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The Guilaizhuang gold ore field is one of the essential tellurium-rich goldfields in eastern China and the only super-large goldfield in western Shandong so far. These gold deposits controlled by the Tongshi subvolcanic dome occur in different depths, geological structures, and geological bodies. Though their mineralization types are diverse, their host wall rocks, formation environment, geological background, and metallogenic characteristics are generally consistent: (1) The Guilaizhuang gold ore field, mainly composed of Precambrian basement rocks and early Paleozoic carbonate cap rocks, is an endogenous medium−low hydrothermal gold concentration area of relatively developed Mesozoic tectonic magmatism. (2) Yangan fault, a derivative structure of the Tanlu Fault Zone, controls the distribution of strata, magmatic rocks, secondary structures, and gold deposits (points) in this area. The sub-faults of the Yangan fault and the radial and circular structures of subvolcanic domes are good places for ore fluid migration and sedimentation. (3) The mineralization types are mainly cryptoexplosive breccia, magnesian carbonate micro-disseminated, porphyry, skarn superposition, and altered fracture zone. The ores generally develop into disseminated, veinlet disseminated, stockwork, crumb, and block structures, reflecting that they were formed in the post-magmatic hydrothermal environment. (4) It shows a distinguished character of coexistence of tellurium and gold super concentration. In addition to common native gold and electrum, there are also tellurium-containing minerals such as bessmertnovite, petzite, hessite, calaverite, etc. (5) The early Jurassic intermediate alkaline magma initially started the gold mineralization process in this area and provided parent rock and material source for the early Cretaceous alkaline magmatic activities. The main mineralization period of the Guilaizhuang gold ore field in western Shandong may be in the early Cretaceous. (6) The ore-forming fluid has the characteristics of low temperature and low salinity. The isotopic characteristics are multi-sourced. They are dominated by magmatic water and atmospheric precipitation, with a small amount of metamorphic water. (7) Au likely combines with Te and S to form transportable complexes for migration in the ore-forming hydrothermal fluid. There is a high tellurium fugacity in the ore-forming hydrothermal fluid. Under medium- and low- temperature conditions, tellurium can easily replace sulfur and enter the sulfide lattice. Under high tellurium fugacity conditions, tellurium is prone to form telluride with elements such as gold, silver and lead to mineralization. The consistency of the regional metallogenic characteristics indicates that the Mesozoic large-scale gold mineralization in the Guilaizhuang area of western Shandong is controlled by a unified geological event and can be classified into a unified subvolcanic medium-low hydrothermal gold metallogenic system.

BACKGROUND In recent years, the study of rare polymetallic ore tends to be increasingly detailed. As one of the important research methods, electron probe quantitative analysis has made great progress in trace element measurement. During analysis, in addition to increasing the beam size and time to reduce the detection limit, more attention should be paid to removing the interference from other elements, especially the main elements. During the routine testing of rare polymetallic samples, Si, Ta, W interfere with each other. Such interference affects the analytical results of trace elements, and is not easily detected due to its low content, thus affecting the accuracy of the final conclusion. OBJECTIVES To determine the interference relationship among Si, Ta and W under different analytical conditions. METHODS Taking SiO2, metal Ta and W of SPI as the research object, each element was analyzed under different conditions by electron probe microanalyzer. RESULTS In the analysis of silicate, TAP-Kα is used for Si, and LIF-Lα is recommended for Ta and W. In the analysis of niobium tantalum ore, it is suggested to use PET-Kα, PET-Mα and TAP-Mβ for Si, Ta and W, respectively; since 100% Ta will produce about 0.1% Si, therefore, the results are more accurate with the interference correction of Ta on Si. CONCLUSIONS It is important to understand the spectral peak stripping method and the principle of element interference and spectral peak overlap, adjusting the parameters according to the actual situation to ensure the accuracy of data.

To accurately predict the dehydration rate of tobacco leaf during bulk curing and precisely control curing process parameters, three models for predicting the dehydration rate of tobacco leaf were established based on machine learning. Taking the middle leaves of cv. CB-1 as the material, the images and dehydration rates of tobacco leaves were realtimely collected during curing process. Image processing technology was used to extract 10 color features and 10 textural features of the leaves, and 2 color features (a*/b*, R) and 2 textural features (gradient entropy, nonuniformity of gradient distribution) were selected through variable clustering and Pearson correlation analysis. The three established prediction models, the grid search support vector machine (GS-SVM), genetic algorithm optimized BP neural network (GA-BP), extreme learning machine (ELM) models, were subject to training with the four selected features of the images in the training set and the dehydration rates of tobacco leaves. The dehydration rates of tobacco leaves predicted by the three models were compared with the actual dehydration rates. The results showed that all the three prediction models could accurately predict the dehydration rates of tobacco leaves during bulk curing with the root mean square error (RMSE) ≤0.014 0 and coefficient of determination (R²) ≥0.996 1. The prediction errors for the leaves at yellowing stage (0-40 h) and color-fixing stage (40-100 h) were lower than those at stem-drying stage (100-140 h). This technology provides a support for the development of intelligent control system for tobacco leaf curing. [ABSTRACT FROM AUTHOR]

