The Late Permian coals from the Huayingshan Coalfield of southwestern China are significantly enriched in Zr (695μg/g), Nb (75.9μg/g), Se (6.99μg/g), Hf (10.1μg/g), and rare earth elements and Y ...(1423μg/g). Previous studies showed that the sediment-source region for these coals was the Kangdian Upland, which was formed at an early stage of the late Permian Period. The source rocks have a basalt composition, and those studies attributed the enrichment of the above high field strength elements (HFSEs) to derivation from the Kangdian Upland.
Geochemical and mineralogical data presented in this study show that the dominant sediment-source regions for the coal and roof strata of the Huayingshan Coalfields are the Dabashan Uplift, Hannan Upland, and Leshan–Longnvsi Uplift. The highly-elevated concentrations of HFSEs in the coals are due to hydrothermal fluids. Three tonstein layers derived from alkali rhyolite were identified. These tonsteins are characterized by highly-enriched HFSEs and by strong negative Eu anomalies in the rare earth element distribution patterns.
The major carriers of the rare earth elements in the coal are rhabdophane and silicorhabdophane, the latter of which is also enriched in Zr. Zirconium, however, mainly occurs in zircon. Rhabdophane and silicorhabdophane in the coal are mainly distributed along the bedding planes and occur as cell-fillings. Zircon in the coal occurs as cell-fillings and is of authigenic origin. Anatase in the partings and coals contains Nb, and occurs as fracture-filling and colloidal forms. The modes of occurrence of the above minerals indicate that they were derived from hydrothermal fluids. Mercury and Se mainly occur in sulfide minerals (pyrite and marcasite).
•The dominant sediment-source region for the coal is not the Kangdian Upland.•The highly-elevated HFSEs contents in the coals are due to hydrothermal fluids.•Three tonstein layers derived from alkali rhyolite were identified•Rare earth elements mainly occur in rhabdophane and silicorhabdophane.•Zircon and anatase in the coals are mainly of authigenic origin.
Although the geochemical and mineralogical characteristics and provenance of Permian-Triassic boundary (PTB) widespread volcanic ashes from southern China have been well investigated, the volcanic ...ashes just prior to the end-Permian mass extinction (EPME) have rarely been studied. This paper presents the mineralogical and geochemical compositions of volcanic ashes from the latest Permian coal-bearing strata of southwest China. Based on the relative abundances of kaolinite and mixed-layer illite/smectite (I/S), the volcanic ashes in the present study can be divided into tonsteins and K-bentonites, which are dominated by kaolinite and I/S, respectively. The I/S in K-bentonites formed during burial diagenesis in a non-marine environment, indicated by their low contents of sulfur and low ratios of Sr/Ba. Based on the general geothermal gradient and vitrinite reflectance of coals, the I/S was deduced to have formed under a temperature less than 100 °C. Collectively, the occurrence of vermicular kaolinite, as well as high-temperature quartz and euhedral primary zircon identified in tonstein samples indicate an intermediate-felsic pyroclastic origin for the volcanic ashes, while rounded quartz and mica grains both in tonsteins and K-bentonites reflect the products of erosion from sediment source regions. The negative Eu anomalies, rare earth elements (REY) distribution patterns, low contents of Sc, V, Cr, Co, Ni and Zn, and Al2O3/TiO2 values, suggest that the tonsteins and K-bentonites are related to felsic volcanic eruptions. The relationship between Al2O3/TiO2 vs. Nb/Yb and Al2O3/TiO2 vs. Zr/TiO2 ratios indicate that the tonsteins and K-bentonites were derived from at least two felsic sources: (1) some distal volcanic arc(s) and (2) the top of the Kangdian Upland exposing the alkaline-felsic volcanic rocks formed during the waning activity of the Emeishan plume and the basement of the Kangdian Upland exposing older felsic rocks.
•Seven volcanic ash layers were recognized in the latest Permian coal-bearing strata.•The volcanic ashes with felsic origin are recognized as tonsteins and K-bentonites.•The volcanic ashes were associated with the Emeishan plume and the volcanic arcs.
Aluminum-hydroxide (boehmite)-rich Pennsylvanian coals of high volatile A bituminous rank were found previously in the Jungar Coalfield, Inner Mongolia, China. This paper reports new results on 48 ...bench samples of the CP2 coal from the adjacent Adaohai Mine, Daqingshan Coalfield, Inner Mongolia, and provides new insights into the origin and modes of occurrence of the minerals and elements present in the CP2 coal.
