Lead-zinc Mineralization Research Articles

Diagenetic and hydrothermal events revealed by an Ediacaran dolomite breccia from the Araras-Alto Paraguai basin, southern Amazon Craton

The establishment of extensive carbonate platforms characterized the Ediacaran period during CaCO3 oversaturation events and the exceptional creation of accommodation space associated with the aftermath of the Marinoan glaciation (∼635 Ma). Carbonate deposits in the Araras Group record the early Ediacaran period, stage 1, in the Amazon Craton. The Serra do Quilombo Formation is an intermediate unit characterized by heavily fractured and faulted dolomites, as well as the presence of dolomite-cemented breccias (CB) overlying thick limestone packages associated with diagenetic and hydrothermal modifications. These features are commonly attributed to structurally controlled hydrothermal dolomitization (HTD) and are of significant economic importance as hydrocarbon reservoirs and Mississippi Valley-type (MVT) lead-zinc mineralization hosts. This study aims to unravel the origin of cemented breccias and the diagenetic/burial processes within the unit, focusing on dolomitization processes. Dolomite samples were analyzed using petrographic, scanning electron microscopy, microprobe, micro-Raman, cathodoluminescence, and isotopic analyses (δ13C, δ18O, 87Sr/86Sr) to unravel their burial history. CBs are sub-vertical to sub-horizontal bodies with complex geometries, generally cutting bedding at high angles, indicating hydrofracturing processes related to vertical flows of hydrothermal fluids (hydraulic breccia) and present the typical cockade texture of expansion breccias in dilatational faults. The substitutive matrix RD1 is the main constituent of the Serra Quilombo Formation, its low correlation between δ13C and δ18O (R2 = 0.009), the well-preserved fabric, and the similarity with the isotopic values (C and Sr) documented for Ediacaran carbonates, suggest that the syndepositional dolomitization. The first generation of dolomite cement (DC1) and the last phase of dolomitic cementation (saddle dolomite - SD) occur, filling pores, CBs, and fractures. The cockade texture of the breccias evidences a low precipitation rate or a pause in precipitation between DC1 and SD. Concurrently, DC1 has isotopic signals of δ18O = −4.34 ± 1.32‰ (n = 18) and 87Sr/86Sr = 0.708831 (n = 2), while SD has values of δ18O = −9.57 ± 2.51‰ (n = 15) and 87Sr/86Sr = 0.711464 (n = 3). The large isotopic fractionation between DC1 and SD suggests different dolomitizing fluids. This relationship shows an increase in 87Sr in the fluid as the temperature increases; moreover, the enrichment in 87Sr of the fluid is explained by the interaction of this fluid with rocks from the crystalline basement. Thus, the main conduit for the ascent of this radiogenic fluid would be faults with deep roots spatially close to tectonically active zones. Lastly, the presence of tectonic stylolites cutting cemented breccias and rotated zebra-like strata-bound structures suggests that brecciation occurred before the installation of fragile post-Ordovician transtensional structures, preceding the establishment of Paleozoic Basins on the South American Platform.

Variability of lead-zinc sulfide ore slurry rheological properties and its influence on flotation conditions

We investigated how the rheological characteristics of a flotation slurry change in response to variations in mineral species, slurry concentration, and particle size; slurry pH; and trap and rheological control reagent concentrations using slurries containing galena, sphalerite, quartz, and kaolinite. The results indicate that reducing particle size and increasing slurry concentration leads to varying degrees of increase in apparent viscosity and yield stress. At the same particle size, the slurry exhibits the following order of apparent viscosity and yield stress: kaolinite > galena > sphalerite > quartz. In addition, as the slurry’s apparent viscosity and yield stress increase, the rheology decreases, creating progressively unfavorable conditions for the flotation of lead, zinc, and other target minerals. Furthermore, changes in pH have no significant effect on the slurry’s rheology when the slurry is comprised of vein minerals. Moreover, galena and sphalerite depict particle agglomeration in the slurry. Ultimately, the addition of sodium silicate as a rheological control reagent substantially enhances the slurry’s rheological properties. This results in a system where problematic minerals like kaolinite are more effectively dispersed, thereby promoting efficient lead-zinc mineral flotation. Regarding the flotation of lead sulfide and zinc minerals, the addition of kaolinite raises the apparent viscosity of the mixed slurry, hindering the flotation of the target minerals. Conversely, quartz lowers the apparent viscosity aiding the flotation separation process. Understanding the relationship between flotation conditions and the pulp’s rheological properties can provide valuable guidance for subsequent flotation tests.

