Iron Ore District Research Articles

A supergene-hydrothermal origin of the itabirite-hosted high-grade iron ores in the Mbarga prospect, Mbalam iron ore district, southern Cameroon, Congo Craton

The Mbarga itabirite deposit in the Mbalam iron district on the northwest edge of the Congo Craton (CC) hosts two main types of iron ore enrichments: supergene and specularite ores. This study presents mineralogical, geochemical, and isotopic datasets on these ores to determine their genesis.Ore microscopic studies indicate that the itabirites are of the oxide facies type, with magnetite showing partial to extensive alteration to hematite-martite. The supergene ores consist of hematite + martite + goethite ± gibbsite ± magnetite ± quartz, while the specularite ores are mainly composed of hematite + martite ± quartz. Magnetite microchemistry suggests formation under low-T hydrothermal conditions (~200–300 °C) with high fO2. Geochemical analyses show that the supergene and specularite ores have higher Fe2O3 (88.27 to ~100 wt%) and lower SiO2 (<0.01 to 0.18 wt%) contents than the itabirites (31.95 wt% Fe2O3, 67.16 wt% SiO2). The enrichment of Fe in the supergene ores is attributed to the depletion of major oxides and trace elements due to weathering and supergene enrichment, while the high Fe content in the specularite ores stems from the precipitation of iron-rich, but trace- and rare earth elements (REE)-deficient hydrothermal fluids. The slightly higher Al2O3 content and positive Ce anomalies in the supergene ores suggest the retention of Al-bearing minerals (gibbsite) and reveal highly oxidative conditions during martitization. Stable isotope analyses reveal that the supergene and specularite ores have δ18O values of −2.5 to −0.3 ‰ and − 2.0 to −3.4 ‰, and δ2H values of −75 to −123 ‰ and − 70 to −119 ‰, respectively, suggesting the involvement of isotopically light-evolved meteoric water in their formation. In contrast, the itabirites exhibit heavier δ18O (8.5 to 10.2 ‰) and δ2H (−85 to −91 ‰) values, suggesting formation from mixed magmatic and metamorphic fluid sources. A “polygenic-supergene-hydrothermal” model is suggested for the formation of the Mbarga itabirite-hosted iron ores.

Bulk geochemistry, Rb–Sr, Sm–Nd, and stable O–H isotope systematics of the Metzimevin high-grade iron ore deposit, Mbalam iron ore district, southern Cameroon

Bulk geochemistry, Rb–Sr, Sm–Nd, and stable O–H isotope systematics of the Metzimevin high-grade iron ore deposit, Mbalam iron ore district, southern Cameroon

Prospective assessment of the associated minerals complex in the Konksky and Bilozersky iron ore districts from the Middle-Dniprean mega-block of the Ukrainian shield

Purpose.To determine the material composition, formational types and justify the prospects for the development of metallic and non-metallic minerals complex accompanying ore occurrences and iron deposits in the Konksky and Belozersky iron ore regions of the Middle Dnieper megablock of the Ukrainian Shield. Methods.In the process of carrying out research tasks, traditional methods of studying the material composition of minerals were used - petrographic, mineragraphic, interpretation of X-ray diffraction, thermal, and chemical analyzes were carried out. An ore formation analysis of ore occurrences of minerals accompanying iron in the Konksky and Belozersky iron ore regions was carried out. Findings.The features of the geological structure, material composition, and the influence of secondary alterations of rocks and ores on the prospects for the ore content of associated minerals accompanying iron deposits and occurrences in the study areas are characterized. The ore formation types, the genesis of ore occurrences are substantiated, and the prospects for the integrated use of raw materials accompanying iron ore deposits in the Konksky and Belozersky regions are determined. The originality.The systematic generalization of factual material regarding geological and ore formations in the Konkskaya and Belozerskaya greenstone structures, the substantiation of the possibility for using the results for metallogenic forecasting, in particular, hidden ore and the substantiation of the possibility of integrated use of the subsoil of the study areas. Practical implementation is justified by the possibility of using research results in the process of exploration and development work for a complex of associated minerals within the research area. An assessment of the prospects for the use of minerals accompanying deposits of strategically important iron ore raw materials will make it possible to ensure the comprehensive use of the subsoil of iron ore areas.

