Potassium alkaline lamproite-carbonatite complexes: petrology,genesis, and ore reserves

This paper studies the petrology of K-alkaline lamproite-carbonatite complexes, which are widespread in Siberia. They are exemplified by the Murun and Bilibino massifs in West and Central Aldan. In these massifs, the entire range of differentiates was first found, from K-ultrabasic-alkalic rocks through basic and intermediate ones to alkali granites and unique residual calc-silicate rocks (benstonite Ba-Sr carbonatites and charoite rocks). Also, intrusive equivalents of lamproites occur in these massifs, and the Murun massif was probably formed from highly differentiated lamproite magmas. In many K-alkaline complexes, silicate and silicate-carbonate magma layering takes place. Stages of magmatism are described for both massifs. Binary and ternary petrochemical diagrams exhibit the same compositional trend from early to late rocks.In this paper, lamproites are considered from the chemical point of view; their diagnostic properties are described in terms of chemical and mineral composition. From geological, petrological, and geochemical data, formational analysis of alkaline complexes was performed, four formational types of world lamproites were first identified, and diamond content criteria were developed for them.The carbonatite problem was studied from the petrological point of view, and four formational types of carbonatites were identified using geological, geochemical, and genetic criteria. It has been suggested that for dividing carbonatite complexes into four formational types the following criteria be used: the alkalinity type (Na or K) of alkalic rocks in the complex and the time when the carbonatite liquid separates from silicate melts in different stages of primary magma differentiation. These linked parameters influence the ore content type of carbonatite complexes.A formation model for K-alkaline carbonatite complexes is given, and the Tomtor alkaline carbonatite massif with tuffaceous rare-metal ores is described to prove that they have ore reserves. The geochemistry of C, O, Sr, and Nd isotopes shows that K-alkaline complexes, depending on their geotectonic setting, can originate from three types of mantle sources: depleted mantle, enriched mantle 1 (EM1), and enriched mantle 2 (EM2). It is concluded that ore-bearing ultrabasic-alkaline complexes of lamproites and carbonatites can melt out of different types of mantle, whose composition only slightly influences their ore content. Apparently, the main factors are the low degree of selective mantle melting (less than 1%) and plumes supplying fluid and alkaline components, which stimulate this melting. Later on, the processes important for the accumulation of ore and trace elements are long-term magma differentiation and its layering during crystallization.     

敦煌地块钠长碎裂岩型金矿床的地质特征

敦煌地块东段前长城系敦煌群是该台块最古老的结晶基底，为一套绿岩建造。金矿床赋存于敦煌群顶部第四岩组火山岩和稍晚的基性斜长角门石岩被强烈钠交代而形成的钠长岩体内，并严格受控于脆－韧性剪切带。与金矿化有关的钠交代原岩有基性侵入岩、中酸性火山岩、花岗岩（可能有）等，但其最终交代产物均为钠长岩和石英脉组合，为一种特殊的金矿类型。     

Late Paleozoic granitoids of western Transbaikalia: magma sources and stages of formation

Geochemical and geochronological studies of the main types of granitoids of the Angara-Vitim batholith (AVB) and granites of the Zaza complex in western Transbaikalia were carried out. U-Pb (SHRIMP-II) and Rb-Sr dating yielded the age of autochthonous gneiss-granites of the Zelenaya Griva massif (325.3±2.8 Ma), quartz syenites of the Khangintui pluton (302.3±3.7 Ma) and intruding leucogranites of the Zaza complex (294.4±1 Ma), monzonites of the Khasurta massif (283.7±5.3 Ma), and quartz monzonites of the Romanovka massif (278.5±2.4 Ma). The U-Pb and Rb-Sr dates show that the Late Paleozoic magmatism in western Transbaikalia proceeded in two stages: (1) 340–320 Ma, when predominantly mesocratic granites of the Barguzin complex, including autochthonous ones, formed, and (2) 310–270 Ma, when most AVB granitoids formed. We suggest that at the early stage, crustal peraluminous granites formed in collision geodynamic setting. At the late (main) stage, magmatism occurred in postorogenic-extension setting and was accompanied by the formation of several geochemical types of granitoids: (1) typical intrusive mesocratic granites of the Barguzin complex, similar to those produced at the first stage; (2) melanocratic granitoids (monzonitoids, quartz syenites), which were earlier dated to the early stage of the AVB evolution; (3) leucocratic medium-alkali (peraluminous) granites of the Zaza intrusive complex; and (4) some alkali-granite and syenite intrusions accompanied by alkaline mafic rocks. The diversity of granitoids that formed at the late stage of magmatism was due to the heterogeneous composition of crust protoliths and different degrees of mantle-magma participation in their formation.     

