The territory of Eastern Colombia occupies the western part of the Amazonian Craton and is composed of Precambrian rocks overlain by a sedimentary cover. This region hosts occurrences of endogenous gold mineralization and numerous placer deposits. Collapsed quartz veins and exposures of gold-bearing conglomerates have been identified. The area is considered promising, although it remains virtually unexplored. No medium- or large-scale geological mapping or exploratory drilling has been conducted there. To determine the potential geological and industrial types of gold deposits, an overview of the main deposit types typical for the cratons of South and West Africa and South America is presented. Analysis of cratonic gold endowment indicates that the most probable types for Eastern Colombia are vein and vein-stockwork gold deposits of the quartz–sulfide type. To a lesser extent, stratiform deposits may occur in areas of banded iron formations, and gold-bearing quartz conglomerate bodies are likely to be present at the base of Paleoproterozoic sequences. The gold potential of this territory is considered to be high, as it lies within the gold-bearing metallogenic zones of the Amazonian Craton. The research was supported by Ministry of Education and Science of the Russian Federation, Project No. 075-15-2025-657 «Gold Metallogeny of the Western Colombian Shield and the Development of Digital Predictive Criteria for Concealed Deposits».

This article is devoted to the study of the state of the resource base of iron ore raw materials in Kazakhstan, as well as to the overview of the main geological and industrial types of iron ore deposits in the Republic. During the study, the territorial division of the country’s iron resources into regions was made, the geological features of occurrence were considered and the most promising regions of the country were identified in terms of increasing balance reserves of iron ores. The paper analyzes the geological conditions of localization of ore bodies, structural and tectonic factors of their formation, as well as spatial variability of the qualitative characteristics of ores. In total, 4 main geological and industrial types of iron deposits are identified, which are spatially distributed unevenly. It is noted that significant iron reserves are located in Eastern, Southern and Western Kazakhstan, however, only a few deposits in the region are economically viable for extraction at present. In turn, Central Kazakhstan is considered as one of the key objects of further geological research, since its stratiform deposits of siliceous-carbonate formation are characterized by the presence of complicated geological and structural features, and their potential can make a significant contribution to the replenishment of iron mineral resources. Particular attention is paid to the application of spatial modeling and geostatistical analysis methods, which allow objectifying assessment of reserves, clarifying spatial patterns of mineral substance distribution and increasing reliability of ore content forecast. The obtained results can be used to optimize the strategy of geological exploration and scientific substantiation of the prospects for the development of iron ore deposits in Central Kazakhstan.

We characterize the morphology and arsenic contents of pyrite framboids versus pyrite microcrystals in the Upper Cambrian pyrite stratiform deposit of the Wiśniówka area (south-central Poland). The framboids form isolated spherical or ellipsoidal aggregates varying from 4 to 70 µm across or irregular agglomerations (polyframboidal aggregations) attaining 150 µm in size. Each of them is made up of loosely- or closely-packed, equidimensional, equimorphic, locally multifaceted nano- and microcrystallites (nano- and microglobules) ranging mostly from tens of nanometres to 1.5 µm in diameter. Some framboids show a well-preserved pyritized spider-web-like matrix (organic biofilm) with embedded pyrite crystallites. Unlike pyrite microcrystals, framboids lack mineral inclusions and do not form paragenetic associations with hydrothermal index minerals. Some corroded framboids are completely overgrown by pyrite microcrystals averaging 10–15 µm in diameter. In contrast to pyrite microcrystals enriched in As (0.06–6.33 wt.%), framboid occurrences are distinctly depleted in this metalloid which varies from <0.015 to 0.43 wt.% in recrystallized forms of primary framboids. In pyrite framboids cobalt usually predominates over nickel (with a Co/Ni median ratio of ~3) as opposed to pyrite microcrystals in which cobalt is barely traceable. This study indirectly shows that framboids represent products of microbial activity presumably as low-temperature bacterial sulphate reduction. Their formation may have preceded high-temperature multi-stage influxes of metal(loid)- and H2S-rich hydrothermal fluids into the depositional basin giving rise to crystallization of pyrite microcrystals and their aggregations that vary from tens to hundreds of micrometres in diameter. This pyrite type prevails over framboids in the upper parts of the Podwiśniówka-Wiśniówka Duża profile. The morphological, microtextural and geochemical relationships between pyrite framboids and pyrite microcrystals suggest two different pathways of pyrite formation.