Porosity–permeability characteristics and mineralization–alteration zones of the Maoping germanium-rich lead–zinc deposit in SW China

The Maoping superlarge germanium-rich lead–zinc deposit is a typical nonmagmatic hydrothermal deposit that is structurally controlled in the Sichuan–Yunnan–Guizhou lead–zinc polymetallic metallogenic area. The orebodies are distributed in several formations. This paper is based on large-scale alteration mapping combined with porosity and permeability measurements. We delineated the mineralization–alteration zones of different ore-bearing formations, explored the geological significance of porosity and permeability, and proposed prospecting directions. The research results indicate that during the mineralization period, the ore-forming metal fluids migrated from the deep part of the SSW region to the shallow part of the NNE region along the ore-guiding structure (Maoping Fault). Through the ore distribution structure, depressurization boiling occurred in the open space of the NE-trending interlayered sinistral compressive–torsional faults in several ore-bearing formations, resulting in fluid precipitation and the formation of different brecciated hot-melt dolomite lead–zinc mineralization zones. From the orebody to the wallrock, the C2w Formation and D3zg Formation are divided into four different mineralization–alteration zones. Tectonic activity affects the properties, migration, and precipitation of fluids, thereby controlling the alteration characteristics generated during fluid migration and thus changing the porosity and permeability. The porosity and permeability of strata on the NW flank of the anticline are greater than those of strata on the SE flank. On the NW flank, the greater the degree of mineralization–alteration is, the greater the porosity and permeability are, and the porosity of the orebody is lower than that during dolomitization. Finally, we believe that the NW flank of the anticline is an important area for prospecting. The pyrite + striped altered dolomite zone (Zones II–III) in the C2w limestone and the pyrite + strong dolomite zone (Zones II–III) in the D3zg dolomite are important prospecting indicators.

Decoupling of Cu and Zn in sediment-hosted base metal deposits: Evidence from LA-ICP-MS analyses of fluid inclusions and trace elements in minerals at Baiyangping, China

Copper and lead–zinc mineralization in basinal rocks worldwide commonly shows distinct spatiotemporal zonation. The Baiyangping deposit in the Lanping Basin, southwest China, is a large sediment-hosted polymetallic deposit that shows clear and pronounced zoning of Cu versus Pb-Zn mineralization. Here, we analyzed trace elements in pyrite and sphalerite and fluid inclusions in sphalerite, celestine, quartz, and dolomite to seek insights into the origins of the ore-forming fluids and the processes that govern the separation of Cu- from Zn-rich ores. We show that while the later Zn-rich mineralization is characterized by fluid inclusions showing typical hallmarks of basinal brine composition (low homogenization temperature < 230 °C, high salinity > 20 wt% NaCl eq., dominated by Na-K-Ca-Mg chlorides), the earlier Cu-rich mineralization shows markedly distinct composition that more closely resembles deeply-circulated water that has equilibrated with crystalline basement rocks (higher homogenization temperature of 210–280 °C, variable but lower salinity of ∼ 5–15 wt% NaCl, dominated by Na-K-Li chlorides). Pyrites formed during the earlier Cu-rich stage show elevated Cu, Co, Sb and Zn, while pyrites formed during the later Pb-Zn stage are more enriched in As, Pb and Mn. We interpret that the earlier-formed Cu-rich ores were deposited by deeply sourced fluids that ascended along basement-penetrating reverse faults, whereas the later Zn-rich ores were formed by subsequent circulation of fluid from within the basin, whose flux was promoted by shallower strike-slip faults. Hence, the two ore types reflect discrete pulses of chemically distinct hydrothermal fluids. We suggest that the evolving structural controls and fluid pathways during prolonged ore formation allowed sequential pulses of fluids that had acquired different metal budgets by equilibration with different sources. We suggest that this type of two-step process may be more common in sediment-hosted base metal deposits than single-fluid cooling sequential order of precipitation.

Geological setting, lead-zinc mineralization characteristics and its potential prospects in the Na Bop - Pu Sap area, Cho Don, Northeastern Vietnam

