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• Hydrological variations in coastal plain are reconstructed by the magnetic method. • Greigite/pyrite bearing layers reflect waterlogged condition. • Hematite/goethite bearing layers reflect drier periods of soil formation. • Rapid hydroclimate fluctuations interrupt continuous Neolithic occupation. The Yaojiang Valley (YJV) on the southern Hangzhou Bay Plain, eastern China, was home to Neolithic cultures that date back to 8 ka. Reconstructions of ancient human cultures on the coastal plain in response to sea-level and hydroclimate changes have been well documented. However, centennial-resolution geological records are still lacking. Here, we present a combined approach of environmental (mineral) magnetism, geochemistry and diffuse reflectance spectroscopy (DRS) on a sediment core (YJ1503) in YJV to decipher the centennial hydroclimate oscillations of the coastal plain since early Holocene. Our results show that ferrimagnetic greigite and paramagnetic pyrite bearing layers correspond to periods of reducing condition that were caused by a higher water table while the presence of antiferromagnetic hematite/goethite corresponds to drier periods favorable for soil formation. Centennial scale fluctuations of magnetic mineralogy around the 8.2 ka cooling event and 7.5–6.6 cal ka BP reflect frequent and unstable environments, with limited Neolithic occupation. A strong drought event occurred around 6.0 cal ka BP, which was preceded by an extensive marine inundation event in the study area. This inundation event interrupted rice farming. Our study indicates that magnetic mineralogy can be used to reconstruct high-resolution hydrological processes in coastal plain and floodplain environments. These results are important to understand hydroclimate variation and Neolithic civilization response in environmentally sensitive areas. [ABSTRACT FROM AUTHOR]

Abstract: The rapid industrial development in the Yangtze River watershed over the last several decades has drawn great attention with respect to heavy metal pollution to the Yangtze River estuary and nearby coastal areas. In this study, a 236cm long sediment core was retrieved from the Yangtze River subaqueous delta (122°36′ E, 31°00′ N) in 2008 and analyzed for magnetic properties and geochemical compositions to investigate heavy metal pollution history. The activity of 137Cs peaked at depth 140cm, with a broad plateau between 120cm and 140cm, suggesting an average sedimentation rate of 3.11cmyr−1 for the upper 140cm layer. Magnetic susceptibility (χ), saturation isothermal remanent magnetization (SIRM), anhysteretic remanent magnetization (χARM) and heavy metal enrichment factors (EF) all showed an upward increase trend above depth 140cm, suggesting that increased ferrimagnetic mineral concentration was accompanied by heavy metal enrichment in the sediment. Geochemical and granolumetric analyses showed that sediment sources and particle sizes played minor roles in the variations of magnetic properties. The effect of diagenesis, which can lead to the selective removal of magnetic minerals, was noticeable in the lower part of the core (140–236cm). Co-variation between magnetic properties (χ, SIRM and χARM) and EF of Cu and Pb suggests that the elevated ferrimagnetic mineral concentration can be used as an indicator of heavy metal pollution in the reconstruction of environmental changes in estuarine and coastal settings. [Copyright &y& Elsevier]

In this paper, the relationship between rare earth elements (REEs) geochemical behavior and their ionic radii was studied. According to the basic law called the effect on geochemistry of lanthanides, five types and some of subtypes of REEs occurrence, both in magmatic rocks and their minerals, were found, which may correspond to the evolutionary way of magmatic rocks. Analysis of REEs data for an amazonite-topaz granite pluton in East Xinjiang, one of the administrative regions of West China, and Cenozoic alkaline volcanic-intrusive rocks in the Xialiaohe depression of Bohai Bay Basin, China show that types II1, III and IV of effect on geochemistry of lanthanides not only reflect fluid complexation and fractional crystallization existed in magmatic evolution directly, but also can determine semi-quantitatively the strength of fluid complexation and fractional crystallization. Therefore, the effect on geochemistry of lanthanides, a new way to study semi-quantitatively evolution of magmatic rocks, is probably practicable. Moreover, the mafic lavas of different sources from the margin of Gonghe Basin, Qinghai Province, China, can be effectively distinguished in the diagram which can be drawn with some parameters of linear equation of LREEs and its ion radius. [ABSTRACT FROM AUTHOR]

