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Project titleOre bearing capacity of carbonatites and their relationship with large igneous provinces: the example of the Chadobetsky alkaline complex (Chuktukonsky and Terinovsky massifs), Krasnoyarsk region

AffiliationV.S. Sobolev Institute of Geology and Mineralogy, Siberian branch of Russian Academy of Sciences,

KeywordsCarbonatites, Nb, rare earths, petrology, ore content, large igneous province of Siberia

Annotation
Alkaline-ultramafic carbonatite complexes of the Siberian Craton are important objects in the field of understanding the fundamental petrological foundations of the genesis, origination mechanisms, and sources of matter of specific fluid-saturated alkaline-potassium silicate-carbonate melts that characterize the composition of mantle depths of more than 250 km. At the same time, these unique melts contain a number of useful and strategically important ore components, such as rare (Nb, Ta, Tl, Zr, etc.) and rare earth (La, Ce, Nd) elements, which often form industrial objects on the territory of the Russian Federation. Most of these minerals are widely in demand in modern industry: mechanical engineering and shipbuilding, aviation, alloys, catalysts, medicine, defense production and many others other industries. The main goal of the project is to establish the petrological (geological, mineralogical, geochemical, geochronological and physicochemical) factors of formation and metal content of alkaline-ultramafic carbonatite complexes in Siberia, using the example of the ore-bearing Chadobetsky complex, within which the Chuktukon deposit, which is large in terms of reserves of rare earth-niobium ores, has been explored. At the same time, the petrological factors of the ore content of the Chadobetsky complex, which we obtained, like any model, certainly require verification with other alkaline objects of the Siberian craton, and, first of all, those associated with the activity of the Siberian superplume. Therefore, the main objects of study for the extension of the project are similar-aged and/or compositionally similar alkaline intrusions of the Siberian Craton: aillikites and damtjernites of the Victoria pipe (Anabar alkaline province), alkaline-ultramafic and alkaline-carbonatite complexes of the Maimecha-Kotui province (Guli, Bor-Uryakh and Odikhincha), the Khushma alkaline complex, and the Ilbokich aillkitic intrusion. It is the petrological studies of the above objects that will allow us to clarify and adapt the ore-bearing factors of the Chadobetsky complex. The relevance of solving the scientific problem posed within the framework of the project lies in an integrated approach to solving problems using modern analytical facilities based on certified analytical centers of the Russian Academy of Sciences. The study under the project involves the following types and methods of research: (1) detailed petrographic and mineralogical study of rocks and ores (EPMA, SEM, Raman); (2) obtaining and clarifying age characteristics (U-Pb and Ar-Ar); (3) study of the distribution of rare and rare earth elements in the rock and mineral (LA-ICP MS, ICP MS, EPMA, SEM); (4) assessment of the physicochemical parameters of the generation of melts and fluids, study of their composition and metal content (thermal-cryometry, Raman spectroscopy, SEM, EPMA, LA ICP-MS); (6) construction of petrogenetic models for the evolution of melts and fluid regime, determination of the mechanisms of concentration, distribution and redistribution of ore components. The scientific novelty of the research lies in obtaining absolutely new modern data on the conditions for the generation of specific alkaline magmas, the features of their composition and mantle substrates; links between the formation of alkaline carbonatite complexes and a large igneous province in the Siberian craton; the nature of the evolution of primary magmatic melts; fluid regime and conditions of fluid generation at different stages of evolution of the studied systems, mechanisms of concentration, distribution and redistribution of ore elements. The petrological data obtained within the framework of the project contain modern fundamental information about the genesis and evolution of deep-seated high-potassium alkaline-carbonate melts, and determine the features of the high ore content of the investigated complexes, which can be applied in practical terms to search for potentially new ore objects associated with alkaline complexes Russia.

