti diffusion constrains time scales of multistage magmatic-hydrothermal processes. • Individual fluid pulses formed rapidly within tens of thousands of years. • Multiple short-lived mineralised pulses contribute to form porphyry Mo deposit. The duration (or time scales) of multistage combined magmatic and hydrothermal events provides key information constraining the metallogenic history of porphyry deposits, but the duration (time scale) of the mineralising hydrothermal process remains uncertain. Here, we report zircon U–Pb isotopic age, fluorite Sm–Nd isochron ages, and Ti-in-quartz diffusion chronometry for the giant Chalukou porphyry Mo deposit with reserves of 2.46 Mt @ 0.087 wt% Mo in NE China. The deposit is genetically related to hydrothermal fluids associated with a Late Jurassic (148–147 Ma) porphyritic magmatic event coincident with our new fluorite Sm–Nd isochron age of 148 Ma. Porphyry Mo mineralisation is characterised by the superposition of multiple generations of crosscutting quartz-bearing veins including: quartz veins with minor magnetite and hematite associated with K-silicate alteration (A-veins), quartz-molybdenite veins with K-feldspar alteration halos that host the bulk of the Mo mineralisation (B-veins), and late base-metal mineralisation with phyllic alteration (D-veins), as well as post-mineralisation veins with argillic alteration. Hydrothermal veins from the Chalukou porphyry Mo deposit contain multiple generations of quartz that are distinct in their Ti concentrations and scanning electron microscope-cathodoluminescence images. The A-veins preserve subhedral to euhedral characteristics with alternating CL bright and dark growth zoning. The A-veins probably formed at a near-lithostatic pressure of ∼ 1.35 kbar and contain CL-bright quartz assaying 31–71 ppm Ti with Ti-in-quartz temperatures averaging 603 ± 30 °C, and CL-dark quartz assaying 6–25 ppm Ti with Ti-in-quartz temperatures averaging 496 ± 36 °C. The mineralised B-veins also CL-dark quartz, although they display less growth zoning with lower Ti assays of 0.4–27.9 ppm. These veins have near 0.7 kbar pressure and Titanium-in-quartz temperature averaging 390 ± 79 °C. The D-veins are dominated by CL-dark quartz and systematically lower Ti concentrations of 0.4–8 ppm, being lower than the relatively latter vein generations, formed at a temperature of 348 ± 58 °C and pressure of 0.4 kbars. The Ti diffusion in quartz has become a successful method constraining time scales and duration of magmatic and hydrothermal processes. Ti diffusion modelling indicates that the A-veins were deposited and cooled in a period between 2500 and 50,000 years. This shows that the earliest magma-related hydrothermal fluids activities formed within tens of thousands of years. [ABSTRACT FROM AUTHOR]