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"Trapiche-like" texture is distinct from "trapiche" texture as typically observed in emeralds, amethysts, and aquamarines. It is also occasionally encountered in sapphires from Changle, eastern North China Craton. The advent of the trapiche-like texture has enhanced the ornamental value of sapphire, although its origin is still unclear. In this study, techniques, such as Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV-Vis) spectroscopy, Raman spectroscopy, electron probe microanalysis (EPMA), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), have been applied to test the spectroscopic data of the cores, arms, and blue sectors of trapiche-like sapphires from Changle and explore the mineralogical characteristics of different domains. The main component of the core, arms, and blue sectors of trapiche-like sapphire is corundum (Al2O3), with trace elements including Fe, Ti, Mg, Cr, V, Ga, etc. From arms to cores to sectors, trace elements show a trend of increasing and then decreasing. Nb and Ta elements are more enriched in the arms than in the sectors, indicating the existence of rutile. With changes in physicochemical conditions during magma evolution, rutile melted, and related voids were filled with glassy inclusions, which formed the arms of trapiche-like sapphires. Field observations of primary deposits, as well as petrological and geochemical analyses, reveal that the trapiche-like sapphire of Changle belongs to magmatic sapphire. [ABSTRACT FROM AUTHOR]

The widely distributed Eocene mafic microgranular enclaves in the Lhasa Terrane of southern Tibet carry important information regarding crust–mantle interactions in collisional zones. Here, we report geochronological and geochemical data of granitoids and mafic enclaves from Quxu in the southern Lhasa Terrane. Zircon LA‐ICP‐MS U–Pb dating indicates that the Quxu granitoids and enclaves were synchronously emplaced at ca. 50 Ma. The granitoids are medium‐ to high‐K calc‐alkaline, metaluminous (A/CNK = 0.82–0.90) and have high Al2O3 (14.48–16.57 wt%) and low MgO (2.81–2.99 wt%). The mafic enclaves (SiO2 = 50.55–54.57 wt%) have 5.12–5.37 wt% MgO and an Mg# of 49–51, with weakly negative Eu anomalies (Eu/Eu* = 0.85–0.91). The Quxu granitoids and enclaves have similar zircon Hf isotopic compositions, with εHf(t) values ranging from +7.62 to +13.32. A comprehensive study of the data available for coeval rocks from the Gangdese Batholith indicates that the Quxu granitoids were derived from partial melting of the lower crust, while the parental magmas of the mafic enclaves were most likely derived from lithospheric mantle beneath southern Tibet. The Quxu granitoids are interpreted as the result of mixing between the lower crust‐derived melts and lithospheric mantle‐derived mafic melts, which are likely the magmatic response to the breakoff of the Neo‐Tethyan Oceanic slab at about 50 Ma. [ABSTRACT FROM AUTHOR]

The process and mechanism of gold mineralization are frontier issues. The Dunbasitao deposit is the most important gold deposit discovered along the Armantai suture zone, East Junggar, NW China, which indicates the potential for future ore exploration in this area. Orebodies are mainly hosted in Lower Carboniferous Jiangbasitao Formation volcano-sedimentary rocks, and the ores are characterized by multistage pyrites. Based on microscopy and backscattered electron imaging studies, pyrites are classified into five types: the pre-ore framboidal/colloidal Py0; the early-stage coarse-grained, cubic, and homogeneous Py1; and the middle-stage fine-grained, cubic/pyritohedron Py2 that includes Py2a (core), Py2b (mantle), and Py2c (rim). The results of the EPMA and in situ LA-ICP-MS analyses show that trace elements of pyrite mainly occur in two forms: solid solutions and invisible or visible inclusions. Mn, Co, Ni, and As enter the pyrite lattice, whereas Ti occurs as mineral inclusions, and Au, Cu, Zn, Sb, and Pb can occur in both forms. Au and As show a positive linear relationship with r = 0.850. Py2b has much higher Au contents (20.1 to 201 ppm) than other pyrite types (Py0: 0.01 to 0.36 ppm; Py1: 0.01 to 0.02 ppm; Py2a: 0.31 to 2.48 ppm; and Py2c: 0.18 to 18.0 ppm). The Dunbasitao deposit is classified as an orogenic gold deposit using the two latest machine learning classifiers based on pyrite trace element data. Fluid immiscibility, sudden cooling, and the substitution of S1− with As1− might be crucial mechanisms leading to Au precipitation. Initial ore-forming fluids brought major amounts of As, Au, Co, Ni, Se, Zn, Ag, Cd, Sn, and other elements, and the Jiangbasitao Formation host rocks contributed a certain amount of As, Ni, Cu, Sb, Pb, and Bi, at least. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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]

