Ore-magmatic System Research Articles

An apatite to unravel petrogenic processes of the Nova-Bollinger Ni-Cu magmatic sulfide deposit, Western Australia

The trace element signature and U-Pb systematics of apatite are useful in identifying petrogenic processes and tracking crust through the ∼375–600 °C thermal interval. Furthermore, as apatite is more abundant in mafic rocks than other more conventional U-Pb chronometers (e.g. zircon), it may be better suited to constrain magmatic ore systems. This work focuses on a case study of apatite from the Nova-Bollinger Ni-Cu magmatic sulfide deposit in the Fraser Zone of the Albany Fraser Orogen, Western Australia. LA-ICP-MS analysis is used to characterise the U-Pb systematics and trace element chemistry of apatite across four rock types at Nova-Bollinger. These analyses are combined with whole-rock geochemistry and petrography to resolve the poorly understood thermal evolution of Nova-Bollinger after peak metamorphic conditions.Apatite U-Pb data indicate an initial 15 °C/my cooling rate to 1284 ± 12 Ma from peak metamorphic conditions of ∼850 °C at 1304 ± 22 Ma. After 1284 Ma the cooling rate dramatically slowed to 1.2 °C/my until at least 1225 ± 17 Ma. Most apatite retains an igneous trace element signature where thermal diffusion has not influenced trace element concentrations, suggesting that any exposure to temperatures above ∼670 °C was short-lived or trace element diffusion was slow. Furthermore, trace element chemistry discriminates apatite that crystallised from an evolved intercumulus disequilibrium liquid, and apatite that crystallised in equilibrium with the mineral assemblage of more fractionated rocks. The new results from this study highlight the change from a fast to slow cooling regime in this litho-tectonic zone, likely driven by ebbing regional magma emplacement. This new information enables better understanding of the tectono-magmatic evolution of the Proterozoic Nova-Bollinger deposit and the broader Fraser Zone.

Deposits of the Udokan-Chineysky ore-magmatic system of Eastern Siberia

The aggregate of ore deposits localized in the Udokan-Chineysky ore district is unique and is the result of multi–stage, polygenetic formation. The deposits of copper and other metals formed at various depths occur within a limited area. The oxide and sulfide ore are spatially associated in the sedimentary rocks pertaining to the Paleoproterozoic Udokan Supergroup and the intrusive mafic–ultramafic rocks of the Chineysky Complex. The granite rocks of the Kodar Complex and gabbro rocks of the Chineysky Complex also date back to Paleoproterozoic. The same age has been established for metasomatic Nb–Ta–Zr–REE–Y and U mineralization in the albitized terrigenous rocks of the Udokan Supergroup (Katugin deposit and Chitkanda prospect) and U–Pd prospects hosted in terrigenous rocks. The U–REE mineralization superposed on the titanomagnetite deposits in the Chineysky pluton has not analogues in the world’s practice. The occurrences of uranium mineralization have been noted in form of pitchblende and U–Th rims around chalcopyrite grains at the Unkur copper deposit hosted in sedimentary rocks. The enrichment in U and Pb has been documented in crosscutting quartz veinlets with bornite mineralization at the Udokan deposit.

«РУДНАЯ МАГМА». ЧТО ЭТО С ПОЗИЦИИ ГРАНИТНОЙ РУДНО-МАГМАТИЧЕСКОЙ СИСТЕМЫ?

The concept of “ore magma” remains an obscure hypothesis in ore formation. The article considers the process of natural overgrowth of trivial primary basaltic magma into an ore-bearing granite melting and further into the ore-forming “ore magma” as the concentration of volatile and ore components. The dark side of the problem lies in the fact that during the ore formation the “ore magma” liquates into contrasting phases and leaves practically no traces of itself (with rare exceptions). But the concept of the ore magma has received a logical scientific justification from the standpoint of ore-magmatic systems.