Expected results
Research within the framework of the extension of the project is aimed at additional study, confirmation and adaptation of the formation model of the Chadobetsky complex. Verification of the model of formation and ore genesis of the Chadobetsky complex will be carried out with typical alkaline and ore-bearing objects of the Siberian craton, alkaline complexes of close age and/or similar in composition: aillikites and damtjernites of the Victoria pipe (Anabar alkaline province), alkaline-ultramafic and alkaline-carbonatite complexes of Maimecha-Kotuy province (the Guli, Bor-Uryakh, and Odikhincha intrusions), the Khushma alkaline complex, and the Ilbokich aillkite intrusion. The results obtained are aimed at filling the "spaces" in the model of evolution of alkaline-ultrabasic carbonatite melts, which are relevant and poorly studied in petrology in the international arena. In particular, questions will concern the role of highly fractionated alkali-silicate and carbonate melts in the transport and concentration of metals during the formation of alkali-ultramafic complexes; (2) physical- chemistry of the processes of separating the fraction of the fluidized carbonate alkaline melt; as well as (3) material characteristics of pelletal lapilli, reflecting the composition of the parental melt of ultramafic alkaline lamprophyres captured at different depths in the stages of evolution. More details about the issue of the "spaces" in alkaline-ultramafic carbonatite petrology are shown in paragraph 4.2 of the application. Expected key results: 1. An additional study of the composition and features of the genesis of ultrabmafic lamprophyres of the Chadobetsky complex was carried out. A detailed material characterization (Raman with area and depth mapping, SEM, EPMA, LA-ICP MS) of the composition of pelletal lapilli in aillikites and damtjernites of the Chadobetsky complex (first and third phases of intrusion) will be obtained, showing the formation mechanisms, as well as the composition and evolution of deep ore-bearing melts of alkali-ultrabasic lamprophyres under the Siberian craton. 2. Material characterization (Raman, SEM, EPMA) of illikite pyroclasts of Triassic alkaline-ultramafic rocks of the Anabar alkaline province will be determined using the Victoria pipe as an example. Verification with the Chadobetsky complex was carried out. 3. New data will be obtained on the composition of melt inclusions (SEM, EPMA, Raman) in olivine, spinels, and other minerals in the aillikites of the Victoria pipe (Anabar); the trace element composition of olivine macrocrysts and phenocrysts was studied (LA ICP-MS); verification will be carried out with data on inclusions in the aillikites of the Chadobets complex, which will allow us to speak about the composition and evolution of melts of alkaline-ultramafic carbonatite magmas and its evolution under the Siberian craton in different periods of the manifestation of alkaline-ultramafic magmatism. 4. New detailed mineralogical (SEM, EPMA) and melt and fluid inclusion studies (SEM, EPMA, Raman, thermo-cryometry) of alkali-ultrabasic and alkali-carbonatite objects of Maimecha-Kotuy province (the Guli, Bor-Uryakh, and Odikhincha intrusions) will be obtained. Based on the results of these studies, it is planned to reveal the role of highly fractionated alkali-silicate and carbonate melts in the transfer and concentration of metals, including Ti, Nb, Ta, U, Th, Cu, Ni, and platinum group elements during the formation of alkali-ultramafic complexes. On the example of the studied intrusions of the Maimecha-Kotuy province, the principles of the transformation of alkaline mafic and ultramafic rocks and the formation of ore mineralization under the action of residual alkaline-silicate and carbonate melts will be formulated. The petrological and geochemical characteristics of the studied rocks will be compared with those of other objects studied in the Project and the possibility of participation of similar processes in the formation of other objects and deposits of the Siberian Craton associated with alkaline carbonatite complexes will be assessed. 5. Melt and fluid inclusion studies in olivine from aillikites of the Ilbokich intrusion will be carried out. Verification with data on inclusions in olivine and other minerals of the Chadobetsky complex. 6. New mineralogical, geochronological (Ar-Ar) and geochemical (XRF, ICP MS) data on the Khushma alkaline complex will be obtained; the rocks were compared with the Chadobetsky complex. 7. As a result of research under the project, the addition, verification and adaptation of petrological (geological, mineralogical, geochemical, geochronological and physicochemical) factors of formation and ore genesis of alkaline-ultramafic carbonatite complexes of the Siberian Craton, which are of the same age and similar in composition to the Chadobetsky alkaline complex, will be carried out. The mineral ore indicators and physical and chemical conditions of their ore formation established within the framework of the project can be used in assessing the prospects of mineralization and technological properties of ores. Thus, the results of the study under the project will undoubtedly make a significant fundamental contribution to the solution of global issues of the generation and evolution of alkaline magmas, their ore content, and their relationship with large igneous provinces. The obtained data will allow presenting the results at the international level at the annual major international conferences (EGU, ECROFI, SGEM, Goldschmidt or AGU) and Russian meetings (Alkaline magmatism of the Earth, New in the knowledge of ore formation, etc.), as well as publishing at least eight articles in high-ranking logs of the WoS/SCOPUS system. In practical terms, as noted above, the results obtained can be used to search for and evaluate promising ore objects of rare metal mineralization in Siberia and Russia, as well as in assessing the technological properties of ores, which must be taken into account when developing schemes for extracting ore components at mining and processing enterprises in Russia.

