REE Deposit Research Articles

Paleozoic remelting of carbonatite in Bayan Obo (China): Further insights into the formation of a giant REE deposit

Currently, it has been confirmed that the ore-hosting dolomite of the giant Bayan Obo deposit is the Mesoproterozoic igneous carbonatite, but the roles, that the Paleozoic tectonothermal events played, are still poorly understood. In this study, we present a comprehensive investigation on the geochemistry of various carbonates to understand the generation of the Bayan Obo carbonatite. Hydrothermal monazite Th-Pb dating (peaking at ∼ 420 Ma) identified an atypical coarse-grained dolomite, which occurring as veins, and cutting through typical fine dolomitic facies. Typical coarse dolomitic facies and atypical coarse-grained dolomite are significantly different in terms of MgO, FeO, MnO, Y, Al, Si, V, Ti, Ni, Sc, and ∑REE contents and the C-O-Sr isotopic compositions, and atypical coarse-grained dolomite has lower Ba and Sr contents, lower Co/Ni ratio, with strong Eu positive anomaly and more scattered element concentration, suggesting that it has a different origin from typical coarse dolomitic facies, crystallizing from a relatively low-temperature and oxidized environment. The pervasiveness of magma flow structure and magnetite mass in the contact zone between the granite plutons and the fine dolomitic facies indicates that, at ∼ 270 Ma, the heat flux from granitic magma triggered melting of the fine dolomitic facies, forming remelted calcitic carbonatite. In addition, Th-Pb ages of monazite ranging from 1350 Ma to 240 Ma and the REE-poor properties of both remelted carbonatites suggest that both Paleozoic thermal events only caused REE activation and redistribution, without introducing additionally exogenous ore-forming metals. Accordingly, we propose that the dolomite mass in Bayan Obo are Mesoproterozoic mantle-derived carbonatites (including ore-hosting dolomite and carbonatite dike), which underwent remelting at ∼ 440 Ma and ∼ 270 Ma, respectively.

Origin and metal-enrichment mechanism of sedimentary rare earth element deposits in Yunnan and Guizhou provinces, western Yangtze Block, China

In southwest China, claystone layers occur in the lower part of the late Permian Xuanwei Formation, immediately overlying the Permian Emeishan flood basalts. The lowermost claystone layers are characterised by high contents of rare earth elements (REEs; 1100–16,000 ppm, average 2700 ppm), indicating a new type of REE deposit. However, the origin of this deposit and the enrichment mechanisms are unclear. We collected samples from 10 sections of the Xuanwei Formation, including REE-rich claystones, siltstones, iron claystones, and tuff. Detrital zircons gave U–Pb ages of 275–245 Ma, εHf(t) values of –16.7 to 8.9, and TDM2 model ages of 0.70–2.32 Ga. The field, petrological, geochemical, and isotopic data suggest: (i) the REE-rich claystones were deposited over 2.6 Myr in the period 257.22–254.62 Ma at a very low average rate of deposition (0.076–0.61 cm/ka), and (ii) the REE-rich claystones were derived from a region of denudation in the inner zone of the Emeishan Large Igneous Province, with the ore metals sourced mainly from syenite but with minor contributions from high-Ti basalts and felsic igneous rocks. The siltstones near the base of the Xuanwei Formation were derived mainly from felsic volcanic rocks with minor contributions from basalt. The iron-bearing claystones resulted from weathering of the Emeishan flood basalts. Our study shows a surface REE migration pattern of “weathering of REE-rich matrix → fluid migration → physical or chemical precipitation”, which is consistent with the origin of the REE-rich claystones.

Mineralogical and Geochemical Evidence of Paragenetic Unity of Igneous Silicate and Carbonatite Rocks of the Tomtor Massif in the North-East of the Siberian Platform

The Tomtor massif is a polychronous ring zonal complex of alkaline ultramafic and carbonatite rocks containing unique Nb and REE deposits. Mineralogical and geochemical studies of minerals from different types of silicate rocks and carbonatites of the Tomtor massif were performed. For excluding traces of the interaction between silicate and carbonatite melts, we limited ourselves to the study of independent small secant bodies located in the immediate vicinity of the massif itself. The presence of through mineral series in various silicate igneous rocks and carbonatite ores of high-titanium chromium spinels, rare-metal, ore and other exotic phases with similar compositional trends was defined. Such studies will help reveal the mineralogical criteria for the genetic relationship between silicate melts and associated carbonatite derivatives, which can form rich rare elements mineralization. Also, such studies help to improve the petrochemical and mineralogical criteria for dividing potentially diamond-bearing magmatites (typical kimberlites) from non-diamond-bearing kimberlites, alpicrites and other non-diamond-bearing rocks convergent to kimberlites, which are formed under different physicochemical conditions. The existence of polychronous complex ore–magmatic ring complexes, such as the Tomtor massif, indicates the existence of large deep intraplate magma-generating chambers in the lithospheric mantle.

