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Data-driven prospectivity modeling based on deep learning, particularly supervised learning, has demonstrated outstanding performance for mineral exploration targeting in the past years, thanks to its powerful feature learning ability. However, this approach necessitates a substantial amount of large, high-quality labeled training data, and the scarcity of known mineral deposits poses significant challenges in constructing a high-performance mineral prospectivity prediction model. Self-supervised contrastive learning can alleviate this problem by exploiting large amounts of readily available unlabeled data. In this study, we utilized geochemical element data from the Malanyu district to train a self-supervised contrastive learning model. This model was then employed to predict gold mineral prospectivity, and its accuracy was compared with supervised learning method. The results show that the self-supervised contrastive learning model has higher performance in prospectivity prediction than the supervised learning model and its recognition accuracy reaches 100.00%, which is 7.41% higher than that of the supervised learning model ResNet50 and 14.81% higher than that of the supervised learning model MobileNetV2. At the same time, the prediction results of gold prospecting have a strong consistency with the known gold deposits in this district. This study demonstrates the feasibility of applying the self-supervised comparative learning model to the prediction of gold prospects, and it is of great significance to realize intelligent prediction of mineral resources. Article Highlights: A self-supervised contrastive learning model is proposed for predicting gold prospectivity. The model can learn valuable feature representations from a large amount of readily available unlabeled geochemical data. Compared to the supervised learning method, the proposed model not only reduces reliance on the number of known deposits but also achieves higher accuracy. [ABSTRACT FROM AUTHOR]

Efficient separation of Carlin-type gold deposits is a challenge for the utilization of gold ores. The majority of gold in Carlin-type gold ores occurs as invisible gold within pyrite, resuiting in the poor crysta1lization of pyrite. The previous investigation has shown that oxidation caused the homogenization effect, thereby resuiting in adhesion, thus, deteriorafing the separation resuits of Carhn-type gold deposits. Based on the understanding of interacfions mechanssm between pyrite and dolomite,a technical prototype of "strengthening dsspersion" to opttmize the separation index of Carlintype gold deposits was preliminari1y proposed and highly selective reagents sodium amino phosphate was se!ected to realize the apphcation of the technical prototype, good separation indccators have been obtained in the laboratory. In this paper,the turbidity test was used to verify the effects of se!ected reagents on strengthening dispersion, meanwhlle, the artificial mixed ore and the real ores of high-and low-grade Carlin-type gold deposit were used to demonstrate the effect of reagent on mineral separation. The resuits showed that; sodium aminophosphate can achieve the expected goal of increasing the Fe and Au recovery in the concentrate, and decreasing the MgO floating ratio, whUe,increasing the Au enrichment ratio to about 3. 5. The above resuits show that sodium amino phosphate can improve the separation effidency between pyrite and dolomite by strengthening the dsspersion of oxidized pyrite and dolomite particles,so as to optimiie the flotation index of Carlintype gold mine. The prototype technology provides a reference for the development of effic!ent separation between pyrite and dolomite minera!s,and has the potential for popuiarizafion and apphcation. [ABSTRACT FROM AUTHOR]

Tick Hill gold deposit is a unique gold mineralisation style in the Mary Kathleen Fold Belt in the Mount Isa Inlier. The gold at Tick Hill is generally pure without silver and was formed during two discrete metamorphic-deformation events (D1 and D3). Early gold was observed as inclusions or coarse grains hosted within D1 peak-metamorphic diopside, scapolite and hornblende from the garnet–biotite–hornblende (tschemakite)–plagioclase (andesine)–quartz assemblage. Late gold is closely associated with bismuth selenide, chlorite, albite, sericite and K-feldspar, and formed during D3. The syn-D1 garnet–plagioclase–hornblende–quartz–biotite assemblage was used to constrain the pressure and temperature (P–T) conditions of metamorphism and mineralisation using the garnet–plagioclase–hornblende–quartz barometer and the hornblende–plagioclase, garnet–biotite and garnet–hornblende thermometers. The results show that peak metamorphism at Tick Hill reached P–T conditions of 6.0–7.6 kbar and 720–760 °C. These P–T conditions together with gneissic and migmatisation textures recorded in different rock types at the Tick Hill area indicate that the peak metamorphism preserved in the area occurred at the amphibolite–granulite facies, compared with the amphibolite facies at the southern Mary Kathleen and Eastern Fold Belt. The D3 chlorite, which formed during stage 2 to stage 4 mineralisation events, displays a wide range of compositions reflecting a gradual retrograde temperature change from ∼380 °C to ∼130 °C. The pressures during D3 could not be reliably determined, but the presence of various Bi-selenides suggests that towards the waning stages of D3, the rocks may have been exhumed to a pressure less than 1 kbar. The 1790–1770 Ma D1 peak metamorphism at Tick Hill reached 6–7.6 kbar and 720–760 °C. The 1525–1520 Ma D3 hydrothermal mineralisation at Tick Hill Deposit occurred at temperatures between ∼380 °C and ∼130 °C. The main D3 gold accumulation episodes at Tick Hill occurred at temperatures ranging from ∼380 to 160 °C. [ABSTRACT FROM AUTHOR]

Silver is probably the closest isotopic proxy to track monoisotopic gold and has been shown to have great potential to yield new information on the origin and enrichment processes of gold. This study describes the development of a tailored analytical protocol for accurate analysis of Ag isotopes and provides the first Ag isotope data for the Paleoproterozoic Rajapalot Au-Co deposit, Finnish Lapland. Six native Au samples yield ε109Ag values (relative to NIST SRM 978a) from −6.8 to +2.1 and are within the range of Ag isotopic compositions reported for native Au samples. The mean of the analyzed Au samples is ε109Ag = −3.8 ± 1.7 (2SD) with most of the samples with negative ε109Ag values (−6.7 to −2.0); one sample has a positive ε109Ag value of +2.1 ± 0.5. Silver isotope fractionation in the Rajapalot Au deposit was likely associated with physicochemical processes related to deposition and/or re-mobilization of the ore rather than with source region inheritance. It is suggested that redox reactions involving Ag+ ↔ Ag0 phase change primarily account for the isotopic differences within the deposit. Our results also suggest that the Rajapalot Au-Co deposit was formed via multistage ore-forming processes and/or that the primary ore was re-mobilized, which caused isotope fractionation along fluid pathways. Silver isotope variation within a deposit may mark a fractional crystallization trend with the lightest isotopic composition representing the earliest precipitate. Hence, Ag isotopes show potential as an isotopic vectoring tool in search of Au-enriched domains. [ABSTRACT FROM AUTHOR]

The gold deposit offshore of Northern Sanshandao is an ultra-large-scale gold deposit discovered in the Jiaodong ore area in recent years. This deposit is a fractured-zone altered-rock-type gold deposit; however, its ore genesis and precise mineralization processes are still highly controversial. Based on petrographical observation, the trace elements, sulfur isotopes, and rubidium–strontium isotopes of the gold-bearing pyrite were analyzed using LA-MC-ICP-MS to obtain the source of the ore-forming fluids and ore genesis. The results show that Au has a good positive correlation with Ag, As, and Cu. It is speculated that the As in the pyrite of the gold deposit offshore of Northern Sanshandao is in the form of As−, replacing S− and entering the pyrite, causing its lattice defects, and thus promoting the entry of Au+ into the gold-bearing pyrite. The Co/Ni ratios mainly range between 0.1 and 10, indicating that the mineralization process has experienced different forms of hydrothermal evolution and the mixing of different fluids. The results of the in-situ sulfur isotope analysis show that pyrite δ34S in the mineralization period is characterized by a high sulfur value. The authors of this study believe that the initial sulfur isotope composition has mantle-derived components. The large-scale, deep cutting, and high degree of fragmentation in the Sanshandao fault zone are conducive to the interaction between fluids and rocks, as well as the mixing and addition of seawater, resulting in the characteristic high δ34S value. The Sr isotopic compositions indicate a crust–mantle mixing attribute of the mineralized material source. The Rb–Sr isochron age of the pyrite is 118.5 ± 0.65 Ma, which represents the age of gold mineralization. According to the characteristics of the trace elements and sulfur isotopes, it is inferred that the gold deposit minerals offshore of Northern Sanshandao originated from deep magmatic-hydrothermal reservoirs, and the mixing of seawater and Au–As-rich hydrothermal fluids was the formation mechanism of huge amounts of gold precipitation. [ABSTRACT FROM AUTHOR]