Abstract: The Late Permian coals in the Heshan Coalfield of southern China are preserved within marine carbonate successions and characterized by super-high organic sulfur (5.13–10.82%). Minerals identified in the coals include quartz, kaolinite, illite, mixed layer illite/smectite, albite, pyrite, marcasite, calcite, and dolomite, along with trace amounts of smectite, fluorite, strontianite, REY-bearing carbonate minerals, jarosite, and water-bearing Fe-oxysulfate. The coals are very rich in trace elements including F (up to 3362μg/g), V (up to 270μg/g), Se (up to 24.4μg/g), Mo (up to 142μg/g), U (up to 111μg/g), and, to a lesser extent, Sr, Y, Zr, Nb, Cd, Cs, heavy rare earth elements, Hf, Ta, W, Hg, and Th. Previous studies attributed the high organic sulfur and elevated trace elements to the seawater influence or the formation of soil horizons before the accumulation of peat in the basin. However, mineralogical and geochemical data presented in this study have shown that the sediment-source region and multi-stage hydrothermal fluids are the dominant influences on the mineralogical composition and elevated trace elements in the coal, although seawater influence also contributed to the composition of the mineral matter. For example, a large proportion of the quartz and clay minerals, as well as almost all the albite, in both the coal benches and the parting mudstones were derived from detrital materials of terrigenous origin in the Yunkai Upland. High concentrations of lithophile trace elements were also derived from the sediment source region. Minerals including fluorite, calcite, dolomite, strontianite, and REY-bearing carbonate minerals were derived from multi-stage hydrothermal activities. High concentrations of V, Mo, and U that occur through the coal seam sections were probably derived from hydrothermal solutions during peat accumulation or at the early diagenetic stages. The hydrothermal fluids also corroded the syngenetically-formed minerals (quartz, albite, and pyrite) and caused re-distribution of lithophile elements from partings to the underlying coal benches, resulting in higher key element ratios (Yb/La, Nb/Ta, and Zr/Hf) and more abundant heavy rare earth elements in the coal benches than in the immediately overlying partings. [Copyright &y& Elsevier]

Abstract: The Late Permian coal in the Fusui Coalfield of southern China is characterized by high Fe-sulfide and organic sulfur contents (2.60 and 2.94%, respectively). Trace elements including Zr (354μg/g on average), Hf (9.18μg/g), Y and rare earth elements (REY, 302μg/g), Li (97.9μg/g), and Cs (7.02μg/g) are significantly enriched in these coals. In addition to Hg and Se enrichment in the roof and floor of the coal, fluorine, Mo, and U are enriched in the roof; the floor is rich in Cl, S, Fe, Pb, and Cd. Compared to the upper continental crust, REY in the parting and coal bench samples are characterized by heavy-REY and light-REY enrichment, respectively; the coals, partings, and host rocks (roof and floor) have negative Eu anomalies. The coal benches have higher ratios of U/Th, Yb/La, Nb/Ta, and Zr/Hf, and more abundant heavy rare earth elements than their adjacent partings. These geochemical anomalies are attributed to the composition of terrigenous materials derived from the Yunkai Upland, multi-stage (syngenetic and epigenetic) hydrothermal fluid activities, and intensive leaching and re-distribution of lithophile elements from partings to the underlying coal benches. Both the organic and sulfide sulfur are also derived mainly from the hydrothermal fluids rather than the marine influence. The minerals in the samples studied, including kaolinite, quartz, and REE-bearing minerals, are of both terrigenous and hydrothermal origin. Al-oxyhydroxides, crystalline FeSO4(OH), water-bearing Fe-oxysulfate, and goyazite were derived from the hydrothermal activity. Kaolinite, quartz, REE-bearing minerals, and apatite from the sediment source region were also subjected to destruction by hydrothermal fluid leaching. [Copyright &y& Elsevier]