Features of structural tectonics and geochemistry of Tomulakh metamorphism zone

The methods of geological and geochemical modeling for prospecting of mineralization in areas associated with the deposits of the Talnakh ore-forming system are considered. The geological and geochemical model is based on the geological and structural analysis of the spatial relationships of geochemical anomalies, which allows us to quantify the geochemical types of halos caused by both the multi-stage formation of deposits and the presence of different types of mineralization, which contributes to solving the forecasting problems. The subject of the study is the anomalous Tomulakh metamorphism zone (TMZ), the tectonic conditions of its formation, the material composition of metamorphic and metasomatic formations and facies, and their geochemical expression. The TMZ, located in the north of the ore-bearing Kharaelakh intrusive of the Talnakh ore-magmatic system, is traced along the Axial-Dyangin fault. The high density of faulting and the composition of the tectonic breccias in the upper exocontact zone ensure propagation of metamorphosing fluids over a considerable distance in the vertical and lateral directions. Within the TMZ, which is the flank part of the fluid-magmatic system, fluids evolve in space and time from alkaline to acidic. Alkaline and acidic near-fracture metasomatites developing along tectonic breccias are marked by the geochemical associations Y-Mo-Zr and Be-Mo-Zr. Ore mineralization in the form of rare scattered inclusions of pyrite, chalcopyrite, pyrrhotite, and sphalerite is mapped by the Zn-Cu-Ni-Co specialization. The development of ore mineralization in the contact-metamorphosed rocks of the upper Devonian TMZ is considered as a continuation of the contact halo of the Ni-Cu-Co specialization of the Kharaelakh intrusive. Calciteanhydrite metasomatites (americophile) and anhydrite marble in the top exocontact TMZ occur in the zone of dispersed mineralization and Sr anomalies traceable along the Axial-Dyingin fault and being the extension of the contact envelope of the Kharaelakh intrusion. It is assumed that the TMZ is formed under the influence of the fluid-magmatic Talnakh ore-forming system.

The Features of Native Gold in Ore-Bearing Breccias with Realgar-Orpiment Cement of the Vorontsovskoe Deposit (Northern Urals, Russia)

This paper describes native gold in ore-bearing breccias with realgar-orpiment cement from the Vorontsovskoe gold deposit (Northern Urals, Russia). Particular attention is paid to the morphological features of native gold and its relation to other minerals. The latter include both common (orpiment, barite, pyrite, prehnite, realgar) and rare species (Tl and Hg sulfosalts, such as boscardinite, dalnegroite, écrinsite, gillulyite, parapierrotite, routhierite, sicherite, vrbaite, etc.). The general geological and geochemical patterns of the Turyinsk-Auerbakh metallogenic province, including the presence of small non-economic copper porphyry deposits and general trend in change of the composition of native gold (an increase in the fineness of gold from high-temperature skarns to low-temperature realgar-orpiment breccias) confirm that the Vorontsovskoe deposit is an integral part of a large ore-magmatic system genetically associated with the formation of the Auerbakh intrusion.

The Aksug Porphyry Cu–Mo Ore-Magmatic System (Northeastern Tuva): Sources and Formation of Ore-Bearing Magma

Abstract ––Two stages are recognized in the evolution of the Aksug ore-magmatic system (OMS): (1) formation of the Aksug granitoid pluton and (2) emplacement of small ore-bearing intrusions. Intrusive bodies of the two stages are composed of rocks of the same type and bear copper mineralization: poor dispersed and large-scale veinlet-disseminated, respectively. The pluton and small intrusions are formed by gabbroid and granitoid rocks, with similar petrogeochemical characteristics of igneous rocks of the same type. The plutonic gabbroic association includes gabbro, gabbrodiorites, and pyroxene–amphibole diorites/quartz diorites. The small subvolcanic gabbroic intrusions are gabbrodiorite and diorite porphyrites. The trace element patterns of the gabbroids are similar to those of igneous rocks in subduction zones. The gabbroids are characterized by isotope parameters εNd(500) = +6.1 to +7.2 and (87Sr/86Sr)500 = 0.7022–0.7030 and model age TNd(DM) = 0.85–0.74 Ga. As follows from the geochemical parameters, the depleted mantle metasomatized by subduction fluids was the source of basaltic magma. The plutonic granitoid association includes tonalites, plagiogranites, and amphibole diorites/quartz diorites; the small subvolcanic granitoid intrusions are tonalite porphyry and quartz diorite porphyrites. The trace element patterns and Nd and Sr isotope compositions of the granitoids are much similar to those of the gabbroids. According to the geochemical parameters, tonalitic and plagiogranitic magmas formed through the melting of juvenile mafic crust, and dioritic magma resulted from the mixing of basaltic and tonalitic/plagiogranitic magmas. In the course of the OMS formation, metals and volatiles were introduced by basaltic and granitoid magmas from the metasomatized mantle and juvenile mafic crust. The compression setting during the pluton formation hampered the separation of ore-bearing fluids, which led to poor dispersed mineralization. The extension setting during the emplacement of small intrusions favored the intense separation of ore-bearing fluids. The interaction of magma and fluids of the small intrusions with rocks of the pluton was accompanied by the removal of metals from the latter and their involvement in the ore-forming process. This increased the ore potential of the magmatic system and favored the formation of rich mineralization at the final stage of its evolution.