Jurassic-Cretaceous magmatic rocks are widely distributed in the Jiaodong area, North China. These magmatic rocks are closely associated with gold deposits, but their petrogenesis and geodynamic background are still controversial. The Late Jurassic-Early Cretaceous granitic rocks exposed in the Guocheng area, Jiaodong Peninsula are the focus of this paper. Zircon U-Pb dating, Hf-O isotope and whole rock geochemical analysis are used to determine the petrogenesis of these rocks. Combined with previous data, the geodynamic processes of granite formation in different time intervals are investigated which provide new petrological evidence for understanding the magmatic-mineralization and tectonic background of the Jiaodong area. Samples were collected from the Queshan and Shazibu plutons. The Queshan pluton is a mylonite granite, one sample of which yields a 206U-238Pb zircon age of 156 Ma, while the Shazibu pluton is a quartz monzonite, one sample of which records a 206U-238Pb zircon age of 117 Ma. The two plutons have variable zircon Hf-O isotopic compositions: zircon εHf(t) values of the Queshan pluton are −29.2 to −22.8, and δ18O values are 7.30–7.84 ‰, while the Shazibu pluton has relatively high zircon εHf(t) values (−21.6 to −21.0) and δ18O values of 7.48–8.43 ‰. Whole-rock geochemical data shows that the Queshan pluton has high Sr/Y (60.7–169) and (La/Yb)N (34.6–65.9) values and low Y (3.11–10.3 ppm) and Yb (0.29–0.85 ppm) contents, akin to adakites, whereas granites of the Shazibu pluton are A-type with high Zr+Nb+Ce+Y contents (354–420 ppm) and zircon saturation temperatures (752–795°C). Based on the geochemical and isotopic data, the Late Jurassic Queshan pluton is the product of partial melting of thickened lower crust of the North China Block, while the Early Cretaceous Shazibu pluton formed via fractional crystallization of mafic rocks derived from partial melting of the lower crust of the North China Block. Although both plutons were derived from the lower crust of the North China Block, the nature of the lower crust was modified by involvement of more depleted mantle-derived materials during the Early Cretaceous. From the Late Jurassic to the Early Cretaceous, the rock types (from the adakite to A-type granite) and the nature of the magma source suggest a shift in geodynamic processes. Combined with previous research, the Late Jurassic Queshan pluton is proposed to have formed under low-angle subduction of the ancient Pacific Plate, while the Early Cretaceous Shazibu pluton formed subsequently during Pacific Plate rollback and extension. The Early Cretaceous transformation of tectonomagmatic environments provided favourable conditions for the formation of large-scale gold deposits in the Jiaodong region. [ABSTRACT FROM AUTHOR]

Geostatistical cascade modeling of Mineral Resources is challenging in vein-type gold deposits. The narrow shape and long-range features of these auriferous veins, coupled with the paucity of drill-hole data, can complicate the modeling process and make the use of two-point geostatistical algorithms impractical. Instead, multiple-point geostatistics techniques can be a suitable alternative. However, the most challenging part in implementing the MPS is to use a suitable training data set or training image (TI). In this paper, we suggest using the radial basis function algorithm to build a training image and the DeeSse algorithm, one of the multiple-point statistics (MPS) methods, to model two long-range veins in a gold deposit. It is demonstrated that DeeSse can replicate long-range vein features better than plurigaussian simulation techniques when there is a lack of conditioning data. This is shown by several validation processes, such as comparing simulation results with an interpretive geological block model and replicating geological proportions.

Nyang-wale area is located in the northwestern part of Tanzania, within the Sukumaland greenstone belt to the south of Victoria. The area hosts multiple banded iron formation-type gold deposits, with ore bodies occurring in shear zones within the banded iron formation, exhibiting distinct stratigraphic control characteristics. Through the analysis of the geological characteristics of the discovered deposits, combined with magnetic anomaly features, electrical anomaly features, and soil geochemical characteristics, the prospecting direction of the banded iron formation-type gold deposits in Nyang-wale area was analyzed. It is suggested that, based on the current mining activities, the primary prospecting direction in this area should focus on the search for concealed greenstone areas, followed by integrated development, in order to achieve significant break throughs. [ABSTRACT FROM AUTHOR]

Maotoushan Gold Deposit is located in the eastern part of Chifeng City, Inner Mongolia Autonomous Region. It is widely distributed in the gold deposits of the northern margin of the North China Craton. This paper systematically expounds the geological characteristics of Maotoushan Gold Deposit, suggesting that the ore bodies are located in the Lower Permian Jiujuzi Formation, and the mineralized rocks consist of metamorphic sandstone, red chert, and carbonaceous slate. Gold is present in the form of hydrothermal superimposed quartz veins and veinlets, which are consistent with the attitude of the strata, indicating a sedimentary-dynamic metamorphic gold deposit. The metallogenic regularities and ore-controlling factors of Maotoushan Gold Deposit are summarized, and prospecting indicators are proposed, providing theoretical references for the exploration and prospecting of similar gold deposits along the northern margin of the North China Craton. [ABSTRACT FROM AUTHOR]

Jijiawa Gold Deposit is located in Xiongershan gold - silver polymetallic ore concentration area in western Henan Province. Some progress has been made in deep prospecting in recent years. In order to carry out further pros- pecting, the IP sounding method has achieved good results in Jijiawa Gold District. The apparent polarizability parameters are sensitive to the ore-bearing geological bodies, and the highly polarized geological bodies are detected in the north of the No. 16 exploration line. It is inferred that there is a concealed ore-bearing porphyry body extending from northeast to southwest in the depth of the deposit. Through borehole primary halo sample testing, high-temperature element W anomalies are found on the No. 16 exploration line, indirectly verifying the prediction results of IP sounding. This study result has certain reference significance for prospecting the vein gold silver polymetallic deposits in Xiongershan gold - silver polymetallic ore concentration area. [ABSTRACT FROM AUTHOR]

Plenty of gold deposits related to Late Mesozoic craton destruction are widely distributed in eastern North China Craton. However, significant differences in research degrees, ore-forming characteristics, and proven reserves exist among different regions in the North China Craton. The Liaodong Peninsula has similar regional geological characteristics to those of the Jiaodong Peninsula, with both experiencing craton destruction during Late Mesozoic, but the two areas have substantial differences in terms of gold mineralization and the proven gold resources. Based on regional geology, Mesozoic magmatic-tectonic evolution and ore geology, combined with integrated geophysical exploration and big data AI resource prediction, in this paper, we propose that the ore-forming materials of Late Mesozoic gold deposits in Liaodong were mainly originated from mantle-derived melts and/or fluids induced by craton destruction. The gold deposits were primarily controlled by NE-NNE-trending faults, mainly classified as fracture-controlled altered rock-type and sulfide-bearing quartz vein-type. Moreover, our study predicts that the Yalu River fault zone and its related secondary faults, as well as the periphery and deeper parts of known goldfields, are the important regions for future gold resource exploration. The Yalu River metallogenic belt has an enormous potential for gold resources, and the Liaodong Peninsula has a potential to add thousands of tons of gold resources. [ABSTRACT FROM AUTHOR]

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Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Shiwu gold deposit is located in the middle of Jinshan nappe structure in Wannian nappe in the northern part of the eastern section of the Qinzhou-Hangzhou junction belt. The ore body is strictly controlled by secondary ductile shear zone, and the ore types are mainly mylonite and ultra mylonite type. The characteristics of the ore and the occurrence state of gold minerals in the Shiwu gold deposit were studied by light microscope observation, X-ray diffraction analysis (XRD), chemical composition analysis, scanning electron microscope analysis ( SEM). The research shows that the metal minerals is mainly pyrite, followed by arsenopyrite, with a particle size range of 0. 04 mm to 0. 4 mm. The gangue minerals are mainly quartz, and the gold mineral is only native gold. The occurrence state of gold mineral is mainly fissure gold (64. 92% ) and intergranular gold (23. 99% ). Classified by particle size, it mainly consists of grained gold (57. 24% ) and microgranular gold (27. 01% ), with a particle size range of 0. 005 mm to 0. 037 mm. When the grinding fineness reaches 75% at 0. 074 mm, full sulfide flotation can effectively enrich and recover gold minerals. Through comparative research on beneficiation processes, the final gold recovery rate of the “ fast flotation-fast flotation tailings re-flotation” beneficiation process is the highest (93. 89% ). [ABSTRACT FROM AUTHOR]

Geographic information system-based mineral prospectivity mapping (MPM) aims to generate targets by combining multiple proxy layers containing geology, geochemistry, and geophysics information based on an available understanding of geological processes and translating it into critical targeting criteria. However, factors such as an imperfect geological understanding with numerous heuristic natures and intrinsic biases, the inaccuracy and sparsity of datasets, and multiple selections of predictive methods adversely affect the results of MPM and jeopardize the reliability of decision-making in exploration. Thus, a series of knowledge-driven and data-driven MPM approaches to counterbalance these disadvantages have been proposed. Uncertainty is defined as a metric of the various scales of the likelihood and consequences, which is helpful to quantitatively represent the above risks. In this paper, the uncertainty in the final three-dimensional prospectivity map is analyzed and interpreted in terms of quantification, visualization, and comparison of different predictive approaches, and a novel technology is proposed based on a (1 + ε) approximate global optimum strategy derived from the truth discovery society. It outputs the globally optimal truth (p*) as the overall mathematical expectation and a set of weights w i as the representation of reliability. Here, a previous study of the Haoyaoerhudong gold deposit, which is one of the largest black-rock-series-type gold mines in China, was reevaluated. The method demonstrated the following advantages: (i) sorted the reliability of potential models built by multiple predictive variables and different mathematical methods, (ii) provided a "best-guess-decision" prospectivity result by combining the best reliability model from w i and the signal-to-noise ratio (SNR) of the risk–return model, and (iii) provided a statistically final uncertainty model by combining p* and risk information. [ABSTRACT FROM AUTHOR]

Motivated by the potential of focused-electron-beam-induced deposition (FEBID) in the fabrication of functional gold nanostructures for application in plasmonic and detector technology, we conducted a comprehensive study on [Au(CH3)2Cl]2 as a potential precursor for such depositions. Fundamental electron-induced dissociation processes were studied under single collision conditions, and the composition and morphology of FEBID deposits fabricated in an ultrahigh-vacuum (UHV) chamber were explored on different surfaces and at varied beam currents. In the gas phase, dissociative ionization was found to lead to significant carbon loss from this precursor, and about 50% of the chlorine was on average removed per dissociative ionization incident. On the other hand, in dissociative electron attachment, no chlorine was removed from the parent molecule. Contrary to these observations, FEBID in the UHV setup was found to yield a quantitative loss and desorption of the chlorine from the deposits, an effect that we attribute to electron-induced secondary and tertiary reactions in the deposition process. We find this precursor to be stable at ambient conditions and to have sufficient vapor pressure to be suitable for use in HV instruments. More importantly, in the UHV setup, FEBID with [Au(CH3)2Cl]2 yielded deposits with high gold content, ranging from 45 to 61 atom % depending on the beam current and on the cleanliness of the substrates surface.