Compared to the same coal in the adjacent mines, the CP2 coal in the Adaohai Mine has a higher rank (Ro, ran=1.58%), which is attributed to igneous intrusions during the Late Jurassic and Early Cretaceous Epochs. The proportion of inertinite (35.3%) in the coal is higher than that in other Late Paleozoic coals in northern China but lower than that in the Jungar coals.
Minerals in the CP2 coal include diaspore, boehmite, gorceixite, calcite, dolomite, siderite, clay minerals (kaolinite and ammonian illite), and trace amounts of anatase, fluorapatite, quartz, and pyrite. Based on mineral proportions in the coal bench samples, the CP2 coal may be divided into four Zones (I to IV) from bottom to top. The major mineral in Zones I and IV is kaolinite. Zones II and III are mainly composed of ammonian illite, diaspore, boehmite, gorceixite, calcite, dolomite, and siderite. Diaspore-, boehmite-, and gorceixite-forming materials were derived from oxidized bauxite in the weathered crust of the Benxi Formation in the sediment-source region during peat accumulation. However, gorceixite may have formed earlier than diaspore; the diaspore was derived from gibbsite that was subjected to dehydration by the heat of the igneous intrusions. The ammonian illite may have been formed at a relatively high temperature by interaction of kaolinite with nitrogen released from the organic matter in the coal during metamorphism caused by the igneous intrusion. The calcite and dolomite occur as epigenetic cell- and fracture-fillings and were probably derived from the igneous fluids.
Compared to the common Chinese and world coals, the CP2 coal is enriched in CaO (1.69%), MgO (0.32%), P2O5 (0.214%), F (207μg/g), Ga (16.3μg/g), Zr (446μg/g), Ba (276μg/g), Hg (0.33μg/g), and Th (12.4μg/g), but has a lower SiO2/Al2O3 ratio due to the higher proportions of diaspore, boehmite, and gorceixite in the coal. The F occurs mainly in gorceixite and fluorapatite. The major carriers of Ga are diaspore and kaolinite but not gorceixite. Barium mainly occurs in gorceixite and barite. Mercury was probably derived from the igneous intrusion and is distributed in both the organic matter and the minerals. The elements are classified into five associations by cluster analysis, Groups A, B, C, D, and E. Group A represents a REE-Be-Y-Se-Ga-Ge-Sc-In-Pb-Bi-Nb-Ta-TiO2-W-Hg-Sb-Zr-Hf-Th-U association. Most of the elements in Group A are lithophile elements that occur in aluminosilicate minerals. Group B (Sn-Te-Zn-Cd-V-As-Cr-Cu-Mo-Ni-Re) is weakly correlated with ash yield and is associated with unidentified trace sulfide minerals. Elements in Group C (Ad-Na2O-Al2O3-SiO2- Li-K2O-Rb-Cs-Tl association) probably occur in the clay minerals and diaspore. Group D consists of P2O5, Ba, F, Sr, S, and Cl, and with the exception of S, they occur in minerals (gorceixite and fluorapatite). Oxides of Fe2O3-MnO-CaO-MgO make up Group E and mainly occur in the carbonate minerals. The coals are enriched in light REEs and the LREEs–HREEs have been highly fractionated, with an average (La/Yb)N of 8.71. The heavy REEs in the coals have a stronger organic affinity than the LREEs.
► High proportions of diaspore, ammonian illite, and gorceixite were found in coal. ► Diaspore was derived from gibbsite dehydration due to the heat of igneous intrusions. ► Ammonian illite formed by interaction of kaolinite and nitrogen released from coal. ► The calcite and dolomite were derived from the igneous fluids.
•Novel 3D Dirac semimetal was used as a platform to design a PIT system.•The bandwidth of the PIT window can be broadened by adjust the structural parameter.•The PIT window can be tuned without ...refabricating the structures.•A higher FoM value was obtained in our design.