Deep-sea mineral deposits as a future source of critical metals, and environmental issues - a brief review

For the whole world to deliver net zero by 2050, large-scale mining is more critical for metals such as lithium, cobalt, platinum, palladium, REE, gallium, tungsten, tellurium, and indium as these metals are essential for green technology applications such as making wind turbines, solar panels, fuel-cells, electric vehicles, and data storage systems required to transition to a low-carbon economy. Since land-based mineral deposits are depleting fast, seabed resources are seen as a new resource frontier for mineral exploration and extraction. They include mainly deep-ocean mineral deposits, such as massive sulfides, manganese nodules, ferromanganese crusts, phosphorites, and REE-rich marine muds. Manganese nodules contain mainly manganese and iron, but also valuable metals like nickel, cobalt, and copper, as well as REE and platinum, which are used in making several high-technology and green technology products. For example, deep-sea mud enriched in REE (> 2000 µg/g) was found in the western North Pacific Ocean. High concentrations of REE range from 1,727 to 2,511 μg/g in the crust samples collected from the Afanasy Nikitin Seamount (ANS) in the Indian Ocean. However, these deposits usually have lower REE grades than land-based REE deposits such as carbonatite-hosted deposits but form greater potential volumes. Though the mining companies and their sponsoring countries are in the process of developing the required technologies to mine the three deep-sea environments: abyssal plains, seamounts, and hydrothermal vents, due to severe concerns about the possible environmental damages, the International Seabed Authority (ISA) has not granted any mining permissions so far, although deep-sea mining becomes inevitable in the future green energy revolution.

REE remobilization of allanite: Implications for the formation of ion-adsorption REE deposits, South China

古城矿床为华南地区新发现的一个同时富含轻重稀土的离子吸附型稀土矿床，矿体位于粗粒黑云母花岗岩风化壳中。褐帘石是粗粒黑云母花岗岩中一种重要的副矿物（占比约为0.09 vol %），U-Pb年龄分析结果显示其结晶年龄为102.8 ± 4.3 Ma。化学成分分析结果显示原生褐帘石具有富轻稀土的特征，其轻稀土、重稀土和轻稀土/重稀土比值分别为179,778 ~ 189,429 ppm、2,165 ~ 4,595 ppm和41 ~ 84。这些原生褐帘石轻稀土含量约占全岩轻稀土总量的97 %，为古城矿区轻稀土元素的主要来源。褐帘石结构与成分分析指示稀土元素的存在会导致其晶体结构中LREE与O原子构成的化学键键长增加而键强减弱。在被岩浆-热液流体交代时，这些化学键发生破裂，进而导致轻稀土元素会被淋滤出来并进入到热液流体中，并在随后主要进入了氟碳钙铈矿中。综上，褐帘石被交代后形成氟碳钙铈矿的过程中轻稀土元素发生了活化、迁移和富集，且在该过程中轻稀土元素之间发生了分馏。本研究表明，原生褐帘石被热液流体交代有利于轻稀土元素的富集成矿，但对重稀土矿化的贡献较小。

Petrogenesis of the Newly Discovered Early Cretaceous Peralkaline Granitic Dikes in Baerzhe Area of Jarud Banner, Inner Mongolia: Implications for Deciphering Magma Evolution

The super-large Baerzhe Be–Nb–Zr–REE deposit in NE China is hosted in the Early Cretaceous peralkaline granites. In this work, the newly discovered granitic dikes developed around the Baerzhe deposit were studied for the first time, focusing on their genesis and genetic relationships with the Baerzhe peralkaline granites. Zircon U-Pb dating of these granitic rocks (including the granite porphyry, rhyolite and miarolitic granite) yielded Early Cretaceous ages of 125–121 Ma. Their mineral assemblages and geochemical features suggest that they share similar features with the peralkaline A-type granites. Their geochemical data and zircon Hf isotopic compositions (εHf(t) = +3.4 to +10.5) indicate that the peralkaline granitic rocks were formed by the partial melting of dehydrated charnockite with extensive plagioclase crystal fractionation, which resulted in a peralkaline affinity. There are two types of distinct zircons in the studied samples: the type I zircon with a bright rim and dark core, which may represent a cumulate mineral phase captured together with aggregates during eruption, and the type II zircon with a higher evolution degree crystallized in the residual melts. Combined with the simulation results using whole-rock trace elements, we proposed that the peralkaline granitic dikes represent more evolved interstitial melts than the Baerzhe granitic magma. In the Early Cretaceous extensional tectonic settings, mantle-derived magma upwelled, which induced the melting of the lower crust and prolonged the evolutionary process of the magma crystal mush.