Single crystals of norsethite-type carbonate BaMn(CO3)2 up to 200 μm in size were synthesized in a closed cavity under high pressure–temperature (P–T) conditions. Electron microprobe analyses revealed the composition of 49.00–49.09 wt% BaO and 22.66–22.74 wt% MnO, which correspond well to the ideal formula of Ba1.0Mn1.0(CO3)2. Accurate crystalline structural data were determined from single crystal X-ray diffraction (XRD). The R 3 ¯ c space-group with a doubled c-axis and R 3 ¯ m space-group were used to refine the crystal structure of BaMn(CO3)2. It is proved that R 3 ¯ m is the most probable space-group for the BaMn(CO3)2 crystal structure because no superstructure reflections were observed in the X-ray images. The unit cell parameters were identified to be a = 5.0827(2) Å and c = 17.2797(10) Å in the rhombohedral symmetry of the R 3 ¯ m space-group with a final R-value of 0.0184. High-pressure Raman spectroscopy was performed up to 10 GPa at room temperature, and Raman band shifts ( d ν i d P ) were quantified. Each Raman vibration underwent resolvable splitting and the corresponding d ν i d P showed a pronounced jump as the pressure reached 3.8 GPa arising from a pressure-induced transition. [ABSTRACT FROM AUTHOR]

Single crystals of impurity-free siderite were grown successfully using high-temperature-pressure annealing. The size of crystals ranged up to 100 µm, and they exhibited a rhomboid shape upon cleavage along the (101) plane. The composition of Fe0.9988±0.0011CO3 was quantified using electron probe analysis. Accurate crystalline structural data were investigated by means of single crystal X-ray diffraction (XRD) and the unit cell dimensions obtained in the rhombohedral symmetry of the R3¯c space group were a = 4.6861(3) and c = 15.362(2), and the final R = 0.0499. Using in situ synchrotron XRD, the high-pressure behavior of impurity-free siderite was investigated up to 20 GPa at ambient temperature. The pressure-volume (P-V) EoS was fitted by a third-order Birch-Murnaghan equation, and the isothermal bulk modulus was K0 = 97.5(11) GPa for K0′ = 4. High-pressure Raman spectroscopy was performed at up to 30 GPa at ambient temperature, and the Raman bands shifted as the increase of pressure (dνidP) was determined. In combination with the high-pressure Raman results and the bulk modulus K0, the mode Grüneisen parameters of each vibration were calculated. Meanwhile, high-temperature Raman spectroscopy was carried out at up to 300 °C and the Raman band shift (dνidt) was also quantified. [ABSTRACT FROM AUTHOR]

The Emeishan basalt has a high Cu background value (170x10-6 on average), and thus provides a ore-forming material source for copper ores. The collected samples were exposed in basalt lavas of the third segment of the Emeishan basalt eruptive cycle. By using a set of automatically cycling glass apparatuses, weathering-leaching experiments by three kinds of rainwater on the collected samples were carried out in the open system (at normal temperature and normal pressure). The analysis results showed that the most intensive export of Cu occurred under acidic rainwater-induced weathering-leaching conditions, almost 2-3 orders of magnitude the export of Cu by modern air rainwater, and 1-2 orders of magnitude higher than the export of Cu by CO2 rainwater. In addition, the total amount of Zn, Cu, U, Ni and Sr exported by acidic rainwater are greater than 1%. All this indicates that copper in the Emeishan basalt provided the copper source for Cu mineralization at the contact between the basalt and the Maokou Formation limestone at the bottom. [ABSTRACT FROM AUTHOR]

Single crystals of impurity-free siderite were grown successfully using high-temperature-pressure annealing. The size of crystals ranged up to 100 µm, and they exhibited a rhomboid shape upon cleavage along the (101) plane. The composition of Fe0.9988±0.0011CO3 was quantified using electron probe analysis. Accurate crystalline structural data were investigated by means of single crystal X-ray diffraction (XRD) and the unit cell dimensions obtained in the rhombohedral symmetry of the R3¯c space group were a = 4.6861(3) and c = 15.362(2), and the final R = 0.0499. Using in situ synchrotron XRD, the high-pressure behavior of impurity-free siderite was investigated up to 20 GPa at ambient temperature. The pressure-volume (P-V) EoS was fitted by a third-order Birch-Murnaghan equation, and the isothermal bulk modulus was K0 = 97.5(11) GPa for K0′ = 4. High-pressure Raman spectroscopy was performed at up to 30 GPa at ambient temperature, and the Raman bands shifted as the increase of pressure (dνidP) was determined. In combination with the high-pressure Raman results and the bulk modulus K0, the mode Grüneisen parameters of each vibration were calculated. Meanwhile, high-temperature Raman spectroscopy was carried out at up to 300 °C and the Raman band shift (dνidt) was also quantified. [ABSTRACT FROM AUTHOR]