The Lo Gam structural zone is recognized as a crucial area for the occurrence of lead-zinc deposits in Northeast Vietnam, encompassing the distinguished territories of Cho Dien and Cho Don. Specifically, within the Cho Don area, the Na Bop-Pu Sap area emerges as particularly noteworthy owing to the considerable scale and quality of its lead-zinc ore deposits. In order to comprehensively investigate the geological attributes and lead-zinc mineralization phenomena prevalent in Na Bop-Pu Sap, a suite of analytical techniques including petrographic analyses, mineralogical examinations, scanning electron microscopy (SEM), and ICP-MS were employed. Furthermore, stable isotope investigations and single mineral sphalerite analyses were conducted to assess the origin of metal constituents and the physicochemical conditions conducive to ore genesis. The Na Bop-Pu Sap area is under the influence of the NW-SE fault system, with the ore structure predominantly manifesting as bands and veins aligned parallel to the foliations of hosted rock. This configuration suggests a close association between the formation of lead-zinc ore and the foliation processes occurring within the shear zones. The assemblage of ore minerals within the region primarily comprises galena, sphalerite, pyrite, pyrrhotite, and arsenopyrite. Integration of S and Pb isotopic analyses alongside single mineral sphalerite assessments reveals that the ore-forming solutions emanate from both magmatic activity and sedimentary sources, with lead-zinc ore deposition occurring at temperatures ranging from low to medium. Projections suggest that the Na Bop-Pu Sap mining area may exhibit relative degrees of erosion extending to depths of approximately 600 meters below the existing terrain surface. This comprehensive examination of the ore characteristics in the Na Bop-Pu Sap mine area yields invaluable insights, thereby advancing our understanding of the potential for deep-seated lead-zinc mineral resources within the Northeastern Vietnam.

Geology and Geochemistry of Lead-Zinc Mineralization in Ameri, Southeastern Nigeria

The Geology and geochemistry of Lead-Zinc Mineralization has been carried out in parts of Ameri, South eastern Nigeria. The study area was mapped and lithological units and structural features were identified and studied. A total of twenty-seven (27) samples from five (5) wells (AMR 014, AMR 036, AMR 038, AMR 048, and AMR 049) of the study area were collected, prepared and subjected to geochemical analysis for both major and trace elements using EDX3600B X-ray fluorescence spectrometer. The analytical data were statistically computed using principal component factor analysis PCFA, statical package for social science SPSS, descriptive statistics DS, correlation matrix CM and were also adopted for various geochemical plots using Excel Microsoft office, geochemical data kid GCD Kid and Suffer software for geological map digitization, to determine the geochemical characteristics of the Lead-Zinc ore, the host rock and the environment of formation. The geology of the study area is strategically part of the Lower Benue Trough of Nigeria, it is made up of shale intruded by several small to medium sized mesocratic – melanocratic, phaneritic intrusives which are alkaline in nature with a slight variation in their mineralogical and textural characteristics. Structurally, the fractured zones or veins marked along the Enyigba and Ameka lodes could also be responsible for the mineralization of the Ameri Lead-Zinc. The Lead-Zinc in Ameri is associated with other gangue minerals such as marcasite, pyrite, quartz veins, carbonate materials, chalcopyrite, siderites, sphalerites and it shows that the Lead-Zinc mineralization in the study area is hosted by shales, which are probably parts of the slightly deformed cretaceous sedimentary rocks made up of essentially Albian shales and subordinate siltstones. Values of lead within this shear zone ranges from 0.06% - 64.58%, 0.02% - 64.35%, 0.01% –0.14%, 0.03% - 0.11% for AMR 036, AMR 038, AMR 048, AMR 049 respectively, while Zn ranges in value from; 0.09% - 53.98%, 0.08% - 1.11%, 0.19% - 58.64%, 0.08% - 56.11%. The value of lead and zinc within the hanging wall are 0.06% and 0.08%, 0.03% and 0.06%, 0.04% and 0.12%, 0.04% and 0.13% for AMR 036, AMR 038, AMR 048, AMR 049 respectively. Paleo-redox condition of Low Cu/Zn ratios from 0.001-0324, 0.001 – 0.307, 0.075-0.424, 0.001-0.309 and 0.001-0.321 for AMR 014, AMR 036, AMR 038, AMR 048, AMR 049 indicate more oxidizing conditions. This is confirmed by the Ni/Co ratio of 0.00-58.50, 0.00- 43.625, 0.00- 35.333, 0.00-1.704, 0.211- 1.472 for AMR 014, AMR 036, AMR 038, AMR 048, AMR 049 respectively mostly below the ratio indicated to be oxidic with little anoxic environmental affinity. The total Alkalis versus Silica plot from the intrusaive revealed their basic to ultrabasic nature, as the bivariate plots of the analyzed samples shows positive and /or strong relationship between the trace elements in the Ameri lodes and their respective certified concentration values which is also an indicator that the elements are probably from same hydrothermal source with the Lead-Zinc of the study area.

