Concealed Ore Bodies Research Articles

Nanoparticles in various media on surfaces of ore deposits: Study of the more than 1000 m deep concealed Shaling gold deposit

Surface nanoparticles in nature have become important research objects because they contain information about the deep Earth. In this study, nanoparticles were analyzed via Transmission Electron Microscopy (TEM) in gradient media (groundwater, ascending gas, and soil) on the surface overlying the concealed Shaling gold deposit in China, which was buried more than 1000 m below the surface. The morphologies, ultramicroscopic structure, and chemical composition of the nanoparticles were analyzed via High-Resolution TEM (HRTEM), Selected Area Electron Diffraction (SAED), and Energy Dispersive Spectroscopy (EDS). These nanoparticles were characterized as (i) Amorphous Nano-Particles (ANPs), (ii) Amorphous-and-Crystalline-mixed Nano-Particles (A&C mixed NPs), and (iii) Crystallized Nano-Particles (CNPs). Furthermore, the newly proposed A&C mixed NPs were further classified into wrapped-, adsorbed- and coexisting-type nanoparticles. The ANPs exhibited a disorderly arrangement, A&C mixed NPs comprised amorphous materials as well as crystalline grains, and CNPs predominantly consisted of crystallized bodies. Oxidized particles derived from concealed ore bodies contain ore-related information and migrate to the surface via the flow of groundwater and ascending gas along faults. Among these particles, amorphous-bearing nanoparticles can contain elements with similar geochemical behaviors, such as Ca and Zn. Overall, this study provides a new basis for the exploration of concealed ore bodies.

Multi-scale exploration of giant Qulong porphyry deposit in a collisional setting

With the increasing demand for copper resources, exploration methods based on the discovered porphyry Cu deposits (PCDs) to target concealed orebodies are of greater importance. Single parameter is no longer sufficiently effective against concealed deposit exploration, and different combinations of survey techniques are required. The Qulong porphyry Cu-Mo deposit is the largest collisional PCD found in China. Here we evaluated the relationship between variations in multiple parameters and alteration to define exploration footprints around the porphyry Cu centers. In order to improve the exploration efficiency and accuracy, we combined geophysical (magnetic susceptibility and resistivity) and popular geochemical exploration methods (i.e., short wavelength infrared spectroscopy- SWIR, portableX-ray fluorescence- pXRF, and indicator minerals) to the drill hole ZK005 of Qulong PCD in southern Tibet seeking for a firm interpretation. Four orebody indicators were established in study of Qulong deposit, which are: (i) the fluctuations of Ca/K, Mg/Fe, Sr/Ti, and Si/Al ratios, (ii) long-wavelength white mica (2207–2214 nm) and short-wavelength chlorite (2247–2253 nm), (iii) sub-high magnetic susceptibility and (iv) low resistivity. Multi-scale prospecting methods can improve prospecting efficiency and narrow down the target area. Based on the local environment, selecting an appropriate combination of methods can improve exploration efficiency in the brownfields at a lower cost.

Ore-forming elements and their distribution of nanoparticles in the updraft from the Sanshandao concealed deposit, China

The search for concealed ore deposits has increasingly gained attention, due to the gradual depletion of surface resources over time. It is necessary to develop non-traditional geochemical theories and methods to locate concealed deposits. In this study, the morphological characteristics and chemical compositions of particles carried by the updraft of the Sanshandao deposit are observed through transmission electron microscopy. Results presented direct evidence that the composition of nanoparticles in the updraft is affected by the geological background, concealed ore bodies, and oxidation. Cl and Na in the study area are found to be higher than those in other deposits owing to the influence of seawater intrusion. Elements associated with ore-forming are contained in the updraft in the form of nanoparticles, which usually have the same distribution pattern and element assemblage in their particles. Oxygen is found to widely exist in the nanoparticles and matched well with the particle distribution. These combinations of elements from orebodies are not observed in the nanoparticles in the background area. Thus, we considered that nanoparticles associated with the orebodies are formed in the underground orebodies and migrate upward to the surface. Mapping can be used to understand the elemental composition and distribution of the nanoparticles. Based on the composition and distribution of nanoparticles, the elemental characteristics of the underground orebody can be inferred, and the minerals and the distribution range of the concealed orebodies can be predicted.