Tectogenesis as a factor influencing the stability of rock masses of the Northern iron ore district of the Kryvbas

&#x0D; &#x0D; &#x0D; In the Northern iron-ore district of the Kryvbas basin, mining of deposits of poor magnetic ores is underway in two quarries – Pervomaiskyi and Hannivsky. Oftentimes, their mine contours contain low-valuable or unusable magnetite-silicaceous quarzites of containing ferrous and slate horizons. As a result, excavated ore mass contains ores and partly containing rocks of various mineral and chemical compositions and physical and technical properties. This caused diversity (15 mineral kinds) of the compositions of ores mined from the both deposits. Variability of mineral compositions of ores and rocks is due to manifesta- tions of numerous geological processes such as sedimentation, metamorphism, tectogenesis, metasomatism, supergene, etc. Various mineralogical, geochemical courses of the processes resulted in variability in physical, technical characteristics of ores and containing rocks, and this, in turn, caused various stability of rock masses during drilling-explosive works and mining. Stability of pit walls of the quarries of iron-ore deposits of the Kryvyi Rih basin is a sharp issue for mining enterprises. Solutions to those issues have been analyzed in various aspects. A number of factors take effects on the indicator of stability of rock masses within deposits, particularly mineralogical, geochemical, tectonic, etc. This paper looks at the influence of the tectonic factor specifically, which actively manifests within the Pervomayskyi and Hannivskyi deposits as fractures, breccias, mylonite of ores and rocks. During the surveys, there were designated tectonically altered kinds of ores and rocks within the both deposits, which take effects on seismic stability of pit walls of the both quarries, and also we put areas with various tectonic intensities on schematic maps. For this purpose, we used geological methods of study (selection of samples, mapping), mineralogical (determining quantitative proportions of minerals, texture, structure of ores and rocks). The study provides the data of mineralogical estimates of tectonically altered types of ores and rocks of productive layers of the Pervomaiskyi and Hannivskyi deposits of the Kryvyi Rih basin. We charted maps with areas of various manifestations of tectonic changes within productive layers of the both deposits.&#x0D; &#x0D; &#x0D;

ЗАГАЛЬНА ГЕОЛОГІЧНА ІСТОРІЯ ЯК ОСНОВА ЄДИНОЇ СТРАТИГРАФІЧНОЇ ШКАЛИ ДОКЕМБРІЙСЬКИХ ПОРІД ПЕРШОТРАВНЕВОГО ТА ГАННІВСЬКОГО РОДОВИЩ КРИВОРІЗЬКОГО ЗАЛІЗОРУДНОГО БАСЕЙНУ

Hannivske deposit of poor magnetite ores is part of the Kryvyi Rih iron ore basin. The deposit is located in the southern part of the Eastern-Hannivka belt at the Northern iron ore district of Kryvbas. Two sets of rocks are involved in the geological structure of the Hannivske deposit: crystalline rocks of the Archaean and Proterozoic, as well as rocks of the Cenozoic sedimentary cover. Archean rocks are represented by plagiogranites and plagiomigmatites of the Dnipropetrovsk Complex (AR2dn) and amphibolites of the Konkska Series (AR3kn). The Proterozoic complex of rocks is formed by the Kryvyi Rih Series (PP1kr), which is divided into five Formations (from bottom to top): Novokryvorizka (PR1nk), Skelyuvatska (PR1sk), Saksaganska (PR1sx), Gdantsivska (PR1gd) and Gleyuvatska (PR1gl). The productive stratum of the Hannivske deposit is the overlying pack of the first ferrous horizon of the Saksaganska Formation of the Kryvyi Rih Series, which, according to the generally accepted stratigraphic scheme of Kryvbas, corresponds to the fifth-sixth ferrous horizon of Saksaganska Formation of Kryvyi Rih Series. Crystalline rocks of the Archaean and Proterozoic are covered by a layer of sedimentary rocks of the Cenozoic: Paleogene (P), Neogene (N) and Quaternary (Q) periods. In the southern part, the Eastern-Hannivka belt (Hannivske deposit) connects with the Pervomayka deposit by a series of numerous sublatitudinal and diagonal faults. In the north-northwest direction, there is a gradual decrease in thickness and wedging of the Eastern-Hannivka belt, including the iron ore stratum. Metasomatic processes in their intense display are observed in the productive stratum of the Hannivske deposit locally, but a significant part of it is covered by weak metasomatic changes. A feature of metasomatic processes was the formation of metasomatic bodies along linear tectonically weakened zones or at their intersection nodes. Multi-stage formation of the Hannivske deposit, active display of various geological processes in the productive and containing stratums (sedimentation, metamorphism, tectogenesis, metasomatosis, hydrothermal, astroblemic phenomena, syngenetic and epigenetic magmatism, hypergenesis, etc.) determined the mineralogical and chemical diversity of the Hannivske deposit ores, the presence in its productive and capacious layers, the manifestation of many metallic and non-metallic minerals, the formation of a complex mineral and raw material base of the deposit.