Features of the Geological Structure and Polymetallic Mineralization of the Uspensky (Central Kazakhstan) and Dalnegorsky (Far East) Ore Districts

Polymetallic deposits of lead and zinc are of great importance in the economy of the developed countries of the world. Kazakhstan is among the world leading countries in terms of reserves and production of lead and zinc. There are large ore regions with polymetallic mineralization; these are the deposits of the Atasu and Uspensky ore regions in Central Kazakhstan. The former are genetically related to the final (taphrogenic) phase of the development of the large orogenic structure in the Central Kazakhstan (the Devonian volcano-plutonic belt), with the period of Late Frasnian-Famenian-Early Carboniferous formations of thick carbonate and carbonate-terrigenous sediments, including significant reserves of stratiform lead-zinc ores. Polymetallic mineralization of the Uspensky zone is singled out as an independent genetic Alaygyr type, and the tectonic nature of the ore-bearing Uspensky zone, as well as mineralization of this type, is still the subject of constant discussions. In this regard, the comparative characteristics of the Dalnegorsky and Uspensky ore regions, which have certain similarities in geodynamics, magmatism and metallogeny, are of great importance not only for solving the issues of the general patterns of formation, factors and criteria for controlling lead-zinc mineralization but also for an objective assessment of the ore potential of these and similar areas with polymetallic mineralization. Research methods: comparative analysis of the results of petrographic, chemical and mineralogical studies of ores enclosing near-ore metasomatically altered rocks and intrusions of different age and composition.

Criteria and signs of lead-zinc mineralization within the Maityubinsky anticlinorium

The paper presents research work to establish genetic characteristics of lead-zinc mineralization in the Ulytau-Arganatinsky structural-facial zone. Expanding the mineral resource base of Central Kazakhstan is one of the most urgent tasks because selecting the criteria and characteristics determines the aspects of prospecting and exploration work, as well as their results, which is the goal. In this regard, the following tasks are being solved: identifying the geodynamic position, the genesis of mineralization, the connection of the rock's physical properties with geophysical anomalies, as well as displaying tectonic disturbances and deep faults in them; establishing the connection of mineralization with the carbonaceous-terrigenous package of deposits of the lower subformation of the Zhilandinsky formation of the Upper Proterozoic; structural confinement of mineralization to large faults along which there was a movement of plutogenic hydrothermal solutions forming mineralization, and areas of metamorphically altered rocks, as well as aureole zones of Pb, Zn, Ag, Cd graphite quartz, phyllites and the other shales of the Zhilandysay and Kumolinsky formations, dispersion zones of Cu, Mo, V, Ag, Sc, Ye and REE near the Kyzymchek fault. The established criteria and features can be used when organizing geological exploration work in the search for polymetallic mineralization within the Maityubinsky anticlinorium in zones adjacent to deep mantle faults.

Contribution of Landsat 8 OLI imagery to mapping of lithological series and lineaments: implications for Pb-Zn mineralization exploration in the Boudahar Massif, Eastern High Atlas, Morocco

The Boudahar massif is located in the southern part of the eastern belt of the Moroccan High Atlas and it corresponds to a reef mass of about ten kilometers in length. Jbel Boudahar is a district of lead-zinc-barite mineralization, known by a strong artisanal exploitation of its ores. This district is characterized by its topography with a contrast of altitude and an arid environment, which makes the information acquired more valuable. The processing of Landsat 8 OLI data allowed us to extract a lithological and structural map, aiming to make correlations to understand the distribution of lead-zinc mineralization. To this end, several tests were carried out, including the composition of color, principal component analysis and band ratio transformation. The location of the main deposits at Jbel Boudhar coincides well with the lineament derived from band 1 of principal component analysis and with the dolomitic pliensbachian formations mapped by MNF and BR from Landsat Oli8. A remote sensing geological prospecting model has been established for the Jbel Boudhar lead-zinc deposits, providing a basis for future prospecting of new deposits in a similar context.

Occurrence Characteristics of Lead–Zinc Mine and Low-Flying Aeromagnetic Prospecting in a Forested Region of Yichun City

Understanding the characteristics of lead–zinc mine occurrences and mastering effective investigative techniques are paramount in modern ore prospecting. This research focuses on the forested region of Yichun city in China, with a specific emphasis on the strategic mineral resource of a lead–zinc mine. The study examines the distribution patterns of this mineral and employs advanced aeromagnetic exploration methods. Firstly, we analyzed the geological structure and features of the region by leveraging the latest high-precision aeromagnetic data collected using dynamic delta wing technology. This analysis was complemented by an assessment of the geological conditions of the research area, existing lead–zinc deposits, ground magnetic surveys, and verification studies. With the goal of establishing a meaningful correlation between aeromagnetic anomalies and lead–zinc deposits, we employed various potential field conversion techniques, including the reduction to the pole, vertical derivatives, upward continuation, and residual anomaly analysis techniques. Secondly, we investigated the metallogenic sites within this region and provided a comprehensive summary of the metallogenic circumstances and characteristics related to aeromagnetic prospecting. Thirdly, we employed human–computer interaction fitting inversion techniques to predict the potential for lead–zinc mine prospecting in areas exhibiting aeromagnetic anomalies. The study underscores the significance of high-amplitude and large-scale aeromagnetic anomalies in the study area. Furthermore, we examined the interplay between intrusive rocks, strata, and structural elements within the region to identify favorable conditions for lead–zinc mineralization. As a result of our analysis and discussions, a location was predicted where a lead–zinc mine may exist. The research methodology outlined in this article provides valuable insights for future lead–zinc mine exploration efforts in areas characterized by similar geological conditions.