Granite diapirism in the Rum Jungle area,Northern Australia

Early studies in the Rum Jungle area suggested an intrusive relationship between the Rum Jungle and Waterhouse “Granites”, and the overlying sediments. It was later shown that the granitic “intrusions” were Archaean basement complexes onto which Lower Proterozoic sediments had been deposited. Polyphase folding was postulated as being responsible for doming of the basement and cover rocks.This paper proposes to show that the domed structures in the Rum Jungle area, and the emplacement of Middle Proterozoic granites in the Pine Creek Geosyncline were related, and caused by diapiric intrusion of granites, in a solid state, into basement complexes and cover rocks.Structural and metamorphic evidence in support of diapiric intrusion in the Rum Jungle area includes: pebble deformation within steeply dipping beds of quartz conglomerate; disappearance of polyphase fold structures away from the basement complexes; bending of folded country-rock strata into concordance with the complex—sediment contact; and metamorphic and metasomatic alteration of sediments in contact with the basement complexes. Gravity data show mass deficiencies in the Archaean complexes which possibly coincide with young granite diapirs.     

Nepheline-bearing rocks from the Poohbah Lake complex,Ontario: Malignites and Malignites

Malignites from the Poohbah Lake complex of northwestern Ontario, Canada are melanocratic cumulates. Cumulus pyroxene and apatite are poikilitically enclosed in a groundmass of large plates of intercumulus orthoclase and nepheline. Nepheline-feldspar fingerprint-like intergrowths occur. Nephelines are commonly zeolitized and pyroxenes altered to aggregates of biotite and/or garnet by deuteric alteration. Pyroxenes are weakly zoned from Di₇₁ Hd¹⁸Ac₁₁ to Di₆₃Hd₂₂Ac₁₅, and are similar to the least evolved pyroxenes of other alkaline rocks. Nephelines all have compositions within the Morozewicz-Buerger convergence field and feldspars have a limited compositional range from Or⁸⁸ to Or⁹⁵. Perthites are absent.Inconsistancies in the usage of the terms malignite and juvite are discussed and it is considered that a non-genetic petrographic classification of nepheline syenites leads to the obscuration of a group of potassic nepheline syenites, characterized by the presence of nepheline plus orthoclase which are typically associated with saturated to over-saturated alkaline rocks, contain pseudo-leucite or nepheline-orthoclase intergrowths, are emplaced in mobile belts and are not associated with rocks of the ijolite-carbonatite suite.A genetic classification of nepheline syenites is suggested and it is proposed that; (1) mafic-rich nepheline syenites be referred to as mela-nepheline syenites (sensu lato) rather than as malignites; (2) the term malignite be used for magmatic potassic nepheline syenites characterised by the presence of nepheline plus a single potassium-rich feldspar (orthoclase or microcline) and devoid of exsolution perthite under subsolvus conditions; (3) the metasomatic malignites and juvites of ijolite-carbonatite complexes be referred to as varieties of fenites.     

Genesis of alkalic rocks in Ural

As a rule, infiltrational metasomatism in axial parts of geosynclines terminates in the formation of a eutectic granitic magmatic solution. However, in case such solutions fail to develop while the accessions of the alkalic solutions continue, a miaskitic magmatic solution may arise, the parent of miaskites. Thus the crystallization of miaskites is contingent upon a progressive local metamorphism, in geologically rare and special environments in which the substratum acquires gradually a eutectoid, i.e. the miaskitic. The widely different series of intrusive alkalic rocks, from nephelinolites and alkalic gabbroids to plagioclase and corundum syenites, are the result of their reactions with their hosts, the mechanisms and the types of which depend upon the geological-structural conditions and other variables. – V. P. Sokoloff.     

