Geological Issues Research Articles

The Neoarchean granitoids in the Yanlingguan area, western Shandong, North China Craton record the transition from TTG to K-rich granitoids

The Neoarchean is an important period of continental crustal growth worldwide. Determining how the continental crust increases in size and was finally cratonized at the end of the Archean is therefore an important scientific issue in geology. This study involved field investigations, SHRIMP U-Pb zircon dating, zircon in situ Hf isotopic analysis, and whole-rock geochemistry of Neoarchean granitoids at Yanlingguan, a typical Neoarchean area in the western Shandong granite-greenstone belt, North China Craton. Three samples of diorite/TTG that occur as enclaves in monzogranite record the oldest magmatic zircon 207Pb/206Pb ages of 2738–2731 Ma. They have low ΣREE (total REE) contents (37.5–72.4 ppm), low (La/Yb)n (8.9–25.5) and variable Eu/Eu* (0.90–1.86). The Xinfushan trondhjemite has a weighted mean 207Pb/206Pb age of 2599 ± 4 Ma for magmatic concordant or near-concordant zircons from six samples. The trondhjemites have large REE variations, with ΣREE, (La/Yb)n, and Eu/Eu* being 36.3–150.9 ppm, 23.9–91.1 and 0.57–2.00, respectively. The Lianhuashan monzogranite has a weighted mean 207Pb/206Pb age of 2502 ± 6 Ma for magmatic concordant or near-concordant zircons from four samples. These rocks have ΣREE contents, (La/Yb)n and Eu/Eu* of 42.9–573.7 ppm, 2.4–89.1 and 0.31–1.20, respectively. The geochemisal data indicate that the 2.7 Ga diorite/TTG rocks formed by fractional crystallization of mafic magma under low-pressure conditions. In contrast, the 2.6 Ga trondhjemites were most likely formed by a mixture of magmas derived from partial melting of low-K mafic and the earlier tonalitic rocks; whereas the 2.5 Ga monzogranites were derived by partial melting of the earlier TTG rocks, with addition of some sedimentary material. These events commenced with the subduction and melting of early Neoarchean oceanic crust, likely influenced by mantle plume activity, through an increase in crustal melting and consequent increase in the K2O/Na2O ratio in the 2.6 Ga TTG, and culminated in the production of the widespread generation of K-rich monzogranites at 2.5 Ga. Western Shandong thus underwent an increase in crustal maturity as it transitioned from TTG-dominated magmatism to K-rich granite, marking cratonization of the North China Craton at the end of the Neoarchean.

Dynamic characteristics of soil pore structure and water-heat variations during freeze-thaw process

Freeze-thaw processes in cold regions alter soil pore structure and properties, leading to engineering geological issues. Soil pores are crucial, but research on their changes and freeze-thaw impacts is limited. This study used MRI-Cryogenic Soil Moisture Analyzer (MRI-CSMA) to explore pore structure, water, and temperature changes in saturated loess during freeze-thaw, and Scanning Electron Microscopy (SEM) to compare changes before and after. The results indicate that during the freezing process, the temperature in the frozen zone of the soil sample exhibited a staged change characterized by rapid cooling, transitional cooling, and stabilization at low temperatures, while the temperature decrease in the unfrozen zone showed no significant stages. Freeze-thaw action significantly affected the macropores and mesopores in the frozen zone, with an average increase of 15 % in macropores, a decrease of 16 % in mesopores, and minimal change in micropores (about a 1 % increase). In the unfrozen zone, there was a slight increase in micropores and mesopores (2 % and 3 %, respectively), and a 4 % decrease in macropores. Furthermore, during the freezing process, macropores in the unfrozen zone gradually decreased, while mesopores and micropores increased, leading to soil structure densification and promoting water migration towards the freezing front. This resulted in an initial increase followed by a decrease in water content near the freezing front during the early stages of freezing, confirming the view that pore structure compression drives water migration in the early stages of soil freezing. This study provides important insights for addressing engineering geological issues in cold regions under freeze-thaw conditions.