The Xiaoqinling area is located in the eastern part of the Qinling Orogen and experiences early and late Mesozoic gold mineralization controlled by structural deformation. The relationship between the two stages of mineralization and the orogenic process of the Qinling Orogen is unclear. We investigated the deformation and alteration of E-W striking veins in the Xiaoqinling area. The geometric features revealed that all the veins developed within the E-W-striking Guanyintang brittle-ductile shear zone. The vein was subparallel to the shear zone, dipped at 30°-60°, and had a wave-like appearance. The Guanyintang shear zone underwent three deformation stages: sinistral shearing (D1), dextral thrusting (D2), and sinistral normal faulting (D3). The development of ore- bearing quartz veins was controlled by deformation during D2, and the auriferous pyrite and minor chalcopyrite developed along the shear foliations. Re-Os dating of the molybdenite revealed a well-constrained isochron age of 230.2 ± 2.6 Ma, indicating the E-W striking shear zone developed in Late Triassic. This early Mesozoic shearing deformation in Xiaoqinling represents the early Mesozoic metallogenesis is correlated with the collisional orogeny of the Qinling orogen. [ABSTRACT FROM AUTHOR]

We present in situ LA-ICP-MS U-Pb dating of xenotime and monazite in assemblages with native gold and Au (Ag) tellurides from the Xiaoqinling lode gold district in central China. Composite xenotime and monazite grains formed through coupled dissolution-reprecipitation reactions reveal two discrete gold mineralization events. The first gold mineralization event, recorded by monazite (158.6 ± 3.3 Ma, Tera-Wasserburg lower intercept age) and xenotime cores (157.11 ± 0.83 Ma, weighted mean 206Pb/238U age), is characterized by the mineral assemblage of lingbaoite (AgTe3)-sylvanite ([Au,Ag]2Te4)-stützite (Ag5–xTe3)/native tellurium-sylvanite-stützite. The second gold mineralization event, recorded in the rims of xenotime (135.46 ± 0.93 Ma, weighted mean 206Pb/238U age), is characterized by the mineral assemblage of native gold-calaverite (AuTe2)-petzite (AuAg3Te2)-tellurobismuthite (Bi2Te3). Our study implies that the large-scale Jurassic mineralization event in eastern China, related to flat subduction of the paleo-Pacific plate beneath the eastern China continent, also caused widespread gold mineralization in the Qinling-Dabie Orogen, in addition to production of its world-class porphyry Mo deposits. The fact that only a few Jurassic gold mineralization ages have been reported before, may be due to the lack of suitable geochronometers to record the earlier Jurassic hydrothermal processes, which have been overprinted by the better-recognized Early Cretaceous gold mineralization event. This study also presents a rare example of xenotime compositional alterations and resetting of U-Pb ages induced by low to moderate salinity carbono-aqueous fluids at low temperatures. The textural relationships between gold minerals in contact with such composite xenotime crystals demonstrate that they could have precipitated before, coeval with, or after the dated domains. Since low to moderate salinity carbonoaqueous fluids are commonly involved in the formation of lode gold deposits, it is crucial to examine xenotime textures and recognize potential alteration textures before carrying out isotopic dating of xenotime collected from these deposits. Without prior compositional and textural characterization, attempts to date such composite crystals could yield mixed dates and meaningless ages. [ABSTRACT FROM AUTHOR]

Radiometric mapping could play a prominent role in locating the host rock or alteration that leads to gold mineralization. Nevertheless, in low-sulfidation epithermal gold deposits, the radiometric signatures have to be priorly characterized due to their geometry. It is comprised of a small ore vein system within the large alteration zones. The Pongkor gold mine is a low-sulfidation epithermal deposit and was selected for this purpose. The method started with the surface identification of radiometric signatures on altered and unaltered rocks near Pongkor using portable spectrometers. They are followed by the characterization of the underground mining front, which is comprised of different types of veins and host rocks. The results show that the altered rocks were characterized by a high K% and a low eTh/K ratio. Vice versa, the mineralized veins show low radioelement concentrations. Following the characterization of the geometry of alteration zones and mineralized veins, a study of the relationship between radioelements detected by radiometric mapping and gold pathfinder elements was conducted. Gold pathfinders of Mn, Fe, Zn, As, and Pb were selected for correlation studies with the radioelement. The pathfinders and radioelements were more significantly correlated in veins compared to the host rock. Based on this study, radiometric mapping has the potential and benefit of being applied in the exploration of low-sulfidation epithermal gold deposits. An alteration zone could be delineated by K or eTh/K as an anomaly indicator, and the vein bodies could also be delineated using low K or eTh as an anomaly indicator. [ABSTRACT FROM AUTHOR]

By studying both the microscopic physical and chemical typomorphic characteristics of typical mineral pyrite samples associated with representative gold deposits on the north-central margin of the North China Platform, this paper seeks to identify macroscopic metallogenic mechanisms of gold deposits and to reveal the formation mechanism of lattice gold in pyrite. Typomorphic characteristics of pyrite reveal that pyrite grain size has a negative correlation with gold content. Cubic pyrite, as the dominant crystal form, contains more gold than pentagonal dodecahedral pyrite. Both pyrite crystal forms and chemical compositions indicate that the replacement style of gold deposit formed in a low saturability, low sulfur fugacity, and at temperatures either much higher or much lower than its best forming temperature; comparatively, that of the quartz vein style of gold deposit occurred under conditions with the best temperature, rich in sulfur, and with high sulfur fugacity. The Au/Ag ratios of the pyrites show that both the replacement and quartz vein styles of deposits are mesothermal and hypothermal, while the Co/Ni ratios of the pyrites indicate that the quartz vein style is of magmatic-hydrothermal origin. The X-ray diffraction intensity of pyrite rich in gold is lower than that of pyrite poor in gold at the quartz vein style. In general, with an increase in gold content in pyrite, the total sum intensity ΣI decreases. The pyroelectricity coefficient has a negative correlation trend with the values of (Co + Ni + Se + Te)-As and (Co + Ni + Se + Te)/As. The pyrite pyroelectricity of the replacement style is N-type, indicating that it formed under low sulfur fugacity, while that of the quartz vein style is a mixture of P-N types, indicating that it formed under high sulfur fugacity. On the pyroelectricity-temperature diagram, pyrite of the replacement style is mainly distributed between 200 and 270 °C, while that of the quartz vein style varies between 90–118 and 274–386 °C, demonstrating a multistage forming process. In contrast to previous researchers' conclusions, the authors confirm the existence of lattice gold in pyrites through the use of an electron paramagnetic resonance (EPR) test. Au in the form of Au+, entering pyrite as an isomorph and producing electron–hole centers, makes the centers produce spin resonance absorption and results in EPR absorption peak II. The intensity of auriferous pyrite absorption peak II has certain direct positive correlations with pyrite gold content. The #I and #III absorption peaks of pyrites possibly result from the existence of Ni2+ and/or Cu2+. γ1, γ2, and γ3 are the strongest and most typical absorption peaks of the infrared spectra of the pyrites. Generally, with the increase in gold content in the pyrite samples, γ1, γ2, and γ3 tend to shift to higher wavenumbers, and the gold content in the pyrite samples has a positive correlation with their relative absorbance. [ABSTRACT FROM AUTHOR]

The use of artificial intelligence technology for ore prospecting and prediction has become a frontier area in mineral exploration, solving the problem of insufficient accuracy in geological maps for prospecting and prediction and model training. In this study, the ONE-HOT encoding method is proposed and utilized to grid the geological maps. In association with geochemical data, multi-channel two-dimensional grid window data are used as input, and data augmentation methods such as translation, rotation, and scaling are employed to expand the training. An improved ResNet neural network prediction model is used and optimizes hyperparameters through numerous experiments and comparisons. Ore prospecting and prediction was conducted in the Shiquan area, and the results show that the prospective area identified by this method covers 6. 5 % of the entire region, including all known gold deposits. Additionally, 8 new prospective areas without known gold deposits were predicted. The proposed ONE-HOT encoding method effectively utilizes existing geological map data, and the ResNet neural network prediction model performs significantly better than typical CNN network models and weight of evidence methods. [ABSTRACT FROM AUTHOR]