Heavy metal content and microbial characteristics of soil plant system in Dabaoshan mining area, Guangdong Province.

The disordered mining of Dabaoshan lead-zinc mineral resources in Shaoguan has brought serious harm to the regional ecological environment. In order to investigate the heavy metal pollution status and microbial characteristics of soil plant system in mining area, The distribution of heavy metals in the soil, the activity of soil microorganisms and the accumulation characteristics of heavy metals in the dominant plant Miscanthus floridulus were studied. The results indicated that metal element contents of Miscanthus floridulus in sequence were: Zn>Pb>Cu> Cd. This study demonstrated that the elemental content of the Miscanthus floridulus plant showed Zn>Pb>Cu>Cd, with Zn being the most significantly correlated with soil elements, followed by Pb. Compared with the control group, the Miscanthus floridulus-soil system possessed obviously different soil microbial features: intensiver in microbial basal respiration strength, and higher microbial eco-physiological parameters Cmic/Corg and qCO2, but lower in soil microbial biomass. The results showed the soil enzymatic activities decreased significantly with increase of contamination of heavy metals, especially dehydrogenase and urease activities. With the increase of the content of heavy metals in the mining area soil, the intensity of soil biochemical action in the mining area (Q1, Q2) soil decreased significantly, and the biochemical action showed a significant negative correlation with the content of heavy metals in the soil. Compared with the non mining area (Q8) soil, the intensity of soil ammonification, nitrification, N fixation and cellulose decomposition decreased by 43.2%~71.1%, 70.1%~92.1%, 58.7%~87.8% and 55.3%~79.8% respectively. The decrease of soil microbial activity weakened the circulation rate and energy flow of C and N nutrients in the soil of the mining area.

Application of X-ray computed tomography scanning in describing partition curves of dense medium cyclones

The partition curve is an important tool to evaluate the separation performance of mineral separators like dense medium cyclones (DMCs). This curve is constructed by float-and-sink (FaS) analysis which involves the use of heavy liquids and suspensions. This traditional technique is hazardous to the environment, laborious, and time-consuming. Here, a new technique using X-ray computed tomography (XCT) scanning was successfully developed and applied for describing the partition curve of a DMC at an Australia-based lead–zinc mineral processing plant. The DMC feed, concentrate and reject streams were sampled and sieved into several size classes. The chemical assays and averaged densities according to each class were analysed by X-ray fluorescence spectrometry and gas pycnometry, respectively. The partition behaviour was investigated by XCT analysis. A model was proposed to determine the mass yield value – an important parameter to define partition curves – by mass balance and reconciliation, which is generally unknown during the sampling of continuous separation processes. From the reconstructed XCT images, we obtained detailed information on individual particles such as volume, surface area, mass, and density. Cumulative mass distribution curves and partition curves of the DMC for different size classes were then constructed and agreed with the FaS analysis. Using the XCT technology can help overcome the issues of the traditional FaS analysis. Moreover, this technology would allow for evaluating DMC separation efficiency with continuous, online, and real-time monitoring and control.

Environmental contamination characteristics of heavy metals from abandoned lead–zinc mine tailings in China

China holds large-scale lead–zinc mineral resources; however, mining activities often cause severe contamination by heavy metals. This study systemically assessed contamination by eight heavy metals (Cu, Zn, Cd, Pb, Cr, Hg, Ni, and As) in mine tailings, soil, and groundwater from 27 contaminated sites across China. Regarding mine tailings, 1% of the mine tailing samples were hazardous waste and 20% were class II non-hazardous waste. Regarding soil, Zn and Pb showed the highest mean concentrations, at 5574.67 mg/kg and 2034.88 mg/kg, respectively. The indexes of geo-accumulation (Igeo) of eight heavy metals ranged from −3.62 to 7.67, while Zn, Pb, and Cd showed the highest environmental risk levels as the priority pollutants. The contamination levels of these heavy metals in groundwater were generally in the order of Zn&amp;gt;As&amp;gt;Pb&amp;gt;Ni&amp;gt;Cd&amp;gt;Cu&amp;gt;Hg&amp;gt;Cr. In this study, 20% of the soil and 10% of the groundwater samples exceeded the corresponding quality limits. The content of heavy metals in soil, groundwater, and mine tailing were positively correlated, demonstrating the main pollution source and transport paths. The pollution levels of heavy metals in soil and groundwater were listed in the foremost and moderate positions compared with similar sites from other countries, respectively. These results may help determine the pollution levels of lead–zinc mining regions and direct the remediation activities of target sites to support the environmental management of abandoned mining and tailing waste in China.

