Fluorite mineralization associated with different types of magmatism is common in the Western Transbaikalia. This study deals with Arshan, Yuzhnoe, and Ulan-Ude fluorite occurrences, which are the most significant examples of carbonatite-related fluorite mineralization in the region. The present paper focused on new fluorite geochemistry and fluid inclusion data, is aimed at revealing conditions of the fluorite mineralization formation, highlighting its genetic relationship with magmatism, compared to other deposits of this type. All the three locations belong to the Late Mesozoic Central Asian carbonatite province. Fluorites here are characterized by high rare earth elements (REE), Sr, and elevated La/Yb values. Fluid inclusions data imply that the formation of fluorite mineralization is a long process extending from late magmatic to the hydrothermal stage. Early fluorite crystallized from sulfate-carbonate orthomagmatic fluids at temperatures up to 500 °C. True hydrothermal fluorite was formed from the same fluids that were probably mixed with meteoric waters, which caused the temperature to drop to below 420 °C and led to an increase in the chloride component. The REE compositions of fluorite from the studied locations are similar to compositions of REE-rich fluorites from carbonatite-related deposits around the world. Full article

The Ilmeno–Vishnevogorsk (IVC), Buldym, and Chetlassky carbonatite complexes are localized in the folded regions of the Urals and Timan. These complexes differ in geochemical signatures and ore specialization: Nb-deposits of pyrochlore carbonatites are associated with the IVC, while Nb–REE-deposits with the Buldym complex and REE-deposits of bastnäsite carbonatites with the Chetlassky complex. A comparative study of these carbonatite complexes has been conducted in order to establish the reasons for their ore specialization and their sources. The IVC is characterized by low ⁸⁷Sr/⁸⁶Sr_i (0.70336–0.70399) and εNd (+2 to +6), suggesting a single moderately depleted mantle source for rocks and pyrochlore mineralization. The Buldym complex has a higher ⁸⁷Sr/⁸⁶Sr_i (0.70440–0.70513) with negative εNd (−0.2 to −3), which corresponds to enriched mantle source EMI-type. The REE carbonatites of the Chetlassky complex show low ⁸⁷Sr/⁸⁶Sr_i (0.70336–0.70369) and a high εNd (+5–+6), which is close to the DM mantle source with ~5% marine sedimentary component. Based on Sr–Nd isotope signatures, major, and trace element data, we assume that the different ore specialization of Urals and Timan carbonatites may be caused not only by crustal evolution of alkaline-carbonatite magmas, but also by the heterogeneity of their mantle sources associated with different degrees of enrichment in recycled components. Full article

We investigated hellandite-group mineral phases from the Roman Region, alkali syenite ejecta, by multimethod analyses. They show a complex crystallisation history including co-precipitation of hellandite-(Ce) with brockite, resorption, sub-solidus substitution with mottanaite-(Ce), exsolution of perthite-like ferri-mottanaite-(Ce), overgrowth of an oscillatory-zoned euhedral shell of ferri-mottanaite-(Ce) and late, secondary precipitation of pyrochlore in the cribrose hellandite-(Ce) core. LREE/HREE crossover and a negative Eu anomaly in hellandite-group minerals follows fO₂ increase during magma cooling. The distinction among the hellandite-group minerals is based on the element distribution in the M1, M2, M3, M4 and T sites. Additional information on miscibility relationship among the hellandite sensu strictu, tadzhikite, mottanaite, ferri-mottanaite and ciprianiite endmembers derives from molar fraction calculation. We observed that change in composition of hellandite-group minerals mimic the ligands activity in carbothermal-hydrothermal fluids related to carbonatitic magmatism. Full article