Study of groundwater pollution for drinking purposes in the Starooskolsko-Gubkinsky iron ore district (KMA region)

Study of groundwater pollution for drinking purposes in the Starooskolsko-Gubkinsky iron ore district (KMA region)

ГІС ДЛЯ МОНІТОРИНГУ СТІЙКОСТІ ГІРНИЧИХ МАСИВІВ ПІВНІЧНОГО ЗАЛІЗОРУДНОГО РАЙОНУ КРИВОРІЗЬКОГО БАСЕЙНУ

Pervomayske and Gannovske deposits of the Northern iron ore district are characterised by the variable structure of the productive and host strata, as well as the variability of their physical and technical parameters. This fact necessitates a detailed study of the mineral composition of rocks and other geological factors that affect the stability of rock massifs. The issue of variability of stability of rock massifs is acute for mining enterprises. The stability of rock massifs is conditioned by the manifestation of geological (syngenetic and epigenetic) processes. So the influence of mineralogical, physical and technical characteristics of ores and host rocks influences the variability of their strength indicators, stability of rock massifs in the faces of Pervomaysk and Gannovka quarries. The influence of physical and technical properties of ores and rocks was studied on the basis of research of their mineralogical, chemical, textural and structural features. The strength of rock massifs of iron ore deposits is also influenced by anthropogenic factors, the effect of which is conditioned by technical and technological parameters of mining activities. Mapping the areas of influence of various geological processes on the productive and host strata of Pervomayske and Gannovske deposits will increase the efficiency of drilling and blasting and mining operations. This work is devoted to the construction of 3D models, on the example of Pervomayskoye deposit. On the models different on stability areas of the deposit are allocated on the basis of mineralogical, stratigraphic, tectonic factors, and also on the basis of study of physical and technical parameters of ores and host rocks. A generalised model of the deposit is also given, taking into account the above-mentioned factors. The obtained models of stability of rock massifs of the deposit taking into account the influence of natural factors can be used for perspective planning of blasting, mining operations and for prevention of emergency situations connected with seismic activity of the sides of iron ore pits.

ГЕОЛОГІЧНІ ПІДСТАВИ ДЛЯ РОЗРОБКИ 3D МОДЕЛІ СТІЙКОСТІ ГІРСЬКИХ МАСИВІВ РОДОВИЩ ПІВНІЧНОГО ЗАЛІЗОРУДНОГО РАЙОНУ КРИВОРІЗЬКОГО БАСЕЙНУ

The stability of rock massifs depends on a number of factors: geological, mineralogical, physical and technical, which affect it in different ways. The problem of stability of rock massifs is facing all iron ore enterprises, because it leads to accidents and violation of mining technology. Enterprises of the Kryvyi Rih basin are not an exception. Development of the specialised geoinformation system will solve actual problems of designing of seismically stable sides of quarries and prevention of landslides of rock massifs. This work is devoted to the main stages of software product development. It will take into account the influence of geological factors on the stability of rock massifs. Justification of expediency of taking into account mineralogical and geological factors was carried out on the example of the Hanivske deposit, which belongs to the Northern iron ore district of the Kryvyi Rih basin. The outlined proposals are based on the calculation of the stability reserve factor of rock massifs, taking into account the variability of the structure of the productive and host strata of the Hanivske deposit. In addition, no less important indicator is the influence of the geological factor, which takes into account the stratigraphic scheme of the deposit and its tectonics. The results of previous studies were taken into account when developing the recommendations. The basis for the correct functioning of a specialised geoinformation system are actual block geological models of the deposit, the database of which should contain information on mineral and chemical composition of ores and rocks, indicators of their physical and technical properties, manifestation of discontinuities, presence of aquifers, areas of metasomatic changes and weathering. The authors emphasised the importance of creating in the software product the function of selecting the method of calculating the stability coefficient of the sides. As a result, the software product should identify areas with stable, intermediate stability and unstable sides within the field. Automation of calculations of stability of rock masses and their visualisation will optimize monito