GEOLOGY, MINERAL COMPOSITION OF ORE AND ALTERED HOST ROCKS OF MASSIVE SULPHIDE MINERALIZATION OF THE AKZHARSKY ORE FIELD (SOUTH URALS)

The article describes the geological structure of the Akzharsky ore field, of five individual massive sulphide mineralization: Yuzhnoye, Yuzhno-Akzharskoye, Novoye, Bezymyannoye and Burozheleznyakovoye. The results of a microscopic study of the mineral composition of ores and altered host rocks are discussed. It is shown that all ore mineralizations are concentrated at a single lithological-stratigraphic level, but differ from each other in details of the structure, scale and mineral composition of mineralization. Massive ores prevail, and embedded and densely embedded ores are subordinate. The composition of the ore is mainly chalcopyrite-pyrite, to a lesser extent sphalerite-chalcopyritepyrite and pyrite. In the direction from south to north of the ore field, there is a change in the direction of increasing «polymetallicity» in ore mineralogy. Texture and structure of the ores of the Akzharsky ore field are rather uniform. Linear structures predominate (from banded to schistosely banded). Massive structures have a sharply subordinate distribution; brecciated ones are noted in isolated cases. Hydrothermal alterations formed mainly in rhyodacite-basalt strata from foot wall of ore bodies and, according to mineral composition, belong to propylites. They are characterized by an unstable set of mineral facies, weak contrast of metasomatic zones, and extremely uneven of rocks alteration. It has been established that the volcanic complexes of the ore field contain deposits not typical for the Ural massive sulphide ore province, differing in the mineral composition of ores, the conditions of their geological setting and the nature of the rocky alterations. This made it possible to concretize the concept of the relationship between the considered mineralization and volcanism and significantly supplement the already known typical models of pyrite-bearing ore-magmatic systems.

Leading genetic types of base metal deposits of Rudny Altai

Purpose. Study on the processes contributing to the formation of pyrite-polymetallic mineralization in the Rudny Altai, development of recommendations for directions for further research. Methodology. Analysis of literature and fund materials, field studies within known ore fields and deposits, sampling and laboratory studies: spectral analysis, studies on the chemical composition of host rocks (ISP-MS Agilent 7500cx), study on the mineral composition of the main types of mineralization (JSM 6390LV)). Findings. A model of pyrite-polymetallic mineralization genetically related to the Devonian basalt-andesite-rhyolite Early Hercynian riftogenic volcanism (D1e-D3fr) was developed. Originality. The spatial confinement of a number of industrial deposits, areas of sulfide mineralization and near-ore-hydrothermally altered rocks to the areas of pinching out of inter- and sub-stratal subvolcanic porphyries of the Middle Upper Devonian and overlying porphyrites, creating a kind of ore-magmatic systems (OMS), has been established. Practical value. A new stage of deep geological study on the territory of the Rudny Altai and promising ore-bearing structures with the introduction of modern methods of deep geological and mineragenic mapping is recommended.

ВЕРТИКАЛЬНАЯ ЗОНАЛЬНОСТЬ МЕДНО-МОЛИБДЕНОВОЙ ФОРМАЦИИ КУЗНЕЦКОГО АЛАТАУ (ХАКАСИЯ)

The previously identified zoning of the copper-molybdenum formation based on a comparison of geological features of the Sorskoye, Ipchulskoye and other deposits, is confirmed by a comparison of their deep structure and general model of the ore-magmatic system. As a result, it was possible to determine the distribution of ore matter and the degree of concentration of fluids and metals in the evolutionary chain in the first approximation: the initial granite melt-leucogranite residual chamber – ore-forming apophyse from the chamber. The maximum concentration in apophyse is 1000–2000 times higher than the initial content in an ordinary granite. This makes it possible to consider the fluidized apophyse melt as “ore magma” responsible for the ore formation.