The newly discovered Yongshan gold deposit in Leping City, Jiangxi Province is located in the southeastern Shanmen-Yongshan Au polymetallic metallogenic prospect area, belonging to the northern part of eastern Qinzhou-Hangzhou Metallogenic Belt. According to field geological survey and indoor comprehensive research, the ore-controlling characteristics of Yongshan gold deposit in Leping City were studied with the discussion of the relationship between the NE-NEE-trending ductile shear zone across the mine from west to east and gold mineralization. This paper summarized ore-forming factors and analyzed its ore-searching prospects based on the characteristics of soil geochemical anomalies. The results show that the Yongshan gold deposit occurs in the Neoproterozoic shallow metamorphic rock strata with obvious ductile deformation, the NE-trending ductile shear zone is the main ore-controlling and ore-guiding structure, and the upper member of Fengshuling Formation is the ore-bearing wall rock. The Yongshan gold deposit is determined as ductile shear tectonic-altered rock type and its NE-trending ductile shear zone has a good ore-searching prospects. The discovery of this gold occurrence provides a new thought to the gold searching in the northern part of eastern Qinhang Metallogenic Belt, expanding the prospecting space in this area. [ABSTRACT FROM AUTHOR]

Three-dimensional Mineral Prospectivity Mapping (3DMPM) is an innovative approach to mineral exploration that combines multiple geological data sources to create a three-dimensional (3D) model of a mineral deposit. It provides an accurate representation of the subsurface that can be used to identify areas with mineral potential. These 3D geological models are the typical data source for 3D prospective modeling. Geological data sets from multiple sources are used to construct 3D geological models. Since in practice there is a significant imbalance in the ratio of mineralized to non-mineralized classes, the classification results will be biased in favor of the more observed classes. Borderline-SMOTE (BLSMOTE) is an oversampling technique used to solve the problem of unbalanced datasets and works by generating synthetic data points along the boundary line between the minority and majority classes. This helps to create a more balanced dataset without introducing too much noise. Non-mineralized samples can be generated by randomly selecting non-mineralized locations, which means that uncertainties are generated. In this paper, we take the shallow-forming low-temperature hydrothermal deposit Guizhou Lannigou gold deposit as an example to extract the ore-controlling elements and establish a 3D geological model. A total of 50 training samples are generated using the sampling method described above, and 50 mineralization prospects are generated using Random Forests. A return–risk analysis was used to explore the uncertainties associated with synthetic positive samples and randomly selected negative samples, and to determine the final mineral potential values. Based on the evaluation metrics G-mean and F-value, the model using BLSMOTE outperforms the model without the synthetic algorithm and the models using SMOTE and KMeansSMOTE. The optimal model BLSMOTE18 has an AUC of 0.9288. The methodology also performs superiorly with different levels of class imbalance datasets. Excluding the predictions where the results highly overlap with known deposits, five target zones were circled for the targets using a P-A plot, all of which have obvious metallogenic geological features. Among them, Target1 and Target2 have good potential for mineralization, which is of great significance for future mineral exploration work. [ABSTRACT FROM AUTHOR]

TESCAN Integrated Mineral Analyzer (TIMA) is an analysis system based on a scanning electron microscope that incorporates multiple X-ray spectrometers and other detectors. It could automatically identify minerals and produce images. TIMA has been widely applied in earth sciences, including petrology, mineralogy, geochemistry, petroleum, and paleontology, particularly in the rapid analysis of some geological samples with complex mineral composition and structure and small grain size, and a large number of repetitive samples to obtain statistical data for research purposes. In order to achieve the goals of analysis and save costs, it is crucial to select the optimal analytical conditions, but this aspect is often overlooked. This article takes sample of gold-bearing pyrite-sericite- quartz altered rock from the Huachanggou gold deposit in Lueyang County, Shaanxi Province, as an example. Using TIMA, the samples were analyzed under different scanning modes, analysis types, and various experimental parameter settings. The study compared the mineral phase composition data, image quality of mineral phase maps and elemental distribution maps in a small field, as well as statistical data such as mineral grain size. The results indicate that the main factors influencing the quality of TIMA analysis Eire the backscattered electron (BSE) pixel spacing, energy-dispersive X-ray spectroscopy (EDS) test dot spacing, and X-ray acquisition counts. The selection of analytical conditions primarily depends on the mineral composition, mineral grain size, and the purpose of the analysis. [ABSTRACT FROM AUTHOR]

Tourmaline is a borosilicate mineral with general formula of XY3Z6[T6O18](BO3)3V3W. Experimental studies demonstrate a wide range of stability for tourmaline-supergroup minerals to record different geological processes. They occur in metamorphic, granitic pegmatites, and clastic sedimentary rocks and are associated with hydrothermal activities (Dutrow and Henry, 2011; Slack and Trumbull, 2011). Textural and compositional features of tourmaline can be used as an indicator of environment in which it crystallized. Tourmaline from porphyry deposits generally show a. frequently crystal zoning, b. development from Fe-rich to Mg-rich, and c. total Mg content is ~2 apfu in copper deposits and 1-2 apfu in Au deposits (Baksheev et al., 2012). It is believed that the world-class Dashkasan gold deposit records the transformation of porphyry to low-sulfide epithermal (Richards et al., 2006). The Dashkasan gold deposit located in the Kurdistan Province can be a significant region for better understanding the origin and the evolution of ore-forming fluids using chemistry of tourmaline. For the present study, we also tried to apply fluid inclusions data on quartz-tourmaline-pyrite veins from the Dashkasan deposit.Materials and MethodsPolished-thin sections of various tourmalines of the Dashkasan deposit were examined using a Cameca SX100 Electron Probe Micro Analysis (EPMA) at the Iran Mineral Processing Research Center, Karaj. Fluid inclusion studies were performed on quartz crystals of quartz-tourmaline-pyrite veins. The microthermometric parametes of fluid inclsions were measured by Linkam-THMS-600 stage at the University of Isfahan.Results and DiscussionThe Dashkasan gold deposit with 52 Mt of oxidized ore and average grades of 1.77 g/t Au is hosted by the Middle-Miocene porphyritic dacite/rhyodacite and dacitic breccia rocks. The main minerals are quartz, K-feldspar, hornblende and biotite mainly altered.. This deposit is characterized by the transition from the porphyry to the epidermal system with the presence of tourmaline minerals in phyllic and silicification alteration associated with gold veins. As petrographic examination shows tourmaline occurs as disseminated, vein/veinlet, and breccia textures in three types: Tur-1 occurred as needle shape in dacitic rocks associated with phyllic alteration; Tur-2 crystallized as radial shape mainly coexisting with silicification; and Tur-3 with elongated shape is present in dacitic breccia with phyllic alteration.Mineral ChemistryThe geochemical composition of three types tourmalines points to the nature and the evolution of ore-forming fluids. Electron microprobe analyses of the studied tourmalines indicate that the Tur-1 and Tur-3 are dravite, and the Tur-2 is dravite to schorl in composition and they belong to alkaline group. The third type, unlike the other two, is characterized by poor zoning and higher values of Na, K, Fe, Mg and lower values of Ca. On Fetot-Ca-Mg ternary diagram, they plotted in the Ca-poor metapelites, metapsammites, and quartz-tourmaline rocks host. Magmatic genesis inferred from the higher Fe/(Fe+Mg) ratio for Tur-1 and Tur-2, while this ratio in the Tur-3 is different and shifted towards hydrothermal source.Microthermometric StudyRichards et al. (2006) present the fluid inclusion assemblages from quartz-tourmaline veins in sericitized wall rocks in the Dashkasan deposit consisting of hypersaline and rare vapor-rich inclusion. They have homogenization temperatures of 246° to 360 ℃, yielding salinities of 34.4 to 46.1 wt% NaCl equiv. (Richards et al., 2006). Fluids inclusions studies on quartz-tourmaline-pyrite veins related to transition between stage-1 and stage-2 of mineralization in the Dashkasan shows a salinity values from 15.9 to 16.8 wt% NaCl equiv. and homogenization temperature values between 185° to 254 °C.ConclusionsOn the basis of optical and scanning electron microscopy, three tourmaline types(Turs -1,-2 and -3) in the Dashkasan deposit, can be distinguished. Despite the lack of zoning in Tur-1 and Tur-2, the third type displays the poor zoning. The first-and the third-types of tourmalines are dravite (Mg-rich), whereas the second-type is dravite to schorl in composition. Magmatic genesis is reflected by higher Ʃ(Fe+Mg) and FeO/(MgO+FeO) ratios for the first two types. While these ratios in the Tur-3 is different and shifted toward hydrothermal source. To sum up, the occurrence of quartz-tourmaline-pyrite veins in the Dashkasan deposit is due to the existence of a fault system under the physicochemical performance of the ore-mineralized fluid by a sudden depressurization and probably gradual mixing with shallow water.AcknowledgmentsWe thank Dr. Gholizadeh and Dr. Shabanian for their assistance with experiments for EPMA. This study was financially supported by the University of Isfahan.