Equilibrium Cu isotope fractionation in copper minerals: a first-principles study

Copper is of importance in geosciences, biosciences, and industry. Its isotopes can be used to study planetary processes, trace Cu biogeochemical cycling, identify the type of Cu-bearing ore minerals, investigate the formation of ore deposits, and explore concealed ore-bodies. However, Cu isotope fractionation parameters of the majority of copper minerals remain poorly known, impeding the application of Cu isotopes as a geochemical tracer. In this study, the first-principles methods are used to compute Cu isotope fractionation parameters of chalcocite (Cu2S), covellite (CuS), villamaninite (CuS2), chalcopyrite (CuFeS2), cubanite (CuFe2S3), bornite (Cu5FeS4), cuprite (Cu2O), malachite (Cu2(CO3)(OH)2), azurite (Cu3(CO3)2(OH)2), antlerite (Cu3(SO4)(OH)4), brochantite (Cu4(SO4)(OH)6), liebauite (Ca3Cu5Si9O26), Cu-bearing enstatite (Mg31/16Cu1/16Si2O6), and native copper (Cu). The reduced partition function ratio of 65Cu/63Cu (103 ln β65−63) decreases in the order of Cu silicates > Cu carbonates > Cu sulfates > Cu oxide > native Cu > Cu sulfides. The103 ln β65−63values of these minerals display a weak correlation with oxidation state and Cu coordination number, while display a strong correlation with the average Cu-S bond lengths in Cu sulfides and the average Cu-O bond lengths in Cu oxysalt minerals with the same Cu coordination number. For Cu2S and Cu5FeS4 polymorphs, the extent of Cu isotope fractionation arising from polymorphic transformations is different. Our calculated results are useful for understanding the enrichment of Cu isotopes in nature. Cu isotope fractionation between sulfides and silicates may be a potential geothermometer.

A 3D Geological Model Constrained by Gravity and Magnetic Inversion and its Exploration Implications for the World‐class Zhuxi Tungsten Deposit, South China

AbstractThe Zhuxi tungsten deposit in Jiangxi Province, South China, contains a total W reserve of about 2.86 Mt at an average grade of 0.54 wt% WO3, representing the largest W deposit in the world. Numerous studies on the metallogeny of the deposit have included its timing, the ore‐controlling structures and sedimentary host rocks and their implications for mineral exploration. However, the deep nappe structural style of Taqian–Fuchun metallogenic belt that hosts the W deposit, and the spatial shape and scale of deeply concealed intrusions and their sedimentary host rocks are still poorly defined, which seriously restricts the discovery of new deposits at depth and in surrounding areas of the W deposit. Modern 3D geological modeling is an important tool for the exploration of concealed orebodies, especially in brownfield environments. There are obvious density contrast and weak magnetic contrast in the ore‐controlling strata and granite at the periphery of the deposit, which lays a physical foundation for solving the 3D spatial problems of the ore‐controlling geological body in the deep part of the study area through gravity and magnetic modeling. Gravity data (1:50000) and aeromagnetic data (1:50000) from the latest geophysical surveys of 2016–2018 have been used, firstly, to carry out a potential field separation to obtain residual anomalies for gravity and magnetic interactive inversion. Then, on the basis of the analysis of the relationship between physical properties and lithology, under the constraints of surface geology and borehole data, human–computer interactive gravity and magnetic inversion for 18 cross‐sections were completed. Finally, the 3D geological model of the Zhuxi tungsten deposit and its periphery have been established through these 18 sections, and the spatial shape of the intrusions and strata with a depth of 5 km underground were obtained, initially realizing “transparency” for ore‐controlling bodies. According the analysis of the geophysical, geochemical, and geological characteristics of the Zhuxi tungsten deposit, we discern three principles for prospecting and prediction in the research area, and propose five new exploration targets in its periphery.