The opening of the Benue Trough as well as the sinistral displacement of the strike slip fault that displaced the whole inlier has been well documented in recent times. Fractures formed are believed to have occurred at the time of the opening of Benue Trough in the Cretaceous. Large sedimentary basins were developed with carbonates and continental platforms that provided ideal conditions for the formation of suits of sandstone hosted, stratiform deposits such as barite, celestine and fluorite of Cretaceous age. Barite is the economic mineral and the shape of the ore bodies is considered massive, the gangue minerals are calcite, traces of celestine and silica. A fluid inclusion and stable isotope analysis (S and O) for barite was conducted. The result shows a melting ice temperature between −24 °C and −15 °C (salinities of 13.6 to 24 wt. % NaCl equiv.) and a homogenization temperature ranged between 60 °C to 155 °C. Isotopic analysis of barite showed δ34SVCDT ranges from +18.1‰ to +19.8‰. Sulfur and Oxygen isotope data for the barite from the study area is consistent with a sulfur source formed during the Cretaceous, which coincides with the age of the Bima Formation. The oxygen isotope analysis showed a range between δ18OVSMOW 9.9‰ and 12.2‰ for the mineral. Fluid inclusion microthermometry and isotopic measurements lead us to conclude that brines from the Upper Benue Basin led to the replacement of evaporite strata (gypsum) by barite and its subsequent deposition within veins and fractures of the Bima Formation.

The sulfide mineralization at Xylagani is hosted in metamorphosed mafic massive and pillow lava. It has an Early–Middle Jurassic age and belongs to the Makri unit, which represents the upper crustal section of the Evros ophiolite in the Circum Rhodope Belt, Northern Greece. The protolith of the host rock is basalt that has a boninitic-to-low-Ti tholeiitic composition and was formed in an intra-oceanic supra-subduction zone within a juvenile forearc-to-volcanic arc setting. The volcanic rocks were subjected to ocean-floor metamorphism at very low-grade prehnite–pumpellyite facies and low-grade greenschist facies at temperatures of up to 360 °C and pressures between 1 and 4 kbar. The mineralization shows typical features of a stratabound–stratiform deposit and occurs as silicified lenses and layers with disseminated and massive sulfides and gold. Based on host rock composition, geotectonic setting, and base metal content, the mineralization at Xylagani is classified as a Cu-rich mafic volcanic-associated deposit, i.e., Cyprus-type VMS (volcanogenic massive sulfide). The mineralization consists of pyrite, chalcopyrite, gold, pyrrhotite, sphalerite, galena, and tennantite-(Zn). It was formed at a subseafloor setting where hydrothermal fluids circulated through the host volcanic rocks, resulting in a pervasive alteration (silicification and chloritization) and the development of a replacement VMS deposit. The very low-to-low-grade orogenic metamorphism and related deformation during the Alpine collision in the Middle Jurassic to Early Cretaceous periods remobilized the mineralization and formed milky quartz veins with rare sulfides, crosscutting the metavolcanic rocks.

The concealed Molai Zn-Pb±(Ag,Ge) stratiform deposit in southeastern Peloponnese is hosted in Triassic intermediate tuffs, ignimbrites and subaerial andesitic flows. The host rocks display trace element signatures of a Supra-Subduction Zone (SSZ) setting. Three ore-forming stages are recognized, with stages I and II related to formation of the epigenetic, stratiform, massive-to-semi-massive ore and a late stage III associated with vein-type mineralization. The O and D isotope geochemistry of gangue chlorite and epidote reveal mixing with fresh meteoric water during the weaning stages of the hydrothermal activity of the late stage II due to uplifting of the hydrothermal system. Sphalerite is the major ore phase, with three different varieties formed during stages I (Sp-I) and II (Sp-II and Sp-III). All sphalerite varieties coexist, depicting gradual change in the chemistry of the ore-forming fluids. Molai ores are characterized by elevated Ag and Ge contents. Tetrahedrite is the major Ag carrier, while among the three sphalerite varieties, early Sp-I comprises the highest Ge contents. The Molai Zn-Pb±(Ag,Ge) deposit is characterized by intermediate features between bimodal felsic massive sulfides and subaerial epithermal systems based on the shallow formation depth, the presence of hydraulic breccias associated with phase separation, the ore formation along high-angle faults, the relatively low ore-forming temperatures below 250 °C obtained from geothermometry, and the absence of the typical structure of bimodal felsic type ores.