Current Geological Issues and Future Perspectives in Deep-Time Source-to-Sink Systems of Continental Rift Basins

Current Geological Issues and Future Perspectives in Deep-Time Source-to-Sink Systems of Continental Rift Basins

The Urban Geo-climate Footprint approach: Enhancing urban resilience through improved geological conceptualisation

Urban resilience is critical to allow cities to withstand the challenges of the 21st Century. One factor that is often overlooked in such assessments is the role of the subsurface. A novel methodology called the Urban Geo-climate Footprint (UGF) has been developed to classify cities quickly and comprehensively from geological and climatic perspectives. The method operates on the fundamental assumption that cities with similar geological-geographical settings will face similar challenges, due to both common geological issues and associated climate impacts. The UGF approach has been applied to 41 European cities in collaboration with 17 Geological Surveys of Europe, the results of the UGF analysis are presented along with a regional classification of the geological resilience indicators. The UGF tool provides a semi-quantitative representation of the pressures driven by geological and climatic complexity for the cities presented, providing for a first time such classification of the urban environment. The advantage of this methodology lies in increasing awareness among non-experts and decision-makers of the interplay between geological settings, climate change pressures, and anthropogenic activities. Furthermore, it facilitates the exchange best practices among city planners to increase resilience, supporting knowledge based decision making to promote actions and policies, that enhance geoscience-informed climate justice.

Quantitative Assessment of Geosites and Mine Heritage as a Resource: The Case Study of Lungro Salt Mine (Calabria, Italy)

In this work, the old Lungro mining site was studied by applying two classification methods (Brilha and IELIG Method), considering the site-specific scientific, educational, touristic, and degradation aspects, to promote it as a geosite. The results were compared with those from other worldwide areas, and a potential re-evaluation in the tourism sector was suggested, considering historical data and geological issues. The methods used evaluate the Lungro site an average score from a scientific perspective, and from high to very high for the tourist-educational aspects. On the contrary, lower scores were found regarding the degradation of the site due to natural phenomena, led to a lower total score. The obtained results are comparable with other similar restored mining areas, located in various parts of the world which today represent important geotourists sites recognized internationally.Based on these results, the safest, most cost-effective, and straightforward way to preserve and restore the site is by creating a “Geotourism Route.“. This choice would increase awareness of the area, providing the general public, including the curious and “non-experts”, with an understanding of various geological processes and the extensive history of the mine. A campaign to promote and preserve the Lungro site as a geoheritage will be encouraged, with significant implications for tourism at the local, national, and international levels.

Petrogenesis of A-type leucocratic granite magmas: An example from Delbegetei massif, Eastern Kazakhstan

The genesis of leucogranite magmas is important issue of geodynamics, petrology and ore geology because leucogranites are associated with collisional belts, partial melting of sedimentary source rocks, and may host rare metal (Sn, W, Li, NbTa, and Be) mineralization. To establish the petrogenesis of large leucogranite intrusions, detailed studies of petrography, mineralogy, fluid regime, and the material and isotopic composition of rocks are required. The paper reports results of the studies of the Delbegetei massif of the intrusion in Eastern Kazakhstan. The massif is composed predominantly of leucocratic granites, while syenogranites are subordinate. Rocks of the massif belong to shoshonitic and high-K calc-alkaline series; demonstrate a predominance of K over Na, high ferroan and high contents of LREE and HFSE; which allows them to be classified as A-type granites. The age of Delbegetei massif, estimated by the UPb zircon dating, varies in the range 249–240 Ma, which correspond the Early-Middle Triassic. The differences in rock composition and in temperatures of zircon saturation allow supposing that syenogranites and leucogranites formed from different parental magmas. Syenogranite magma formed as a result of partial melting of metamorphosed volcanic rocks (andesidacites or dacites) with possible influence of mafic magmas. Leucogranite magma formed as a result of fluid-present partial melting of metaterrigenous sedimentary rocks. Leucogranite magma underwent the feldspars differentiation in the fluid-present conditions. This led to composition variations of leucogranites. Analysis of the geological position, age and composition of the rocks allows concluding that the Delbegetei massif formed at the Early Triassic in an intraplate geodynamic setting and that the activity of the Siberian mantle plume is the most probable reason for their formation.

