Search

By analyses on the trace elements of coals, host-rocks and wall-rocks, this study aims to trace the sources and evaluate the utilization prospects of REE+Y (REY) in coals from Bayili Coal Mine (Wensu, Xinjiang, China). The distribution patterns of REY in the coals are divided into two groups, flat-type and heavy REE-enrichment type (H-type). The REY of the former was mainly from the gneisses of the basement of the coal-bearing basin, and that of the later was partly from hydrothermal solution. The host-rocks show two types of REY patterns, middle REE-enrichment type (M-type) and H-type, which are due to the injection of REY from acid terrestrial water and hydrothermal solution, respectively. Almost all the coal samples are plotted into the promising area on the diagram of percentage of critical elements (REYdef, rel) vs ratio of sum of critical elements to the sum of excessive elements (Coutl) and half of the coal samples have high contents of Ga closing to the cut-off grade of Ga deposit as by-product, which indicate that the REY and Ga in Bayili Coal Mine are of utilization prospects as by-product.

The alkaline mineral amendment is a practical means of alleviating Cd concentration in rice grain (CdR) in the short-term; however, the long-term remediation effect of mineral amendment on the CdR and the eco-environmental controls remains unknown. Here a mineral (Si–Ca–Mg) amendment, calcined primarily from molybdenum tailings and dolomite, was applied biannually over 6 years (12 seasons) to acidic and moderately Cd-contaminated double-rice cropping ecosystems. This study investigated the inter-annual variation of Cd in the rice-soil ecosystem and the eco-environmental controls in subtropical rice ecosystems. CdR was reduced by 50%–86% following mineral amendment. The within-year reduction in CdR was similar between early rice (50%–86%, mean of 68%) and late rice (68%–85%, mean of 74%), leading to CdR in all early rice and in 83% of late rice samples below the upper limit (0.2 mg kg−1) of the China National Food Safety Standards. In contrast, the inter-annual reduction in CdR was moderately variable, showing a greater CdR reduction in the later 3 years (73%–86%) than in the former 3 years (54%–79%). Three years continuous mineral amendment was required to guarantee the safety rice production. The concentrations of DTPA-extractable and exchangeable Cd fractions in soil were reduced, while the concentration of oxides-bound Cd was increased. In addition, the soil pH, concentrations of Olsen-P and exchangeable Ca and Mg were elevated. These imply a lower apparent phytoavailability of Cd in the soil following mineral amendment. An empirical model of the 3-variable using soil DTPA-Cd, soil Olsen-P, and a climatic factor (precipitation) effectively predicted temporal changes in CdR. Our study demonstrates that Cd phytoavailability in soil (indexed by DTPA-extractable Cd) and climatic factors (e.g., temperature and precipitation) may directly/indirectly control the inter-annual reduction in CdR following mineral amendment in slightly and moderately Cd-contaminated paddy ecosystems.

Three generations of calcite veins filling in fractures have been recognized in Dabashan Thrust and Fold Belt in China. Reconstruction of the paleostress states corresponding to and studies on fluid inclusions and stable isotopes from the wall-rocks and the veins filled in the fractures have been carried out. The first vein, which occurs in the fractures limited to competent bed and perpendicular to the layer, was precipitated from liquids during diagenesis. Homogenization temperatures (Th) of fluid inclusions in the veins range from 126°C to 267°C, which are similar to those obtained by the wall-rocks, i.e., from 152°C to 227°C. The second-generation veins were filled in three groups of faults corresponding to NE-SW compression. Homogenization temperatures of the fluid inclusions show bimodal distribution, with peak Th-population values from 140°C to 210°C and 230°C to 270°C. The salinity values exhibit evidently two groups either. The bimodal distribution of both homogenization temperatures and salinities indicates that the fluid flowing within the fractures posses two stages of evolution. The third-generation vein was filled in NNW-SSE to NWW-SEE trending strike-slip faults, which were formed under NW-SE tectonic compression. The homogenization temperatures obtained by fluid inclusions in the veins range from 101°C to 257°C. The wide change in Th values possibly indicates that re-equilibrium has occurred for the fluid inclusions during the activity of the faults. The δ 13 C and δ 18 O values of the wall rocks range from -1.6‰ to 5.6‰ and 16.7‰ to 25.2‰, respectively. The values of δ 18 O are similar to or lower slightly than marine carbonate(29‰). The δ 13 C and δ 18 O values of the first-generation veins are from -1.8‰ to 2.2‰ and 18.4‰ to 23.1‰, respectively, which are similar to those of wallrocks except showing smaller variation. The δ 13 C and δ 18 O values of the second-generation veins range from -9.2‰ to 4.7‰ and 13.2‰ to 27.9‰. Compared to wallrocks and the first-generation veins, the second-generation veins exhibit larger variability in both δ 13 C and δ 18 O values. The third-generation veins show similar situation to the second-generation veins in δ 13 C values and the large variation in carbon isotopic compositions with the δ 13 C values from -9.2‰ to 4.8‰. But the δ 18 O values are not as large variable as that of the second-generation veins, and the δ 18 O values are from 12.8‰ to 19.8‰. The δD values measured by fluid inclusions from the second- and third-generation veins are from -62‰ to -90‰ and -74‰ to -87‰, respectively. On the plot of δ 18 O fluids vs δD fluids , parts of samples are fall in the scope of formation water, some samples show slightly lower δD values relative to formation water.