In this paper, we provide insight into the evolution of syenite magmas based on geological data and petrographic, geochemical, and O-Nd isotope parameters of rocks of the Saibar intrusion located within the Minusinsk Trough, Altay-Sayan area. The intrusive suite includes predominant syenites, few bodies of melanocratic and leucocratic nepheline syenites (foyaites), and granites. In addition, dykes of granites and mafic rocks are present. The U-Pb zircon age from the melanocratic foyaites was determined to be 457 ± 10 Ma? Examined rocks show fractionated light rare earth element patterns, normalized to chondrite, with (La/Sm)_n varying from 4 to 9, and a weakly fractionated distribution of medium and heavy rare elements, with (Dy/Yb)_n from 0.35 to 1.23 and (Sm/Yb)_n from 0.63 to 2.62. The spidergram normalized to the primitive mantle shows negative Ba, Sr, Nb, Ta, Ti, and Eu anomalies (Eu* = 0.48–0.60) and positive Rb, Th, and U anomalies. The δ¹⁸O values vary within 6.3 to 10.2‰, and εNd(t) from +4.1 to +5.0. We observe gradual transitions from syenites to foyaites. Assimilation by syenite magma of the host carbonate rocks was followed to transition from silica-saturated to silica-undersaturated conditions and removal of anorthite from the melt, which then led to nepheline. Granites of the main phase show depleted lithophile incompatible elements in comparison with syenites and foyaites. They originate via interaction of magmas at the marginal part (endocontact zone) of the intrusion, corresponding to north contact of the granites with the host felsic rocks. In comparison, the rock composition of granite dykes is enriched in lithophile incompatible elements, except for Zr, Hf, and Ti. These rocks are formed due to the differentiation of syenite magma without a significant effect of host rock assimilation. Mantle magmas must be used as parent magmas for syenites based on analysis of the formation model of other alkaline intrusions, which are similar in age to the Saibar intrusion. In the line of syenite intrusions of the Altai-Sayan province, the Saibar intrusion is no exception, and its origin is related to the evolution of mafic magmas that arose during the melting of the mantle under the influence of a mantle plume. Full article

The Mushgai Khudag complex consists of numerous silicate volcanic-plutonic rocks including melanephelinites, theralites, trachytes, shonkinites, and syenites and also hosts numerous dykes and stocks of magnetite-apatite-enriched rocks and carbonatites. It hosts the second largest REE–Fe–P–F–Sr–Ba deposit in Mongolia, with REE mineralization associated with magnetite-apatite-enriched rocks and carbonatites. The bulk rock REE content of these two rock types varies from 21,929 to 70,852 ppm, which is much higher than that of syenites (716 ± 241 ppm). Among these, the altered magnetite-apatite-enriched rocks are characterized by the greatest level of REE enrichment (58,036 ± 13,313 ppm). Magmatic apatite from magnetite-apatite-enriched rocks is commonly euhedral with purple luminescence, and altered apatite displays variable purple to blue luminescence and shows fissures and hollows with deposition of fine-grained monazite aggregates. Most magmatic apatite within syenite is prismatic and displays oscillatory zoning with variable purple to yellow luminescence. Both magmatic and altered apatite from magnetite-apatite-enriched rocks were dated using in situ U–Pb dating and found to have ages of 139.7 ± 2.6 and 138.0 ± 1.3 Ma, respectively, which supports the presence of late Mesozoic alkaline magmatism. In situ ⁸⁷Sr/⁸⁶Sr ratios obtained for all types of apatite and calcite within carbonatite show limited variation (0.70572–0.70648), which indicates derivation from a common mantle source. All apatite displays steeply fractionated chondrite-normalized REE trends with significant LREE enrichment (46,066 ± 71,391 ppm) and high (La/Yb)_N ratios ranging from 72.7 to 256. REE contents and (La/Yb)_N values are highly variable among different apatite groups, even within the same apatite grains. The variable REE contents and patterns recorded by magmatic apatite from the core to the rim can be explained by the occurrence of melt differentiation and accompanying fractional crystallization. The Y/Ho ratios of altered apatite deviate from the chondritic values, which reflects alteration by hydrothermal fluids. Altered apatite contains a high level of REE (63,912 ± 31,785 ppm), which are coupled with increased sulfur and/or silica contents, suggesting that sulfate contributes to the mobility and incorporation of REEs into apatite during alteration. Moreover, altered apatite is characterized by higher Zr/Hf, Nb/Ta, and (La/Yb)_N ratios (179 ± 48, 19.4 ± 10.3, 241 ± 40, respectively) and a lack of negative Eu anomalies compared with magmatic apatite. The distinct chemical features combined with consistent Sr isotopes and ages for magmatic and altered apatite suggest that pervasive hydrothermal alterations at Mushgai Khudag are most probably being induced by carbonatite-evolved fluids almost simultaneously after the alkaline magmatism. Full article

