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Early Ordovician A-type granites in the northeastern (NE) Songnen Block NE China were studied to better understand the geodynamic settings in this region. This research presents new zircon U-Pb ages and whole-rock geochemical data for the Early Ordovician granites in the NE Songnen Block. Zircon U-Pb dating indicates that the granite in the Cuibei, Hongxing, and Meixi areas in the NE Songnen Block formed in the Early Ordovician with ages of 471-479 Ma. The granites show geochemical characteristics of high SiO2 and K2O compositions and low FeOT, MgO, CaO, and P2O5 compositions. They belong to a high K calc-alkaline series and display a weak peraluminous feature with A/CNK values of 0.98-1.14. The rocks have a ∑REE composition of 249.98-423.94 ppm, and are enriched in LREE with (La/Yb)N values of 2.87-9.87, and display obvious Eu anomalies (δEu = 0.01-0.29). Trace elements of the studied granites are characterized by enrichment in Rb, Th, U, Pb, Hf, and Sm, and depletion of Ba, Nb, Ta, and Sr. They display geochemical features of high Zr + Y + Nb + Ce values (324-795 ppm) and Ga/Al ratios consistent with A-type granites. Based on particular geochemical features, such as high Rb/Nb (7.98-24.19) and Y/Nb (1.07-3.43), the studied A-type granites can be further classified as an A2-type subgroup. This research indicates that the Early Ordovician A-type granites were formed by the partial melting of ancient crust in an extensional setting. Lower Sr/Y and (Ho/Yb)N ratios indicate that plagioclase and amphibole are residual in the source, and garnet is absent, implying that the magma was generated at low levels of pressure. By contrast, the contemporaneous granites in the SE Xing’an Block suggest a subduction-related tectonic setting, and its adakitic property indicates a thickened continental crust. We suggest that the Paleo-Asian Ocean plate between the Xing’an and Songnen blocks subducted northward during the Early Ordovician. Meanwhile, the NE Songnen Block was exposed to a passive continental margin tectonic setting. [ABSTRACT FROM AUTHOR]

Abstract: Agricultural soil pollution is a serious problem that can endanger ecology, food safety, and human health. The study evaluated the accumulation and distribution of major and trace elements in the agricultural soil of the Gannan area in the northwest Songnen-Plain, a very important base of grain production in northeastern China. To identify the concentrations and sources of pollutants and also to assess the soil environmental quality, a total of 2400 topsoil (0–20cm) samples and 10 subsoil (180–200cm) samples were collected. Then 6 major elements (CaO, Fe2O3, K2O, MgO, Na2O, SiO2), 18 trace elements (As, B, Cd, Co, Cr, Cu, F, Hg, I, Mo, Mn, N, Ni, P, Pb, Se, S, and Zn), pH, and Corg (organic carbon) were analyzed. The accumulation of Cd, Cu, Pb, Zn, Hg, and F was apparent in the agricultural soils. Correlation coefficient analysis showed that most major and trace elements, as well as pH and Corg, were significantly positive correlated in agricultural soil. Principal component analysis (PCA) indicated two main anthropogenic sources for trace elements in agricultural topsoil. The first component including B, Cr, Cu, Mg, Ni, and Zn, represented a mixture of atmospheric deposition and livestock manures; whereas the second component, relating to Ca, F, Cd, Hg, Se, and P, suggested the inorganic fertilizers and lime, as well as agrochemicals. Spatial distribution patterns using GIS contour maps and an integrated soil pollution index were established for the selected metal concentrations. In general, the range of RI (the potential ecological risk index) was from 43.6 to 556, with a mean value of 106, indicating low ecological risk in this study area. This study indicated that more attention should be paid to metal pollution of agricultural soil in the rural area to safeguard both soil and food safety. [Copyright &y& Elsevier]

Abstract: In the present study, magnetic measurements were combined with geochemical analysis and stable Pb isotopic ratios to reveal the distribution and origination of trace metal pollutants in kindergarten dusts from a typical urban environment of Wuhan, central China. The geoaccumulation index (I geo) of magnetic properties was more prominent than those of individual metals. The magnetic susceptibility (MS) and trace metals (Zn, Pb, and Cu) in this study together with published results from other Chinese cities formed a liner relationship, suggesting that metal contaminants in Chinese urban areas had similar MS to metal ratios, which could be used as an indicator for identification of pollution sources between Chinese cities and the other Asian cities. Stable Pb isotopic ratios (1.1125–1.1734 for 206Pb/207Pb and 2.4457–2.4679 for 208Pb/207Pb) in the urban dusts from Wuhan were characterized by higher 208Pb component in comparison with those from other Chinese cities. This result combined with principal component analysis (PCA) indicated that metal pollutants in the dusts were derived from industrial activities and coal combustion, whereas the traffic emissions were no longer a predominant pollution source in urban environment. Our study demonstrated that environmental magnetic methods could not only reveal the overall situation of trace metal contamination, but also prove evidence in the identification of pollution sources. [Copyright &y& Elsevier]

The geochemical characteristics of atmospheric deposition can help trace the origin and assess the impacts of pollutants. Northeast China has always been a region seriously affected by sandstorms. This study aims to explain the potential source of sandstorms in Gannan County, Heilongjiang Provence, by collecting dust and analyzing geochemistry in one year where there is no significant industrial or anthropogenic pollution. Input fluxes of deposition show that Zn and Mn were more prevalent (36.7 g·hm−2·a−1 and 77.93 g·hm−2·a−1, respectively) than other elements. The geochemical composition of atmospheric deposition samples from 17 collection points in Gannan County were determined with regard to 20 elements including nine heavy metals, two metalloids, three nonmetallic elements, a transition metal, and five other major elements. The discriminate function (DF) and chemical index of alteration (CIA) indices indicate that Gannan County (agricultural production area) and Harbin (densely inhabited district) have similar geochemical characteristics of dry deposition. The integration of Na/Al and Ca/Mg ratios with an air mass back-trajectories model shows effects from Russian dust sources (36.6%) and from the northwest desert of China (13.3%). The results will assist in developing strategies for reducing dry deposition pollution inputs to agricultural soils in the area and will effectively target policies to protect soils from long-term contaminant accumulation. [ABSTRACT FROM AUTHOR]