Geoscience for Cities: Delivering Europe’s Sustainable Urban Future

European Union (EU) policy is clear in its ambition to deliver a sustainable urban future for Europe. In this paper, we consider the role of urban geoscience to help achieve these ambitions. We highlight the relevance of geology to urban subsurface planning and wider EU policy and strategy. Despite the lack of explicit mention of urban underground space in key policy documents, we identify a significant number of priority urban issues for which geological characterisation is a pre-requisite and for which the geological system forms part of the solution, such as mitigation of climate impacts, delivering net zero energy, and implementing nature-based solutions. We reflect on the paradigm shift of urban geoscience as a geological discipline, rooted initially in engineering geology but which has moved towards an interdisciplinary, solution-focused science operating at the inter-section of environmental–social–built systems. In this regard, we highlight cutting-edge urban geoscience research aligned to current urban challenges and note, in particular, the significance of digital technologies to enable 3D urban characterisation, support data-driven decision-making for planning and development, and serve as a means to communicate geology to urban practitioners. The role of the urban geoscientist as an agent of change to enhance integrated science, improve the accessibility of geological issues, and accelerate the translation of national–regional geology to local settings and to urban policy drivers should not be underestimated.

Reactive transport modeling constraints on the complex genesis of a lacustrine dolomite reservoir: A case from the Eocene Qaidam Basin, China

Reactive transport modeling (RTM) is an emerging method used to address geological issues in diagenesis research. However, the extrapolation of RTM results to practical reservoir prediction is not sufficiently understood. This paper presents a case study of the Eocene Qaidam Basin that combines RTM results with petrological and mineralogical evidence. The results show that the Eocene Xiaganchaigou Formation is characterized by mixed siliciclastic-carbonate-evaporite sedimentation in a semiclosed saline lacustrine environment. Periodic evaporation and salinization processes during the syngenetic-penecontemporaneous stage gave rise to the replacive genesis of dolomites and the cyclic enrichment of dolomite in the middle-upper parts of the meter-scale depositional sequences. The successive change in mineral paragenesis from terrigenous clastics to carbonates to evaporites was reconstructed using RTM simulations. Parametric uncertainty analyses further suggest that the evaporation intensity (brine salinity) and particle size of sediments (reactive surface area) were important rate-determining factors in the dolomitization, as shown by the relatively higher reaction rates under conditions of higher brine salinity and fine-grained sediments. Combining the simulation results with measured mineralogical and reservoir physical property data indicates that the preservation of original intergranular pores and the generation of porosity via replacive dolomitization were the major formation mechanisms of the distinctive lacustrine dolomite reservoirs (widespread submicron intercrystalline micropores) in the Eocene Qaidam Basin. The results confirm that RTM can be effectively used in geological studies, can provide a better general understanding of the dolomitizing fluid-rock interactions, and can shed light on the spatiotemporal evolution of mineralogy and porosity during dolomitization and the formation of lacustrine dolomite reservoirs.

Micro-occurrence characteristics and charging mechanism in continental shale oil from Lucaogou Formation in the Jimsar Sag, Junggar Basin, NW China.