Background. New viewpoints on the formation of lead and zinc (Pb and Zn) ore deposits in the People’s Democratic Republic of Algeria are presented.Aim. To develop a geological and structural model for the formation of Pb and Zn ore deposits in Algeria within the paleovolcanic structure.Materials and methods. An analysis of the existing materials on the Pb and Zn deposits of the Algerian Republic was conducted. A structural and genetic scheme for the formation of stratiform Pb and Zn deposits in carbonate rocks was proposed using the example of the sulfate-fumarole activity of Mount Erebus volcano.Results. The stratiform ore deposits of Pb and Zn are of the same age (Oligocene), regardless of the age of the host carbonate rocks.Conclusion. The stratiform deposits of Pb and Zn are the products of a volcanic sulfate-fumarole activity of hydrotherms under the cover of carbonate deposits formed on the slopes of a paleovolcanic structure of the Jurassic-Oligocene age.

Fe–Cu mineralization of Tangal-e-Sefid; a magnetite rich massive sulfide deposit from Kuh-e-Sarhangi district, Central Iran

The mineralization and geochemical features of the Tolparovo ore occurrence are studied to reveal the contribution of diagenetic and epigenetic processes in the formation of copper mineralization in redbed deposits. The methods of electron microscopy, ICP MS, X-ray fluorescence, X-ray phase, atomic absorption, thermogravimetric analyses, and C and O isotopic composition were used. The ore is confined to the fault zone and feathering dolomite–calcite veins, having formed at temperatures of ~330–200 °C and pressures of 0.8–0.2 kbar. Similar to other copper redbed occurrences of the Bashkirian uplift, the Tolparovo copper ore occurrence is confined to basal Neoproterozoic deposits. Siliciclastic and carbonate deposits of this level were accumulated at low paleoequator latitudes in arid climates of continental and coastal–marine environments close to evaporite ones. Rocks of this stratigraphic interval demonstrate increased background concentrations of copper (~2–5 times exceeding the clark), which explains the stratification of redbed copper ore occurrences, indicating a predominantly sedimentary copper source. However, most of the redbed copper ore occurrences of the Bashkirian uplift are located in tectonic zones and are associated with the dikes of the Inzer gabbrodolerite complex. This connects the generation of ore occurrences with the formation of the Southern Urals Arsha Large Igneous Province (707–732 Ma) and the activity of postmagmatic fluids. Magmatic processes were presumably activated due to the collapse of the Rodinia supercontinent. It is shown that copper mineralization in stratiform deposits may result from a joint manifestation of dia- and epigenesis processes.

In situ illite Rb-Sr dating indicates the coevality of Carlin-type gold deposits inside and around the isolated carbonate platform in western Guangxi, China

The Beiwagou Pb-Zn deposit, located in the western part of the Liaodong Peninsula, is a carbonate-hosted stratiform deposit with a Pb + Zn reserve of 0.08 Mt @ 4.14% (Pb + Zn). The orebodies occur as conformable layers and lenses and are strictly controlled by strata (the Paleoproterozoic Gaojiayu and Dashiqiao Formations) and lithology (plagioclase amphibolite and dolomitic marble). Given that previous studies have focused only on the mineralization features and mineralogy of deposits, herein, we report in situ trace element analyses of pyrite using LA-ICP-MS, together with in situ sulfur isotopes of pyrite, to constrain the composition, substitution mechanisms, source of sulfur, and sulfate reduction pathways of pyrite in the Beiwagou deposit. Based on pyrite morphology, texture, and chemistry, four pyrite types were identified: subhedral, porous-to-massive pyrite (Py1) related to chalcopyrite; subhedral, porous crushed pyrite (Py2) associated with fine-grained sphalerite; rounded and porous pyrite (Py3) related to the Zn-rich part of the laminated ore; and anhedral, porous-to-massive pyrite (Py4) associated with pyrrhotite, arsenopyrite, sphalerite, and galena. Py1 is characterized by high As, Ag, Cd, In, Au, Cu, and Zn concentrations and low Te, Bi, and Mo concentrations, whereas Py2 has high concentrations of Co and Ni and low concentrations of other trace elements, such as Cu, Zn, Bi, and Te. Py3 is characterized by elevated As concentrations, low Co, Ni, In, W, Te, and Tl concentrations, and varying Pb concentrations, whereas Py4 has low Ag, Cd, In, Zn, Cu, and Mn concentrations and varying W, Co, Ni, Pb, Sb, and As concentrations. Significant correlations between some elements in each pyrite type suggest substitution mechanisms, such as (Zn2+ + Cu2+ + Mn2+ + Cd2+) ↔ 2Fe2+, Ag+ + (Sb)3+ ↔ 2Fe2+, and (Te+ + Ag+) + Sb3+ ↔ 2Fe2+, and the existence of a negative correlation between Co and Ni implies competition between both elements. The strongly positive δ34S values (12.11‰–23.54‰) are similar to that of seawater sulfates and likely result from thermochemical sulfate reduction (TSR). In conclusion, the Beiwagou Pb-Zn deposit is a typical SEDEX deposit and mineralization likely occurred during diagenesis.