Petrology of banded iron formation-related country rocks at the northern limit of the Mbalam iron ore district, southeastern Cameroon

Banded iron formation (BIF)-related country rocks at the northern limit of the Mbalam iron ore district constitute part of the Archean to Proterozoic greenstone belt of the Congo Craton (CC). In this study the petrology of BIFs and amphibolites from the lower part of the Njweng ridge is presented in a bid to decipher the source of the sediments and their inherent iron enrichment. The BIFs vary from oxide to silicate facies categories, composed mainly of magnetite bands alternating with quartz bands and their mineralogy is dominated by magnetite, hematite and quartz. The amphibolites contain quartz, magnetite, amphibole, biotite, garnet with a distinct schistocity. The Fe2O3 and SiO2 content of the BIFs reach highs of 54.55 wt% and 57.83 wt%, respectively. The average Fe2O3 content of 46.7 wt% coupled with SiO2 and Al2O3 as deleterious elements indicate a relatively low-grade iron ore. Gold content reaches a maximum of 1.1 ppb. Low Al2O3, TiO2 and High Field Strength Elements (HFSE) indicate BIF derivation from detritus-free chemical sediments. Their Fe/Ti, Fe/Al and Si/Al ratios are typical of marine BIF systems with hydrothermal overprint. On Post Archaean Australian Shale (PAAS)-normalized Rare Earth Elements-Yttrium (REE-Y) patterns the BIFs present a slightly negative Ce anomaly and positive Eu and Y anomalies; characteristics typical of modern seawater. The amphibolites are enriched in Light Rare Earth Elements (LREE) relative to Heavy Rare Earth Elements (HREE) and show peaks of Y, Nb, La Ta and their Au content attains a maximum of 1.7 ppm. Gold contents in the BIFs and amphibolites indicate the BIF-related country rocks as a potential primary source of the alluvial gold mined in the Mbalam district. &#x0D; &#x0D; Les gisements de Fer rubanés (BIFs) localisés à la limite Nord du district ferrifere de Mbalam, sont partiellement représentatives des ceintures de roches vertes Archéennes à Protérozoïques dans le Craton du Congo (CC). Dans cette étude, la pétrologie des BIFs et amphibolites de la partie inferieure de la crête de Njweng est présentée afin de déceler la source des sédiments ainsi que leur enrichissement en Fer. Différentes catégories de BIFs variant des facies à oxydes aux silicates, sont composées principalement de bandes à magnétite avec alternances de bandes quartzeux. Leur minéralogie est dominée par la magnétite, l’hématite et le quartz. Les amphibolites contiennent du quartz, magnétite, l’amphibole, biotite, et grenat avec une schistosité distincte. La teneur en Fe2O3 et SiO2 des BIFs atteint un maximum en poids de 54,55 % et 57,83 % respectivement. La teneur moyenne en Fe2O3 de 46,7 % en poids, associée au SiO2 et Al2O3 comme éléments délétères, indique un minerai de fer à teneur relativement faible. Les teneurs en Or atteignent un maximum de 1,1 ppb. Les faibles teneurs en Al2O3, TiO2 et élément de champ électrostatique élevé (HFSE) indiquent que les BIFs dérivent d’un environnement sédimentaire chimique d’origine non détritique. Leur rapports Fe/Ti, Fe/Al et Si/Al sont typiques des systèmes BIFs marin avec une signature hydrothermale. Sur les modèles tarres rares-yttrium normalisés par schiste australien post- archéen (PAAS), les BIFs révèlent une légère anomalie négative de Ce couplée à une anomalie positive de Eu et Y, caractéristique d’un environnement marin récent. Les amphibolites sont enrichies en tarres rares légères par rapport aux tarres rares lourdes et montrent des pics de Y, Nb, La et Ta, Leurs teneurs en Au atteignent un maximum de 1,7 ppm. Les teneurs en Or dans les BIFs et les amphibolites indiquent que les formations de fer rubanées (BIFs) en place dans le district de Mbalam sont une source potentielle d’or.