3DWofE: An open-source software package for three-dimensional weights of evidence modeling

Abstract The shortage of outcropping ore deposits and the inefficiency of traditional mineral exploration methods for discovering deep-seated deposits have increased the necessity of developing three-dimensional modeling methods for in-depth exploration. The 3DWofE is a Python-based open-source software package that provides the tools required for three-dimensional modeling of concealed ore bodies by developing a data-driven prospectivity modeling method called weights of evidence. This software enables users to create three types of models which include posterior probability, uncertainty, and studentized posterior probability. These models can guide exploration geologists through identifying potential regions of target mineralization in depth.

Deep Geological Structures Associated With Terrestrial Volcanic Hydrothermal Metallogenic System: Evidence From Geophysical Survey in Taohemu Superlarge Silver‐Polymetallic Deposit, Inner Mongolia

AbstractTaohemu deposit is a superlarge silver‐polymetallic deposit discovered in the Great Xing'an Range metallogenic belt of China in recent years. The deposit occurs in the terrestrial volcanic rock sequences of Late Jurassic age. The ore bodies consist mainly of rhyolitic tuffs, brecciated tuffs, and volcanic breccia bearing Ag‐Pb‐Zn mineralization, and are largely conformable with the surrounding layered volcanic and volcaniclastic rocks with a gradual transitional relationship manifesting as strata‐bounded features in general. The mineralization system appears to be generally controlled by a paleo‐volcanic chamber. It is suggested that the late volcanic hydrothermal fluids flowed within the permeable layers of rhyolitic pyroclastics consisting mainly of volcanic breccias and breccia‐bearing tuffs. This resulted in the formation of superlarge Ag‐Pb‐Zn polymetallic ore deposit metasomatism and fracture filling. The majority of the deposit occurs as shallowly dipping concealed ore bodies, as defined by sparsely distributed drill holes. Because of its short discovery history, new mineralization style and low degree of comprehensive research, the boundaries of most ore bodies have not been effectively delineated along vertical and lateral extensions. At present, it is crucial to strengthen the comprehensive studies on the deposit, conduct more detailed geological exploration, and establish the metallogenic and prospecting models. For this reason, we have designed and implemented long sections of magnetotelluric (MT) and controlled‐source audio magnetotelluric (CSAMT) sounding across the Taohemu ore field and obtained a large number of geological structures and valuable underground exploration results that provided reliable geophysical support for promoting deep resource exploration.

Chlorite as an exploration indicator for concealed skarn mineralization: Perspective from the Tonglushan Cu–Au–Fe skarn deposit, Eastern China

Compositional variations of chlorite have been increasingly used to trace the magmatic–hydrothermal fluid evolution, as well as exploration vector toward concealed orebodies. This method has been widely applied to porphyry Cu (–Au) systems, but related research on skarn systems remain scarce. The Tonglushan Cu–Au–Fe deposit (86.3 Mt @ 1.66% Cu, 0.94 g/t Au and 39.4% Fe) is one of the largest Cu–Au polymetallic skarn deposits in the Middle–Lower Yangtze River metallogenic belt (MLYRB, Eastern China). Based on detailed petrographic observation, we present new EPMA and LA–ICP–MS elemental data for the Tonglushan chlorite, and discuss their implications on hydrothermal fluid evolution and exploration of concealed skarn orebodies there. At Tonglushan, chlorite alteration is well developed in the main Cu–Au sulfide ore stage. Three types of chlorite have been identified, i.e., disseminated chlorite replacing biotite and/or hornblende in the ore-causative quartz monzodiorite (porphyry), vein-type chlorite in quartz–chlorite–sulfides veins along/near the internal and external intrusive contact, and replacement-type chlorite that replaced garnet, diopside, epidote and Fe oxides in the skarn mineralization center.All the Tonglushan chlorite samples belong to trioctahedral chlorite and have similar crystallization temperatures (163–351 °C). The substitution mechanisms of Fe2+ ⇔ Mg2+, Tschermark (AlivAlvi ⇔ Si (Mg2+, Fe2+)) and di-trioctahedral (3(Mg2+, Fe2+) ⇔ □ + 2Alvi) are likely important for the Tonglushan chlorite formation. Replacement-type chlorite shows higher contents of FeOT, mobile elements (e.g., Ca, Na, B, Sr, Pb, Zn and Sn) and ore-forming elements (e.g., Cu and Co), whereas the disseminated chlorite has higher contents of Ti, Li, LILEs (e.g., K, Rb, Ba and Cs) and incompatible elements (e.g., V, Sc, Co and Ni). Meanwhile, the vein-type chlorite has similarly high contents of Ti, Li, V, Sc and Ni to the disseminated chlorite, but has higher FeOT and Cu contents but lower MgO content than the latter. Such compositional differences may have mainly attributed to the protolith (or precursor minerals) and hydrothermal fluid chemistry. Integrating the chlorite petrographic features and chemical compositions, we suggest that elevated FeOT and B contents and Fe/(Fe + Mg) ratios, and lower MgO, Al2O3, Ti, V and Sc contents can serve as proximal indicator for exploring concealed skarn orebodies at Tonglushan, as well as other similar Cu–Au–Fe skarn deposits in the MLYRB.