The genesis of stratiform deposits of lead and barite in sedimentary rocks is of great interest from the point of view of replenishing reserves of polymetallic ores. The aim of the work is to establish the regularity of the hydrogenic formation of ores in limestones, taking into account the influence of the nanosurface of pores and cracks based on a mathematical model of the movement and characteristics of ore-bearing solutions in the pores. The thicknesses of the surface layer of limestones and minerals included in the ore-containing strata and sulfide minerals are calculated. The results indicate that they are nanostructures with special physical properties different from the rest of the substance, which is confirmed by the regularity of the formation of a heavy sulfur isotope in ores of various textural types. The influence of hydrotherms with different densities, kinematic viscosity, and velocity on the intensity of mineralization formation in cracks and pores of limestone, as well as the occurrence of new feathering cracks around the fractures of dismemberment, is estimated. The dependence of the hydrothermal flow density on the diffusion of the liquid is established. The equation of kinematic viscosity is derived from the pressure in the solution flow, the velocity of its movement, the mass of particles of ore-forming elements, and sulfur isotopes under thermodynamic conditions of determined Gibbs energies. The relationship of the viscosity of the solution with the surface tension of the nanolayer of limestone particles in cracks and pores is shown, indicating that the greater this energy, the greater the velocity of movement of ore-forming solutions, the fewer branches of newly formed cracks around the dissection crack. The mathematical model is applicable for the numerical analysis of the regularity of mineralization in cracks, taking into account the influence of the nanostructural layer of cracks and pores of limestone in the thermodynamic conditions of the occurrence of an ore-bearing formation.

Paleozoic VMS-type stratiform mineralization overprinted by Mesozoic vein-type mineralization in the Yushui copper deposit, eastern Guangdong, South China

Studies of lithotectonic formations within the Keivy domain of the NE Baltic Shield have shown that the domain was tectonically overlapped by adjacent microcontinents during regional collision processes in the Late Archean. As a consequence, the continental crust of the Keivy domain was submerged, relative to other blocks of the continental crust, and the described domain acquired the features of a classical median massif. Surrounded on all sides by collision systems, the Keivy median massif entered the cratonization regime. This led to intensive processes of denudation of the surrounding domains of the crust and the accumulation of a thick sedimentary cover on the surface. The described processes occurred during the formation of the first supercontinent (Monogea) in the history of the Earth and the manifestation of the Early Precambrian Huronian glaciation, which left its traces on most domains of the Earth’s continental crust. Thus, the processes of peneplain formation within the Keivy massif occurred under the cold weather conditions, high volcanic activity in the peripheral zones, and sedimentary cover saturation with the products of the physical and chemical mineral transformation of tonalite–trondhjemite and greenstone rock assemblages. The unique combination of certain geodynamic and climatic cycles on the Baltic Shield in the Late Archean led to the accumulation of extensive stratiform deposits of alumina raw materials within the Keivy median massif.