Petrogenesis of Alkaline Complex of the Longbaoshan Rare Earth Element Deposit in the Luxi Block, North China Craton, China

The alkaline complex in the southwest region of Luxi Terrane of the North China Craton is spatially correlated with the newly discovered Longbaoshan REE deposit. Its petrogenesis, however, remains ambiguous. In this study, we present an integrated petrology, whole-rock geochemistry, sphene U-Pb and rare earth element data from the Longbaoshan alkaline complex to investigate the petrogenesis, magma source and tectonic evolution. The Longbaoshan alkaline complex consists of mafic to intermediate rocks of hornblende diorite and alkaline hornblende syenite porphyry, biotite monzonite porphyry and aegirine diorite porphyrite. The hornblende diorites show a composition of low SiO2, high MgO, Fe2O3 and moderate Na2O, CaO and are metaluminous and medium-to-high-K calc-alkaline. The hornblende syenite porphyries, biotite monzonites and argirine diorite porphyrites display a relatively higher content of SiO2, Na2O, K2O and Al2O3 and lower contents of MgO, Fe2O3 and CaO and are metaluminous, peralkaline, high-K calcic-alkaline and shoshonite. The sphene U-Pb data shows that the parent magma of the hornblende diorite was emplaced at ca. 120 Ma. All these samples show a common depletion in Th, Nb-Ta and Zr-Hf and enrichment in large ion lithophile elements (e.g., Pb, Ba, Sr) and Light Rare Earth Elements. The magma may have experienced fractionation of pyroxene, amphibole, sphene, apatite and zircon during its evolution. The variable La content, La/Sm, Rb/Sr and (Ta/Th) N ratios indicate that the parent magma may produce by partial melting of a mantle source that was interacted with sediment-derived melts in a subduction setting. Therefore, we propose that the parent magma of the Longbaoshan alkaline complex was derived from a lithospheric mantle which was metasomatized by sediment-derived melt in a prior subduction process. The enriched magma was emplaced through an extension process and experienced subsequent fractionation and assimilation with the continental crust during the rollback of the Paleo Pacific Ocean plate.

Zircon texture and composition fingerprint HREE enrichment in muscovite granite bedrock of the Dabu ion-adsorption REE deposit, South China

More than 90% of the global heavy rare earth elements (HREE) supply is currently from the ion-adsorption REE deposits in South China. However, the mechanism of HREE enrichment in granite bedrock of REE mineralized weathering crusts remains poorly understood. In this study, we present a comprehensive investigation on zircon texture and composition as a proxy to unravel the magmatic-hydrothermal processes which resulted in HREE enrichment of the Dabu muscovite granites. Our results show that zircon in the Dabu muscovite granites can be classified into three types based on morphology, internal structure and chemical compositions. The early-magmatic zircon grains (ZrnI) are prismatic crystals with bright oscillatory zoning, and crystallized early in the granitic magma. The late-magmatic zircon grains (Zrn-II) occur as murky euhedral or subhedral crystals or as overgrowth on ZrnI, and crystallized from a volatile-enriched residual melt in the late magmatic stage. The hydrothermal zircon (Zrn-III) is anhedral without oscillatory zoning, possibly formed via intense hydrothermal alteration of Zrn-II in the hydrothermal stage. Raman spectra show a decrease in degree of crystallinity from Zrn-I to Zrn-III. In-situ compositional and isotopic analyses suggest that zircon geochemistry is a good proxy for the magmatic-hydrothermal processes of the host granite. Zircon UPb dating yields similar ages of 155.3 ± 1.4 Ma (2σ) and 154.1 ± 1.0 Ma (2σ) for Zrn-I and Zrn-II, respectively. The decrease of Zr/Hf from Zrn-I to Zrn-III indicates that the Dabu muscovite granites underwent magmatic to hydrothermal evolution. Furthermore, the decreasing δ18O values of Zrn-I to Zrn-III suggest the increasing involvement of meteoric water in the fluids. Significantly, compared with Zrn-I and Zrn-II, Zrn-III has the highest U, Hf and REE, in particular HREE. The LREE/HREE ratios decrease with the increase of REE contents and the decrease of Zr/Hf ratios from early to late zircon of the granite bedrock of ion-adsorption HREE deposits, which is significantly different from those of carbonatite-alkaline related REE deposits. The significant increase of HREE concentrations in early to late zircon should be ascribed to the introduction of HREE-rich fluids during magma evolution. Therefore, we propose that the HREE-rich fluids from magma exsolution metasomatized the granites to achieve further enrichment of HREE, which is an important prerequisite for the formation of ion-adsorption HREE deposits. Accordingly, we argue that zircon composition can be used as a chemical indicator for the REE behaviors in magmatic-hydrothermal systems that are vital to the formation of REE deposits.