Annotation of the results obtained in 2022
A detailed mineralogical and chemical characterization of the composition of pelletal lapilli in the damtjernites of the Chadobets complex has been obtained, showing the formation mechanisms, as well as the composition and evolution of deep-seated melts under the Siberian craton. A model for the formation of pellet lapilli has been constructed. Comprehensive mineralogical, structural and chemical studies of pellet lapilli from the rocks of the Chadobets complex have shown the closeness of the material composition of the main mineral phases of lapilli and damtjernite juvenile paragenesis. The compositions of phlogopite, carbonate, and fluorapatite of pellet lapilli correspond to the beginning of crystallization trends of early minerals in the damtejrnites of the complex, which unambiguously indicates the juvenile composition of pellet lapilli. At the same time, the difference in the size and composition of the cores, as well as the presence of mineral zonality in pellet lapilli from damtjernites, make it possible to assess the relative conditions of formation and the depth of nucleation of various types of pelletal lapilli (Prokopyev et al., 2023 // Scientific Reports). New data on the composition of minerals in the groundmass pyroclasts of ultramafic lamprophyres of the Victoria pipe (Anabar alkaline province) were obtained, in which the main emphasis is on studying the composition of olivine and monticellite. The data were verified with the rocks of the Chadobets complex and with the known ultrabasic lamprophyres and kimberlites of the world. Olivine macrocrysts and phenocrysts from pyroclastic shells have been studied. They overlap in composition with each other and demonstrate a decrease in the concentrations of Cr, Ni and an increase in Ca and Mn with a decrease in Mg#. Similar trends are characteristic of aillikites and damtjernites of the Chadobets complex. However, the studied olivines from the damtjernites of the Victoria pipe differ from the olivines of the ultramafic lamprophyres of the Chadobets complex in more magnesian compositions. In terms of Mg# (about 0.85), monticellite from the damtjernites of the Victoria pipe overlaps with the compositions of monticellite from the aillikites of Aillik Bay, Canada (Tappe et al., 2009) and differs from the more magnesian monticellite from kimberlites, by the example of kimberlites of the Lac de Gras field, Canada , Abersteiner et al. (2018). New data on the composition of the parental melt and its subsequent evolution have been obtained for alkaline-ultrabasic lamprophyres (damtjernites) from the Victoria pipe (Anabar alkaline province). The data are compared with typical alkali-ultrabasic carbonatite and kimberlite complexes. Melt inclusions in olivines from the Victoria pipe reflect the least differentiated melt, since olivine is one of the liquidus minerals. These inclusions have a potassium carbonate-silicate composition, which makes them similar to alkaline-ultrabasic carbonatite and kimberlite complexes: with melt inclusions in olivines of ailikites of the Neoproterozoic Arbarastakh complex (Doroshkevich et al., 2022), the Devonian Ilbokich Complex (Starikova et al., 2022) and the Chadobets alkaline-carbonatite complex (Prokopyev et al., 2020; Starikova et al., 2021). The composition of melt inclusions in olivine from the Victoria damtjernites is similar to those in the kimberlites of the Udachnaya-Vostochnaya pipe (Kamenetsky et al., 2004; 2008; Golovin et al., 2003; 2007; Sharygin et al., 2007), as well as the Mark kimberlites in Canada ( Abersteiner et al., 2020) and Bulfonstein in South Africa (Giuliani et al., 2015). New data on the composition and processes of ore content of melts of alkaline-ultrabasic and alkaline-carbonatite objects of the Maimecha-Kotui province (on the example of the Guli, Bor-Uryakh and Odikhincha complexes) have been obtained. Verification of data with alkali-carbonatite complexes of the world has been carried out. The studied inclusions were interpreted as conserved intercumulus melts (often with heterogeneously trapped nepheline, perovskite, phlogopite) that existed in ultramafic proto-cumulate. Since these melts were sufficiently differentiated (after jigging most of the olivine), they