The Jiaodong Peninsula is the most important gold mineralization area in China, and the formation of gold deposits is closely related to granitoids. The isotopic ages of the Early Cretaceous granodiorites in the northwestern Jiaodong Peninsula are concentrated in the range of 111~123 Ma, and are coeval with the formation of the gold deposits in the area. However, the studies on the geotectonic settings of the granodiorites, especially their petrogenesis and relationship with gold deposits in the northwestern Jiaodong Peninsula, are scarce. Based on field and petrographic observations, geochemistry, EPMA analysis, zircon U-Pb chronology, and Sr-Nd isotopes of the Early Cretaceous Zhouguan granodiorite in the Jiaodong area, the formation age of Zhouguan granodiorite is determined as 115 Ma ± 0.77 Ma; the analysis of EPMA shows that biotite is mainly composed of Fe-biotite and Mg-biotite, with its MgO content ranging from 9.797% to 11.635%. The crystallization temperature of biotite is in the range of 500 °C~625 °C and the emplacement depth of the rock mass is 3.98~8.71 km. The amphibole in the mass mainly includes magnesiohornblende, pargasite, and magnesiosadanagaite; among them, the former two are of crustal origin, while magnesiosadanagaite is of mantle origin. The crystallization pressure and depth of the former two are in the range of 0.75~3.02 kbar and 2.81~11.4 km, respectively, while the crystallization pressure and depth for the latter is 4.64 kbar and 17.53 km, respectively. The (87Sr/86Sr) values range from 0.710424 to 0.711074 and the (143Nd/144Nd) values range from 0.511530 to 0.511808. The parental magma of the Zhouguan granodiorite is highly oxidized with high-water content that is favorable for Au enrichment. Combined with the Nb-Y and Yb-Ta diagrams, a model describing the formation of Zhouguan granodiorite is proposed. [ABSTRACT FROM AUTHOR]

To explain the anomalous anisotropy in thermal expansion properties reported in rhodochrosite (MnCO3) previously Rao and Murthy (J Mater Sci 5: 82, 1970), Li et al. (High Temp High Press, 2019), the evaluation of crystal structure is thought to be indispensable as an important aspect in mineralogy. In this spirit, single crystals of impurity-free rhodochrosite, up to 100 μm in size, were synthesized under high-pressure–temperature (P–T) conditions. The standard crystal structure, without the impurities common to natural samples, was investigated by means of single-crystal X-ray diffraction (XRD). The unit cell parameters obtained for the R 3 ¯ c symmetry were a = 4.7754(5) Å and c = 15.6484(18) Å, with a final R value of 0.0162. The (MnO6) octahedron exhibits an anomalous bond angle that tends more toward 90° of a regular octahedron, which is totally different from those of MgCO3, FeCO3, and CaCO3. Using the single-crystal XRD from 100 to 370 K, the thermal expansion coefficients were quantified as αa = 5.08 × 10−6 K−1 and αc = 18.06 × 10–6 K−1, as well as αVunit cell = 28.49 × 10–6 K−1. The geometry of (MnO6) octahedron as function of temperature was also determined as αMn–O = 12.14 × 10−6 K−1 and αO–Mn–O ≈ 0.05°/100 K. The anisotropy of MnCO3 (αa/αc = 3.55), similar to that of MgCO3 (~ 3.0, Markgraf and Reeder, Am Mineral, 70: 590–600, 1985), indicates that the difference in bond angle has no significant effect on the thermal expansion properties. According to the standard crystal structures of end members (MgCO3, FeCO3, MnCO3, and CaCO3), the cation substitution in calcite-type structures is proven to agree with the rigid body model and the linear solid solution relationship is highly consistent with those of natural carbonates. [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]