Petrology of Granites of the Tommot Rare-Earth Ore Field (Verkhoyansk–Kolyma Orogenic Belt)

The article presents the results of studying the aegirine–arfvedsonite granites of the Somnitelnyi massif within the Tommot ore field located in the Verkhoyansk–Kolyma orogenic belt (NE Asia). Along with the crustal signatures, the rocks display features of mantle contamination at their origin. Their affinity for A-type granites characteristic of continental rifts and hot spots is shown. The associated Tommot REE deposit is the only one discovered in NE Russia. New data are presented for the previously studied Tommot massif within the same ore field, with a wide compositional range from alkaline-ultrabasic rocks to alkaline syenites. It is established that despite a common geochemical enrichment of both massifs’ rocks with REEs, the Somnitelnyi massif granites cannot be interpreted as the final phase of the Tommot massif emplacement. Specific REE mineralization and high crystallization temperatures (up to 1045 °C) of the Somnitelnyi granites may be explained by the existence within the study area of an undepleted mantle source (“hot spot”), whose maximum activity occurred during the granitic melt generation. The ore bodies of the Tommot deposit consist of fenitized albitites, granite gneisses, and, more rarely, the cross-cutting pegmatite veins. They are confined mostly to exocontacts of the Somnitelnyi massif, are less often in its endocontacts, and are not found in the host rocks and in the inner part of the massif away from the contacts. Principal ore minerals are chevkinite, yttrialite, gadolinite, and fergusonite. Based on the data obtained, the deposit is classified as a metasomatic complex Ce–Y–Nb–Zr deposit associated with the alkaline granites.

SHRIMP U-Pb zircon geochronology of the carbonatite-hosted REE deposit of Kamthai, Late Cretaceous polychronous Sarnu Dandali alkaline complex, NW India: Links to plume-related metallogeny and CO2 outgassing at the K-Pg boundary

The carbonatite plug at Kamthai in the Late Cretaceous polychronous (66–89 Ma) Sarnu- Dandali alkaline complex (SDAC), NW India, is India’s only known carbonatite-hosted rare- earth-element deposit. The SDAC intrudes the Neoproterozoic (∼750 Ma) Malani silicic igneous suite in the Aravalli raton. The Kamthai carbonatite is a calcio-carbonatite dominated by calcite along with barite, strontianite, quartz, zircon and REE-bearing minerals. Textural features suggest an open-system exchange of the magma chamber at varying depths of crystallization. REE patterns are smooth and characterized by strong LREE enrichment, as typical of carbonatites. SHRIMP dating of 12 spots on three magmatic zircons from the carbonatite yielded a concordia age of 66.1 ± 1.4 Ma and an indistinguishable average 206Pb/238U mean age of 68.4 ± 1.8 Ma. The obtained U-Pb ages unambiguously link the carbonatite emplacement to the Deccan Large Igneous Province, i.e. the Réunion hotspot near the K-Pg (Cretaceous-Paleogene) boundary in the polychronous set-up of the SDAC. These ages are also indistinguishable from the 68.53 ± 0.16 Ma magmatic pulse recorded from the nearby Mundwara polychronous alkaline complex and the 69.7 ± 0.2 Ma alkaline sills from the Tethyan suture zone in Pakistan, which are regarded to be earliest manifestations of the Réunion hotspot in the Indian sub-continent. Our results in the context of REE mineralization in the Kamthai deposit have also implications with respect to CO2 outgassing, induced by at least four near-synchronous carbonatitic eruptions in NW India, and to triggering the mass extinction near the K-Pg boundary.

Spatial distribution of 1.4-1.3 Ga LIPs and carbonatite-related REE deposits: Evidence for large-scale continental rifting in the Columbia (Nuna) supercontinent

Large-scale continental rifting and large igneous provinces (LIPs) have played important roles in the breakup and dispersal of supercontinents Pangea and Rodinia. Previous paleomagnetic and geological evidence suggests fragmentation of Columbia (or Nuna) supercontinent during 1.4-1.2 Ga. However, no large-scale continental rift system has been identified in Columbia during this period, although some continental rifting events between 1.6 Ga and 1.2 Ga have been reported. Here we provide a refined ca. 1.4 Ga paleogeographic reconstruction of Columbia based on previously published paleomagnetic data and geological evidence for connections between continental blocks, and consistent with spatial and temporal distributions of the 1.4-1.3 Ga LIPs and smaller intraplate mafic magmatic events interpreted as LIP fragments/remnants. Our results indicate a 1.4–1.3 Ga large-scale continental rift zone located along western Laurentia, western-northern Siberia, southeastern Baltica, western-northern West Africa, southwestern Amazonia, southern-eastern Congo/São Francisco, eastern Kalahari, northern North China and northern North Australia. This rift zone extends about 15,000 km across supercontinent Columbia, and is a main indicator and a proximal reason for its final breakup. The spatial distribution of the 1.4-1.3 Ga carbonatite-related REE deposits shows that this newly identified rift system also controlled Bayan Obo, the world's first and largest REE-Nb deposit in northern North China, and Mountain Pass, the world's second largest REE deposit in western North America. Given the scale of this rift system it can be expected to be the locus of additional carbonatite intrusions as well as other commodity types, and provides important constraints on mechanism and processes for final breakup and dispersal of Columbia supercontinent.