EVALUATION OF DEPTH TO BASEMENT, HEAT FLOW, AND LEAD-ZINC MINERALIZATION FROM ANALYSIS OF AEROMAGNETIC DATA IN SOME PARTS OF SOUTHERN BENUE TROUGH

The techniques of aeromagnetic data analysis were employed to elucidate depth to magnetic basement sources, lead-zinc (pb-zn) mineralisation and heat flow in parts of Southern Benue Trough. The study area covers an area extent of about 18,150 sq. Km, latitude 05 0 30’N - 06 0 30’N and longitude 007 0 30’E - 009 0 00’E. The digital aeromagnetic data consisting of Total Magnetic Intensity with geospatial attributes covering six (6) sheets 302 (Nkalagu), 303 (Abakaliki), 304 (Dangha), 313 (Afikpo), 314 (Ugep) and 315 (Ikom) were used in this study. Several magnetic digital filtering methods such as reduce to pole, low/high pass, etc were applied on the data before analysis for lineaments, mineralisation, and depth to magnetic sources. Zones of broad magnetic anomalies were found in the north eastern and south eastern part of the study area like Otam-Izekwe, Enyigba, Uburu, Abakaliki, Ndieze Izzi, Isiagu, Obubra, Oturekpe, Mkpani, Idomi, Enona, Ugep, etc. Depth estimates to the magnetic basement sources from spectral analysis range from 0.65km to 1.155 km, while depth estimate from source parameter imaging (SPI) stretches from 0.679km to 7.723km. The north western part of the study area is the deepest. Pb-zn mineralization within the study area is found to be structurally controlled trending in NE-SW and NW – SE directions. The heat flow values range from 0.65 – 1.95Wm -2 , pb-zn mineralization is within 0.9 – 1.4Wm -2 and Curie point depth range from 0.75km to 2.1km. Keywords: Depth to basement, Heat flow, Lead-Zinc, Mineralization, Aeromagnetic data DOI: 10.7176/JEES/13-2-06 Publication date: March 31 st 2023

Genetic relationship between the Maoping Pb-Zn deposit and paleo-oil reservoir in the northern Yunnan-Guizhou depression: Evidence from bitumen trace elements and the in-situ sulfur isotope of pyrite associated with bitumen

The coexistence of numerous Mississippi Valley-type (MVT) Pb-Zn deposits and oil/gas reservoirs in the world demonstrates that a close genetic link between them. The northern Yunnan–Guizhou depression (NYGD) is a tectonic unit containing Pb–Zn deposits, paleo-oil reservoirs and shale gas. However, previous studies on the relationship between hydrocarbon accumulation and Pb–Zn mineralization have been ignored. The Maoping Pb–Zn deposit is a large-sized MVT deposit in the NYGD where a large amount of solid bitumen (i.e., a paleo-oil reservoir) occurs, and it is an ideal area to study the relationship between hydrocarbon accumulation and lead–zinc mineralization. In this paper, the bitumen and pyrite associated with bitumen from the Xujiazhai (discovered in this study) and Xiaocaoba paleo-oil reservoirs and the Maoping Pb–Zn deposit are researched. Geological observation has revealed that bitumen occurs in dissolution pores, fractures and intercrystalline pores in dolomite of the Upper Devonian and Carboniferous. The bitumen from Xujiazhai, Maoping and Xiaocaoba with high and similar Raman equivalent reflectance (RmcRo%) indicates they are in over-mature level and may be derived from the cracking of early-accumulated crude oils. The bitumen in the Xujiazhai paleo-oil reservoir and Maoping deposit has an abundant Pb and Zn content, indicating petroleum liquids may act as the transporting agents of metallogenic metal elements, carrying them to sites where mineralization may take place. The source rocks may have provided not only the oil for paleo-oil/gas reservoirs, but also a portion of ore metals for the Pb-Zn mineralization. The bacterial sulfate reduction (BSR) and thermochemical sulfate reduction (TSR) processes were recorded by the pyrite in the paleo-oil reservoir, which was consistent with the mechanism of reduced sulfur formation in the Maoping deposit. In addition, the large negative (−27.7‰ to −5.7‰) and positive (.9‰ to 19.2‰) δ34S values of the pyrite associated with the bitumen in the paleo-oil reservoir were similar to those of the sulfide in the Maoping deposit. We believe that the formation and evolution of the paleo-oil reservoirs are closely related to the metallogenic process of the Maoping Pb–Zn deposit, and the sulfides in them have the same sulfur source and formation mechanism as reduced sulfur. BSR phenomena could occur in prior to migration of the hydrocarbons into the reservoir or low mature oil stage in paleo-oil reservoir; a small amount of H2SBSR was combined with metal ions in ancient oil reservoirs and deposits to form early subhedral, xenomorphic granular, fine-grained strawberry aggregate pyrite and/or gelatinous sphalerite. The paleo-gas reservoir formed by the evolution of the paleo-oil reservoir in the main metallogenic period potentially participated in the mineralization; that is, organic gas acted as a reducing agent and transformed SO42− in the upper Devonian Zaige Formation gypsum strata on the periphery of the Maoping lead–zinc mining area into H2STSR through TSR, providing reduced sulfur and creating the environmental conditions for mineralization. During or after the transformation of the paleo-oil reservoir to a paleo-gas reservoir, the decoupling of metals and organic complexes may have provided the ore metals for mineralization. Massive sulfide precipitation may have occurred during or after the paleo-oil reservoir cracked into the paleo-gas reservoir.