In this paper, we present a numerical and theoretical study on the realization of the tunable plasmon-induced transparency (PIT) effect at terahertz (THz) frequencies in Dirac semimetal (known as “three-dimensional graphene”) metamaterials. The simulations reveal that the PIT effect is generated because of the excitation of the dark mode that can be regarded as a dipole. Further investigation reveals that the bandwidth can be broadened while the resonant frequencies of the PIT remain unchanged. At the same time, the resonant frequency of the PIT window can be dynamically tuned by changing the Fermi energy of the Dirac semimetals instead of refabricating the structures. Moreover, a figure of merit value of about 10.55 is achieved in our proposed design based on the performed sensitivity measurement. Our study can provide guidance for various THz devices in practical applications.
A high-quality Nd0.01:Gd0.89La0.1NbO4 (Nd:GLNO) crystal is grown by the Czochralski method, demonstrating wide absorption and fluorescence spectra and advantage for producing ultrafast laser pulses. ...In this paper, the tunable and passively mode-locking Nd:GLNO lasers are characterized for the first time. The tuning coverage is 34.87 nm ranging from 1058.05 to 1092.92 nm with a maximum output power of 4.6 W at 1065.29 nm. A stable continuous-wave (CW) passively mode-locking Nd:GLNO laser is achieved at 1065.26 nm, delivering a pulse width of 9.1 ps and a maximum CW mode-locking output power of 0.27 W.
In this paper, an acousto-optic (AO) Q-switch based on α-BaTeMo2O9 (α-BTM) crystal is designed and further applied to generate a laser pulse at 639 nm for the first time. The α-BTM AO Q-switch ...demonstrates a large diffraction angle of 0.93° and a high diffraction efficiency of 85% at 639 nm. In the experiment, a maximum AO Q-switched output power of 362 mW is achieved at a repetition rate of 30 kHz, under a maximum absorbed pump power of 3.60 W, corresponding to a slope efficiency of 15.2%. With transmittance of T = 3%, the shortest Q-switching pulse width of 54.7 ns is generated at a repetition rate of 1 kHz. Meanwhile, the beam quality factor M2 of the above laser is measured, presenting the magnitude of 1.14 at both x and y directions. Our findings indicate that α-BTM AO Q-switch could act as an excellent switching device at 639 nm which may help to explore potential applications in the visible field.
High-quality GaInSn liquid nanospheres are successfully fabricated by the ultrasonic method as a novel saturable absorber in the mid-infrared range. An open-aperture Z-scan technique is applied to ...study the saturation absorption property, presenting a modulation depth of 34.3% and a saturable fluence of 0.497 GW/cm
2
at 2.3 μm, respectively. With GaInSn nanospheres as a saturable absorber, a stable Q-switched Er:CaF
2
crystal laser operating at 2.75 μm is realized. The maximum Q-switched output power of 361 mW is obtained under the absorbed pump power of 2.9 W. The shortest pulse width of 500 ns and the highest repetition rate of 67 kHz are generated, corresponding to maximum peak power and single pulse energy of 10.78 W and 5.39 μJ, respectively. These findings indicate a promising potential of GaInSn nanospheres SA for generating nanosecond mid-infrared laser pulses.
•The ratio of the Raman gain coefficient between YVO4 and α-BaTeMo2O9 was 0.53.•20.1mJ 2nd-order Stokes, together with 7.2mJ 3rd-order Stokes were obtained.•The conversion efficiency of the 2nd- and ...3rd-order Stokes radiation was 35.9%.•A maximum 1497nm pulse energy was 14.5mJ, together with 2mJ pulse energy at 1731nm.
The generations of high energy 2nd- and 3rd-order stimulated Raman scattering lasers based on the α-BaTeMo2O9 crystal were demonstrated for the first time. The Raman gain coefficient has been compared with that of the YVO4 crystal. A maximum total Stokes radiation energy of 27.3mJ was obtained, containing 20.1mJ 2nd-order Stokes energy at 1318nm, together with 7.2mJ 3rd-order Stokes energy at 1497nm, giving an overall conversion efficiency of 35.9% and a slope efficiency of 54.5%. With an optical coating design, a total 3rd- and 4th-order Stokes energy of 16.5mJ was generated. The maximum energy for 4th-order Stokes radiation at 1731nm was 2mJ. The pulse durations for the 2nd-, 3rd-, and 4th-order Stokes shift were 10ns, 8.6ns, and 5.2ns, respectively. Our experimental results show that the α-BTM crystal is a promising Raman crystal for the generations of eye-safe radiations.
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