Formation of the Rock Canyon Creek carbonate-hosted REE–F–Ba deposit, British Columbia, Canada: Constraints from Mg-Sr isotopes of dolomite, calcite, and fluorite

The Rock Canyon Creek REE–F–Ba deposit is a carbonate-hosted REE deposit located in the Alkaline Province of British Columbia, Canada, which hosts most REE mineralization. It shares tectonic, stratigraphic and structural similarities with nearby Mississippi Valley-type deposits. To constrain the dolomitization and mineralization processes, the δ26Mg, 87Sr/86Sr, and elemental compositions of dolomite, calcite, and fluorite were determined. The δ26Mg values of dolomite from the unmineralized zone (−1.83 ‰ and −1.67 ‰) are consistent with marine evaporative dolomite, but those from the mineralized zone (−0.97 ‰ to −0.17 ‰) are higher and more variable. The linear 87Sr/86Sr–Sr/Mg relationships, both in the dolomite and calcite from the unmineralized zone, suggest dolomitization in an evaporative marine environment. The high δ26Mg values with large variation and the non-stoichiometric Ca/Mg ratios in the dolomite from the mineralized zone suggest that this dolomite interacted with a relatively low-temperature hydrothermal fluid (<200 °C). Considering the Na, Ca, Sr, Ba, and LREE-enrichment and low 87Sr/86Sr signature in the dolomite from the mineralized zone as well as mineral paragenesis in the deposit, the most plausible scenario for the formation of the deposit is that marine-evaporitic dolomite re-equilibrated with basinal fluids along permeable zones, and at a later stage, carbohydrothermal REE-bearing fluids infiltrated into the Rock Canyon Creek brecciated zone and deposited the REE mineralization. Late-stage, post-mineralization calcite veins and iron oxides formed in the upper part of the deposit under supergene conditions, as suggested by combination of textural observations, REE patterns, and differences in isotopic compositions between dolomite and calcite from the mineralized zone. This study demonstrates that δ26Mg, 87Sr/86Sr, and element/Mg ratios in carbonate minerals are useful for characterizing mineralizing fluids in carbonate-hosted deposits, and discriminating mineralization-related dolomite from marine evaporative dolomite and unmineralized hydrothermal dolomite.

Geochronological and Geochemical Constraints on the Petrogenesis of Lamprophyre from the Giant Weishan REE Deposit in China

The Weishan REE deposit is located in the southwest of the Luxi Terrane of the North China Craton (NCC), where a large number of lamprophyre dikes are spatially exposed with the deposit. Here, we report petrology, geochemistry and zircon U-Pb geochronology data for the lamprophyre of the Weishan REE deposit in order to develop constraints for the determination of the petrogenesis, magma source and evolution of the lamprophyre and the tectonic environment. LA-LCP-MS zircon U-Pb dating shows that the crystallization age of the lamprophyre is 125 ± 0.86 Ma. The geochemical data suggest that these lamprophyres have high levels of Al2O3, K2O, MgO and alkalis, moderate level of Na2O and low levels of SiO2, Fe2O3 and TiO2, and that they are enriched with LREEs (La, Ce) and LILEs (Rb, Ba) and depleted with regard to HREEs and HFSEs (Nb, Ta, Ti). They displayed negative εHf(t) values of −14.98 to −9.03, TDM1 ages of 1.1–1.4 Ga and TDM2 ages of 1.7–2.1 Ga, which suggest that the magma source originates from an enriched mantle. Low Rb/Sr and high Dy/Yb ratios suggest that the enriched mantle source was partially melted at the amphibole-bearing lherzolite garnet-facies. The high Ba/Th and Sr/Th ratios indicate that the enriched source was derived from subduction dehydration fluids of the oceanic crust. We propose that the mafic dike intrusions are consistent with an Early Cretaceous alkaline magma emplacement in an extensional setting, in which the magma was not contaminated by crustal material during its emplacement.