The micro-occurrence characterization of shale oil is a key geological issue that restricts the effective development of continental shale oil in China. In order to make up for the lack of research in this area, this paper carries out a series of experiments on the shale oil of the Lucaogou Formation using a multi-step extraction method, with the aim of exploring the micro-occurrence types and mechanisms of shale oil in the Lucaogou Formation, as well as exploring its direct connection with production and development. In this paper, shale oil in the reservoir is divided into two categories: free oil and residual oil. The polar substances and OSN compounds are the key factors determining the occurrence state of shale oil. Abundant polar substances and OSN compounds can preferentially react with mineral surfaces (including coordination, complexation, ionic exchange, and so on) to form a stable adsorption layer, making it difficult to extract residual oil in actual exploitation. Free oil is mainly composed of aliphatic hydrocarbons, and its adsorption capacity is related to the length of the carbon chain, i.e. long carbon chain, strong adsorption capacity, and poor movability. Free oil is widely stored in pores and cracks, and that with high mobility can be the most easily extracted, making it the main target at present exploitation. In the current state of drilling and fracturing technology, research should prioritize understanding the adsorption and desorption mechanisms of crude oil, particularly residual oil. This will help optimize exploitation programs, such as carbon dioxide fracturing and displacement, to enhance shale oil production.

Application of geophysical well logs in solving geologic issues: Past, present and future prospect

Geophysical well logs are widely used in geological fields, however, there are considerable incompatibilities existing in solving geological issues using well log data. This review critically fills the gaps between geology and geophysical well logs, as assessed from peer reviewed papers and from the authors’ personal experiences, in the particular goal of solving geological issues using geophysical well logs. The origin and history of geophysical logging are summarized. Next follows a review of the state of knowledge for geophysical well logs in terms of type of specifications, vertical resolution, depth of investigations and demonstrated applications. Then the current status and advances in applications of geophysical well logs in fields of structural geology, sedimentary geology and petroleum geology are discussed. Well logs are used in structural and sedimentary geology in terms of structure detection, in situ stress evaluation, sedimentary characterization, sequence stratigraphy division and fracture prediction. Well logs can also be applied in petroleum geology fields of optimizing sweet spots for hydraulic fracturing in unconventional oil and gas resource. Geophysical well logs are extending their application in other fields of geosciences, and geological issues will be efficiently solved via well logs with the improvements of advanced well log suits. Further work is required in order to improve accuracy and diminish uncertainties by introducing artificial intelligence. This review provides a systematic and clear descriptions of the applications of geophysical well log data along with examples of how the data is displayed and processed for solving geologic problems.

Geodynamic issues of ore deposits in Central Asia

The focus of this study is on a pressing issue in ore geology, specifically the geodynamics of ore formation. The paper delineates a comprehensive methodology for examining the geodynamic context in regions hosting endogenous mineralization. The foundation for reconstructing geodynamics lies in geological and structural investigations into the circumstances surrounding mineralization, complemented by outcomes from physical modeling. Tectonic tension and deformation analyses of ore fields and deposits further contribute crucial insights. The study underscores that understanding the geodynamic setting is paramount for elucidating the processes leading to ore formation. This involves a detailed examination of geological structures, conditions of mineralization, and physical modeling results. By adopting this approach, the research provides a robust framework for reconstructing the geodynamic conditions prevalent during the period of ore formation. As a practical application of this methodology, the paper presents results from the reconstruction of the geodynamic situation during the ore formation period in a gold deposit situated in Western Uzbekistan. These findings contribute to a deeper comprehension of the geodynamic processes associated with the formation of valuable mineral deposits, thereby enhancing our ability to interpret and potentially predict similar occurrences in ore geology.

Magmatic immiscibility and the origin of magnetite-(apatite) iron deposits

The origin of magnetite-(apatite) iron deposits (MtAp) is one of the most contentious issues in ore geology with competing models that range from hydrothermal to magmatic processes. Here we report melt inclusions trapped in plagioclase phenocrysts in andesite hosting the MtAp mineralization at El Laco, Chile. The results of our study reveal that individual melt inclusions preserve evidence of complex processes involved in melt immiscibility, including separation of Si- and Fe-rich melts, the latter hosting Cu sulfide-rich, phosphate-rich, and residual C-O-HFSE-rich melts, with their melting temperature at 1145 °C. This association is consistent with the assemblages observed in the ore, and provides a link between silicate and Fe-P-rich melts that subsequently produced the magnetite-rich magmas that extruded on the flanks of the volcano. These results strongly suggest that the El Laco mineralization was derived from crystallization of Fe-P-rich melts, thus providing insight into the formation of similar deposits elsewhere.

