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• A GIS-based professional package for mineral resources assessment was developed. • SDE and Terrain Rendering were used to manage datasets and visualization. • A gold mineral resources assessment was conducted in Inner Mongolia by the GIS tool. This paper describes a software tool and its application to the China National Mineral Resource Assessment Initiative (CNMRAI). The initiative was carried out throughout China from 2007 to 2013, creating collaborations among geological societies from institutions such as academies, universities, companies, and local geological surveys. A geographic information system (GIS)-based tool was designed, providing functions for database management of the multiple original spatial datasets, modelling, targeting, estimation, and visualization to assist participants in assessing mineral resource potentials. During this initiative, geologists used the tool to generate mineral potential maps and assess undiscovered resources for the 25 major types of mineral resources in China. First, the requirements of the tool were introduced; second, the framework and major functions of the tool were delineated and developed; and third, a case study of gold resource assessment from a project of the CNMRAI in the Bayan Obo region, Inner Mongolia, China, was discussed. In addition, the mineral potential map was displayed by terrain rendering. This paper also provides interpretations of the results of a prospectivity analysis based on conceptual geological models. Discussions of the new requirements and techniques for modelling and assessing will be used to further develop the Mineral Resources Assessment Software (MRAS). [ABSTRACT FROM AUTHOR]

[Display omitted] • Field-portable exploration methods were systematically described in shallow overburden areas for vein-type fluorite deposits. • The advantages and disadvantages of field-portable fluorite exploration methods have been analyzed. • The Effectiveness of RS + VLF-EM + PRXF for exploration has been validated by trenching and drilling. Fluorite deposits are widespread throughout eastern China and commonly occur in vein systems. These vein-type fluorite deposits are the primary source of fluorine worldwide and were predominantly formed during the Mesozoic or Cenozoic periods. In the absence of ore outcrops, fluorite exploration is necessarily concentrated within the shallow overburden area. The Wuliji'Oboo fluorite deposit is an example of a medium–low temperature vein-type subsurface orebody in eastern Inner Mongolia. Five portable technology methods have been implemented within the study area, including multispectral remote sensing (RS) technology, very low-frequency electromagnetic measurement (VLF-EM), portable X-ray fluorescence analyses (PXRF), portable gamma-ray spectroscopy, and partial extraction geochemistry. This paper describes the application principles, influencing factors, and technical solutions for each method. By investigating various examples, the applications of portable technology methods and their associated limitations were evaluated. Combining geological research with multi-spectral RS techniques is essential for optimum fluorite ore body prediction, thus narrowing prospecting targets. First, the target area was scanned using VLF-EM to identify the distribution of potential anomalies. Second, PXRF was used to distinguish the mineralised anomaly. Finally, trenching and drilling were performed to verify the effectiveness of the combination of methods. This study establishes a geology-geophysics-geochemistry-remote sensing integrated exploration model that may provide theoretical and technical support for the prediction of fluorite ore bodies in large Quaternary shallow overburden areas. [ABSTRACT FROM AUTHOR]

• Dictionary learning is used to model gold prospectivity for gold exploration targeting. • The case study shows that the dictionary learning model is no inferior to the logistic regression model and superior to the one-class SVM model. Machine learning and deep learning anomaly detectors have been successfully used to map mineral prospectivity. However, the establishment of machine learning or deep learning anomaly detection models for mineral prospectivity mapping often requires the determination of a set of initialization parameters in the absence of ground truth data. Improper initialization parameters will degrade the performance of these mineral prospectivity mapping models. Different from most machine learning and deep learning algorithms, dictionary learning is a "white-box" algorithm involving only linear transformations, and building a dictionary learning model requires only an empirical definition of the total number of atoms. Therefore, in this paper, two dictionary learning anomaly detectors were established for mineral prospectivity modeling based on the least angle regression-Lasso (LARS-Lasso) algorithm and the iterative shrinkage-thresholding algorithm (ISTA). The following five-step procedure was proposed for mineral prospectivity modeling using the dictionary learning techniques: (a) an overcomplete dictionary is constructed based on the input data; (b) each data point is transformed into sparse coefficients according to the overcomplete dictionary; (c) the sparse representation of each data point is calculated based on the overcomplete dictionary and the sparse coefficients; and (d) the Euclidean norm of the difference between each data point and its sparse representation is calculated and used as the mineral potential of the data point. The dictionary learning models were established to model gold prospectivity in the Jinchanggouliang district, Inner Mongolia, China, and compared with the logistic regression model and one-class support vector machine model in gold exploration targeting. The result shows that (a) the performances of the dictionary learning models are no less than that of the logistic regression (LGR) model and better than that of the one-class support vector machine (OCSVM) model, and (b) the gold prospective areas differentiated by the established models are strongly consistent with geological and metallogenic characteristics in the study area. Therefore, the dictionary learning algorithms are high-performance mineral prospectivity modeling techniques. It is worth to further test the effectiveness of the dictionary learning algorithms for different types of mineral deposits in different areas in mineral exploration targeting. [ABSTRACT FROM AUTHOR]