The Hetai goldfield, located at the northern edge of the Yunkai Massif in South China, is a significant gold deposit hosted within the Hetai ductile shear zone (HSZ). The deformation history of HSZ and its correlation with the gold mineralization are problematic. In this study, we conducted detailed field observations and microstructure analyses together with zircon U–Pb and muscovite 40Ar/39Ar geochronology on mylonitic granites, aiming to study the deformation features and processes of the ductile shear zone (DSZ) along with their further implications to the gold metallogenic mechanisms of the Hetai goldfield (HGF). The HGF and its periphery have undergone three phases of ductile shear event (DS) since the Palaeozoic: The first DS developed from 468 to 413 Ma, with deformation temperatures above 500°C, accompanied by the formation of large‐scale migmatite and magmatism. The second DS developed from 239 to 211 Ma, with deformation temperatures ranging from 400°C to 500°C and resulted in a low‐angle, top‐to‐the‐SE thrusting. The third DS developed from 198 to 162 Ma, with deformation temperatures between 300°C and 400°C and formed steep, dextral strike‐slip shear zones. The DSs in the HGF have close connection with the gold mineralization. The first DS is coeval with the small‐scale gold mineralization or sulfofication and laid the foundation for later large‐scale gold mineralization. The second DS had no obvious gold mineralization, but the DSZ that developed in this period, together with the earlier DSZs, may have provided a migration pathway for the later gold ore‐forming fluid. Occurrence of the third DS was combined with the main gold mineralization, but the large‐scale gold mineralization mainly occurred during 175–157 Ma, that is, the middle and later periods of dextral strike‐slip. Overall, multiphase DS dominated the large‐scale gold mineralization in this area. [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]

In this study, an electron microprobe analyzer (EMPA) was used to map the spatial distribution and the occurrence of invisible gold in pyrite from the Liulincha gold ore belt. EPMA data show that gold mainly occurs as submicroscopic-microscopic inclusions. From the contrast of the major guide elements of pyrite from the Liulincha gold ore belt and those from four hydrothermal-type gold deposits in the Jiaodong region, we can see the pyrites were formed in two stages: the pyrite from wall rock is mainly sedimentogenic, with simple structure; and the pyrite from ore body experienced early sedimentary process to late hydrothermal activity, the pyrite is regular in crystal form and exhibits fractured structure. [ABSTRACT FROM AUTHOR]

Adsorption experiments were made at room temperature and neutral pH value on different types of minerals associated with the Lower Cambrian black shale series polymetallic layers in Hunan and Guizhou provinces on nanometer-sized Pt colloids and PtCl-bearing ionic solutions with an attempt to constrain the relationship between the different types of minerals in the polymetallic layers and the enrichment of platinum group elements (PGEs). Experimental results showed that the different types of minerals show strong selectivity to the adsorption of nanometer-sized Pt colloids and PtCl-bearing ionic solutions. Metallic sulfides, organic matter and clay minerals are the strong adsorbents of PGEs, while quartz, albite, muscovite and other silicate minerals show a week adsorbility to both of them. This phenomenon is well consistent with the geological fact that metallic sulfides, organic matter and clay minerals in the polymetallic layers of the black shale series are the major carrier minerals of PGEs, giving a thorough explanation to the mechanism of enrichment of previous metal elements. Adsorption may be a principal mechanism of enrichment of precious metal elements under lower temperature conditions. The presence of the aforementioned strong adsorbents is the good geochemical barriers for the enrichment of PGEs. [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]