Geochronology and geochemistry of zircons from fertile and barren intrusions in the Sangan mining area (NE Iran): Implications for tectonic setting and mineral exploration

The Sangan mining area is the largest Cenozoic skarn iron ore district in the far eastern part of the Alborz Magmatic Arc in Iran. In this study, we evaluate the zircon composition as an important exploration tool and pathfinder for skarn mineralization to elucidate distinctive zircon signatures diagnostic of metallogenic fertility of the parent magma. Granitoid intrusions in the Sangan mining area are subdivided into the fertile Sarnowsar intrusion composed of syenite, syenogranite, and granite and the barren Sarkhar and Bermani intrusions composited of monzogranite and syenogranite. The Eocene Sarnowsar intrusion was produced by the flare-up magmatism and is an oxidized I-type granitoid suite. Fourteen iron ore bodies occur along the contact of this intrusion with the carbonate country rocks. In the barren Sarkhar and Bermani intrusions, monzogranites have zircon U-Pb ages of 41.7 ± 0.6 Ma and 41.9 ± 0.3 Ma, whereas syenogranites have ages of 37.8 ± 0.3 Ma, 37.9 ± 1.7 Ma, and 37.4 ± 1.8 Ma. These ages span the same time interval as the Eocene flare-up occurrences throughout Iran.

Peculiarities of the raw material base of the Lykhmanivka iron ore region in Kryvyi Rih basin

Lykhmanivka (Inhulets) iron ore district takes the southernmost position in the Kryvyi Rih iron ore basin. In the north, it is bordered by a series of sublatitudinal faults with the Southern Iron Ore District of Kryvbas. The productive strata of the area are Lykhmanivka iron ore pay streak, in the southern part of which the Inhulets deposit of magnetite quartzites is located in the zone of closing of Lykhmanivka syncline. However, in addition to them in the area, there are more than 20 types of other minerals, which are mined by-products and can be successfully used in the national economy. Syngenetic (sedimentation, diagenesis, dynamothermal metamorphism) and epigenetic processes (tectogenesis, metasomatism, hydrothermal processes, hypergenesis), which occurred during the formation of iron ore and host strata area have contributed to the formation of several minerals and rocks, which can be considered as associated complex useful minerals. The relevance of the work is due to the need for detailed research of the localization, formation conditions, directions of use of metallic and nonmetallic minerals of the area, the geological justification for their priority varieties. As a result of these studies, systematization of minerals of the area has been developed, their priority varieties have been identified. Their involvement in mining and processing significantly expands the spectrum of alternative ways of use of minerals and rocks of iron-banded formation, which will contribute to a significant addition to the mineral resource base as in Kryvyi Rih iron ore basin, and in Ukraine as a whole.

ЛОКАЛИЗАЦИЯ И СТРОЕНИЕ ЗАЛЕЖЕЙ ГЕМАТИТОВЫХ КВАРЦИТОВ ЮЖНОГО ЖЕЛЕЗОРУДНОГО РАЙОНА КРИВОРОЖСКОГО БАССЕЙНА

Изложены результаты изучения геологической позиции, размеров, неоднородности строения залежей гематитовых кварцитов, которыми сложена кора выветривания четвертого, пятого и шестого железистых горизонтов саксаганской свиты Скелеватского и Валявкинского месторождений Южного железорудного района Кривбасса. Рассмотрены особенности ее вертикальной и горизонтальной минералогической зональности, проявлений эпигенетических гипергенных процессов маршаллитизации, окварцевания, рудогенеза. Показано, что следствием полигенности образования коры выветривания является большое количество рядовых минеральных разновидностей гематитового сырья. Для организации эффективной его добычи и переработки рекомендована методика компоновки рядовых разновидностей руд в укрупненные, объединенные и генеральные.

Indirect estimate of in loco moisture via normative mineralogy calculation with correction of seasonal effect on itabirite (banded iron formation) of the Pico complex, Quadril\xe1tero Ferr\xedfero, Minas Gerais, Brazil