Medium-low temperature magmatic hydrothermal gold deposits are widely distributed and large in scale, accounting for about 65 % of the gold deposits in China, which is the main mineral source of gold in China. In the process of prospecting, different types of deposits correspond to different prospecting methods. The determination of the metallogenic model of deposits can provide theoretical support for prospecting as well as theoretical guidance for mineral exploration and prediction. In view of this, the ontology construction and inference mechanism of medium-low temperature magmatic hydrothermal gold deposits are studied in this paper with reference to prospecting and prediction theory of exploration area. Using Protege ontology modeling software, the ontology modeling of the deposit is completed. Based on the SWRL inference rule language, the genesis type of the deposit is defined by inference rules. A set of ontology inference mechanisms oriented to the deposit type discrimination is designed. The inference is completed with the HermiT inference device. After a lot of experiments, the ontology inference method of the deposit genesis type proposed in this paper has a good application effect in the discrimination of gold deposit genesis types and can be widely used in the discrimination of other types of deposit genesis. [ABSTRACT FROM AUTHOR]

In order to expand the application of remote sensing prospecting technology in gold prospecting, this paper takes the Zhuanshanzi area in Inner Mongolia as an example, and selects Landsat 8 OLI remote sensing data. On the basis of image data preprocessing, the regional tectonic information is enhanced by the fusion of B7B5B3 band. The principal component analysis is used to extract the alteration anomaly information through threshold segmentation. Based on the geological characteristics and remote sensing interpretation information of the region and Zhuanshanzi Gold Deposit, the prospecting indicator of gold deposits in Zhuanshanzi area is established, and 3 prospect areas for prospecting prediction are delineated. The field verification shows that there is gold mineralization in the prospect area. It is believed that the linear and ring structure and remote sensing anomaly information extraction based on OLI remote sensing images can be used as auxiliary means for gold prospecting prediction. [ABSTRACT FROM AUTHOR]

Located along the southern part of the West Qinling orogenic belt, the Yangshan gold deposit is one of the largest in China. The major gold ores of Yangshan are disseminated in metasedimentary host rocks with minor native gold amounts in stibnite‐gold quartz veins. Pyrite and arsenopyrite are the major Au‐bearing minerals. Hydrothermal muscovite from gold‐bearing quartz veins was dated using the in situ Rb‐Sr method to determine the formation age of the Yangshan gold deposit. The Rb‐Sr isochron date of the muscovite yielded 210.1 ± 5.6 Ma (MSWD = 1.2). This date is near the lower end of the period of the mineralized granitic dykes (210.49–213.10 Ma). Two stages of gold enriching process are recognized in the gold‐bearing pyrite: the first is incorporated with the Co, Cu, As, Ni enrichment; and the second is accompanied by Bi, Co, Ni, Pb, Cu, Sb concentration. The in‐situ sulfur isotopic values of pyrites show a restricted Δ34s range of –1.43 ‰ to 2.86 ‰ with a mean value of 0.43 ‰. Trace‐element mapping and in‐situ sulfur isotopic analysis of pyrite suggest that the sulfur deposits are likely derived from a magmatic source and likely assimilated by sulfur from the sedimentary bedrock. Thus, magmatism plays a critical role in the formation of the Yangshan gold deposit. [ABSTRACT FROM AUTHOR]

In recent years, Guinea has become one of the hot spots for gold investment and exploration in West Africa. At present, the Siguiri Basin is the main gold mining area in Guinea. Beroko Gold Deposit is located in the northwest of the Siguiri Basin, and the stratum is composed of Paleoproterozoic Birimian metamorphic sedimentary rocks, pyroclastic rocks, volcanic rocks, and intrusive rocks; the ore bodies are mainly hosted in the subordinate ductile-brittle shear zone of the Birimian metamorphic sedimentary rocks and granodiorite, and it is closely related to quartz veins; there are mainly three types of gold mineralization: vein gold mineralization, breccia gold mineralization, and disseminated gold mineralization. The alteration types closely related to gold mineralization are silicification, pyritization, chalcopyritization and carbonation（ankeritization). The deposit is jointly controlled by the Paleoproterozoic Birimian stratum, NE, NWW, nearly NS, nearly EW trending fault structures (shear zones), and granodiorite bodies. The deposit type is classified as "orogenic + hydrothermal" gold deposits. The deposit was formed during the Eburnean orogeny（2 060-2 160Ma), and the ore-forming fluid has multiple sources and multiple phases. Four anomalous zones, Au-Ⅰ, Au-Ⅱ, Au-Ⅲ, and Au-Ⅳ were delineated through soil geochemical survey, which provided target areas for prospecting. [ABSTRACT FROM AUTHOR]

Maoling ore concentration area is located in the western of Liaodong Peninsula, where a super largescale and three medium-sized gold deposits have been verified. Most previous studies focus on individual gold deposit and seldom explore the geological features and spatial distribution of gold deposits from the perspective of the scale of ore concentration area. On the basis of comprehensive research on 32 gold deposits( occurrences) in Maoling ore concentration area, according to the theory of hydrothermal mineralization, the genesis type of gold deposits can be divided into 3 types: (Dhydrothermal alteration rock type, which is the main type and the ore body mainly occurs in the elastic metamorphic sedimentary construction of the upper part of the Liaohe Group, with a large gold resource reserve; (2)hydrothermal alteration - quartz vein type, with the ore body mainly occurring in the contact zone between the Liaohe Group and the rock mass; @hydrothermal quartz vein type, with the ore body mainly occurring in the Mesozoic magmatic rock system. The gold deposits in the Maoling mining district are spatially distributed in a near NW direction, consistent with the spatial distribution of the Gaixian Formation of the Liaohe Group, showing a specific gold mineralization property. The gold deposits surround the Mesozoic Wolongquan rock mass, with gold mineralization mainly occurring west of the rock mass and lead - zinc mineralization mainly occurring east of the rock mass. The Maoling ore concentration area is a hydrothermal ore-forming system associated with the metamorphic sedimentary construction of the Liaohe Group and Mesozoic intrusive rocks. [ABSTRACT FROM AUTHOR]

Machine learning algorithms, including supervised and unsupervised learning ones, have been widely used in mineral prospectivity mapping. Supervised learning algorithms require the use of numerous known mineral deposits to ensure the reliability of the training results. Unsupervised learning algorithms can be applied to areas with rare or no known deposits. Reinforcement learning (RL) is a type of machine learning algorithm that differs from supervised and unsupervised learning models in that the learning process is performed interactively by the agent and environment. The environment feeds the agent with reward signals and states, and the agent synthetically evaluates the mineralization potential of each state based on these rewards. In this study, a deep RL framework was constructed for mineral prospectivity mapping, and a case study for mapping gold prospectivity in northwest Hubei Province, China, was used to test the framework. The deep RL agent extracted the information of known mineralization by automatically interacting with the environment while simultaneously mining potential mineralization information from the unlabeled dataset. Its comparison with random forest and isolation forest models demonstrates that deep RL performs better regardless of the number of known mineral deposits because of its unique reward and feedback mechanism. The delineated high-potential areas show a strong spatial correlation with known gold deposits and can therefore provide significant clues for future prospecting in the study area. [ABSTRACT FROM AUTHOR]

The gold deposit offshore of Northern Sanshandao is an ultra-large-scale gold deposit discovered in the Jiaodong ore area in recent years. This deposit is a fractured-zone altered-rock-type gold deposit; however, its ore genesis and precise mineralization processes are still highly controversial. Based on petrographical observation, the trace elements, sulfur isotopes, and rubidium–strontium isotopes of the gold-bearing pyrite were analyzed using LA-MC-ICP-MS to obtain the source of the ore-forming fluids and ore genesis. The results show that Au has a good positive correlation with Ag, As, and Cu. It is speculated that the As in the pyrite of the gold deposit offshore of Northern Sanshandao is in the form of As−, replacing S− and entering the pyrite, causing its lattice defects, and thus promoting the entry of Au+ into the gold-bearing pyrite. The Co/Ni ratios mainly range between 0.1 and 10, indicating that the mineralization process has experienced different forms of hydrothermal evolution and the mixing of different fluids. The results of the in-situ sulfur isotope analysis show that pyrite δ34S in the mineralization period is characterized by a high sulfur value. The authors of this study believe that the initial sulfur isotope composition has mantle-derived components. The large-scale, deep cutting, and high degree of fragmentation in the Sanshandao fault zone are conducive to the interaction between fluids and rocks, as well as the mixing and addition of seawater, resulting in the characteristic high δ34S value. The Sr isotopic compositions indicate a crust–mantle mixing attribute of the mineralized material source. The Rb–Sr isochron age of the pyrite is 118.5 ± 0.65 Ma, which represents the age of gold mineralization. According to the characteristics of the trace elements and sulfur isotopes, it is inferred that the gold deposit minerals offshore of Northern Sanshandao originated from deep magmatic-hydrothermal reservoirs, and the mixing of seawater and Au–As-rich hydrothermal fluids was the formation mechanism of huge amounts of gold precipitation.