Application of Singular Value Decomposition (SVD) to the Extraction of Gravity Anomalies Associated with Ag-Pb-Zn-W Polymetallic Mineralization in the Bozhushan Ore Field, Southwestern China

The Bozhushan Ore Field, located at the western margin of the South China Block, is an important area for Ag-Pb-Zn-W polymetallic mineralization which may be associated with the Late Cretaceous granitic magmaism. In this paper, the singular value decomposition (SVD) was effectively applied to decompose gravity data at scale of 1: 50 000 within the Bozhushan Ore Field to extract deep ore-finding information. Two gravity anomaly images displaying different scales of the ore-controlling factors were obtained. (1) The low-pass filtered image may reflect the deeply buried geological structures, hidden intrusions and concealed ore bodies. The negative gravity anomaly may reflect the overall distribution of granite bodies in the Bozhushan Ore Field. One negative gravity anomaly area may correspond to the exposed part of the Baozhushan granitic intrusion and the other corresponds to the concealed part of the granitic intrusion. The granitic intrusions are the main ore-controlling factors in this ore district. (2) The band-pass filtered image depicts the shallow concealed geological structures and geological bodies within this study area. There are two obvious negative gravity anomalies, which may be created by the hidden granites at different depths at both northwestern and southeastern sides of the exposed granitic intrusion. Thus the two negative gravity anomalies are favorable prospecting areas for various type of polymetallic ore deposits at depth. The gravity anomalies extracted by using the SVD exactly reflect the distribution of the ore deposits, structures and intrusions, which will give new insights for further mineral exploration in the study area.

Characteristics of particles in groundwater and their prospecting significance for the Shijiangshan Pb-Zn-Ag deposit, Inner Mongolia, China

The Shijiangshan concealed deposit in Inner Mongolia, China is located in a semi-arid region with a thick sediment layer on the surface. Samples of particles from deep and shallow groundwater in the deposit were analyzed by transmission electron microscopy (TEM). Corresponding fault gouge and oxide ore powder were collected and analyzed at the same time. These particles had sizes ranging from 5 to 400 nm and contained metallogenic elements, such as Pb, Zn, As, Cu, and Ag. Groundwater particles can reflect the properties of the deep concealed ores because the metal-bearing particles in the groundwater are similar in composition to the deep ores. In this study, particles with a carbon film covering their surface were discovered in groundwater. The carbon coating helped particles to remain in their primitive state, and thus, retain the more direct metallogenic information. Shallow groundwater particles can be used to predict the composition of deep concealed ore deposits. In thick overburdened areas, where local geochemical information on abnormal elemental levels is not obvious and geophysical prospecting methods may have multiple solutions, the accuracy of prospecting can be improved by using particles in groundwater that provide concealed orebody information, making such particles very important for prospecting.