Research progress and key issues of ultra-deep oil and gas exploration in China

Based on the recent oil and gas discoveries and geological understandings on the ultra-deep strata of sedimentary basins, the formation and occurrence of hydrocarbons in the ultra-deep strata were investigated with respect to the processes of basin formation, hydrocarbon generation, reservoir formation and hydrocarbon accumulation, and key issues in ultra-deep oil and gas exploration were discussed. The ultra-deep strata in China underwent two extensional-convergent cycles in the Meso-Neoproterozoic Era and the Early Paleozoic Era respectively, with the tectonic-sedimentary differentiation producing the spatially adjacent source-reservoir assemblages. There are diverse large-scale carbonate reservoirs such as mound-beach, dolomite, karst fracture-vug, fractured karst and faulted zone, as well as over-pressured clastic rock and fractured bedrock reservoirs. Hydrocarbons were accumulated in multiple stages, accompanied by adjusting and finalizing in the late stage. The distribution of hydrocarbons is controlled by high-energy beach zone, regional unconformity, paleo-high and large-scale fault zone. The ultra-deep strata endow oil and gas resources as 33% of the remaining total resources, suggesting an important successive domain for hydrocarbon development in China. The large-scale pool-forming geologic units and giant hydrocarbon enrichment zones in ultra-deep strata are key and promising prospects for delivering successive discoveries. The geological conditions and enrichment zone prediction of ultra-deep oil and gas are key issues of petroleum geology.

Land Subsidence Prediction Model Based on the Long Short-Term Memory Neural Network Optimized Using the Sparrow Search Algorithm

Land subsidence is a prevalent geological issue that poses significant challenges to construction projects. Consequently, the accurate prediction of land subsidence has emerged as a focal point of research among scholars and experts. Traditional mathematical models exhibited certain limitations in forecasting the extent of land subsidence. To address this issue, the sparrow search algorithm (SSA) was introduced to optimize the efficacy of the long short-term memory (LSTM) neural network in land subsidence prediction. This prediction model has been successfully applied to the Huanglong Commercial City project in the Guanghua unit of Wenzhou city, Zhejiang province, China, and has been compared with the predictions of other models. Using monitoring location 1 as a reference, the MAE, MSE, and RMSE of the test samples for the LSTM neural network optimized using the SSA are 0.0184, 0.0004, and 0.0207, respectively, demonstrating a commendable predictive performance. This new model provides a fresh strategy for the land subsidence prediction of the project and offers new insights for further research on combined models.

Medical Geology Related to Different Trace Elements Deficiency and Toxicity Diseases

Abstract: Medical geology is an emerging discipline that, broadly defined, examines the public health impacts of geologic materials and geologic processes. Medical Geology, the study of the impacts of geologic materials and processes on animal and human health, is a dynamic emerging discipline bringing together the geosciences, biomedical, and public health communities to solve a wide range of environmental health problems. Among the Medical Geology described in this review are examples of both deficiency and toxicity of trace element exposure. Goiter is a widespread and potentially serious health problem caused by deficiency of iodine. In many locations the deficiency is attributable to low concentrations of iodine in the bedrock. Similarly, deficiency of selenium in the soil has been cited as the principal cause of juvenile cardiomyopathy and muscular abnormalities. Overexposure to arsenic is one of the most widespread Medical Geology problems affecting more than one hundred million people in Bangladesh, India, China, Europe, Africa and North and South America. The arsenic exposure is primarily due to naturally high levels in groundwater but combustion of mineralized coal has also caused arsenic poisoning. Dental and skeletal fluorosis also impacts the health of millions of people around the world and, like arsenic, is due to naturally high concentrations in drinking water and, to a lesser extent, coal combustion. Other Medical Geology issues described include geophagia, the deliberate ingestion of soil, exposure to radon, and ingestion of high concentrations of organic compounds in drinking water. Geosciences and biomedical/public health researchers are teaming to help mitigate these health problems.