Introduction Tourmaline is a borosilicate mineral with general formula of XY3Z6[T6O18](BO3)3V3W. Experimental studies demonstrate a wide range of stability for tourmaline-supergroup minerals to record different geological processes. They occur in metamorphic, granitic pegmatites, and clastic sedimentary rocks and are associated with hydrothermal activities (Dutrow and Henry, 2011; Slack and Trumbull, 2011). Textural and compositional features of tourmaline can be used as an indicator of environment in which it crystallized. Tourmaline from porphyry deposits generally show a. frequently crystal zoning, b. development from Fe-rich to Mg-rich, and c. total Mg content is ~2 apfu in copper deposits and 1-2 apfu in Au deposits (Baksheev et al., 2012). It is believed that the worldclass Dashkasan gold deposit records the transformation of porphyry to low-sulfide epithermal (Richards et al., 2006). The Dashkasan gold deposit located in the Kurdistan Province can be a significant region for better understanding the origin and the evolution of ore-forming fluids using chemistry of tourmaline. For the present study, we also tried to apply fluid inclusions data on quartz-tourmaline-pyrite veins from the Dashkasan deposit. Materials and Methods Polished-thin sections of various tourmalines of the Dashkasan deposit were examined using a Cameca SX100 Electron Probe Micro Analysis (EPMA) at the Iran Mineral Processing Research Center, Karaj. Fluid inclusion studies were performed on quartz crystals of quartz-tourmaline-pyrite veins. The microthermometric parametes of fluid inclsions were measured by Linkam-THMS-600 stage at the University of Isfahan. Results and Discussion The Dashkasan gold deposit with 52 Mt of oxidized ore and average grades of 1.77 g/t Au is hosted by the Middle-Miocene porphyritic dacite/rhyodacite and dacitic breccia rocks. The main minerals are quartz, Kfeldspar, hornblende and biotite mainly altered.. This deposit is characterized by the transition from the porphyry to the epidermal system with the presence of tourmaline minerals in phyllic and silicification alteration associated with gold veins. As petrographic examination shows tourmaline occurs as disseminated, vein/veinlet, and breccia textures in three types: Tur-1 occurred as needle shape in dacitic rocks associated with phyllic alteration; Tur-2 crystallized as radial shape mainly coexisting with silicification; and Tur-3 with elongated shape is present in dacitic breccia with phyllic alteration. Mineral Chemistry The geochemical composition of three types tourmalines points to the nature and the evolution of ore-forming fluids. Electron microprobe analyses of the studied tourmalines indicate that the Tur-1 and Tur3 are dravite, and the Tur-2 is dravite to schorl in composition and they belong to alkaline group. The third type, unlike the other two, is characterized by poor zoning and higher values of Na, K, Fe, Mg and lower values of Ca. On Fetot-Ca-Mg ternary diagram, they plotted in the Ca-poor metapelites, metapsammites, and quartz-tourmaline rocks host. Magmatic genesis inferred from the higher Fe/(Fe+Mg) ratio for Tur-1 and Tur-2, while this ratio in the Tur-3 is different and shifted towards hydrothermal source. Microthermometric Study Richards et al. (2006) present the fluid inclusion assemblages from quartz-tourmaline veins in sericitized wall rocks in the Dashkasan deposit consisting of hypersaline and rare vapor-rich inclusion. They have homogenization temperatures of 246° to 360 ℃, yielding salinities of 34.4 to 46.1 wt% NaCl equiv. (Richards et al., 2006). Fluids inclusions studies on quartz-tourmaline-pyrite veins related to transition between stage-1 and stage-2 of mineralization in the Dashkasan shows a salinity values from 15.9 to 16.8 wt% NaCl equiv. and homogenization temperature values between 185° to 254 °C. Conclusions On the basis of optical and scanning electron microscopy, three tourmaline types(Turs -1,-2 and -3) in the Dashkasan deposit, can be distinguished. Despite the lack of zoning in Tur-1 and Tur-2, the third type displays the poor zoning. The first-and the third-types of tourmalines are dravite (Mg-rich), whereas the second-type is dravite to schorl in composition. Magmatic genesis is reflected by higher Ʃ(Fe+Mg) and FeO/(MgO+FeO) ratios for the first two types. While these ratios in the Tur-3 is different and shifted toward hydrothermal source. To sum up, the occurrence of quartz-tourmaline-pyrite veins in the Dashkasan deposit is due to the existence of a fault system under the physicochemical performance of the oremineralized fluid by a sudden depressurization and probably gradual mixing with shallow water. [ABSTRACT FROM AUTHOR]

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Gold deposits are widespread in the Xuefeng tectonic belt, which is one of the most important gold- producing areas in China. However, factors controlling gold ores in the tectonic belt have not yet been fully understood. The study of ore-controlling factors is of great significance to the summary of gold metallogenesis and the exploration of gold resources. The ore-controlling factors of gold deposits in the Xuefeng tectonic belt are discussed from the perspec- tive of stratigraphy, tectonics, and magmatism. Based on the spatial and temporal distribution characteristics of the gold deposits, the ore-forming mechanism of these deposits is investigated. The results show that tectonics is a necessary condition for gold mineralization, while the Precambrian stratigraphy and regional magmatic activity are only favorable conditions. The gold mineralization of the Xuefeng tectonic belt is concentrated in the Caledonian and Indosinian - Yanshanian periods, which is consistent with the view that the ore-forming fluids originated mainly from precipitation. Gold deposits in the Xuefeng tectonic belt belong to the metamorphic clastic rock type. [ABSTRACT FROM AUTHOR]

The Murcielago gold placer is located in the Lepaguare Valley, Olancho Department (Central Honduras). The placer mineralogy includes silicates (quartz, garnets, amphibole, Ca-pyroxene, micas, epidote, and tourmaline); calcite; and in the heavy fraction, zircon, ilmenite–rutile, magnetite, hematite, cassiterite, and cinnabar. Gold grains recovered from the Murcielago placer production plant are mainly flattened grains with a moderately to high elliptical shape. The composition of the gold grains varies continuously in the range Au 46 Ag 54 to Au 88 Ag 12 . Few of them are characterized by Au-rich rims of a few microns in size (Ag 3-1 atoms percent (at%)). Gold from the Canan lode deposit, a nearby hydrothermal Au mineralization area, has a composition (from Au 54 Ag 44 to Au 81 Ag 19 ) overlapping the composition of the Murcielago grains. Inclusions in the alluvial gold particles are arsenopyrite, pyrite, acanthite, sphalerite, and hematite. On the basis of the placer mineralogy and the gold grains analyses, possible gold source(s) include the Canan lode and skarn gold deposits in the area. We obtained new data on the Murcielago gold placer that will be the basis for an exploration of the potential sources of gold in the area. [ABSTRACT FROM AUTHOR]

In order to achieve a breakthrough in gold prospecting in Qixia area, 16 elements mainly including Au and Ag which were on the basic of the stream sediment survey in 1∶ 50 000 scale of the Biguo area was analyzed. The distribution characteristics, enrichment and dispersion characteristics and abnormal characteristics of elements were studied, and the R-type clustering analysis and factor analysis of each element were carried out. The results show that the anomalies of Au dominated metallogenic elements in the study area are of high intensity, large scale and good coincidence, which are mainly distributed in the main metallogenic and secondary fault zones in the area. In combination with the geological, geophysical and mineral characteristics in the area, five gold prospecting prediction areas are delineated. There is one deep and peripheral A-level prediction area of Hushan gold mine, One deep B-level prediction area of Taiqian gold mine,and three C-level prediction area in Suntuan daheya, sansukuang and Dahuayuan area. [ABSTRACT FROM AUTHOR]

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A large-scale mineralization occurred in the East Kunlun during the Early Mesozoic, forming a series of lode gold, quartz vein-type Ag-Pb-Zn, porphyry Cu-Mo, and skarn Fe polymetallic deposits. However, the genetic link between these deposits is still unclear. The eastern segment of the East Kunlun has diverse types of deposits which provides an excellent opportunity to decipher the genetic link. Here we summarize the geological features and spatial-temporal distribution of the major types of deposits in the eastern segment of the East Kunlun, and discuss their metallogenic ages, tectonic settings, and sources of ore-forming fluids and materials to explore possible genetic links between them. The results show that they were mainly formed in the Middle-Late Triassic (240-220 Ma), controlled by the Paleo-Tethys continental collision and post-collision extension. Additionally, these different types of deposits in the study area and the surrounding Northern East Kunlun Terrane have similar metal and fluid sources. They are closely related to the extensive deep magmatism developed during this period. We suggest that these deposits formed a giant magmatic-hydrothermal metallogenic system, and different mineralization types might be the products of different evolution stage. The deep subduction and break-off of the Bayankura Plate induced the upwelling of the asthenospheric mantle and the subsequent large-scale magmatic-fluid activities. The metal- and volatile-rich hydrothermal fluids extensively interacted with upper crustal rocks and shallow-derived fluids, and formed a regional-scale magmatic-hydrothermal metallogenic system. Based on the metallogenic system, the eastern segment of the East Kunlun has potential for multi-type paragenetic deposit exploration.