Partial Melting of Lithospheric Mantle and Formation of the Early Cretaceous Alkaline Rocks in the Guandimiao REE Deposit, Luxi Terrane, Eastern China

The Luxi Terrane (eastern China) exposes widespread Early Cretaceous alkaline rocks, whereas their petrogenesis remains controversial, including fractional crystallization, partial melting and crustal contamination regime. Here, we present petrology, geochemistry, sphene U-Pb geochronology and trace element data from the syenogranite, quartz syenite and quartz monzonite of the Guandimiao alkaline complex rocks to investigate their petrogenesis. Geochemical data suggest that these alkaline rocks show alkalic and peralkaline characters, and high Ga/Al ratios, SiO2, light rare-earth element (LREE), Zr and Nb, and low MgO, CaO, Eu contents, corresponding to A-type granites. Sphene trace elements in syenogranite and quartz monzonite show obvious fractionation between LREE and heavy rare-earth element (HREE) and high Th/U ratios, indicating a magmatic origin. They yield U-Pb lower intercept ages of 128 ± 2.3 Ma and 127 ± 1.3 Ma, representing the crystallization ages of these alkaline rocks. The negative correlations between CaO, Fe2O3 (Total), MgO, P2O5, TiO2, MnO and the pronounced depletion in Nb, Ta and Ti suggest that the alkaline rocks were formed by fractional crystallization. Additionally, the positive correlation between La/Hf and La, Th and Th/V, Ce/Yb and K2O, and Tb/Yb and Yb suggest that the alkaline melts are generated by partial melting. Such high Rb/Nb, (Th/Nb)N and Nb/Th ratios indicate crustal contamination during the magma emplacement. We, therefore, propose the magma source of the alkaline rocks in the Guandimiao complex originated by partial melting of lithospheric mantle, which experienced fractional crystallization and crustal contamination processes during its emplacement. Such complex alkaline rocks were probably formed in an extensional back-arc setting induced by the retreat of the subducting Izanagi plate.

Water/rock interactions, chemical weathering and erosion, and supergene enrichment in the Tapira and Catalão I alkaline‑carbonatite complexes, Brazil

Alkaline‑carbonatite complexes from the Alto Parnaíba Igneous Province (APIP) host important supergene concentrations of Nb, REE, P, and Ti. To quantify water/rock interaction and the interplay of chemical weathering and erosion that results in supergene enrichment, the chemistry of solutions draining the Tapira and Catalão I complexes were studied and the transfer of elements within and out of the weathering profiles quantified. Ca2+ and HCO3− are the main ions in surface water samples draining both watersheds, with an average annual flux of 49 t/km2/a of dissolved load. Total dissolved loads are highest during the summer (wet) months. The annual fluxes of Cl−, PO43− and NO3− yield negative values, suggesting significant input of these species from rainwater. The fluvial transport of dissolved elements due to silicate weathering, carbonate dissolution and rainfall input is ~26, 3 and 19 t/km2/a at Tapira and 29, 3 and 18 t/km2/a at Catalão I. Chemical weathering rates of alkaline rocks are ~4 m/Ma at Tapira and ~5 m/Ma at Catalão I. Constitutive mass balance suggests an eroded rock column of 84 m at Tapira and 39 m at Catalão I, with long-term erosion rates of 1.3 and 0.9 m/Ma, respectively. In contrast, long-term weathering rates were 3.0 m/Ma at Tapira and 2.4 m/Ma at Catalão I. Internal collapse of saprolites due to mass loss creates internal basins with an overburden of soils, locally transported material and lake sediments. Carbonate congruent dissolution, silicate incongruent dissolution and hydrolysis, and phosphate and oxide (pyrochlore) dissolution-reprecipitation are the main water/rock interactions in the Tapira and Catalão I alkaline‑carbonatite complexes that promote the enrichment of primary and secondary minerals and produce supergene P, Ti, Nb and REE deposits in the isalteritic saprolites; Ti is residually enriched in the alloteritic saprolite at Tapira.

Genesis of orogenic gold systems in the Daduhe belt: Evidence of long-lived fertile mantle lithosphere as a source of diverse metallogeny on the western margin of the Yangtze Craton, China