Émile Belot’s Models, or an Engineer’s Quest for Scientific Legitimacy

Abstract Between 1905 and 1937, Émile Belot, an engineer and then director of a public tobacco factory, threw himself into scientific research seeking to reconstruct the history of the formation of the solar system. This article goes over and analyses the experimental practices Belot drew on in support of his theory, looking at the equipment he manufactured and operated in his “experimental cosmogony laboratory.” Together with a few other French engineers, Belot persistently sought to prove his legitimacy to address astronomical and geological issues. His machines reproducing the formation of spiral nebulae, volcanoes, or lunar craters acted both as material resources for deciding between rival scientific hypotheses, and as tools which, by analogy, materialised the mechanical nature of the cosmos Belot hoped to study without being confined to the scientific margins.

The ancient eastward-dipping subduction zone reactivated during the Mesozoic between the Alxa and Ordos Blocks: Electrical evidence from an extended MT profile

This paper investigates the characteristics of the electrical structure and key geological issues of the Alxa and Ordos blocks using a lithospheric resistivity model obtained from a west-east trending magnetotelluric sounding profile. The electrical model shows that the lithosphere of the Alxa Block is high resistivity, except for two crustal low-resistivity bodies. The crust of the Helanshan Orogenic Belt is characterized by medium to high resistivity surrounded by two low-resistivity bodies on both sides. The upper crust of the Ordos Block exhibits discontinuous high resistivity. Still, the lower crust and upper mantle show distinctly low resistivity, which connects with the shallow low-resistivity body above it. The lithosphere of the Lüliang Uplift and the Shanxi Graben is generally characterized by high resistivity, with only localized low-resistivity anomaly found near Moho and in the shallow part of the Shanxi Graben. We propose that the Alxa Block has a stable cratonic lithosphere and that the crustal low-resistivity body within it is a remnant of the southward subducted oceanic crust of the Paleo-Asian Ocean. The low-resistivity body in the lower crust of the Trans-North China Orogen is also interpreted as a remnant of oceanic crust; the upper mantle low-resistivity body is proposed to be a partial melt resulting from the upwelling of asthenosphere caused by the combination of westward subduction of the Paleo-Pacific Plate and northeastward growth of the Tibetan Plateau. This low-resistivity anomaly spreads to the shallow crust, with its lateral distribution to the east and west being blocked by the Lüliang Orogenic Belt and the Alxa Block, respectively, then consequently upwelling along the Yinchuan Graben during the Mesozoic and Cenozoic. We propose that the Alxa Block has been subducted to the Ordos Block along the Helan Mountain in the Early-Middle Paleozoic, which may have formed an ancient suture zone. This ancient suture zone was reactivated in the Mesozoic and Cenozoic by the Paleo-Pacific Ocean subduction and northeastward growth of the Tibetan Plateau, becoming a material upwelling channel and ablating the roots of the Helan Mountain.

Potential and challenges of applying artificial intelligence (AI) in geosciences to the search for a high-level waste repository in Germany

Abstract. In a science-based site selection procedure (StandAV), the Federal Republic of Germany is searching for a site with the best possible safety for a repository for high-level waste (HLW) over a period of 1 million years. This is a challenging task, given the size of Germany, its geological variability and the verification period required to ensure the best possible long-term safety. In addition, an enormous amount of heterogeneous geodata has to be processed. The application of artificial-intelligence-based methods in geosciences has great potential for dealing with large heterogeneous data sets. In the German Federal Office for the Safety of Nuclear Waste Management (BASE)-funded project “Application of artificial intelligence (AI) in the site selection process for a deep geological repository (FKZ 4721E03210)”, an interdisciplinary assessment tool is being developed to evaluate the applicability of AI methods in the geosciences. This contribution focuses on the potential and challenges of applying AI in geosciences with respect to key geological activities in the StandAV. Limitations that may arise from the use of AI with respect to key activities in the StandAV are highlighted. The necessary conditions for its future applicability are proposed. The results show that AI methods offer clear advantages over conventional methods for data management and handling large geological datasets and for modelling complex long-term and coupled geological processes. However, AI methods are generally only transferable to the geoscientific questions of the StandAV with methodological and subject-specific adaptations. Furthermore, the use of AI requires sufficient data, both in terms of quality and quantity. The study also shows that AI should only be used in a supportive way to address geological issues in key activities and should not have any decision-making power when used in StandAV. For example, AI can carry the risk of data and developer bias, which in turn can have serious consequences for the correct interpretation of results. High demands must be placed on the traceability of the AI methods used. AI methods that do not meet the transparency requirements of the StandAV carry a significant risk of jeopardising public confidence in the participation process. This could increase the general mistrust and scepticism towards AI in the public perception (Krob et al., 2023). It is strongly recommended that all methods should be evaluated and validated iteratively and that the results should be made available to the public when applied to the key activities of the StandAV.