Petrography and Mineralogy of Granitoids of the Elikchan Massif (North-East of the Verkhoyansk-Kolyma Orogenic Region)

The article presents the results of a study of Elikchan granodiorite-granite massif with complex Sn-Au-Ag mineralization. It is shown that the massif localized in the zones of regional fault, where it was preceded and followed by subaerial volcanic outpourings. Considered typomorphic peculiarities of rock-forming, accessory, and restituir minerals of granitoids and petro- and geochemical features of the rocks. A polygenetic nature of the massif is documented, with the origination of parental melts of the amphibole-biotite granodiorites and granites from the lower and upper crustal protoliths, respectively, under the influence of deep heat and fluid fluxes rising from the metasomatized mantle to the magma-generation level. Geochemical specialization of granitoids on a wide range of ore elements characteristic of latite ore-magmatic systems has been established (Bi, As, Sb, Ag, Sn, W). It is shown that the crystallization of the granodiorites took place in conditions close to those of gold-bearing ore-magmatic systems, and the crystallization of the granodiorites took place in conditions close to those of gold-bearing ore-magmatic systems, and the crystallization of granites in the conditions close to those rare-metal ore-magmatic systems, what obyasnyat preformationist associated mineralization. An important criterion for the potential ore content of specific magmatic formations and its possible implementation is the regime of volatile elements.

Основные дайковые серии северной части Чакылкалянского мегаблока и их потенциальная рудоносность (на примере Яхтонского дайкового роя, Южный Узбекистан)

The study of mineralogical and geochemical properties of gold deposits is an urgent task for the geological industry, especially in the new areas under study. Without reliable information about the geological factors that lead to the formation of ore deposits and the mechanisms of deposit accumulation, it is impossible to ensure reliable scientific forecasting of the mineral potential of the regions, the effective creation of mineral resources of enterprises and mining, the stable operation of the mining industry. Our study of gold deposits was aimed at understanding these important issues of the ore formation problem. This is the urgency of the case. The role of the dictators of the Yakhton ore deposit as important structural material and mineral components of the leading types of ore-magmatic systems is being assessed. A peculiar feature of the geological structure of the ore area is the close paragenetic relationship of mineralization by rocks of the dike kids complex. Mineralization is localized in two stages and has bimetallic properties (gold, tungsten). The mineralization in the upper layer is localized in the corpus carbonate rocks of Yakhton (mainly garnet-pyroxene content). In the lower stage, mineralization is governed by a northeastern tectonic attenuation zone, which includes area concentrations of Au and W and areal mineralized zones that are part of the dike of the Yakhton region. Determining the spatial, age, and genetic relationships of mineralization with magmatism is a major problem of metallogeny.

The non-ferrous and noble metals deposits’ position and manifestation in North Ossetia-Alania regarding the anomalies of potential fields

The relevance is determined by the need to create a scientific basis for the reassessment of known ore regions for the presence of highly liquid gold ores and the search for the new gold ore objects in previously unexplored territories to diversify the mining and metallurgical industries of North Ossetia (Alania). The purpose is to reveal the geophysical signs of non-ferrous and noble metals’ mineralization and potential gold content of ore-magmatic systems. The applied methods include the results analysis of the geophysical data use when performing the work within the prospective gold territories’ limits. A combined map construction of the gravitational and magnetic fields’ local anomalies based on the analysis of amplitude characteristics using a geophysical database of the Geological map of the Russian Federation on a scale of 1: 1,000,000 according to the sheet K-38.39 (Makhachkala) as well as the analysis of the spatial distribution of deposits and the manifestations of non-ferrous and noble metals relative to geophysical anomalies. The results obtained can be formulated as follows: the experience of using geophysical data when performing the work within the limits of the gold prospective territories in the Amur region is analyzed. The results of processing the data of the geophysical surveys results in the mountainous part of the North Ossetia (Alania) territory using modern methods for converting the potential fields are presented. The compiled maps of the gravitational and magnetic field’s local anomalies have been prepared. Within North Ossetia (Alania), spatial features of the deposits and ore occurrences of non-ferrous and noble metals with respect to anomalies of the gravitational and magnetic fields have been revealed. The confinement of the granitoid type ore-magmatic systems to negative anomalies of gravity has been established. It has been shown that potentially auriferous ore-magmatic systems are located within the limits of positive magnetic field anomalies.