can be used as a marker of intra-chamber differentiation of a carbonatized alkaline-ultrabasic melt, and on this basis, the behavior of ore-forming elements during differentiation can be studied. These melts captured by intercumulus chromite (Guli dunites) were rich in U, Th and Nb, and also crystallized Os-Ir-Ru phases near the host chromite. The concentrations of U, Th, Nb, and REE in alkaline carbonatite melts, which were present in the intercumulus of the Odikhinchinsky and Bor-Uryakh peridotites, approach those in ore-bearing carbonatites of the world and confirm the concentration of these metals in the immiscible alkaline carbonatite fraction, which was enriched in S, P, and Cl. Detailed data on the composition of melts (aillikites) of the Ilbokich intrusion (south of the Siberian Craton) have been obtained. Verification with data on the Chadobets complex was carried out. The composition of the daughter phases of primary inclusions in the olivine of the Ilbokich aillikites and their ratios correspond to the bulk of the aillikites themselves: phlogopite and clinopyroxene as the main silicates, a high content of carbonates (calcite, dolomite), Ti-bearing phases, and apatite. The parental melt of the Ilbokich aillikites was significantly enriched in water, carbon dioxide, and P and Ti. Experimental works for kimberlite systems have shown the possibility of the existence of carbonate-silicate immiscibility at ≤4 GPa and 1140-1000°C (Kamenetsky and Yaxley, 2015), 2 GPa and 1000-1200°C (Sharygin et al., 2017). At pressures below 2 GPa, degassing with CO2 release was observed in experiments (Kamenetsky and Yaxley, 2015). A similar degassing process could have occurred during the rapid ascent of the Ilbokich aillikite melts, which led to the capture of secondary inclusions containing high-density CO2. Estimates of the minimum P capture of inclusions with the highest density CO2 were 6.5 kbar (Yamamoto and Kagi, 2008 and references therein); T of the formation of olivine edge parts, 1120–1150°C, was taken as the capture T (Nosova et al., 2018). New mineralogical and geochemical data on the Khushma alkaline complex (Angara-Kotui rift structure, south of the Siberian Craton) have been obtained. The rocks were compared with the Chadobets complex. The obtained mineralogical and geochemical data on the alkaline rocks of the Khushma complex (259.7 ± 3.1 Ma, Ar-Ar, mica), which is closely related to the ultrabasic alkaline carbonatite Chadobetsky complex, showed that they have different alkaline specialization. The rocks of the Khushma complex belong to the sodium series, while those of the Chadobets complex belong to the potassium series. The latter are more enriched in rare earth and highly charged (Nb, Ti) elements. For the rocks of the Khushma complex, the presence (and/or) the predominance of amphibole in the source can be assumed. In any case, all melts, according to geochronological data, arose as a result of a single event caused by the impact of a plume on the metasomatized lithospheric mantle of the southern part of the Siberian craton. New mineralogical, geochronological and geochemical data on the carbonatites of the Verkhnekyidinsky massif (Central Taimyr) have been obtained. The rocks are compared with carbonatites of Siberia and the world. Mineralogical and melt and fluid inclusion data on fluorite-barite-bastnasite carbonatites of Central Taimyr correlate with data on carbonatites of the Central Asian province (Central Tuva and Western Transbaikalia) and determine the specifics of the formation and ore genesis of rare-earth carbonatites of folded belts (Prokopyev et al., 2023 // Lithos, minerals). The age of carbonatites in Central Taimyr is 246.5±1.9 Ma (U-Pb, bastnäsite, Fig. 19) (Prokopyev et al., 2023 // Lithos). The role of the plume component in the source of Central Taimyr carbonatites, as well as Siberian lamproites (Vrublevskii et al., 2005), was very limited. In contrast, isotopic studies of the complexes of the Maimecha-Kotui province, Siberian kimberlites, and the Chadobets complex (Carlson et al., 2006; Doroshkevich et al., 2019, 2021; Nosova et al., 2020; Kogarko and Zartman, 2011; Sharma et al. ., 1999; Arndt et al., 1998) show that alkaline rocks originated from a moderately depleted mantle.