Simulated Experiment of the Geothermal Resources Exploration in Tangli Hot Spring, Wuning, Jiangxi Province, China

The geogas field can reflect the deep-seated tectonic constructing information. Geogas method can be applied to the exploration of deep geothermal resources. In this paper, based on the advanced geogas model of metal ore, a set of simulation model of geogas transportation for hot spring is built. In the model, hot spring water collected from Wuning, JiangXi province, China is used to simulate hot spring reservoir, and the hot air flow formed by electric hot plate is used to simulate rising geogas flow. The transporting materials from hot spring reservoir are sampled in 20, 40, 60, 80 and 100 d respectively. More than 30 elements in these samples are determined with ICP-MS. The experimental results confirm that many elements in hot spring can be transferred out by geogas flow, transportation rate and transportation ratio of different elements is of obvious differences. The migratory activity of most elements in hot spring is greater than that in concealed ore body, thus the transportation amount of the element is easily recognizable. The elements with high transportation ratio and high concentration, including Cd, Cu, Pb, Sc, Y, Zn, are most helpful to indicate towards hot springs, the result provides reference to application of geogas survey on geothermal resource exploration.

Microscopic characterisation of metallic nanoparticles in ore rocks, fault gouge and geogas from the Shanggong gold deposit, China

Geogas prospecting is a potential method for exploring concealed ore bodies. However, a knowledge gap still exists regarding the relationship between metal-bearing nanoparticles (NPs) found in geogas and concealed ore bodies. In this paper, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were applied to study the occurrence of metal-bearing NPs in ore, gouge and geogas samples collected from a fault zone and a background area of the concealed Shanggong gold deposit. SEM observations of ore rocks showed that gold was mainly concentrated in microfractures and its distribution was correlated with that of Mo, S, Pb, and Co. According to the results of SEM, gold can coexist with pyrites in the form of sub-microscopic particles, as NPs or dispersed in a lattice. TEM analysis and in situ SEM observations of ore rocks suggested that gold and other metallic particles can form during the process of mineralization. After mineralization, it is hypothesized that NPs can be generated by faulting and weathering. Meanwhile, morphological and chemical composition analyses indicate that aggregation and biological activity can change the status of NPs occurrence in fault gouges. TEM showed that there were more particles in the ascending geogas collected in the fault zone than in the background area. In terms of composition, particle samples collected from the background area were primarily non-metallic oxides and aluminium silicate. More metallic NPs containing Zn, Cu, Cr and Ni were observed in geogas collected in the fault zone. As for morphology, while the NPs in the fault zone geogas showed various morphologies, spherical dominated in geogas from the background area. These results suggest that NPs in ore rocks and gouge can be rapidly channelled to the surface through faults. The driving forces of NP transportation may include of temperature and pressure differences and the earth's magnetic field. This knowledge consolidates the view that NPs in geogas can provide information about the deep Earth. This study increases our knowledge of NPs in gold deposits, fault gouges and geogas, and enhances our understanding of NP generation and migration mechanism sin fault systems.

Chlorite chemistry of Tongshankou porphyry-related Cu–Mo–W skarn deposit, Eastern China: Implications for hydrothermal fluid evolution and exploration vectoring to concealed orebodies