Pt-bearing Fedorovo-Pansky Layered Complex (Kola Peninsula): Sm-Nd geochronology and Nd-Sr characteristics

Results of isotope-geochronological Sm-Nd studies of the Paleoproterozoic platiniferous Fedorovo-Pansky layered intrusive are presented. Implementation of a complex of isotope-geochemical methods (Sm-Nd, U-Pb, Rb-Sr) allowed a more reliable and precise study of the age, formation patterns, and conditions of ore substance localization in the major units of the complex, i.e., the Fedorova Tundra and Kievey deposits. Geological, mineralogical, and isotope-geochronological data combined facilitate the identification of three ore-magmatic systems within the Fedorovo-Pansky ore area: 1) early troctolite-gabbronorite (2526-2507 Ma); 2) major ore-bearing norite-gabbronorite-anorthosite (2502-2470 Ma); 3) anorthosite (2447 Ma). The main industrial PGE mineralization of the Fedorovo-Pansky ore area is related to the norite-gabbronorite-anorthosite ore-magmatic system with the age of 2500-2470 Ma. Analysis of Sm-Nd model ages for the Fedorova Tundra (2.9 - 3.4 Ma) and West-Pana (2.8 - 3.1 Ma) blocks of the complex indicated that the age range for the Fedorova Tundra intrusive chamber is inclined to more ancient ages, which is confirmed by geological observations of individual intrusive chambers of the complex blocks.

Deep structure and geodynamic conditions of granitoid magmatism in the Eastern Russia

We investigated the deep structure of the lithosphere and the geodynamic conditions of granitoid magmatism in the Eastern Russia within the borders of the Far Eastern Federal District. The relevance of the work is determined by the need to establish the geotectonic and geodynamic conditions of the granitoids petrogenesis and ore genesis in the Russian sector of the Pacific Ore Belt. The purpose of the article is to study the deep structure of the lithosphere and determine the geodynamic conditions of granitoid magmatism in the East of Russia. The author's data on the magmatism of ore regions, regional granitoids correlations, archive and published State Geological Map data, survey mapping, deep seismic sounding of the earth's crust, gravimetric survey, geothermal exploration, and other geophysical data obtained along geotraverses. The magma-controlling concentric geostructures of the region are distinguished and their deep structure is studied. The connection of plume magmatism with deep structures is traced. The chain of concentric geostructures of Eastern Russia controls the trans-regional zone of leucocratization of the earth's crust with a width of more than 1000 km, which includes the Far Eastern zone of Li-F granites. Magmacontrolling concentric geostructures are concentrated in three granitoid provinces: Novosibirsk-Chukotka, Yano-Kolyma, and Sikhote-Alin. The driving force of geodynamic processes and granitoid magmatism was mantle heat fluxes in the reduced zones of the lithospheric slab. The distribution of slab windows along the Pacific mobile belt's strike determines the location of concentric geostructures and the magnitude of granitoid magmatism in the regional provinces. Mantle diapirs are the cores of granitoid ore-magmatic systems. The location of the most important ore regions of the Eastern Russia in concentric geostructures surrounded by annuli of negative gravity anomalies is the most important regional metallogenic pattern reflecting the correlation between ore content and deep structure of the earth's crust.

Zircon as a Mineral Indicating the Stage of Granitoid Magmatism at Northern Chukotka, Russia

A comparative study of the zircon composition and texture in granites of a three-stage Late Cretaceous magmatism in the Chaun area, Chukotka, Russia, was conducted in biotite granites (BG), quartz monzonites-monzogranites (MG), and zinnwaldite granites (ZG). The significance of the study entails determining the mineralogical indicators of similar granitoids in areas of multi-stage petrogenesis. It is shown that in the rock series of Northern Chukotka, BG → MG → ZG, a morphological evolution of zircon takes place: a reduction in size, elongation, a growing complexity of the crystallography, and an individual texture. In later generations of zircon, as a result of the recrystallization and metasomatism, rare-metal overgrowths, defects in the crystal structure, pores and fissures, and mineral inclusions appear, whereas the crystal-face indices and patterns become more complicated. We can observe the geochemical evolution of zircon: a gradual change in the concentration of trace elements (Hf, U, Y, Th, Nb, and Ti), rare earth elements (Yb, Er, and Dy, as well as Ce and Nd), and uncommon elements (Ca and Al). Rare elements (REE, Y, Hf, Nb, U, and Th) at the post-magmatic stage of the regional history acquired economic abundances. Zircon is therefore indicative of productive ore-magmatic systems.