Olivine from the deep mantle-derived rocks, such as ultramafic lamprophyres, carries important information about the composition of the mantle source, the processes of mantle metasomatism, the origin of specific silicate-carbonate melts, as well as the composition and mechanisms of crystallization of these rocks. Textures and compositions of olivine from the carbonate-rich ultramafic lamprophyres (aillikites) of the Terina complex, along with their mineral and melt inclusions, exposed that olivines have different sources. Two populations of olivines were considered: macrocrysts (>1 mm) and groundmass olivines (<1 mm). Groundmass olivines are phenocrysts and characterized by weak variations in Mg# (84–86.5), a sharp increase in Ca and Ti contents, and a decrease in Ni and Cr from core to rim. They have higher concentrations of Li, Cu, Ti, and Na compared to macrocrysts. Among the macrocrysts, the following populations are observed: (1) high-Mg olivines (Mg# 89–91) with high Ni and low Ti contents, which are interpreted as xenocrysts from the slightly depleted lherzolite mantle; (2) high-Ca olivines (Mg# 84–88, CaO 0.13–0.21 wt %), which have patterns similar to groundmass olivines and are interpreted as cumulates of early portions of aillikite melt; (3) macrocrysts with wide variations in Mg# (73–88), low CaO contents (0.04–0.11 wt %), and positive slope in Ca vs. Al and negative slope in Ca vs. Mn, which are interpreted as disintegrated megacrysts from the Cr-poor megacryst suite. The megacryst suite could have been formed in the pre-trap period during the melting of the metasomatized subcontinental lithospheric mantle (SCLM). The aillikite melt evolution is traced by secondary melt inclusions in olivine macrocrysts: early phlogopite-diopside-calcite-apatite association, containing Ti-magnetite and ilmenite, is followed by an association with magnetite and sulfides (pyrrhotite and pentlandite); finally, at a late stage, inclusions with a predominance of Ca-Na-carbonates and sulfates and enriched in U, Th, Y, REEs, Sr, and Ba were captured. Full article

The main mass of the Sevathur carbonatite complex (Tamil Nadu, India) consists of dolomite carbonatite with a small number of ankerite carbonatite dikes. Calcite carbonatite occurs in a very minor amount as thin veins within the dolomite carbonatite. The age (²⁰⁷Pb/²⁰⁴Pb) of the Sevathur carbonatites is 801 ± 11 Ma, they are emplaced within the Precambrian granulite terrains along NE–SW trending fault systems. Minor minerals in dolomite carbonatite are fluorapatite, phlogopite (with a kinoshitalite component), amphibole and magnetite. Pyrochlore (rich in UO₂), monazite-Ce, and barite are accessory minerals. Dolomite carbonatite at the Sevathur complex contains norsethite, calcioburbankite, and benstonite as inclusions in primary calcite and are interpreted as primary minerals. They are indicative of Na, Sr, Mg, Ba, and LREE enrichment in their parental carbonatitic magma. Norsethite, calcioburbankite, and benstonite have not been previously known at Sevathur. The hydrothermal processes at the Sevathur carbonatites lead to alteration of pyrochlore into hydropyrochlore, and Ba-enrichment. Also, it leads to formation of monazite-(Ce) and barite-II. Full article