Abstract: The formation of a broad tidal flat along the coast of the northern Jiangsu Province of China depends largely on the sediment supply from the Yellow and Yangtze Rivers although the relative contributions from each of these two large rivers remain uncertain. Knowledge of sediment sources to the tidal flat is critical for understanding the evolution of this muddy coast impacted by the large rivers. The present study focuses on tracking the sediment source of the tidal flat deposits based on sediment magnetic properties and geochemical analyses as well as statistical analysis. The study shows that sediments to the north of Yangkougang (site 9) have lower values of saturation isothermal remanence magnetization (SIRM), magnetic susceptibility (χ), demagnetization parameter S−100 ratios, lower Fe/Al values and higher Ca concentrations, while the opposite is true for samples south to Haozhigang (site 18). In addition, SIRM values of the <16μm and >63μm fractions generally display increasing trend from north to south. These results suggest that sediment sources rather than particle size variation are the dominant factors influencing the bulk magnetic properties. In light of the sediment composition comparison between the Yellow River and Yangtze River, factor analysis is used to identify sediment source of the tidal flat sediments. It is indicated that the Yellow River in its former course is the dominant supplier for sites to the north of Yangkougang (site 9), while the Yangtze River is the dominant supplier for sites to the south of Haozhigang (site 18). The coast between Yangkougang (site 9) and Haozhigang (site 18) is a transition zone influenced by both rivers. The inferred provenance contrasts are consistent with the pattern of coastal geomorphological evolution. Our data also suggest that sediments eroded from the former Yellow River delta have contributed to the evolution of the Yangtze Estuary in historical time. This study demonstrates that a combined magnetic and geochemical fingerprinting techniques in couple with statistical analysis is valuable for identifying sediment sources of tidal flats and deltas influenced by large rivers in the world. [Copyright &y& Elsevier]

Abstract: Loess deposits are widely distributed over the islands in the Bohai Gulf and neighboring regions of northern China. The coastal loess, located to the east of the Chinese Loess Plateau (CLP), is believed to have a local source from exposed marine sediments and a distant source from inner arid regions in Asia. In this study, magnetic, geochemical and diffuse reflectance spectroscopic analyses were conducted on the loess to explore its relationship with the loess on the CLP and its paleoclimatic implications. We find that the coastal loess shows similar geochemical composition, background susceptibility and magnetic enhancement to loess on the CLP. Magnetic minerals characteristic of pedogenesis are more important in the paleosol layer, with fine ferrimagnetic minerals abundant in paleosol layer SB1 and hematite in paleosol layer SB2. Geochemical evidence suggests that weathering intensity in paleosol SB2 is similar to or even stronger than in paleosol SB1. Pedogenic enhancement of magnetic susceptibility in the study area is not so strong, which may be due to enhanced hematite formation as opposed to ferrimagnetic mineral production and preservation. [Copyright &y& Elsevier]

Abstract: Variations in the magnetic susceptibility of Chinese loess have been used to indicate pedogenic intensity and therefore past climate across the Chinese Loess Plateau (CLP). However, the relationship between climate and magnetic properties has not been fully resolved, and therefore a study of loess sections distributed over a wider climatic region is timely. In this study, we have investigated a 22.1 m loess section (named the Xiashu Loess) at Dagang, China, by integrating both rock magnetic and geochemical proxies. This loess profile is situated in a modern subtropical climate region with annual mean precipitation and temperature of 1100 mm and 15.4 °C, respectively, and therefore has experienced a stronger weathering intensity due to its lower latitude, higher temperature and rainfall. Geochemical and magnetic evidence indicate the same source area for the Xiashu Loess as for loess in northern China. The magnetic mineral assemblage of the Xiashu Loess is dominated by a higher concentration of superparamagnetic (SP)/single domain (SD) magnetite/maghemite grains in strongly weathered paleosols than in the loess layers, consistent with the production of fine-grained ferrimagnetic minerals during pedogenic processes. Nevertheless, compared to loess in the CLP, the Xiashu Loess shows: 1) reduced contrasts in magnetic susceptibility (χ), Hard Isothermal Remanent Magnetization (HIRM) and remanence of coercivity (B cr) between loess and paleosols units, which indicates that the loess units have undergone stronger pedogenic alterations; 2) lower peak values of HIRM and χ in paleosols. In addition, the ratios SIRM/χ, χ ARM/SIRM (where SIRM and χ ARM are Saturation Isothermal Remanent Magnetization and the susceptibility of Anhysteretic Remanent Magnetization, respectively) and B cr are found to be significantly correlated with the quotient (CaO⁎ +Na2O+MgO)/TiO2, a geochemical indicator of pedogenic intensity. Overall, it seems that pedogenic processes in the Xiashu Loess lead to a relative increase in fine-grained ferrimagnetic SP/SD grains but depletion of anti-ferromagnetic minerals. Magnetic and geochemical proxies indicate strengthened East Asia summer monsoon during Marine Isotope Stages 13, 11 and 5, which is in good agreement with the records from the CLP and the South China Sea. [Copyright &y& Elsevier]