The poorly documented Daduhe gold belt on the western margin of the Yangtze Craton, an important metallogenic belt in southwest China, is characterized by typical orogenic gold systems against a highly anomalous geodynamic setting. A synthesis of regional and deposit geology, mineralization ages, and S-O isotopic compositions of 33 gold deposits from the Danba-Kangding-Shimian-Mianning area of the belt reveals regional metallogenic patterns, establishes a consistent genetic model, and demonstrates a source equivalent to other diverse mineral systems on the western margin of the Yangtze Craton. The Daduhe orogenic gold deposits are controlled by the lithosphere-scale Xianshuihe and Anninghe strike-slip faults in the northern and southern segments of the belt, respectively. The alteration and ore mineral assemblages of the Daduhe orogenic gold deposits define a wide range of hypozonal, mesozonal, and epizonal sub-types. They formed during two episodes: 1) Early Jurassic gold mineralization related to closure of the Paleo-Tethys Ocean, with a large hypozonal gold deposit on the margin of the Danba dome in the northern segment; 2) Cenozoic gold mineralization associated with continental collision on the Tibetan Plateau, with small mesozonal and epizonal gold deposits in shear zones in migmatite basement and at contacts with cover sequences in both the northern and southern segments. At the belt and deposit scales, the ore-controlling structures for both mineralization episodes are NNE-trending second-order extensional faults or their intersections with the dominant NW-trending compressional faults. The three deposit sub-types have overlapping δ34S of 0 ∼ 10‰, δ18Ofluid of 6 ∼ 11‰, and low He-Ar isotope ratios, all consistent with derivation of ore fluids from metasomatized mantle lithosphere. Importantly, the Daduhe orogenic gold deposits have similar S-O-He-Ar isotope compositions to the giant IOCG, Cu-Ni-PGE, Fe-V-Ti, anomalous porphyry Cu-Mo-Au, and carbonatite-related REE deposits in the Panxi region on the shared margin of the western Yangtze Craton. This suggests that these diverse mineral systems have a common source of ore fluids and metals derived from fertile mantle lithosphere during different geodynamic and metallogenic events. Such a widespread hydrous metal-rich deep source with lithosphere-scale faults as ore fluid pathways, and a depth continuum of orogenic gold deposits in the Daduhe belt suggest a high prospectivity and a higher future gold endowment for the belt. This study adds to an increasing awareness of the diversity of mineral systems on specific craton margins globally.

Rare earth mining and consumption global trends and mining perspectives for the Mushugay Khudug deposit in southern Mongolia

In this work the 3 ore body drill core samples. 6 host rock samples from the main ore body of the Mushugay Khudug REE deposit in southern Mongolia were selected as most representative samples and studied by XRD and ICP-MS. LA-ICP-MS method to evaluate elemental and structural composition data of the deposit. According to our determinations the main orebody of the Mushugay Khuduk deposit contain up to 130 kg/ton of REEs. Despite the moderate total mineable reserve the main ore body of the Mushugay Khuduk deposit might compete economically with world's biggest REE mining deposits such as Bayan-Obo (Inner Mongolia. China) or Mountain Pass (California. USA) if consider the deposit's higher REE grade and easier to mine local geological condition. The important advantage of the Mushugay Khuduk deposit is that the relative contents of most valuable HREEs Eu. Tb. Dy. and Lu are significantly higher than that of Mountain Pass or Rayan-Obo. The relative net content of these four elements is 0.1% for Mountain Pass and 0.4% for Bayan-Obo. while the ore samples of the Mushugay Khuduk deposit has 0.75% according to our determinations.

Ultramafic-alkaline-carbonatite Tajno intrusion in NE Poland: A new hypothesis about the massif formation and related mineralization

This manuscript presents results of the newest petrographic, mineralogical and bulk chemical, as well as H, C and O stable isotope study of carbonatites and associated silicate rocks from the Tajno Massif (NE Poland). The Tajno Intrusion is a Tournaisian-Visean ultramafic-alkaline-carbonatite body emplaced within the Paleoproterozoic rocks of the East European Craton (EEC). Carbonatites of the Tajno Massif can be subdivided into the calciocarbonatite (calcite), ferrocarbonatite (ankerite), and breccias with an ankerite-fluorite matrix. Due to location at the cratonic margin and abundance in the REE, Tajno classifies (Hou et al., 2015) as the carbonatite-associated REE deposit (CARD), and more precisely as the Dalucao-Style orebody (the breccia-hosted orebody). High Fe2O3 (13.8 wt%), MnO (2.1 wt%), total REE (6582 ppm), Sr (43895 ppm), Ba (6426 ppm), F (greater than10000 ppm) and CO2 contents points for the involvement of the slab – including pelagic metalliferous sediments – in the carbonatites formation. Spatial relations and Sr isotope composition ((87Sr/86Sr)i = 0.7043–0.7048; Wiszniewska et al., 2020) of alkali clinopyroxenite and syenite suggest that these are products of differentiation of the magma, generated by the initial melting of the SCLM due to influx of F-rich fluids from subducted marine sediments. Carbonatites Sr isotope composition ((87Sr/86Sr)i = 0.7037–0.7038), and Ba/Th (16–20620) and Nb/Y (0.01–6.25) ratios, link their origin with a more advanced melting of the SCLM, triggered by CO2-rich fluids from the subducted AOC and melts from sediments. The Tajno Massif – and coeval mafic-alkaline intrusions – age, high potassic composition, and location along the craton margin nearly parallel the Variscan deformation front, are suggesting Variscan subduction beneath the EEC. The oxygen isotope compositions of clinopyroxene (δ18O value = 5.2‰) and alkali feldspar (δ18O value = 5.7‰), from alkali clinopyroxenite and foid syenite, respectively, are consistent with mantle-derived magmas. Isotopic compositions of carbonatites and breccias (carbonate δ18O = 8.7‰ to 10.7‰; δ13C = -4.8‰ to −0.4‰) span from values of primary carbonatites to carbonatites affected by a fractionation or sedimentary contamination. The highest values (δ18O = 10.7‰; δ13C = -0.4‰) were reported for breccia cut by numerous veins confirming post-magmatic hydrothermal alteration. The lowest carbonate δ18O (9.3‰ to 10.7‰) and δ13C (−5.0‰ to −3.8‰) values are reported for veins in alkali clinopyroxenites, whereas the highest δ18O (11.2‰) and δ13C (−1.2‰ to −1.1‰) values are for veins in syenites and trachytes. Isotopic composition of veins suggests hydrothermal origin, and interaction with host mantle-derived rocks, as well as country rocks. In silicate rocks of the Tajno Massif, fluid influx leads to the development of Pb, Zn, Cu, Ag, Au sulfide mineralization-bearing stockwork vein system, with carbonate, silicate and fluorite infilling the veins. Bulk-rock contents of molybdenum (925 ppm), rhenium (905 ppb) and palladium (29 ppb) are notable. The Re-rich molybdenite association with galena, pyrite and Th-rich bastnäsite in carbonate veins is similar as in Mo deposits associated with carbonatites, implying the mantle source of Mo and Re.