Recent years, the depletion of shallow mineral resources has drawn increasing attention to the exploration of hidden ore bodies in deep of skarn type deposits. Chemical composition of chlorite is an effective tool for tracing the hydrothermal fluid evolution, and has been increasingly used for deep-level exploration of porphyry Cu (–Au) deposits (PCDs). However, the technique was rarely applied onto (porphyry-related)-skarn deposits. The Tongshankou Cu–Mo–W deposit (0.55 Mt Cu @ 0.86%, 0.01 Mt Mo @ 0.10% and 0.12 Mt WO3 @ 0.19%) is one of the largest skarn–porphyry deposits in the Middle–Lower Yangtze River Metallogenic Belt (MLYRB) in Eastern China. In this study, new petrographic and trace element data of the hydrothermal chlorites from Tongshankou were presented to constrain the ore-fluid evolution, and to explore the vectoring potential of the concealed orebodies at Tongshankou. Four types of chlorite have been identified, i.e., G-type chlorite that replaced the original magmatic biotite or hornblende, V-type chlorite in chlorite–quartz–sulfides veins in the granodiorite porphyry (alteration zones I and II), S-type chlorite that replaced garnet in the intensive skarn alteration zone (III) and M-type chlorite–quartz–calcite–sulfides veins that cut the (dolomitic)-marble in the distal alteration zones IV and V.All the four types of chlorites are typically trioctahedral chlorite. The Fe-Mg, Tschermark and di-trioctahedral substitution mechanisms likely control the geochemical variations of the Tongshankou chlorites. Empirical thermometer indicates that the Tongshankou chlorites were crystallized at 169–322 ℃. Compared with typical metamorphic chlorites, the higher Zn and Sr contents but lower Al content in the Tongshankou chlorites can potentially distinguish the skarn-type hydrothermal chlorites from typical metamorphic ones. Compared with the chlorites in the typical PCDs, the Tongshankou G-type chlorite has higher Fe, Zn, As and Sn contents, but lower Al, Mg, Co and Cu contents, which likely reflect its protolithic and/or fluid geochemical inheritance. The Tongshankou V-, M- and S-type chlorites have high contents of mobile elements (such as Sr, Ca, Sn and B) and metals (such as Fe, Cu, As, Zn and Pb), indicating that they were directly precipitated from the hydrothermal fluids. From the granodiorite porphyry to the marble wallrocks, the spatial chlorite geochemical variations at Tongshankou indicate that the increasing Zn, Mn, Ga, Ge and Pb contents, and decreasing V, Sc and Ti contents are potential vectors toward concealed mineralized porphyries at Tongshankou. Our study highlights that the chlorite geochemistry is a potential tool for ore-fluid tracer and vectoring tool toward concealed skarn–porphyry orebodies in the MLYRB.

Short wavelength infrared (SWIR) spectroscopy of phyllosilicate minerals from the Tonglushan Cu-Au-Fe deposit, Eastern China: New exploration indicators for concealed skarn orebodies

The Middle–Lower Yangtze River Metallogenic Belt (MLYRB) is one of the most important Cu–Au–Fe–Mo skarn–porphyry metallogenic belts in Eastern China. After several decades of mining, the shallow-level mineral resources have been gradually exhausted, which call for new exploration tools for concealed orebodies. The Tonglushan Cu–Au–Fe skarn deposit (86.3 Mt @ 1.66% Cu, 0.94 g/t Au and 39.4% Fe) is located in the western MLYRB. Skarn alteration/mineralization are mainly hosted in the contact zone between Cretaceous (~141 Ma) quartz monzodiorite (and its porphyry) and the Lower Triassic carbonate rocks. Based on the mineral assemblages and their macro/microscopic textural relationships, the Tonglushan Cu–Au–Fe mineralization/alteration can be divided into five stages: pre-ore (S1: skarn–potassic alteration), Fe ore (S2: retrograde alteration and Fe-oxides), Cu–Au ore (S3: quartz–sulfides), carbonate alteration (S4) and supergene alteration (S5). Apart from the major skarn and retrograde alteration and carbonate minerals, abundant fine-grained phyllosilicate minerals, including chlorite, white mica (illite, muscovite and phengite), smectite (montmorillonite and saponite) and kandite (kaolinite, dickite and halloysite) group minerals have been identified at Tonglushan by SWIR spectrometry. Integrating petrographic observations and SWIR spectral analysis, four alteration zones (with distinct phyllosilicate assemblages) have been distinguished from the intrusion outward: (I) ore-barren quartz monzodiorite and its porphyry (montmorillonite–illite–chlorite), (II) endoskarn close to the skarn–hydrothermal mineralization center (montmorillonite–illite–chlorite–kaolinite–dickite), (III) skarn–hydrothermal mineralization center (saponite–chlorite), and (IV) the external contact zone in (dolomitic) marble (montmorillonite–chlorite ± kaolinite ± dickite).For the Tonglushan altered rock samples, SWIR spectrometry has identified wavelength shifts in the Fe–OH, Al–OH and sub-Al–OH absorption features of chlorite, white mica–montmorillonite and kandite, respectively. Chlorite Fe–OH absorption occurs at longer wavelengths (>2,250 nm), white mica–montmorillonite Al–OH absorption occurs at unusually long (>2,212 nm) and short (<2,202 nm) wavelengths, and kandite sub-Al–OH absorption occurs at longer wavelengths (>2,170 nm) in strongly-altered skarn proximal samples. Moreover, the presence of kaolinite, dickite, saponite, actinolite, phlogopite and/or chlorite–quartz–sulfides veins in these samples can be used as new vectors to explore deep-level mineralization centers at Tonglushan. The distribution of various kinds of phyllosilicate alteration minerals at Tonglushan, especially the white mica and kandites (with higher crystallinity) in the deep contact zones, indicates that the neutral to acidic hydrothermal fluids may have been generated with the precipitation of Fe-oxides and sulfides. This study also highlights the potential of SWIR spectroscopy of phyllosilicate minerals for exploring concealed skarn orebodies in the MLYRB.