HYDRO-GEOCHEMICAL AND QUALITY ASSESSMENT OF GROUNDWATER FROM SEDIMENTARY FORMATION IN THE MIDDLE BENUE TROUGH, NIGERIA

Nasarawa State in Nigeria, is host to several mineral deposits. The groundwater resources in the State plays an important role in the socio-economic life of the people in terms of domestic, industrial and agricultural water supply. The effect of climate change, on the surface and groundwater resources, couple with the anthropogenic and geogenic activities on the quality of the various groundwater sources remained uncertain. Two hundred (200) water samples were collected randomly from boreholes and hand-dug wells from five locations (20 each) in Nasarawa South: Keana, Obi, Lafia and Awe Local Government Areas of the State, referred to as Middle Benue trough. 100 samples were collected during peak of dry season and another 100 during peak of rainy season. Cations, anions and heavy metals were analyzed using atomic absorption spectrometry (AAS); with aim of determining their concentrations in relation to suitability within the tolerance limit. The results revealed that heavy metals such as lead (Pb), manganese (Mn), Magnesium (Mg) and arsenic (As) have concentrations above World Health Organization (WHO 2017) and SON (2015) standards. The high concentrations are mostly associated with the Baryte and Lead-zinc mineralization present in Keana / Awgu formations in the Middle Benue Trough. Zinc (Zn), copper (Cu), cadmium (Cd), and iron (Fe2+) have their concentrations within World Health Organization (WHO 2017) drinking water permissible limits. The cations and anions present in the groundwater in the study areas had varying levels in terms of physico-chemical and bacteriological quality. In some areas bacteriological contamination rendered water sources unfit for human consumption, but suitable for agricultural purposes. Therefore, regular monitoring of the water sources in the affected areas are highly recommended.

ПОРІВНЯЛЬНА ХАРАКТЕРИСТИКА ГЕОЛОГІЧНОЇ БУДОВИ І СВИНЦЕВО-ЦИНКОВОЇ МІНЕРАЛІЗАЦІЇ УСПЕНСЬКОГО (ЦЕНТРАЛЬНИЙ КАЗАХСТАН) І БЕРЕГІВСЬКОГО (ЗАКАРПАТТЯ) РУДНИХ РАЙОНІВ

The purpose of the article is to conduct a comparative description of the Uspensky in Central Kazakhstan and Beregivsky in Transcarpathian ore regions in order to clarify the factors and criteria for lead-zinc mineralization, patterns of location, formation and localization of polymetallic deposits. The study used general geological methods of research, in particular, methods of geological survey, prospecting and exploration of deposits, a comparative analysis of areas with different geological structures, etc. As a result, it was found that the main factors of polymetallic mineralization are structural, lithological-stratigraphic, magmatic and metasomatic, manifested at different levels of organization of ore matter, at different times, in different geological and structural conditions. The scientific novelty lies in the fact that the conducted studies allow us to recommend the findings regarding the factors and criteria of polymetallic mineralization as scientific and methodological foundations for forecasting and prospecting for leadzinc deposits in other regions of the world, including Ukraine. The practical significance lies in the fact that the new data obtained on the Atasu type of deposits in Kazakhstan allow us to successfully solve many issues of the genesis of such polymetallic deposits, show their relationship and patterns of formation in connection with submarine volcanic activity. These data, in their significance, undoubtedly go far beyond the limits of the Uspensky belt and Central Kazakhstan and are close to other materials of polymetallic deposits of the world.