Isotopic and geochemical features of the genesis of igneous complexes and ore-magmatic systems in the Chukotka sector of the Russian Arctic coast

Research subject. The isotopic composition (Pb-Pb, Sm-Nd, Rb-Sr, Os/Os, Hf/Hf, 3 He/4 He, etc.) of magmatic complexes and ore-magmatic systems (OMS) of two ore clusters (Kupolsky and Ilirneysky) located in the subpolar Western Chukotka was studied. These ore clusters differ from each other both in their structural position and the age of their magmatic complexes, within which the largest deposits of Au-Ag type are known. Materials and methods. The Pb-Pb, Rb-Sr, SmNd, Re-Os, Lu-Hf, 3 He/4 He, 40Ar/36Ar and sulphur isotopic systems were studied at the VSEGEI centre for isotopic studies (St. Petersburg), as well as at the Institute of Geology, Geochemistry and Ore Deposits (IGEM, Moscow) and the Laboratory of Stable Isotopes of the Far Eastern Geological Institute (FEGI, Vladivostok). Re and Os were measured using an ELEMENT-2 inductively coupled plasma single-collector mass spectrometer. Sulphur isotopic ratios were measured using a Finnigan MAT 253 isotope mass spectrometer. Results and conclusions. On the basis of the isotope-geochemical data obtained, an assumption was made that various deep sources participated in the magma generation, and the differentiated composition of late melts may reflect the melting processes of the crust upper horizons. When comparing the data on the magmatism of the Ilirneysky and Kupolsky ore clusters, a different degree of crustal rock influence on melt generation was revealed. The Kupolsky ore cluster is characterised by a large influence of mantle sources in intraplate magmatism associated with ore formation processes. This is likely to have determined a greater amount of mineralisation in the Kupolsky cluster compared to the Ilirneysky ore cluster.

Metallogenic Setting and Evolution of the Pados-Tundra Cr-Bearing Ultramafic Complex, Kola Peninsula: Evidence from Sm–Nd and U–Pb Isotopes

The article presents new Sm–Nd and U–Pb geochronological data on rocks of the poorly studied Pados-Tundra Cr-bearing complex. It is part of the Notozero mafic–ultramafic complex (western Kola Peninsula) and occurs at the border of the Paleoproterozoic Lapland Granulite Belt and the Archean Belomorian composite terrain. The Pados-Tundra complex hosts two major zones, the Dunite and Orthopyroxenite Blocks. Dunites are associated with four levels of chromite mineralization. Isotope Sm–Nd studies of dunites, harzburgites, and orthopyroxenites from the central part of the complex have been carried out. The isochron Sm–Nd age on 11 whole-rock samples from a rhythmically layered series of the complex is 2485 ± 38 Ma; the mineral Sm–Nd isochron for harzburgites shows the age of 2475 ± 38 Ma. It corresponds with the time of large-scale rifting that originated in the Fennoscandian Shield. When the rhythmically layered series of the intrusion and its chromite mineralization were formed, hornblendite dykes intruded. The U–Pb and Sm–Nd research has estimated their age at ca. 2080 Ma, which is likely to correspond with the occurrence of the Lapland–Kola Ocean. According to isotope Sm–Nd dating on metamorphic minerals (rutile, amphibole), the age of postmetamorphic cooling of rocks in the complex to 650–600 °C is 1872 ± 76 Ma. The U–Pb age on rutile from a hornblendite dyke (1804 ± 10 Ma) indicates further cooling to 450–400 °C. The conducted research has determined the early Proterozoic age of rocks in the rhythmically layered series in the Pados-Tundra complex. It is close to the age of the Paleoproterozoic ore magmatic system in the Fennoscandian Shield that developed 2.53–2.40 Ga ago. Later episodes of alterations in rocks are directly related to main metamorphic episodes in the region at the turn of 1.9 Ga. Results of the current study expand the geography of the vast Paleoproterozoic East Scandinavian Large Igneous Province and can be applied for further studies of similar mafic–ultramafic complexes.