Combination use of gravimetry, CSAMT and SOTEM methods in geophysical prospection of a polymetallic silver-copper deposit: Case studies in the Inner Mongolia, China

Geophysical methods, which use physical properties to reveal the structure of the underground spaces, have been widely applied in geological exploration. However, a single geophysical approach only reflects the distribution of a kind of physical property and therefore has its limitations. To improve the reliability of geophysical methods in actual geological exploration, in this paper, we are trying to combine the use of a variety of geophysical exploration methods, such as gravity, control source audio magnetotelluric method (CSATMT) and electrical source short offset transient electromagnetic method (SOTEM), to a specific metal in Inner Mongolia. Firstly, the gravimetry method is applied to figure out the anomalous area, and then the CSAMT method is adopted to probe the deep electrical distribution. Finally, the SOTEM method is applied for further auxiliary verification. Results show that the underground structure is well revealed by combing the use of these methods. This paper can be used as a reference for the exploration of concealed ore bodies in polymetallic ore deposits. To use a combination of methods to measure. In the geological exploration of a polymetallic silver-copper mine in Inner Mongolia, a variety of geophysical exploration methods such as gravity measurement, controllable source audio magnetotelluric measurement and electrical source short offset transient electromagnetic method were combined, and geological data were combined. The better exploration results provide reference for the layout of the drilling location of the drilling project, and provide assistance for the prospecting breakthrough of the concealed ore body in the polymetallic mining area.

Geosciences in Central South University: A state-of-the-art review

In recent decades, colleagues working in the Discipline of Geological Resources and Geological Engineering at Central South University made significant progress in theoretic study and application of geophysics, ore deposit and shale gas geology, 3D predictive modeling of concealed resources, and geological engineering. In geophysics, world-class progress was achieved in the development, data processing, equipment, and scientific survey of electromagnetic method in onshore and offshore environments and the tectonic evolution of the Tibetan Plateau. Especially, advanced wide-field electromagnetic exploration method and equipment as a highlight technique won the first prize of National Science and Technology Invention of China. In ore geology, progressive and complex characteristics of most nonferrous ore deposits and the geodynamic relationship between crust-mantle reaction and mineralization in south China were revealed. Progressive metallogenic models of certain typical ore deposits were established based on the study of fluid inclusion and geochemistry. According to characteristics of complex metallogenic system of polygenetic ore deposit, key ore-controlling factors were found and summarized. The investigation on unconventional resources advanced China???s shale gas resource evaluation system. In 3D predictive modelling of metallogenic, a large-scale location prediction model was established for exploration of crisis mines and concealed ore deposits. Our developed 3D predictive modeling techniques for concealed orebodies were widely used to explore deep mineral resources in China. In geological engineering area, the key technologies for deep drilling into complex formations were developed. Especially the drilling fluid and tools were utilized in the fieldwork. The rock and soil mechanics analysis method and anchor technologies were also established and applied to engineering practice.

Nanoparticles in groundwater of the Qujia deposit, eastern China: Prospecting significance for deep-seated ore resources

The characterization of nanoparticles in groundwater is recognized as an important tool that can be applied to mineral exploration. In this paper, we investigate the concealed orebodies of the Qujia gold deposit in the Jiaojia orefield of eastern China by analyzing ore-related nanoparticles in groundwater using transmission electron microscopy. The nanoparticles contain variable amounts of ore-related elements (e.g., Ag, Cu, Zn, La, Ce, Pb, Pt, and S). Some of these elements are rarely found in natural settings unrelated to orebodies or mineral extraction, but are strongly linked to concealed orebodies in the study area. These nanoparticles, which are diverse in their shapes, aggregated features, and degrees of crystallinity, can be grouped in terms of composition as: (i) native metal nanoparticles, (ii) metal-based nanoparticles, and (iii) carrier nanoparticles associated with trace elements. We propose that these three main types of nanoparticles enable the efficient transport of ore-forming elements in groundwater. The results of this study provide insights into the migratory behaviour of ore-related nanoparticles in groundwater, and our methods could be applied for detecting deep-seated mineral deposits.