The Rizhao Hujialin area is located in the central Sulu ultrahigh-pressure orogenic belt, where garnet clinopyroxenite is exposed in the upper part of an ultramafic rock complex and serpentinized dunite is exposed in its lower part. Based on textural criteria, the garnet clinopyroxenites were divided into three types: Equigranular garnet, porphyroclastic garnet, and megacrystic garnet pyroxenites. The garnet clinopyroxenites have convex-upward chondrite-normalized rare earth element patterns, large positive Pb anomalies, and depletion of high-field-strength elements (e.g., Nb, Zr, and Ti), suggesting a mantle source protolith overprinted by fluid metasomatism. Petrographic, mineral chemistry, phase equilibrium modeling, and zircon U–Pb geochronology data show that the evolutionary stages of the Hujialin garnet clinopyroxenites were as follows: Stage I: formation of the magmatic protoliths; stage II: formation of megacrystic garnet pyroxenite accompanying subduction; stage III: formation of porphyroclastic or equigranular garnet clinopyroxenite with a mineral assemblage of garnet + clinopyroxene + ilmenite + humite accompanying initial exhumation at ~215.0 ± 5.7 Ma; stage IV = progressive cooling and decompression associated with the crystallization of water-bearing minerals such as clinochlore and pargasite at 206 Ma; and Stage V = late epidote amphibolite-facies retrograde metamorphism producing a mineral assemblage of garnet + clinopyroxene + amphibole + chlorite + epidote + ilmenite at ~180–174 Ma associated with fluid activity in shear–tensional fractures and/or pores. The P-T conditions of the peak metamorphism were estimated at 4.5 ± 0.5 GPa and 800 ± 50 °C. Retrograde metamorphism recorded conditions of 1.0 GPa and 710 ± 30 °C during the exhumation and cooling process. The mineral transformation from early high-Al clinopyroxene to garnet and to late diopside records the general metamorphic evolution during subduction and exhumation, respectively. One zircon U–Pb analysis presents the Palaeoproterozoic age of 1817 ± 40 Ma, which is coeval with widespread magmatic and metamorphic events in the North China Craton. [ABSTRACT FROM AUTHOR]

Mass alkaline magmatic activities in Western Shandong during the late Mesozoic controlled the mineralization processes of gold and rare earth element (REE) polymetallic deposits in the region. The Chishan alkaline complex is closely associated with the mineralization of the Chishan REE deposit, which, as the third largest light REE deposit in China following the Baiyenebo (Inner Mongolia) and Mianning (Sichuan) deposits, is considered a typical example of alkaline rock mineralization throughout the North China Craton. To determine how the Chishan alkaline complex and REE deposit interact with each other, a systematic study was conducted on the petrology, rock geochemistry, zircon U–Pb geochronology, Lu–Hf isotopes of the quartz syenite, and alkali granite contained in the Chishan alkaline complex. The results reveal that the deposits feature similar geochemical characteristics typical of an alkaline rock series—both are rich in alkali, high in potassium, metaluminous, and poor in Ti, Fe, Mg, and Mn. In terms of REEs, the deposits are strongly rich in light REEs but poor in heavy REEs, with weak negative Eu anomalies. In terms of trace elements, they are rich in large ion lithophile elements Ba, Sr, and Rb but poor in high field-strength elements Nb, Ta, and Hf. Zircon LA-ICP-MS U–Pb dating indicated that the quartz syenite and alkali granite formed in Early Cretaceous at 125.8 ± 1.2 Ma and 127.3 ± 1.0 Ma, respectively; their εHf(t) values are −22.67 to −13.19, with depleted model ages (TDM) ranging from 1296 Ma to 1675 Ma and crustal model ages (TDMC) of 2036–2617 Ma. The Chishan alkaline complex originated from partial of the EM I-type (enriched mantle I) lithospheric mantle with assimilation of ancient crustal materials. The complex is of the same origin as the REE deposit, and developed in an extensional setting that resulted from plate subduction and lithospheric thinning and upwelling in the eastern area of the North China Craton. [ABSTRACT FROM AUTHOR]