Moisture is a critical variable in iron-ore processing, handling and transportation. During beneficiation, excessive moisture may lead to screen and chute clogging. In transportation, moisture values above transportable moisture limit may cause cargo instabilities, especially in regard to vessels. Moisture is a non-stationary variable that depends on spatial and time distributions. Therefore, classical estimate methods such as ordinary kriging are not appropriate to calculate moisture values. Here, we present an extension of the Normative Mineralogy Calculation to indirectly estimate moisture, considering seasonal influence. This study in based on three iron-ore mines, Galinheiro, Pico and Sapecado. They are located in the Quadrilátero Ferrífero of Minas Gerais, Brazil, a world-class iron-ore district. The method proposed herein provides useful information that can be applied elsewhere. Our results indicate that compact ores show low moisture values with little seasonal influence, while soft ores and canga (iron-rich duricrust) are strongly influenced seasonally due to higher porosity and greater capacity of retaining water in the crystal structure of minerals, such as goethite. Moisture variations may exceed 2% along the year. Such variations are enough to preclude the beneficiation of certain iron ores during the rainy season. For this reason, moisture has been regarded as an essential variable in short-term mining.Article HighlightsMoisture is a critical variable in iron-ore processing, handling and transportation. Moisture depends on spatial and time distributions; hence classical methods are not appropriate to quantitatively estimate it. This study proposes an indirectly estimate of moisture considering seasonal influence.Compact iron ores are little influenced seasonally, while soft iron ores and canga (duricrust) are strongly affected by the rainy season due to their higher porosity and greater capacity of retaining water.The seasonal effect on moisture is an essential variable that must be consider to better effectiveness of iron-ore mining sequencing and beneficiation.

Mineralogy, petrochronology, geochemistry, and fluid inclusion characteristics of the Dardvay skarn iron deposit, Sangan mining district, NE Iran

The Sangan mining district, with a proven reserve of 1 Gt of 35 to 60% iron, is a world-class iron ore district in Iran, and located in the far eastern part of the Cenozoic Alborz Magmatic Arc. The east–west trending Sangan mining district consists of fourteen iron deposits, spatially associated with the Eocene Sarnowsar composite intrusion (syenite to syenogranite and granite), subvolcanic (quartz monzonite and syenite) and volcanic rocks (andesite and rhyolite). Syenogranite and quartz monzonite rocks in the Dardvay skarn are classified as oxidized I-type granites, with an average SiO2 content of 69.25–65.91 wt%, Al2O3 content of 13.71–13.98 wt%, total alkali (Na2O + K2O) content of 8.55–8.02 wt%, respectively. LA-ICP-MS zircon U-Pb dating on three syenogranite samples yield U-Pb ages of 39.6 ± 0.7 Ma, 39.3 ± 0.3 Ma, and 39.1 ± 0.4 Ma, whereas two zircon samples from skarn zones yield U-Pb ages of 39.7 ± 0.4 Ma and 39.5 ± 0.4 Ma, indicating a Middle Eocene mineralization event closely related to the Sarnowsar syenogranite. Zircon grains from a host rhyolite yield a U-Pb isochron age of 40.2 ± 0.4 Ma and previous published age for quartz monzonite is 42.3 ± 0.8 Ma. The Dardvay deposit is developed along the contact of the Sarnowsar syenogranite with dolomitic limestone with distinct exoskarn and endoskarn zones. The endoskarn zone is limited in extent, whereas the exoskarn is more extensive and includes pyroxene and garnet skarn zones close to the Sarnowsar syenogranite and epidote-phlogopite-actinolite skarn distal to it. The composition of clinopyroxenes plot along the diopside-hedenbergite join in the diopside and augite fields. The garnet composition ranges from Ad60Gr38 to Ad40Gr59. Three main paragenetic stages of skarn formation and ore deposition have been recognized at the Dardvay deposit: (1) a prograde stage developed at 380° to >550 °C with a fluid salinity between 16 and 66 wt% NaCl equivalent, (2) a retrograde stage which formed at 175°–325 °C with fluid salinity of 2.3 and 33.4 wt% NaCl equivalent, and (3) a post-ore-stage with quartz veins that developed at 180°–300 °C with salinity range of 8.3 to 17.7 wt% NaCl equivalent. Oxygen isotope analyses were conducted on magnetite from retrograde stage, resulting in a narrow variation of δ18O between 1.2 and 1.6 per mil with δ18O fluid of 10.3 to 10.7 per mil. Fluid inclusion and oxygen isotope analyses suggest that a possible mechanism for magnetite deposition is boiling and dilution with surface (meteoric) fluids, which together with increasing pH and decreasing T explains iron ore formation.