We present the results of environmental magnetic, granulometric and geochemical analyses of sediments of the Oujiang River, China. The aim of the study was to assess the influence of hydrological sorting and sediment source on sediment composition from upstream down to the river mouth. The results reveal that the sedimentary magnetic properties are dominated by ferrimagnetic minerals. In the fluvial reach, the proportion of imperfect antiferromagnetic minerals is relatively high due to strong soil chemical weathering in a subtropical climate. From upstream down to the river mouth, the proportion of ferrimagnetic minerals increases consistently, and the magnetite becomes finer-grained as a result of hydrological sorting. In the tidal reach, the sediments consist of a mixture of fluvial and marine-sourced sediments derived from the Yangtze River as a result of the strong tidal influence. A combination of the demagnetization parameter S − 100 mT and element ratios (Fe/K and Al/Mg) enables the discrimination of the sediments of the fluvial reach from those of the tidal reach. Due to the rock types and subtropical weathering conditions in the catchment, the sediments of the Oujiang River are significantly different to those of the Yangtze River. Our results potentially contribute to the study of the provenance of the muddy sedimentary deposits in the inner East China Sea. They demonstrate that sediment sorting has a significant effect on bulk magnetic properties and geochemical compositions during transport from source to sink. In addition, magnetic and geochemical characterization of sized fractions of sediment can provide more reliable information regarding sediment source tracing. [ABSTRACT FROM AUTHOR]

Abstract: The No. 12 Coal (Late Permian) in the Songzao Coalfield, Chongqing, southwestern China, is characteristically high in pyrite and some trace elements. It is uniquely deposited directly above mafic tuff beds. Samples of coal and tuffs have been studied for their mineralogy and geochemistry using inductively coupled plasma-mass spectrometry, X-ray fluorescence, plasma low-temperature ashing plus powder X-ray diffraction, and scanning electron microscopy equipped with energy-dispersive X-ray analysis. The results show that the minerals of the No. 12 Coal are mainly composed of pyrite, clay minerals (kaolinite, chamosite, and illite), ankerite, calcite, and trace amounts of quartz and boehmite. Kaolinite and boehmite were mainly derived from sediment source region of mafic tuffs. Chamosite was formed by the reaction of kaolinite with Fe–Mg-rich fluids during early diagenesis. The high pyrite (Sp,d =8.83%) in the coal was related to marine transgression over peat deposits and abundant Fe derived from the underlying mafic tuff bed. Ankerite and calcite were precipitated from epigenetic fluids. Chemical compositions of incompatible elements indicate that the tuffs were derived from enriched mantle and the source magmas had an alkali-basalt character. Compared to other coals from the Songzao Coalfield and common Chinese coals, the No. 12 Coal has a lower SiO2/Al2O3 (1.13) but a higher Al2O3/Na2O (80.1) value and is significantly enriched in trace elements including Sc (13.5μg/g), V (121μg/g), Cr (33.6μg/g), Co (27.2μg/g), Ni (83.5μg/g), Cu (48.5μg/g), Ga (17.3μg/g), Y (68.3μg/g), Zr (444μg/g), Nb (23.8μg/g), and REE (392μg/g on average). Above mineralogical compositions, as well as similar ratios of selected elements (e.g., SiO2/Al2O3 and Al2O3/Na2O) and similar distribution patterns of incompatible elements (e.g., the mantle-normalized diagram for incompatible elements and chondrite-normalized diagram for rare earth elements) of coal and tuff, indicated that enriched trace elements above were largely derived from mafic tuffs, in addition to a minor amount from the Kandian Oldland. [Copyright &y& Elsevier]