MODEL OF MASSIVE SULPHIDE ORE-MAGMATIC SYSTEM OF AKZHARSKY ORE FIELD (SOUTH URALS)

A model of the evolution of a massive sulphide ore-magmatic system was constructed for the Akzharsky ore field, which is based on the analysis of two groups of elements of a typical model that characterize the magmatic and ore stages of its development. According to the proposed model, the ore deposits of the Akzharsky ore field were formed by a combined method. Copper came with deep hydrothermal solutions, separated in the process of magmatic liquation at the final (ore) stage of the development of the ore-magmatic system. Sulfur also had a juvenile source, as evidenced by the closeness of its isotopic composition in pyrites to the meteorite standard, and iron was extracted from the host rocks as a result of their hydrothermal processing. The onset of the ore process is associated with the formation of propylites and the hydrothermal-sedimentary deposition of hydroxide ferrous mineralization, subsequently transformed into magnetite ores under the influence of metamorphism. Massive sulphide mineralization completes ore formation and is a product of partial processing of early hydroxide ferruginous ores by later pyrite-bearing fluids. Ore formation was shortlived and proceeded under conditions of periodically renewed volcanic activity, which contributed to the rapid burial of ores and prevented the full development of the ore cycle from the earliest to the final mineral paragenesis, as well as the creation of large massive sulphide deposits. The process of massive sulphide ore formation was short-term and onestage, which manifested itself in the relative simplicity and uniformity of the texture and structural features of the ores, telescoping of productive mineralization in a narrow vertical interval, and the absence in some cases of distinct mineral and geochemical zoning.

МОДЕЛИРОВАНИЕ МАГМАТОГЕННЫХ РУДНЫХ СИСТЕМ ЗОЛОТОРУДНЫХ МЕСТОРОЖДЕНИЙ ВОСТОЧНОГО КАЗАХСТАНА

The article is devoted to the results of using system-defined geological modeling for forecasting gold deposits on the territory of the oldest gold mining region in the Republic of Kazakhstan – the West Kalba gold belt (East Kazakhstan). Research is aimed at developing forecast criteria and searches for new ore objects in favorable geological structures. The main attention of the conducted research was focused on a system-defined analysis of geological factors, the interaction of which provides a synergy effect and reveals the patterns of formation of gold ore objects. To solve this problem, the authors made a quantitative assessment of the development sustainability of the ore-generating elements of the system according to S.V. Vasiliev methodology. A quantitative assessment of the stability of individual factors and their interaction made it possible to assess the qualitative state of individual sections and define the natural boundaries of the areas of the corresponding hierarchical level, promising for the search of certain mineral deposits. The specific work was carried out to define the areas promising for the search of deposits based on a quantitative assessment of the individual factors stability. Using geological materials, results of geophysical work, space-geological data, the localization of promising areas within the West Kalba structural-formation zone and the Zhumba ore-magmatic system in East Kazakhstan was done.

THERMOCHRONOLOGY AND MATHEMATICAL MODELING OF THE FORMATION DYNAMICS OF RARE‐METAL‐GRANITE DEPOSITS OF THE ALTAI COLLISION SYSTEM

The article presents an event correlation of the Permian‐Triassic granites of the Altai collision system, which are associated with industrial ore deposits and occurrences (Mo‐W, Sn‐W, Li‐Ta‐Be). The multi‐system and multi‐mineral isotope datings of igneous rocks and ore bodies (U/Pb, Re/Os, Rb/Sr, Ar/Ar‐methods) suggest the postcollisional (intraplate) formation of ore‐magmatic systems (OMS), the duration of which depended on the crustmantle interaction and the rates of tectonic exposure of geoblocks to the upper crustal levels.Two cases of the OMS thermal history are described: (1) Kalguty Mo‐W deposit associated with rare‐metal granite‐leucogranites and ongonite‐ elvan dykes, and (2) Novo‐Akhmirov Li‐Ta deposit represented by topaz‐zinnwaldite granites and the contemporary lamprophyre and ongonit‐elvan dykes. For these geological objects, numerical modeling was carried out. The proposed models show thermal cooling of the deep magmatic chambers of granite composition, resulting in the residual foci of rare‐metal‐granite melts, which are known as the petrological indicators of industrial ore deposits (Mo‐W, Sn‐W, Li‐Ta‐Be). According to the simulation results concerning the framework of a closed magmatic system with a complex multistage development history, the magmatic chamber has a lower underlying observable massif and a reservoir associated with it. A long‐term magmatic differentiation of the parental melt (a source of rare‐metal‐granite melts and ore hydrothermal fluids) takes place in this reservoir.