Sustainable Underground Iron Ore Mining in Ukraine with Backfilling Worked-Out Area

The present paper considers aspects of underground iron ore mining in Ukraine, in particular the level of mine production and reserves of basic ore fields. It analyzes and generalizes the practice of using cemented rockfill under difficult mining and hydrogeological conditions of the Pivdenno-Bilozerske high-grade iron ore field. The Belozersky iron ore district is the only one in Ukraine that, without any technological cycle of beneficiation, can provide both domestic and foreign consumers with high-quality raw iron ore as required by world markets. The PJSC Zaporizhzhia iron ore plant extracts iron ore from the Pivdenno-Bilozerske field with an iron content of more than 60% using the low-waste, environmentally friendly technology of backfilling the mined-out area with a hardening mixture. The peculiarities of the technology for steep deposit mining and the main processes of backfilling operations in terms of preparation, transportation, and construction of the backfill mass with its stability assessment are explained in detail in this paper. As a result of using cemented rockfill, rock mass stability is provided, a considerable part of industrial waste is disposed of in the mined-out area, and the earth’s surface subsidence within the area is prevented (in comparison with mining enterprises in other fields).

Geological exploration and industrial development of the Bilozerskyi iron ore region

The latest information on geological and structural position and geological structure of deposits of rich iron ores of the Belozerskyi iron ore district is summarized, and the state of their industrial development is characterized. During the exploitation of the Pivdenno-Bilozirske and Pereverzivske deposits, due to geological study, mining exploration and additional exploration of deep horizons, specialized and feasibility study a significant amount of new geological data has been received. This data allowed to clarify the position, morphology and internal structure of ore bodies, qualitative, physical and mechanical properties of ores and enclosing rocks, hydrogeological, geological, engineering and mining conditions. The article presents the results of the analysis and interpretation of the latest geological information and actual data on the mine development of deposits – modern views on the geological structure of objects, the characteristics of the basic natural conditions and parameters that affect the efficiency of industrial mining of rich iron ores.&#x0D; The state of geological prospecting in the region is very uneven. The most studied are the Pivdenno-Bilozirska and Pereverzivska fields, which are currently being developed.&#x0D; The rich iron ores of these deposits are classified as high quality in both Ukraine and Europe. These ores do not require beneficiation and are suitable for agglomeration and open-hearth process. This circumstance helps to reduce the cost of mining and increase the commercial efficiency. For the mine development of both deposits, a common infrastructure is used – permanent mine openings, mine shafts, support facilities and services. Joint development of the deposits will ensure the long-term stable operation of the plant without reducing the production of rich iron ores.&#x0D; The deposits are characterized by difficult mining and technical operating conditions. The ore deposits are covered by a cover up to 250–350 meters of loose water-saturated sedimentary deposits. The iron ore strata and the host rocks have heterogeneous physical and mechanical properties.&#x0D; Iron ores are mined using a productive level-room system. Empty rooms are filled consolidating stowing. The advanced drainage and continuous groundwater withdrawal from mines are used in the mining process.&#x0D; The progressive system of iron ores mining ensures: preservation of the productivity and quality of aquifers, which are used for municipal water supply; preservation of the earth’s surface from avalanches and landslides in the mining area; stable environmental conditions at the plant area and in the surrounding area; efficiency and completeness of extraction of iron ores from the bowels; the optimal level of economic indicators of the enterprise.

Constraints of nonseismic geophysical data on the deep geological structure of the Benxi iron-ore district, Liaoning, China

Abstract The Benxi area in Liaoning Province is one of the most important iron-ore districts in China. This study uses nonseismic geophysical data (in the form of gravity–magnetic–magnetotelluric data) and based on the section modeling method to model the deep, three-dimensional geological structure of the Benxi area. Based on the modeling results and deep geological structure characteristics, the Benxi area can be divided into three first-order deep geological tectonic units. A close relationship is between tectonic unit and iron-ore concentrations. First, high-quality iron-ore deposits occur within the tectonic boundary and sedimentary boundary zone of the Jiao–Liao–Ji Belt, reflects the protective effect of sedimentary cover on the iron-bearing formation. Second, enriched iron-ore deposits are mainly developed in Mesozoic granitic intrusion zone, reflects the hydrothermal leaching of silicon in host iron-bearing formations during magma intrusion. Thus, the findings of this study have important implications for future prospecting in the Benxi iron-ore district.