[Display omitted] • A complete Fe isotopic composition and comprehensive overview of the evolution of magnetite for the Huogeqi deposit has been presented by this paper. • The magnetite ore at the Huogeqi deposit has characteristics typical for a hydrothermal skarn deposit. • Hydrothermal magnetite and Cu-Pb-Zn skarns at the Huogeqi deposit probably formed from similar hydrothermal fluids derived from Mesozoic granite. The Huogeqi deposit is a major Cu–Fe–Pb–Zn deposit in China. Numerous studies have been conducted on the genesis of Cu–Pb–Zn sulfides of this deposit; but detailed researches on the genesis of magnetite ore bodies and its relationship to sulfide ores are few. This study utilizes field and microscopic techniques to showcase the hydrothermal characteristics of magnetite ore and tremolite rocks, including net-veined magnetite ore, which cuts across carbonate rock and quartzite, and intrusive contacts between magnetite-bearing tremolite rocks and quartzite, carbonaceous slate, and carbonate rock. Furthermore, calcite with metasomatic relict texture could be widely observed near magnetite and tremolite. Magnetite-bearing tremolite rocks with low contents of trace elements, rare earth elements, and obvious positive anomalies of Eu differed from the mica schist and carbonaceous slate, but were consistent with the carbonate rocks, revealing that the magnetite ore and tremolite rocks have a hydrothermal origin and are closely related to carbonate rocks. The Fe isotopic compositions of 22 magnetite and 17 wall samples were determined using MC-ICP-MS methods. δ56Fe values of magnetite-bearing tremolite rocks varied from −0.57 to −0.15‰ (average, −0.38‰), which differed from those of the mica schist (0.27–0.33‰), quartzite (−0.12 to 0.57‰), and carbonaceous slate (0.30–0.38‰), but were similar to the carbonate rocks (−0.38 to −0.51‰). δ56Fe values of magnetite varied from −0.48 to 0.36‰ (average, −0.11‰), which differed from banded-iron formation and magmatic magnetite deposits but were like skarn deposits. The δ56Fe value of the initial ore-forming fluid was −0.09‰ at 350 °C, which is consistent with the fluid that likely originated from the fluid exsolution of granite. According to theoretical calculations, δ56Fe values of the residual fluid after precipitation of magnetite ores ranged from −1.01 to −0.94‰, and that for pyrite precipitation ranged from −0.02 to 0.07‰, which is consistent with the measured Fe isotopic data of pyrite. Hence, we suggest that the hydrothermal magnetite and Cu–Pb–Zn sulfides of the Huogeqi skarn deposit could be derived from similar hydrothermal fluids. [ABSTRACT FROM AUTHOR]