The relevance of the study is caused by the interest in the gold deposits located in the Bodaibо ore region. The study of this area is reflected in numerous publications, despite this there is no unified idea of the origin of gold deposits formed in the black shale strata. The Ugakhan deposit is the only gold ore object of the Bodaibo ore region localized in the rocks of the Buzhuikhta Formation, and the detailed mineralogical and geochemical study of this ore host strata can be useful to clarify genetic type of gold mineralization and the prospects of the Buzhuikhta Formation for the search for new gold objects. The main aim is clarification of the conditions of the lithogenesis in the concentration of metals in sulfide-bearing metasedimentary rocks of the Buzhuikhta Formation. Objects of the research is the Ugakhan deposit, located in the Irkutsk region of the Bodaibо ore region. Methods. The study of rocks was carried out using an Olympus BX51 optical microscope. The accessory mineralization was analyzed on a Tescan Vega 3 sbu scanning electron microscope equipped with an Oxford Instruments X-act energy dispersive spectrometer. The content of 12 basic oxides in rocks (9 samples) was determined by silicate analysis. The trace elements, including rare earth elements (6 samples, 40 elements), were studied by the ICP-MS method (inductively coupled plasma mass spectrometry) on the ICP-MS Agilent 7700x spectrometer (Japan). All mineralogical and geochemical researches were carried out at the Institute of Mineralogy of South Urals Federal Research Center of Mineralogy and Geoecology UB RAS (Institute of Mineralogy SU FRC MG UB RAS, Miass). Results. Ore-bearing rocks from the Ugahan deposit are represented by intercalation of metasandstones, metasiltstones and black shales. The detrital material in these rocks consists of weakly rounded quartz grains and feldspars (albite and orthoclase) and fragments of microfossils in the micaceous-chlorite-carbonate groundmass. The accessory minerals are tourmaline, zircon, rutile, apatite, titanite, numerous minerals of rare earth elements (monazite, xenotime, rare earth elements-bearing epidote, bastnaesite, ankylite, rare earth elements-bearing thorite, uraninite and coffinite). The sequence of mineral formation testifies to the redistribution of the initially accumulated matter and its concentration with the formation of mineral forms of rare earth elements, Th and U at the all stages of lithogenesis and the metamorphogenic-hydrothermal stage of primary carbonaceous sediment transformations. A comparative analysis of the chemical composition of metasediments shows that a decrease in SiO2 contents is accompanied by an increase in Al2O3, MgO, TiO2, FeO*, K2O, and P2O5 contents in the range: metasandstones → metasiltstones → black shales, In the same range, there is an increase in the contents of Sc, V, Cr, Zn, Ga, Rb, Sr, Y, Zr, Th, U and rare earth elements. A specific feature of metasediments of the Buzhuikhta Formation is the high content of V, Ba, Sr, rare earth elements, Th and U, which is caused by the participation of organic matter in diagenetic processes involving sulfides. The calculated petrochemical modules and their correlations testify to the common nature of sedimentary material and the possible influence of volcanogenic material in formation of sediments.

The Laizishan anticline area is an important part of the Ceheng — Wangmo high gold concentration area in Guizhou province. In the area, a super large gold deposit and many small gold deposits and gold spots are dis-covered. At present, the area still has a good prospecting prospect. This paper systematically summarizes the geological features and tectonic ore control law and points out that Laizishan anticline area has obvious three-stage tectonic ore control characteristics, and that the migration and enrichment of deep-sourced ore-forming fluids are closely related to the three-stage tectonics. The tectonic system composed of hidden syngenetic faults of late Paleozoic + regional Laizishan anticline, interlaminar slip structure + mineral-grade faults and folds has an obvious control effect on gold deposit for-mation. The study established the ore-controlling model of the Laizishan anticline area. [ABSTRACT FROM AUTHOR]

To shed light on the genesis of the Dongping deposit and reveal the behaviour of CO2, Au and other ore elements (e.g., Cu, Fe, Zn, As, Sb, Co etc.) in ore‐forming fluids, petrographic, microthermometric and synchrotron radiation X‐ray fluorescence (SRXRF) analyses of fluid inclusions were conducted. The ore‐forming fluid is characterized as an H2O‐CO2‐NaCl system with medium‐high temperatures and low salinity. Four mineralization stages are identified, namely, feldspar‐quartz (stage 1); pyrite‐white quartz (stage 2); sulfide‐smoky grey quartz (stage 3); and carbonate‐quartz (stage 4). Three types of inclusions were distinguished, based on fluid composition, phase assemblages and mode of homogenization. Type A: H2O‐rich fluid inclusions show 2 phases (liquid H2O (LH2O) + vapour H2O (VH2O)) at room temperature and homogenize to the liquid phase. Type B: H2O‐CO2 fluid inclusions contain 2–3 phases (liquid H2O (LH2O) + vapour CO2 (VCO2); liquid H2O (LH2O) + liquid CO2 (LCO2)); liquid H2O (LH2O) + liquid CO2 (LCO2) + vapour CO2 (VCO2)) at room temperature and homogenized to the liquid H2O phase. Type C: H2O‐CO2 fluid inclusions show 2 phases (liquid H2O (LH2O) + liquid CO2 (LCO2) at room temperature and homogenize to a critical state. CO2 is clearly more enriched in the fluid inclusions of stages 2 and 3 than in stage 1. Stage 1 is dominated by type A (H2O‐rich) inclusions with homogenization temperatures (Th) of 220–359°C and salinities of 1.1–3.1 wt% NaCl equivalent. Type B (CO2‐rich) inclusions gradually increase in stages 2 and 3. The Th range of type B inclusions in stage 2 is 241–397°C with salinities of 2.2–6.9 wt% NaCl equivalent; the Th range of type A inclusions is 217–373°C with salinities of 1.2–8.1 wt% NaCl equivalent. The Th range of type B inclusions in stage 3 is 215–361°C with salinities of 2.9–6.1 wt% NaCl equivalent; the range of type A inclusions is 158–351°C with a salinity of 0.7–5.5 wt% NaCl equivalent. Stage 4 is characterized by type A with Th of 151–250°C and salinities of 0.9–8.3 wt% NaCl equivalent. The mapping results show that elements As, Te and Sb are more concentrated in vapour CO2 than in liquid H2O at room temperature, which suggests that vapour components are more able to transport elements when phase separation occurs. The SRXRF quantitative results show that Au, Cl, S and some other metals are obviously more enriched in the fluid inclusions of stages 2 and 3 than those in stage 1. Additionally, the contents of S in stages 1–3 are much lower than those of Cl, which suggests that gold might migrate mainly in the form of a gold‐chloride complex. Au is more enriched in type B fluid inclusions than in type A fluid inclusions, which suggests that the enrichment and migration of gold are closely related to CO2 and CO2 plays a critical role in the migration and enrichment of gold. The trace elements in the fluid have a similar change trend to those in the Yanshanian syenogranite distributed in the southeastern part of the mining area, which may provide some evidence for an intrusion‐related genesis for the Dongping gold deposit. [ABSTRACT FROM AUTHOR]

Heicigou gold mine is a gold polymetallic mine controlled by a northwest trending fault. The magnetic method and induced polarization results show that the gold-bearing alteration zone is distributed discontinuously in a northwest direction, but the spatial distribution characteristics of the alteration zone have not been effectively identified. Although some drilling work has been carried out in the latter, the number and the depths of the drillings have been insufficient to control the distribution of the alteration zone. According to the measured three-component transient electromagnetic anomaly characteristics, we designed corresponding models and carried out three-component forward simulation on the platform of EMIT Maxwell. We summarized the corresponding relationship between the three-component plane change characteristics and the orientation and occurrence of the low-resistivity medium subsurface. We applied this method to the Heicigou gold deposit and found that the occurrence of the ore-bearing alteration zone is northeast. This discovery solved the problem that the previous magnetic method and induced polarization method failed to solve. It corrected the geologists' incorrect understanding of the spatial distribution of the alteration zone. [ABSTRACT FROM AUTHOR]

Radiometric mapping could play a prominent role in locating the host rock or alteration that leads to gold mineralization. Nevertheless, in low-sulfidation epithermal gold deposits, the radiometric signatures have to be priorly characterized due to their geometry. It is comprised of a small ore vein system within the large alteration zones. The Pongkor gold mine is a low-sulfidation epithermal deposit and was selected for this purpose. The method started with the surface identification of radiometric signatures on altered and unaltered rocks near Pongkor using portable spectrometers. They are followed by the characterization of the underground mining front, which is comprised of different types of veins and host rocks. The results show that the altered rocks were characterized by a high K% and a low eTh/K ratio. Vice versa, the mineralized veins show low radioelement concentrations. Following the characterization of the geometry of alteration zones and mineralized veins, a study of the relationship between radioelements detected by radiometric mapping and gold pathfinder elements was conducted. Gold pathfinders of Mn, Fe, Zn, As, and Pb were selected for correlation studies with the radioelement. The pathfinders and radioelements were more significantly correlated in veins compared to the host rock. Based on this study, radiometric mapping has the potential and benefit of being applied in the exploration of low-sulfidation epithermal gold deposits. An alteration zone could be delineated by K or eTh/K as an anomaly indicator, and the vein bodies could also be delineated using low K or eTh as an anomaly indicator.