与攀西裂谷碱性杂岩有关的成矿系列

在攀西地区,自海西期以来出现两套与大陆裂谷作用有关的岩浆岩共生组合,即基性岩套与碱（酸）性岩套。与基性岩套有成因联系和紧密伴生的印支期碱性正长伟晶岩脉和碱性花岗伟晶岩脉等,普遍具稀有、稀土和铀钍矿化,有的已形成中小型铌钽矿床:碱（酸）性岩套以超基性碱性岩、碱性花岗岩为代表,并具与碱性花岗岩有关的稀有、稀土矿床和铀钍矿化。本文对上述碱性杂岩有关的成矿系列,划分了矿床成因类型,并对主要控制因素作了较为详细的探讨。     

Metasomatites of the Kara gold deposit (Eastern Transbaikalia)

Wall-rock metasomatites of the Kara gold deposit, a high-temperature medium-depth pneumatolytic-hydrothermal formation, have been studied. Gold mineralization is associated with the intrusion of granitoids of the Kara-Chacha massif (J3) and dikes of alkaline rocks (J3-K1), which include hybrid porphyries, “grorudites”, etc. They are characterized by telescoping of ores, expressed best of all on joints of ore-bearing sites.The origin of the Kara-Chacha massif (Amudzhikan-Sretensk complex) is connected with pre-ore areal propylitization. The propylites demonstrate a zonal pattern relative to the massif and ore veins. A composite metasomatic column of propylitized rocks has been compiled.The thickness of intensely altered wall rocks does not exceed 1.5–2.0 m and the structure of these zones is very heterogeneous. Syn-ore metasomatites are found in propylitized rocks. The major factor of syn-ore alteration of host rocks is the active behavior of alkaline elements. Albitization, silicification (in separate sites), tourmaline and pyrite alteration occur at the early quartz-pyrite-tourmaline stage of mineralization. Sodium is supplied at this stage. During the next quartz-actinolite-magnetite stage sodium and potassium are active. The host rocks demonstrate albitization, feldspar alteration, silicification, actinolitization, biotite alteration, and magnetite impregnation. Aegirine in veins is accompanied by occurrence of aegirine, alkaline amphibole, green biotite and, locally, quartz in host rocks. Potassium becomes more significant later, reaching the maximum activity at the quartz-sulfide stage. The development of quartz-arsenopyrite assemblage was accompanied by K-feldspatization, sericitization of host rocks, formation of green and tan biotites, and arsenopyrite impregnation. The formation of K-feldspar, sericitization, silicification, and sulfide impregnation are associated with quartz-sulfide ore. The final quartz-carbonate-polymetallic stage is accompanied by silicification and carbonate alteration of host rocks. Potassium becomes increasingly more active from outer zones of metasomatic columns to inner ones. The gold contents tend to increase with the potassium contribution in zones of hydrothermal alterations.The propylite alteration and syn-ore changes become more intense veinward. It can indicate that hydrothermal solutions with dissolved minerals penetrated through the most reworked zones. However, hydrothermal solutions during propylite alteration and later syn-ore changes of host rocks not always penetrated through the same zones of weakness, such as tectonic dislocations, contacts of various rocks, etc. The rocks, comprising inner zones of the metasomatic column of propylites are quite often observed at a certain distance from veins and accompanied inner zones of metasomatic columns of later syn-ore metasomatites. They sometimes are not associated with ore veins. However, they are demonstrate later superimposed threads and separate impregnations of syn-ore minerals.Abundant telescoping of mineralization and inheritance of mineralization stages complicate the structure of zones with syn-ore metasomatites. In the sites with telescoped mineralization the metasomatites contain minerals intrinsic to all stages of mineralization found at the deposit.     

SOVESTKAYA GEOLOGIYA (SOVIET GEOLOGY) IN COVER-TO-COVER TRANSLATION, 1961 NO. 1

Parts of certain alkalic intrusive massifs contain up to 63 cc methane per kilogram of rock, with smaller amounts of heavier hydrocarbon gases, bitumen, hydrogen, carbon monoxide and carbon dioxide. The authors argue that the hydrocarbons cannot have come from assimilated limestone, because the igneous rocks contain much more of these gases than do the enclosing limestones. Likewise, the hydrocarbons cannot have been introduced by late solutions because they are much lower in hydrothermal and metasomatic fades than in primary minerals of the high temperature intrusive facies. Hydrocarbons are not stable at magmatic temperatures; the authors conclude that these must have formed in the presence of natural catalysts during slow cooling below 500°C, in accordance with industrial synthesis of hydrocarbons. The C¹²/C¹³ ratio of the bitumens is in the range for ordinary petroleum, suggesting that they formed at relatively low temperature, but the carbon of the gaseous hydrocarbons is lighter, which may indicate that they formed at somewhat higher temperatures. -- E. Ingerson.     