• The Bilihe shares similar hydrothermal alterations with porphyry-type deposit. • The typical hydrothermal veins host about one quarter of total gold reserves. • UST quartz formed near melt-fluid interface at the roof of host intrusion • Tiny fluid inclusion-rich UST quartz zones are proposed to grow from the fluid medium. The Bilihe gold deposit is a rare example that economical gold mineralization occurred in unidirectional solidification textures (UST) quartz at the cupola of middle Permian granodioritic intrusion. However, there is a key dispute about whether gold precipitated from low-diffusion silicate melt or high-activity fluid phase. In this paper, based on in-situ trace elements analyzing, SEM-CL mapping, and infra-red and Raman spectroscopy, the magmatic fluids are supposed to play a critical role in the gold mineralization by metal extraction from below magma at magmatic-hydrothermal transition stage. At Bilihe, the UST quartz represents the most fertile unit. Statistic results show the quartz–K-feldspar (KV) and gray banded quartz veins (GBV) also host about 22–27% of total reserves. A decreasing trend in Au/Ag, and Au/S, but elevated Au/Cu ratios of gold compositions indicate a relatively continuous fluid evolution in the Bilihe system. Petrography and spectroscopy studies show that the Bilihe UST quartz can be divided into two different domains, gold-rich brownish and barren colorless zones. The former can contain more water, occurring as tiny fluid inclusion or as structural OH– in muscovite, corresponding to sector CL zones (UQ1) or euhedral oscillatory bands (UQ2). The latter usually contain melt inclusions and correspond to obscure CL-textures (UQ3). Besides, the LA-ICP-MS trace elements show that there is a significant decreasing trends on fluid-mobile elements (e.g., K, Fe, B, and Li) from UQ1 over UQ2 to UQ3. In particular, the trace elements in UQ3 show greater affinity with magmatic quartz phenocrysts but with higher Ge, B, and Li contents, and higher Ge/Ti and Ge/Al, but lower Li/Ti ratios, indicating a highly evolved and fluid-rich environment. Based on previous model, we consider that the Bilihe UST quartz grew in the variable growth mediums, namely fluctuant alternation between fluid-dominant pocket (for UQ1 + UQ2) and silicate melt phase (for UQ3) near the melt-fluid interface at the apex of magma body. The relatively H 2 O-poor nature of parent magma is an important factor to cause the specific crystal growth environment. Mineral thermobarometers demonstrate that the parent magma from deep reservoir has experienced a significant ascent or decompression (from ~ 3–5 kbar to ~ 0.5–1.8 kbar). In addition, high fluxing volatiles, such as B, F and P, effectively protract magma crystallization to form highly evolved melt, and finally resulting in water saturation at shallow level. Thus, gold saturation might reach in earlier exsolving low-salinity fluids at low pressure (as low as 0.5 kbar) and high temperature (~660–700 °C) condition. Then voluminous fluids get release accompanying with hydrofracturing, and some gold sequentially precipitate in the KV with fluids cooling (<550 °C) and later in the GBV with further cooling and flashing during transition from lithostatic to hydrostatic loads. With increasing sulfur fugacity by fluid condensation and further cooling in fluid temperature, secondary gold can precipitate with possible Cu-(Fe) or As-Sb sulfides associated with pervasive intermediate argillic alteration, which intensively overprinted on earlier potassic alteration zone. [ABSTRACT FROM AUTHOR]

• Element geochemistry in coals varies notably in a laterally correlated coal seam. • Various geological factors are responsible for the difference in the elemental geochemistry of the coals. • Some critical metals including REY are redeposited within the coal section as a result of acidic leaching. • The Datanhao coal seam has potential in industrial utilization of certain critical metals. This paper discusses the modes of occurrence of critical elements and their origins in the studied coal and associated rock samples (partings and roof strata) from the Datanhao coal mine, Daqingshan Coalfield, Inner Mongolia, northern China. The studied coals are enriched in trace elements including Zr, Hf, Th, Be, F, Zn, Ga, Nb, Mo, Cd, In, Sn, Ta, Hg, W, Pb, and rare earth elements and Y (REY). Zirconium, Nb, Ta, and Hf are largely associated with anatase in the studied coal and non-coal samples. The main carriers of REY, Th, and U in both coal and non-coal samples are Ca-bearing REE-phosphate minerals, most likely monazite, although U is partly associated with organic matter. Fluorine in the Datanhao coals is mainly associated with kaolinite. Most partings identified as volcanic ash-derived tonsteins from the Datanhao Mine exhibit negative Eu anomalies that, along with the common presence of equant-shaped euhedral volcanic quartz (beta-quartz), indicate a felsic volcanic source located in the Xing'an-Mongolia Orogenic Belt. Other probable sources of clastic material into the basin include the pre-Cambrian granites from the adjacent uplands, which may be responsible for the light rare earth element enrichment of the studied deposits, and associated metamorphic rocks from the adjacent uplands. Owing to acidic hydrothermal fluids, which are most likely related to the Yanshanian (Jurassic to Early Cretaceous) intrusive activity and/or low-temperature basinal waters circulating within the coal-bearing unit during the epigenetic stage, most of the coal benches from the Datanhao mine are also relatively enriched in middle rare earth elements. On the other hand, some coal and non-coal bench samples from the middle Datanhao section are enriched in heavy REE. This, along with the presence of abundant syngenetic or early diagenetic carbonate minerals, indicates deposition in an episodic alkaline environment, the origin of which is mostly probably attributed to evaporation and/or saline water inputs resembling a playa lake environment. As the concentrations of Zr, Hf, Nb, and Ta are all close to or higher than the respective industry cut-off grades or standards for these critical elements, the Datanhao coal seam has potential economic significance for these as an important by-product of the coal mining. [ABSTRACT FROM AUTHOR]