Prediction and evaluation of concealed ore body in 3D environment

3D models of stratigraphy、 rock、 tectonic、 mineralization and so on are established, based on the data of digital uranium exploration achievement, focusing on 3D modeling of uranium deposit、 evaluation of deep uranium resource. Exploration achievement model are formed by the result above accompany with geophysical geochemical prospecting data and Interpretation. The prediction and evaluation of deep deposits which delineated metallogenic advantageous target area are carried out by weights of evidence method. The applications of digital uranium exploration achievement are realized by the application research above, which improving efficiency and broadening application range and depth of digital exploration achievement.

Characterization of metal-bearing particles in groundwater from the Weilasituo Zn-Cu-Ag deposit, Inner Mongolia, China: Implications for mineral exploration

Nanoparticles in groundwater have important implications for facilitating the transportation of metals in groundwater and, to a certain extent, can reveal the geochemical conditions of the groundwater. Therefore, there is an increasing interest in analytical techniques that allow for in-depth characterization of nanoparticles in the groundwater and utilize these characteristics for geochemical prospecting. Metal-bearing particles in groundwater samples from deep-lying orebodies (referred to as “deep groundwater”) of the Weilasituo Zn-Cu-Ag Deposit, Inner Mongolia, China and the groundwater from motor-pumped wells of a catchment basin around Weilasituo were chosen to study. Using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectrometer (EDS), individual particles were characterized. Based on the TEM compositional and structural investigation, Ag-, Pb-, Cu-, Zn-, Sn-, As- and Mo-bearing particles were observed in the groundwater samples collected in the deep ore and the catchment basin. These metal-bearing particles are compositionally and structurally similar to the ore mineral/metal-bearing particles observed in the ore bodies and can directly reflect the ore-forming elemental characteristics, e.g., metallogenic element assemblage and mineralization type, of the Weilasituo deposit. The result indicates that the metal-bearing particles originating from the concealed ore bodies migrate via the groundwater flow and discharge to the catchment basin. This finding implies that the metal-bearing particle phases have great significances in facilitating the transportation of ore-related species and forming the geochemical anomalies in the groundwater. This field-scale study demonstrates that, by applying the analytical transmission electron microscopy, the nanocharacteristics of metal-particles can be utilized to improve the accuracy and sensitivity for geochemical mineral exploration.

Discovery of concealed ore-bodies at the Dongping gold deposit, northern China, revealed by the study of ore-controlling structures

The Dongping gold deposit is the largest gold deposit in the Hebei province, China, with proven gold reserves of more than 100 tons. After the main gold ore-bodies were mined out, the Dongping gold deposit faced a shortage in gold reserves with an uncertain future. As a result, we conducted systematic studies on the ore-controlling structures at the Dongping gold deposit, with the aim of finding additional concealed ore-bodies, should these be present. Gold mineralization at Dongping is controlled by two stages of maximum principal compressional stress (σ1): NW-trending stress that produced the NE- to NW-trending structures, and sub-vertical stress that produced the circular structure, respectively. The sub-vertical compressional stress may have resulted from the emplacement of a concealed intrusive body, which also led to horizontal extensional stress, generating structures surrounding the intrusion. Development of such structures potentially increased the permeability of the local crust, facilitating the mobilisation of gold-bearing hydrothermal fluids that subsequently precipitated along the structures, forming the gold ore-bodies. We propose that the deep part of the Dongping gold deposit at the lithological contact with the concealed intrusive bodies is prospective for the exploration of additional reserves, which is supported by our subsequent drilling and the discovery of concealed gold ore-bodies beneath the deposit.