Structure,age, and ore potential of the Burpala rare-metal alkaline massif,northern Baikal region

The Burpala alkaline massif is a unique geological object. More than 50 Zr, Nb, Ti, Th, Be, and REE minerals have been identified in rare-metal syenite of this massif. Their contents often reach tens of percent, and concentrations of rare elements in rocks are as high as 3.6% REE, 4% Zr, 0.5% Y, 0.5% Nb, 0.5% Th, and 0.1% U. Geological and geochemical data show that all rocks in the Burpala massif are derivatives of alkaline magma initially enriched in rare elements. These rocks vary in composition from shonkinite, melanocratic syenite, nepheline and alkali syenites to alaskite and alkali granite. The extreme products of magma fractionation are rare-metal pegmatites, apatite-fluorite rocks, and carbonatites. The primary melts were related to the enriched EM-2 mantle source. The U-Pb zircon ages of pulaskite (main intrusive phase) and rare-metal syenite (vein phase) are estimated at 294 ± 1 and 283 ± 8 Ma, respectively. The massif was formed as a result of impact of the mantle plume on the active continental margin of the Siberian paleocontinent.     

Genesis of Zn-Cu deposits in the basic Ransko massif (Eastern Bohemia)

Watkinson et al. (1978) have reinterpreted the Zn-Cu deposits in the Ransko massif as xenoliths of volcanogenic ores enclosed in and contact-metamorphosed by a basic magma. A detailed reexamination of different xenoliths within the massif, and their comparison with the cordierite hornfelses carriers of Zn-Cu ores, has shown essential differences between them, and confirmed the previous opinions on the metasomatic origin of the deposits. The cordierite hornfels originated by selective magnesian metasomatism of intrusive rocks rich in feldspar (quartz diorite, troctolite), particularly by the replacement of feldspars by cordierite. Around the stocks of cordierite hornfels, a conspicuous concentric metasomatic zonation of rocks developed in mafic intrusives. The Zn-Cu deposits of the Ransko massif resemble sulfide deposits connected with magnesian metasomatism, especially those of the Hitachi area in Japan.     

Composition and genesis of inner-contact syenites of the Khasurta quartz syenite-monzonite massif,western Transbaikalia

The paper reports data on the geological structure, mineralogy, and geochemistry of inner-contact syenites of the Late Paleozoic Khasurta quartz syenite-monzonite massif in western Transbaikalia. The rocks of the massif intrude Cambrian terrigenous-carbonate deposits transformed (depending on their composition) into apodolomitic magnesian spinel-fassaite skarns or plagioclase-quartz-biotite-cordierite hornfels that replaced amphibole-biotite schists. The skarn zone does not exceed a few dozen centimeters in thicknes. The inner-contact zone of the intrusion a few dozen meters thick consists of leucocratic medium-grained pyroxene syenites, which consist of coarsely perthitic K-Na feldspar (90–95 vol %) with plagioclase (An _40–46) cores, zonal clinopyroxene (up to 5–7 vol %), and sphene (up to 3–4 vol %). The inner-contact syenites differ from all other rocks of this massif in having the highest alkalinity and elevated concentrations of SiO₂ and the lowest contents of CaO, MgO, and FeO. The mineralogical composition of the inner-contact syenites makes them similar to skarn-related metasomatic rocks (Korzhinskii, 1948), but the pyroxenes of these rocks contain melt inclusions homogenizing at 1100°C, a fact testifying to the magmatic genesis of the rocks. The results of our research indicate that the inner-contact syenites were formed with the assimilation of the host dolomites by the syenite melt. The enrichment of the inner-contact syenite melt in CaO and MgO and a significant increase in its liquidus temperature due to CO₂ dissolution (Jahannes and Holtz, 1996) facilitated the crystallization of calcic plagioclase, pyroxene, and magnetite. The fractionation of these minerals resulted in the enrichment of the residual melt in SiO₂ and alkalis, mostly K₂O, and this subalkaline residual melt produced that K-Na feldspar, which is the predominant mineral of these rocks, and sphene. Excess CO₂ drastically suppressed the H₂O activity in the melt and thus hampered the crystallization of amphibole and biotite in the inner-contact zone of the intrusion. Mass-balance calculations indicate that dolomite assimilation was not very extensive and did not exceed 1: 10.     