Publications

1. Ilya Prokopyev, Anna Doroshkevich, Anastasiya Starikova, Semen Kovalev, Yazgul Nugumanova & Andrey Izokh Petrogenesis of juvenile pelletal lapilli in ultramafic lamprophyres Scientific Reports, V. 13, 5841 (year - 2023) https://doi.org/10.1038/s41598-023-32535-2

2. Nugumanova Y.N., Doroshkevich A.G. СОСТАВ ШПИНЕЛИДОВ ИЗ ПОЗДНЕПРОТЕРОЗОЙСКИХ УЛЬТРАОСНОВНЫХ ЛАМПРОФИРОВ БОЛЬШЕТАГНИНСКОГО ЩЕЛОЧНО-УЛЬТРАОСНОВНОГО КАРБОНАТИТОВОГО МАССИВА (УРИКСКО-ИЙСКИЙ ГРАБЕН, ВОСТОЧНОЕ ПРИСАЯНЬЕ) Геодинамика и тектонофизика, еодинамика и тектонофизика. 2022;13(4) (year - 2022) https://doi.org/10.5800/GT-2022-13-4-0656

3. Prokopyev I.R., Doroshkevich A.G., Starikova A.E. , Yang Y., Goryunova V.O., Tomoshevich N.A., Proskurnin V.F., Saltanov V.A., Kukharenko E.A. Geochronology and origin of the carbonatites of the Central Taimyr Region, Russia (Arctica): Constraints on the F-Ba-REE mineralization and the Siberian Large Igneous Province Lithos, Volumes 440–441, March 2023, 107045 (year - 2023) https://doi.org/10.1016/j.lithos.2023.107045

4. Starikova A.Е., Prokopyev I.R., Doroshkevich A.G., Kargin A.V., Nosova A.A., Kovalev S.A. РАСПЛАВНЫЕ ВКЛЮЧЕНИЯ В ОЛИВИНЕ КАК ИСТОЧНИК ИНФОРМАЦИИ О СОСТАВЕ И ЭВОЛЮЦИИ ГЛУБИННЫХ РАСПЛАВОВ АЙЛИКИТОВ (УЛЬТРАОСНОВНЫХ ЛАМПРОФИРОВ) ИЛЬБОКИЧСКОГО ПОДНЯТИЯ ЮЗ СИБИРСКОЙ ПЛАТФОРМЫ. Геодинамика и тектонофизика, Геодинамика и тектонофизика 13(4) (year - 2022) https://doi.org/10.5800/GT-2022-13-4-0655