Earth observation approach for targeting stratiform deposit of manganese in central India

The Zeida Pb–Zn, Ba stratiform deposit is part of the Upper Moulouya mining district at the junction of the Middle Atlas and the Central High Atlas. This paper aims to identify the geodynamic–tectonic setting of the emplacement of this ore deposit, using a multidisciplinary approach combining field and laboratory work associated with paleostress analysis. The lithostratigraphic and gitological studies enable descriptions of Pb–Zn, Ba mineralization impregnated in the Upper Triassic arkose beds unconformably overlying the Variscan biotite-bearing granites. The mineralogical study allowed determination of a primary paragenesis mainly composed of galena + barite with lesser copper and zinc sulfides (chalcopyrite, covellite and sphalerite). The supergene paragenesis is represented by galena oxidation products associated with iron and manganese oxides. The structural analysis revealed a complex fracture network controlling ore deposition with three main directional systems: (i) NNE–SSW to NE–SW system; (ii) ENE–WSW to E–W system, and (iii) WNW–ESE system. The reconstruction of the paleostress fields synchronous with the mineralization emplacement allowed to conclude that these fractures were developed under an extensional tectonic regime linked to the Atlasic rifting, and characterized by horizontal NW–SE-trending σ3 axis, and vertical σ1 axis. The relative age of the emplacement of the Zeida ore deposit is assigned to the Triassic–Liassic period during a regional metallogenic event related to the opening of the Central Atlantic and the Alpine Tethys in the framework of the breakup of the Pangea supercontinent.

Two pulses of metallogenesis of the Liwu Stratiform-like Cu-Rich polymetallic Deposit, western China: Evidences from Geology, Re-Os dating and lead isotope

Purpose. Studying the features of the Zhailma volcano-tectonic depression formation, as well as the principles and factors affecting this structure’s ore formation. Methodology. Analysis of the results of isotope dating of rocks, critical analysis of literature and fund materials, analysis of the genesis and specificity of the Zhailma structure mineralization, features of the volcano-tectonic depression formation. Findings. The Zhailma graben syncline formation is associated with subsidence after ejections of significant masses of acidic magmatic material from stratovolcanoes concentrated on the Zhailma structure. The initiation and development of the graben-syncline is closely related to the processes of tectonomagmatic evolution of the Devonian volcano-plutonic belt. Originality. The search model for stratiform deposits of the Atasu type has been revised, taking into account the original theory of the volcano-tectonic origin of the structure, formed at the final stages of the formation and development of the Devonian volcano-plutonic belt. The genesis of the Atasu-type deposits is considered as sedimentary-hydrothermal one, associated with the processes of diagenesis and catagenesis occurring within sedimentary basins. The presence of two large volcanoes on the northern side of the caldera structure was substantiated: North Zhairem and Ustanynzhal. Practical value. It is recommended to carry out predictive metallogenic and, accordingly, prospecting work for deposits of the Atasu type within the graben-synclines of the Sarysu-Teniz segment of the Devonian volcanic belt, where such deposits of ferromanganese ores as Tur, Bogach and Karaadyr are already being developed in the Aydagarly graben-syncline.

This scientific station provides information about the geological and economic assessment of the Karashoshak deposit. The Karashoshak deposit is part of the Zhilandinsky group of stratiform deposits of copper sandstones. The geological structure of the site has been studied. The results of the studies made on the assessment of the industrial value of the Karashoshak deposit are shown. The main research methods for testing the rehearsal are considered. An analysis of the tested probes was carried out and a dependency graph was drawn up. The methodology of the projects is compiled in compatibility with the geological task, according to the target instruction for the work, as well as taking into account the results of the work carried out so far and at the design stage of exploration

The Bouarfa Iron and Manganese Deposits are contained in the Sinemurian carbonate formations in the eastern High Atlas. It is a large deposit which has allowed the exploitation of more than 1.5 million tons of manganese and which still contains millions of tons of reserves. The mapping carried out shows the extension of the mineralization with oxides and hydroxides of Mn and Fe. The definition of types of mineralization shows that they are essentially stratiform deposits with some bodies and veins in the fault zones. The result of the mineralogical identification and geochemical analyses shows that it is a sedimentary deposit resulting from at least two mineralizing events with a high Fe-Mn content during the installation of the Sinemurian shallow carbonate platform. This is an environment of rapid oxidation and relatively sufficient sulphide inputs under redox conditions.