A Pb isotope investigation of the Lovozero Agpaitic Nepheline Syenite,Kola Peninsula,Russia

For the first time Pb isotope composition was established in Lovozero rocks and raremetal ores, which is important for identifying their sources. The world’s largest layered intrusion of agpaitic nepheline syenite-the Lovozero alkaline massif—is located near the center of the Kola Peninsula in Russia. This superlarge complex plutonic body hosts the economically important loparite and eudiallyte deposits [1]. These deposits contain immense resources of REE, Nb, Ta, Zr, and constitute a world class mineral district. The Lovozero massif belongs to the Kola ultramafic alkaline and carbonatitic province (KACP) of Devonian age. Previous bulk rock studies have shown that the initial Sr and Nd isotope ratios of Lovozero rocks plot in the depleted mantle quadrant of Sr-Nd diagrams [2]. More recently, Hf isotope data obtained by Kogarko et al. (3) confirm that the Lovozero and Khibina massifs with ?_Hf between 6 and 8 are derived predominantly from a depleted mantle source. It was shown that Sr, Nd, and Hf abundances are significantly elevated in the Kola alkaline rocks, and thus their isotopic compositions are relatively insensitive to minor contamination by the overlying crustal rocks. By contrast, Pb in the KACP rocks is a much more sensitive indicator of a crustal component. In this paper we investigate the lead isotopic signature of all resentative types of Lovozero rocks (Table 1) in order to further characterize their mantle sources. The Lovozero massif consists of four intrusive phases. Rocks of phase I (mostly nepheline syenites) comprise about 5% of the total volume, phase II (urtites, foyaite, lujavrites) forms the main portion of the massif comprising 77% in volume, and phase III (eudialyte lujavrites) contributes about 18%. Country rocks are represented by Devonian effusive rocks and Archean gneisses.     

北山—阿拉善地区二叠—三叠纪富碱侵入岩的岩石学特征

甘肃北山－内蒙古阿拉善地区发育有一套以正长岩、石英正长岩、霓辉正长岩、霓霞正长岩类为代表，包括碱性辉长岩、二长岩、石英二长岩、碱长花岗岩和碱性花岗岩等类岩石在内的富碱侵入体。本文总结了它们的空间分布、形成时代、产状、岩石组合和岩石化学特征；指出它们具有近东西向的分布特征，主体形成于二叠－三叠纪时期，具有富碱、碱性岩类的岩石化学特征，构成一条富碱侵入岩带；认为其时空分布特点与华北地台、塔里木地台北缘及邻区碱性岩带一致，是华北－塔里木北缘及邻区巨型碱性岩带的重要组成部分。     

Middle Paleozoic and Early Mesozoic anorogenic magmatism of the South Yenisei Ridge: first geochemical and geochronological data

In this paper we present complex geological, petrographic and geochronological data of the study of intermediate and acid composition intrusive and volcanogenic rocks from the Porozhnaya massif of the South Yenisei Ridge. For the first time in the Yenisei Ridge Devonian and Triassic U-Pb age values (SHRIMP method) have been obtained for leucogranites—387 ± 5 Ma and alkaline trachytes—240 ± 3 Ma, which allows us to attribute them to two different complexes, despite the fact that these rocks were formed within the same Severnaya riftogenic structure. Geochronological Ar-Ar data (392–387 Ma) for micas from paragneisses and leucogranitic dikes of the Yenisei suture zone on whose extension the Severnaya riftogenic structure is located are also given in this study. These data on Devonian tectonic-magmatic events in the South Yenisei Ridge agree well with coeval events of continental rifting—the formation of intrusive and volcanogenic rocks of the Agul graben in the Prisayan region and the Minusa basin in the Altai-Sayan folded area. The forming of alkaline trachytes and alkaline syenites of the Severnaya riftogenic structure, for which an age of 240 ± 3 Ma has been established, is related to the trap magmatism of the Siberian platform.     