Multiple-Stage Mineralization in the Huayangchuan U\u2212REE\u2212Mo\u2212Cu\u2212Fe Ore Belt of the Qinling Orogen, Central China: Geological and Re\u2212Os Geochronological Constraints

The Huayangchuan ore belt is located in the western segment of Xiaoqinling Orogen in the southern margin of the North China Craton (NCC), and hosts voluminous magmatism and significant U−REE−Mo−Cu−Fe polymetallic mineralization. However, geochronological framework of the various mineralization phases in this region is poorly understood. Here, we present new Re−Os isochron ages on magnetite from the Caotan Fe deposit (2 675 ± 410 Ma, MSWD = 0.55), and on pyrite from the Jialu REE deposit (2 127 ± 280 Ma, MSWD = 1.9) and Yuejiawa Cu deposit (418 ± 23 Ma, MSWD = 11.5), and Re−Os weighted average model age on pyrite from the Taoyuan Mo−U deposit (235 ± 14 Ma, MSWD = 0.17). These ages, combined with regional geology and mineralization ages from other deposits, suggest that mineralization in the Huayangchuan ore belt lasted from the Neoarchean to the Late Mesozoic. The mineralization corresponds to regional tectono-magmatic events, including the Neoar-chean alkali magmatism (REE mineralization), Paleoproterozoic plagioclase-amphibolite emplacement (Fe mineralization), Paleoproterozoic pegmatite magmatism (U mineralization), Paleozoic Shangdan oceanic slab subduction-related arc magmatism (Cu mineralization), Early Mesozoic Paleo-Tethys Ocean subduction-related arc magmatism (Mo−U mineralization), and Late Mesozoic Paleo-Pacific oceanic plate subduction direction change-related Mo(-Pb) mineralization. We proposed that the Huayang-chuan ore belt has undergone prolonged metallogenic evolution, and the magmatism and associated mineralization were controlled by regional geodynamic events.

Overview of surficial geochemistry and indicator mineral surveys and case studies from the Geological Survey of Canada's GEM Program

The Geological Survey of Canada carried out reconnaissance-scale to deposit-scale geochemical and indicator-mineral surveys and case studies across northern Canada between 2008 and 2020 as part of its Geo-mapping for Energy and Minerals (GEM) program. In these studies, surficial geochemistry was used to determine the concentrations of up to 65 elements in various sample media including lake sediment, lake water, stream sediment, stream water, or till samples across approximately 1 000 000 km 2 of northern Canada. As part of these surficial geochemistry surveys, indicator mineral methods were also used in regional-scale and deposit-scale stream sediment and till surveys. Through this program, areas with anomalous concentrations of elements and/or indicator minerals that are indicative of bedrock mineralization were identified, new mineral exploration models and protocols were developed, a new generation of geoscientists was trained, and geoscience knowledge was transferred to northern communities. Regional- and deposit-scale studies demonstrated how transport data (till geochemistry, indicator mineral abundance) and ice-flow indicator data can be used together to identify and understand complex ice flow and glacial transport. Detailed studies at the Izok Lake Zn–Cu–Pb–Ag VMS, Nunavut, the Pine Point carbonate-hosted Pb–Zn in the Northwest Territories, the Strange Lake REE deposit in Quebec and Labrador as well as U–Cu–Fe–F and Cu–Ag–Au–Au IOCG deposits in the Great Bear magmatic zone, Northwest Territories demonstrate new suites of indicator minerals that can now be used in future reconnaissance- and regional-scale stream sediment and till surveys across Canada.