Hydrothermal reduction of sulfates by ferrous carbonate: Implications for the origin of reduced sulfur in carbonate-hosted Pb-Zn deposits associated spatially with basalts

Reduced sulfur derived from thermochemical sulfate reduction (TSR) in Pb-Zn deposits is one of the long-debated issues in economic geology. The formation of - 2 valent sulfur (S2-) in Pb-Zn deposits associated spatially with basalts, may be related to the thermal reduction of SO42- by ferrous ions (Fe2+). In the present study, hydrothermal experiments on the reduction of magnesium sulfate (MgSO4) by ferrous carbonate (FeCO3) were carried out to investigate the thermodynamics feasibility, kinetic characteristics and reaction mechanisms for the inorganic reduction of sulfates. The results show that the reduction of MgSO4 by FeCO3 is thermodynamically stronger than TSR of oil, gaseous hydrocarbons and solid bitumen. Moreover, this reduction reaction occurs at threshold temperatures below 300 °C under hydrothermal conditions, yielding the main products of magnetite (Fe3O4), pyrite (FeS2) and pyrrhotite (Fe7S8). The reaction mechanism for the studied multiphase system at 400 − 525 °C involves at least nine elementary steps. The chemical kinetics for the FeCO3 −MgSO4 − H2O system is in accordance with the phase boundary control reaction model with apparent activation energy of 70 kJ/mol. The formation of S2- in carbonate-hosted Pb-Zn deposits associated spatially with basalts is most likely a two-stage sulfate reduction process involving Fe2+ (90 −140 °C) and organic matters (>140 °C) in series. The new findings from the inorganic reduction of sulfates would contribute to clarification of the genesis of Pb-Zn deposits and help to reconceptualize some of the long-standing controversial issues in this field.

Research on Detection and Safety Analysis of Unfavorable Geological Bodies Based on OCTEM-PHA

The caving method and mining disturbance may cause geological issues. The advance prediction of unfavorable geological bodies should be conducted to ensure product safety in the underground mine. In this study, we proposed the OCTEM-PHA analysis process and analyzed the Tongkeng Mine in Guangxi. Further, we conducted opposing-coil transient electromagnetic method (OCTEM) detection on four detection lines in T5-1 stope at mine level 386 by using portable geological remote sensing equipment and created inversion maps. Plot profiles and coupling were analyzed with inversion maps to explore the five types of risk factors presented in the mine. The preliminary hazard analysis (PHA) method was used for five types of risk factors to predict the accident consequence and develop safety countermeasures. The results indicate the following: (1) the OCTEM-PHA safety analysis process for unfavorable geological bodies is realistic and feasible. (2) OCTEM shows an excellent response to both high- and low-resistance anomalies in practical engineering applications. The coupling analysis of profiles and inversion maps helps visually analyze the area of apparent resistivity anomalies. (3) The studied mine did not show overhanging formed by the overlying rock layer and large loose void areas. However, the crumbling mining area should be further optimized for balanced mining, the treatment of groundwater and surface water should be improved, and the comparative analysis with the follow-up detection results should be increased.