English

An integrated geoelectrical study combining electrical resistivity tomography (ERT) and induced polarization (IP) have been used to delineate potential zones of Lead-Zinc mineralization in Umuobuna, Uburu, Ohaozara local government area, southeastern Nigeria. The wenner array configuration was used to acquire resistivity and induced polarization data sets along three traverses of approximate length of 1 km each and spacing of 5 to 25 m, using ABEM Terrameter SAS 1000. The profiles were inverted using RES2DINV software for 2D imaging to delineate possible zones of Pb-Zn mineralization and the geological structures at selected locations in the study area. The ERT surveys were carried out along the IP lines for comparison of anomalies across the profiles. The potential zones of Pb-Zn mineralization display contrasting values of resistivity and chargeability along the traverses. Resistivity values ranging from 7.53 to 7525 ?m and corresponding chargeability values of between -15.6 and 354 ms, respectively were encountered at some intervals along the traverses. These zones occur at width range 19.5 to 74.5 m and depths of between 0.9 and 15.5 m. Having a low to moderate resistivity and a corresponding high chargeability values at similar width range may be suggestive of Pb-Zn mineralization and test drilling is needed at the anomalous sites for confirmation. Key words: Pb-Zn, ERT, IP, resistivity, chargeability, mineralization.

Integrated geophysical investigation for lead and zinc mineralization in Wase, middle Benue Trough, Nigeria

There is an increasing demand for solid industrial minerals worldwide, as countries seek to support their economic growth. Wase, situated in Plateau State, is notable for lead and zinc mineralisation due to tectonic and hydrothermal activities in the region. The study utilises geophysical surveys to map mineralised zones of lead-zinc occurrence. These include ground magnetic survey, very low frequency electromagnetic, electrical resistivity tomography, and induced polarisation (IP). The field data were acquired using a GEMSys Overhauser magnetometer with VLF option and ABEM LS 2 Terrameter. twenty-nine (29) magnetic profiles with 50m spacing and a total length of 24.0 km were obtained and fifteen (15) very low frequency electromagnetic (VLF-EM) profiles with 10 m spacing in the E-W direction. A total length of 12.5 km was acquired across target areas of the magnetic profiles. The multiple-gradient electrode array of the ERT/IP surveys was used for data acquisition, and RES2DINV software by Geotomo was used for the inversion of the acquired data. High chargeability values corresponding to low resistivity values characterised zones with suspected lead-zinc mineralisation. Following this preliminary finding, we advise that further trenching, pitting, or core drilling be carried out to ascertain ore grade, possible beneficiation, and estimate of the reserve.

Audio Magnetotellurics Study of the Geoelectric Structure across the Zhugongtang Giant Lead–Zinc Deposit, NW Guizhou Province, China

Non-invasive geophysical exploration methods a play key role in the exploration of ore deposits. In the present study, the audio-frequency magnetotelluric (AMT) method was applied to metallic mineral exploration. The metallic mineral deposit targeted was the recently discovered super large lead–zinc deposit of the Zhugongtang mining area of Hezhang County in the northwestern Guizhou province in China. The main objectives of this study were to estimate the geoelectric strike and generate geoelectric models that estimate both the depth and distribution of resistivity structures across the deposit. To achieve the objectives, we deployed sixty-one (61) AMT survey sites with an interstation separation of 20 m on a 1280 m survey track perpendicular to the geological strike across the Zhugongtang deposit. We operated in fifty-three (53) frequencies in the range 1–10,400 Hz to record the resistivity distribution of subsurface to a depth of more than 1200 m. The results from the AMT data computations estimated the geoelectric strike that varies between NE285° and NE315°. This range of strikes suggested that structures across the deposit are oriented in the NW–SE direction. Obtained two-dimensional (2D) models elucidated a remarkably low resistivity body (&lt;15 Ωm) at an elevation of less than 1600 m above sea level (&gt;0.50 km depth), thus extending to great depth and were interpreted as lead–zinc mineralization. Furthermore, low resistivity (&lt;63 Ωm) features were imaged both in superficial and deeper depths and interpreted as shale, sandstone, claystone, and silty mudstone units. Dolomite and limestone lithologies were found widely distributed with high resistivity (&gt;1000 Ωm). Bioclastic limestone and dolomite limestone were inferred and characterized by moderate-high resistivity (&gt;250 Ωm) and were not widely distributed. A unit of basalts was found with moderate resistivity (&gt;63 Ωm). In addition, it was also found that regions with high number of faults tend to have low resistivity values compared to regions with a low fault number. In summary, this case study presents the results of applying an AMT approach to explore the conductivity characteristics of structures across the Zhugongtang deposit. The findings may contribute to the literature about this deposit.