Mineralogical,geochemical, and age characteristics of the rocks of the Inagli dunite-clinopyroxenite-shonkinite massif with platinum-chromite and Cr-diopside mineralization (Aldan Shield)

We consider the mineralogical and geochemical features of the rocks of the Inagli dunite-clinopyroxenite-shonkinite massif with platinum-chromite and unique jewelry Cr-diopside mineralization, which is a reference object of concentric zonal complexes. The massif rocks, from dunites to pulaskites, including peridotites, clinopyroxenites, shonkinites, and melanocratic alkali syenites, form a single continuous comagmatic series. This is confirmed by a clear dependence of the compositions of olivine, pyroxene, phlogopites, and Cr-spinels on the MgO content of the rocks and on the behavior of trace elements in them. The similar compositions of pyroxenes and trace-element patterns of clinopyroxenite rocks and Cr-diopsidite veins indicate a genetic similarity of these rocks. The age and mineralogical and geochemical compositions of the rocks and the geologic and morphological features of the intrusion prove that the Inagli massif formed from high-K picritoid melts, which underwent gradual decompression solidification during the ascent and formed a cylindrical diapir-like body at the subsurface level in the Early Cretaceous. The new portions of differentiates supplied from the lower horizons of the magma column determined the complex composition of the massif: It has a concentric zonal structure cut by numerous radial-circular vein bodies of pegmatites and pure anchimonomineral rocks (Cr-diopsidites), in places, of jewelry quality.     

Vostok-2 gold-base-metal-tungsten skarn deposit,Central Sikhote-Alin,Russia

Vostok-2—East Russia’s largest skarn deposit of high-grade sulfide-scheelite ore with substantial base-metal and gold mineralization—was formed during the Mesozoic orogenic epoch of evolution of the Far East marginal continental system as an element of the gold-tin-tungsten metallogenic belt. The deposit is related to the multistage monzodiorite-granodiorite-granite complex pertaining to the ilmenite series and spatially associated with a minor granodiorite porphyry (?) stock, which bears petrological features transi- tional to those of intrusive rocks occurring at Au-W and Au deposits. The hydrothermal metasomatic alteration of host rocks evolved from pyroxene skarn via retrograde postskarn and propylitic (hydrosilicate) metasomatic rocks to the late, low-temperature quartz-sericite metasomatic rocks often with albite, chlorite, carbonate, and apatite. The mineral assemblages of skarn and postskarn metasomatic rocks correspond to those at the reduced-type tungsten skarn deposits. Zoning of the postskarn metasomatic rocks is controlled by granodiorite stock. The hydrothermal metasomatic alteration was accompanied by development of mineralization from scheelite via sulfide-scheelite with pyrrhotite and chalcopyrite to the gold-base-metal-scheelite assemblage with arsenopyrite, Bi-Sb-Te-Pb-Zn sulfides and sulfosalts. Several scheelite generations are recognized. Scheelite of the late generations is enriched in Eu, as is typical of gold deposits. The associated gold mineralization comprises both native gold varying in fineness and Au-bearing arsenopyrite. The significant gold mineralization emphasizes genetic links of this deposit with intrusion-related Au-W and Au deposits of the reduced type.     

Deep structure and metallogeny of the Kirovograd polymetallic ore district,the Ukrainian Shield: Correlation of geological and seismic data

The study of deep structure of the Kirovograd ore district proceeds from a broad treatment of its geological boundaries and combination of metasomatic uranium, pegmatitic lithium, and hydrothermal gold deposits, as well as lodes of magmatic titanium ore within these boundaries. The spatial juxtaposition of the Novoukrainsk-Kirovograd granitoid massif and the Korsun-Novomirgorod rapakivi granite-anorthosite massif is a distinguishing feature of the Kirovograd ore district. The former massif along with stratified metamorphic rocks forms an intrusive-ultrametamorphic basement, whereas the latter massif is autonomous with respect to the basement. Taken together, both massifs make up the Novoukrainsk-Korsun-Novomirgorod composite pluton, which determines the architecture of the Kirovograd ore district not only at the present-day erosion surface but also at deeper levels of the lithosphere. The uranium, lithium, and gold deposits are localized in the intrusive-ultrametamorphic basement and controlled by various combinations of intrinsic and superposed structures; the vertical extent of mineralization is also controlled by their combinations. Some combinations are unique. Primarily, these are triple junctions of superposed faults, which host the largest metasomatic uranium orebodies. At the same time, the deposits are spatially related to the local mediumscale trough in topography of the Moho discontinuity. This mantle trench is discordant relative to the Novoukrainsk-Korsun-Novomirgorod pluton. These and other data discussed in the paper allow us to consider the Kirovograd polymetallic ore district as a Paleoproterozoic center of crustal-mantle magmatic activity and ore formation. This center was formed 2.1-1.7 Ga ago in the course of juxtaposition of three development stages differing in associations of intrusive rocks, style of deformation and metamorphism of rocks, origin and localization of ore deposits.