Evolution of the Kiruna-type Gol-e-Gohar iron ore district, Sanandaj-Sirjan zone, Iran

The Gol-e-Gohar iron ore district in the Sanandaj-Sirjan zone of south-western Iran comprises six major ore bodies. The largest deposit is Gol-e-Gohar No. 3 (Gohar-Zamin) with about 643 Mt @ 53.1% Fe. The host rocks in this district are Late Neoproterozoic meta-sedimentary rocks (para-gneiss, marble), meta-basalt (ortho-amphibolite), and I-type meta-granite (ortho-gneiss). The district is characterized by potassic-sodic (albite-K-feldspar), phyllic (muscovite) and propylitic (chlorite-calcite-dolomite-magnesite with pyrite) hydrothermal alteration, and massive and brecciated Kiruna-type magnetite ± apatite mineralization. There is also boron (B) metasomatism, manifested as tourmaline blastesis. Gol-e-Gohar magnetite contains Mg, Ca and Si up to the percent range, V and Ti in the 100s ppm level, and low Cr, Co, Ni in the tens of ppm range, typical of skarn or IOCG mineralization. The oxygen isotope composition of magnetite is 4.9 ± 0.7‰ δ18O (n = 9) and the iron isotope composition is 0.49 ± 0.05‰ δ56Fe (n = 17). These data suggest that the magnetite ore formed from a magmatic-hydrothermal (high-T) fluid in equilibrium with a granitic source. The hydrothermal carbonate inclusions in late pyrite have δ11B values of 20.3 ± 2.4‰, indicating the imprint of fluids which interacted with the Early Cambrian marine country rocks of the district, such as limestone and/or evaporites. The Gol-e-Gohar iron ore district shows several similarities to the Bafq iron district, located about 400 km to the north, and seems to be a disrupted member of the Kashmar-Kerman arc.

FELDSPAR RAW MATERIAL IN THE REPUBLIC OF KARELIA AND ITS TECHNOLOGICAL ASSESSMENT

The article provides a brief overview of the state of the mineral resource base of feldspar rocks in the Republic of Karelia. Karelia ranks first in Russia in terms of proven reserves of ceramic pegmatites. The feldspar industry is interested the most in potassium and potassiumsodium feldspar (microcline, microcline-pertite, orthoclase, plagioclases), used mainly for the glass and ceramic industries. Rocks and industrial minerals of the Republic of Karelia are of practical interest as a promising mineral raw material for the manufacture of a wide range of porcelain, faience and other types of ceramic products, including various technical silicate materials. Industrial types of feldspar raw material deposits in Karelia are represented by granite pegmatites, rapakivi granites, alaskanites, nepheline and alkaline syenites, acidic volcanic and subvolcanic formations, and anorthosites. Most of the pegmatite deposits have been actively exploited, and some objects with measured reserves are kept as standby reserves. The mineral and technological features of nontraditional feldspar raw materials were studied the most thoroughly for rapakivi granites (Salma massif), overburden rocks of the Kostomuksha iron ore district, quartz porphyry (Rosa-Lamрi), syenites (Eletyozero and Elisenvaara) and anorthosites (Nizhnee Kotozero). The geological and technological study of various objects bearing feldspar raw materials has shown that the textural and structural characteristics and mineral composition of the rocks are mainly conducive to enrichment. Enrichment using magnetic separation methods yields conditioned microcline, quartz-feldspar, nepheline-feldspar concentrates of varying quality, applicable in the faience, electrical, glass and other industries. The integrated approach to the study of mineral raw materials will enable us to assess the feasibility of processing not only feldspar, but also other types of minerals, including waste dumps of large exhausted deposits. Transport accessibility, moderately harsh climatic conditions, and profound knowledge of the mineral resource base opens up broad prospects for the revival and further development of the mining sector in Karelia.

К вопросу о генезисе месторождений Первого Северного железорудного узла

Research subject . This study was aimed at examining iron ore and ore-bearing strata in the Pervy Severny iron ore district in the Northern part of the Tagil depression. This area features several ore occurrences and three small industrial objects, which have been almost completely exhausted, namely the Pervoe Severnoe, Sukhodoyskoye and Peshchernoe deposits. Materials and methods . The research was based on the analysis of published materials and available production reports on the aforementioned objects, as well as the author’s own field observations and search for similar deposits in literature sources. Results . It has thus far been believed that magnetite ores were formed by contact-metasomatic interaction of Givetian limestone and the intrusions of dolerites and gabbrodiorites. However, the area under study is characterized by very few typical skarns. In addition, the ore bodies here are deposited in accordance with sedimentary and volcanic rocks. Iron ore deposits in the Lan-Dill Region in Germany seem to be the closest analogue, which suggests an alternative (volcanogenic-sedimentary) model of the formation of iron ore deposits in the Pervy Severny iron ore district. Conclusion . The use of the volcanogenic-sedimentary model allows search criteria to be specified, thus significantly increasing prospects of detection of new industrial iron ore deposits.