The gold and platinum-group elements (PGE) mineralization of the Guli and Kresty intrusions was formed in the process of polyphase magmatism of the central type during the Permian and Triassic age. It is suggested that native osmium and iridium crystal nuclei were formed in the mantle at earlier high-temperature events of magma generation of the mantle substratum in the interval of 765–545 Ma and were brought by meimechite melts to the area of development of magmatic bodies. The pulsating magmatism of the later phases assisted in particle enlargement. Native gold was crystallized at a temperature of 415–200 °C at the hydrothermal-metasomatic stages of the meimechite, melilite, foidolite and carbonatite magmatism. The association of minerals of precious metals with oily, resinous and asphaltene bitumen testifies to the genetic relation of the mineralization to carbonaceous metasomatism. Identifying the carbonaceous gold and platinoid ore formation associated genetically with the parental formation of ultramafic, alkaline rocks and carbonatites is suggested. Full article

During the period 750–600 Ma ago, prior to the final break-up of the supercontinent Rodinia, the crust of both the North American Craton and Baltica was intruded by significant amounts of rift-related magmas originating from the mantle. In the Proterozoic crust of Southern Norway, the 580 Ma old Fen carbonatite-ultramafic complex is a representative of this type of rocks. In this paper, we report the occurrence of an ultramafic lamprophyre dyke which possibly is linked to the Fen complex, although ⁴⁰Ar/³⁹Ar data from phenocrystic phlogopite from the dyke gave an age of 686 ± 9 Ma. The lamprophyre dyke was recently discovered in one of the Kongsberg silver mines at Vinoren, Norway. Whole rock geochemistry, geochronological and mineralogical data from the ultramafic lamprophyre dyke are presented aiming to elucidate its origin and possible geodynamic setting. From the whole-rock composition of the Vinoren dyke, the rock could be recognized as transitional between carbonatite and kimberlite-II (orangeite). From its diagnostic mineralogy, the rock is classified as aillikite. The compositions and xenocrystic nature of several of the major and accessory minerals from the Vinoren aillikite are characteristic for diamondiferous rocks (kimberlites/lamproites/UML): Phlogopite with kinoshitalite-rich rims, chromite-spinel-ulvöspinel series, Mg- and Mn-rich ilmenites, rutile and lucasite-(Ce). We suggest that the aillikite melt formed during partial melting of a MARID (mica-amphibole-rutile-ilmenite-diopside)-like source under CO₂ fluxing. The pre-rifting geodynamic setting of the Vinoren aillikite before the Rodinia supercontinent breakup suggests a relatively thick SCLM (Subcontinental Lithospheric Mantle) during this stage and might indicate a diamond-bearing source for the parental melt. This is in contrast to the about 100 Ma younger Fen complex, which were derived from a thin SCLM. Full article

The alkaline igneous rocks of the Chompolo field (Aldan shield, Siberian craton), previously defined as kimberlites or lamproites, are more correctly classified as low-Ti lamprophyres. The emplacement age of the Ogonek pipe (137.8 ± 1.2 Ma) and the Aldanskaya dike (157.0 ± 1.6 Ma) was obtained using ⁴⁰Ar/³⁹Ar K-richterite dating. The Chompolo rocks contain abundant xenocrysts of mantle minerals (chromium-rich pyropic garnets, Cr-diopsides, spinels, etc.). The composition of the mantle xenocrysts indicates the predominance of spinel and garnet–spinel lherzolites, while the presence of garnet lherzolites, dunites, harzburgites, and eclogites is minor. The Chompolo rocks are characterized by large-ion lithophile element (LILE) and Light Rare Earth Element (LREE) enrichments, and high field strength element (HFSE) depletions. The rocks of the Ogonek pipe have radiogenic Sr (⁸⁷Sr/⁸⁶Sr (t) = 0.70775 and 0.70954), and highly unradiogenic εNd_(t) (−20.03 and −20.44) isotopic composition. The trace element and isotopic characteristics of the Chompolo rocks are indicative of the involvement of subducted materials in their ancient enriched lithospheric mantle source. The Chompolo rocks were formed at the stage when the Mesozoic igneous activity was triggered by global tectonic events. The Chompolo field of alkaline magmatism is one of the few available geological objects, which provides the opportunity to investigate the subcontinental lithospheric mantle beneath the south part of the Siberian craton. Full article