The adjacent area of Yunnan, Guizhou, and Guangxi provinces, termed the “Golden Triangle”, is one of the world-famous Carlin-type gold ore concentration areas. Previous metallogenic research in this area mainly focuses on the mineralization at the edge of the carbonate platform. However, it rarely involves the interior of the carbonate platform, so the ore body emplacement factors and ore-controlling models are still unclear within the platform. The Longhuo gold deposit, a typical gold deposit located at the platform’s interior in the western Guangxi, was analyzed in detail; the ore-controlling structure and model were fundamentally constructed. The results show that the structures of Longhuo gold deposit can be divided into three periods. (1) The first period is Hercynian sedimentary, which forms the NE-trending F0 syngenetic fault and the platform-trench paleogeographic pattern with the thin-layer siliceous rock-mudstone-siltstone components; the lithology provides the stratigraphic conditions for the formation of the deposit. (2) The second period is Indosinian orogenic, which forms the Longhuo dome and NW-trending Mohao secondary anticline; the anticline provides favorable tectonic conditions for the mineralization. (3) The third period is Yanshan metallogenic characterized by the reactivation of fault F0, which is the main hydrothermal fluid migration channel in the mine area. A large number of parallel secondary normal faults and associated traction folds develop on its western side, and gradually weaken into joints and cleavage zones to the west. These secondary fault-joint-cleavage zones together form the ore-allocating tectonic system of the mine area, guiding the ore-forming fluids to replace and filling the siliciclastic-carbonaceous mudstones and tuffs of Lower Carboniferous Yingtang Formation in Mohao secondary anticline core to form bedded ore bodies. Therefore, the Longhuo gold ore body is jointly controlled by lithology and tectonics. According to the metallogenic model, combined with geophysics-geochemistry-remote sensing data, it is predicted that near the western side of the NE-trending fault F0, the secondary anticline core of the deep part of Longhuo gold deposit is the favorable prospecting target. The ore-bearing stratum is Lower Carboniferous Yingtang Formation. The intersection of fault F0 and the core of Longhuo dome is the favorable prospecting target for mineralization in the periphery of Lower Devonian Yujiang Formation, especially near the unconformity in contact with Cambrian. [ABSTRACT FROM AUTHOR]

This work attempts to study the spectral characteristics of the hydrothermal alteration zones developed around the auriferous reefs in the spectral range of 350 nm to 2500 nm. The samples representing proximal alteration, distal alteration and unaltered host rock were collected from four reefs (Oakley's reef, Strike reef, Zone I reef and Middle reefs) exposed in the Hutti Underground Mine, India. All the auriferous reefs are hosted in amphibolite, except the Middle reef, which occurs in acid volcanic rock. Spectral characterization of the continuum-removed average whole-rock reflectance spectra of the samples was carried out with ENVI software, followed by spectral deconvolution in Origin Pro software. The resulting absorption features were correlated with the mineralogy obtained from XRD and petrographic studies. It is noted that the abundance of chlorite, amphibole and calcite are key to differentiate the alteration zones developed around the reefs hosted in amphibolite. The diagnostic spectral features can identify chlorite and amphibolite at 2250 nm, 2340 nm, and 2310 and 2390 nm, respectively. A comparison of absorption band depth and XRD-derived semi-quantitative mineral abundances showed that band depths of 2250 nm and 2390 nm can be used to measure the abundance of chlorite and amphibole in the sample. The 2340 nm feature is influenced by chlorite ± biotite + calcite. The abundance of chlorite shows a decrease from the proximal zone towards the unaltered host rock, whereas the abundance of amphibole is low in the proximal alteration zone and increases towards the unaltered host rock. In the case of acid volcanic rocks, the sericite controls the spectral characteristics, with a diagnostic absorption feature at 2206 nm. The above spectral characteristics can be used as a guide for exploring gold mineralization. [ABSTRACT FROM AUTHOR]

The effect of enrichment with Nd in sulfides from magmatic Cu-Ni-PGE complexes and sulfide ores from hydrothermal Pb-Zn, Au-Mo, and gold deposits was found and characterized. This paper concerns the report and analysis of isotopic geochemical data on the sulfide ores from the large Paleoproterozoic mafic–ultramafic magmatic Cu-Ni-PGE complexes of Fennoscandia and the literature data on sulfide ores from the Qingchengzi Pb-Zn deposit (northeastern China), Tokuzbay gold deposit (southern Altai, northwestern China), and Dahu Au-Mo deposit (central China). The mineral/rock partition coefficients for Nd and Sm (the DNd/DSm ratio) are defined as a prospective tool for the reconstruction of the sulfide mineral formation and geochemical substantiation of possible sources of ore-forming fluids for deposits of various genetic types. The observed selective Nd accumulation indicates either hydrothermal or metamorphic (metasomatic) impact, which is associated with increased Nd mobility and its migration or diffusion. Due to this process, there is a relative Nd accumulation in comparison with Sm and a consequent increase in the DNd/DSm ratio. At the isotopic system level, this leads to a sufficient decrease in the Sm/Nd ratio for the secondary sulfides of such kind. The revealed effect may serve as an isotopic geochemical marker of recent processes. These processes are quite frequently associated with the most important ore formation stages, which bear the commercially valuable concentrations of ore components. Sulfides from magmatic Cu-Ni-PGE complexes are more characterized by the selective accumulation of Nd in the sequential sulfide mineral formation. For sulfides from hydrothermal deposits, the effect of Nd enrichment is more intense and closely related to ore-forming fluids, under the influence of which sulfide mineralization is formed in multiple stages. The study aims at expanding the knowledge about fractionation and the behavior of lanthanides in ore-forming processes and allows the development of additional criteria for the evaluation of the ore potential of deposits with different geneses, ages, and formation conditions. [ABSTRACT FROM AUTHOR]

Gouli area is an important gold ore concentration area in the eastern section of the East Kunlun tectonic belt. At present, a series of large and medium-sized gold deposits and many gold spots have been found, such as Guoluolongwa, Asha and Walega. A comprehensive study on the geological characteristics of Asha, Guoluolongwa and Walega gold deposits in Gouli area shows that: The gold deposits in Gouli area were mainly formed in the late Indosinian period, during which the intense magmatic activity provided materials and heat source for the formation of gold deposits; The mineralization is controlled by fault structures, among which Kunzhong fault and its secondary Xiangride-Delong fault are the main ore-guiding and ore-controlling structures, while the lower order NE and NW faults are the main ore-hosting structures; The ore-forming fluid of the gold deposit in Gouli area is the fluid system of H2O-CO2-NaCl-CH4 with medium to low temperature （130.0℃-360.0℃), medium to low salinity （1.83％-18.00％） and low density (0.62-1.03g/cm³) The study of S, Pb, H and O isotopes of ores show that the ore-forming materials are derived from the magmatism of orogenic belt, and the ore-forming fluids are mainly magmatic water in the early stage, mixed with atmospheric precipitation in the late stage. The genetic type of gold deposit in Gouli area is orogenic gold deposit related to late Indosinian orogeny. [ABSTRACT FROM AUTHOR]

The Hadamengou deposit is the largest gold deposit in Inner Mongolia. However, given that the sources of ore-forming alkaline magmatic hydrothermal solutions and ore-controlling structures are still controversial, the theories behind the genesis of the deposit have been controversial. In this study, four controlled-source audio magnetotellurics (CSAMT) and spectral induced polarization (SIP) profiles in the mining area were used to obtain the underground resistivity model and the pseudo section map of the apparent frequency dispersivity based on fine inversion. In the resistivity model, there are two high-resistivity blocks with resistivity greater than 3000 Ω m and three low-resistivity channels with resistivity less than 50 Ω m. Combined with the regional geological and drilling data, it is inferred that the high-resistance bodies, R4 and R5, may be alkaline magmatic intrusions related to multiple stages of magmatic hydrothermal activities, ranging from the Precambrian to Yanshanian periods. The highly conductive channels, C3, C5, and C4, may represent the Baotou-Hohhot fault, secondary faults, and ductile shear zone, respectively, which were formed in the Precambrian era and underwent multiple activations during the Hercynian to Yanshanian period. According to the spatial relationship, it is inferred that the ductile shear zone is an important ore-controlling and ore-hosting structure. However, the Baotou–Hohhot fault may be a pre-metallogenic fault rather than an ore-controlling fault. By comparing the resistivity model with the pseudo section of the apparent frequency dispersivity, it was found that all the known gold veins are located in the superimposed area of low resistivity and high-frequency dispersivity. It is speculated that the ductile shear zone outside the alkaline magmatic rock with the superimposed characteristics of low resistivity and high-frequency dispersivity is the favorable area for mineralization. [ABSTRACT FROM AUTHOR]

Three-dimensional Mineral Prospectivity Mapping (3DMPM) is an innovative approach to mineral exploration that combines multiple geological data sources to create a three-dimensional (3D) model of a mineral deposit. It provides an accurate representation of the subsurface that can be used to identify areas with mineral potential. These 3D geological models are the typical data source for 3D prospective modeling. Geological data sets from multiple sources are used to construct 3D geological models. Since in practice there is a significant imbalance in the ratio of mineralized to non-mineralized classes, the classification results will be biased in favor of the more observed classes. Borderline-SMOTE (BLSMOTE) is an oversampling technique used to solve the problem of unbalanced datasets and works by generating synthetic data points along the boundary line between the minority and majority classes. This helps to create a more balanced dataset without introducing too much noise. Non-mineralized samples can be generated by randomly selecting non-mineralized locations, which means that uncertainties are generated. In this paper, we take the shallow-forming low-temperature hydrothermal deposit Guizhou Lannigou gold deposit as an example to extract the ore-controlling elements and establish a 3D geological model. A total of 50 training samples are generated using the sampling method described above, and 50 mineralization prospects are generated using Random Forests. A return–risk analysis was used to explore the uncertainties associated with synthetic positive samples and randomly selected negative samples, and to determine the final mineral potential values. Based on the evaluation metrics G-mean and F-value, the model using BLSMOTE outperforms the model without the synthetic algorithm and the models using SMOTE and KMeansSMOTE. The optimal model BLSMOTE18 has an AUC of 0.9288. The methodology also performs superiorly with different levels of class imbalance datasets. Excluding the predictions where the results highly overlap with known deposits, five target zones were circled for the targets using a P-A plot, all of which have obvious metallogenic geological features. Among them, Target1 and Target2 have good potential for mineralization, which is of great significance for future mineral exploration work.