Geochemistry of trace elements and Sr-Nd isotopes of foraminifera shell from the Okinawa Trough

Trace elemental associations and Sr-Nd isotopic compositions are of important to recognition of biogenic material from mixed marine sediments. The foraminifera shell from the Okinawa Trough strongly enriches Sr,P,Mn and Ba, enriches Li,U,Th,Sc,Co,Cu,Pb,Zn,Cr,Rb,Y,Sb and light rare earth elements,slightly enriches V,Ga,Zr,Nb,Cd and middle rare earth elements,is short of Mo,In,Sn,Cs,Hf,Ta,W,Ti,Bi and heavy rare earth elements. The mechanism of elemental enrichment in forminifera is the concentrations of trace elements in sea water and selective absorption of trace elements during foraminifera living, as well as the geochemical affinity between major elements and trace elements.The REE (rare earth elements)partition pattern of foraminifera shell of the Okinawa Trough shows enrichment of middle rare earth elements with slightly negative Ce anomaly,which are different from those of foraminifera of the Pacific Ocean.The Sr,Nd isotopic ratios of the Okinawa Trough foraminifera are 0 709 769 and 0 512 162,respectively, which are different not only from those of oceanic water, but also from those of river water of China's Mainland, the former is slightly higher than those of oceanic water,but much lower than those of river water;the latter is slightly lower than those of oceanic water,but higher than those of river water,demonstrating that the Okinawa Trough sea water has been influenced by river water of China's Mainland.

Geochemical characteristics of Sr isotopes in the LS33 drill core from the Qiongdongnan Basin, South China Sea, and their response to the uplift of the Tibetan Plateau

Making full use of modern analytical and testing techniques to explore and establish new indexes or methods for extracting paleoseawater geochemical information from sediments will help to reconstruct the sedimentary paleoenvironment in different research areas.The connection between the subsidence of the South China Sea basin and the uplift of the Tibetan Plateau has been a scientific concern in recent decades.To explore the information on the sedimentary paleoenvironment,provenance changes and uplift of Tibetan Plateau contained in core sediments(debris),we selected core samples from Well LS33 in the Qiongdongnan Basin,South China Sea,and analyzed the contents of typical elements(Al,Th,and rare earth elements)that can indicate changes in provenance and the Sr isotopic compositions,which can reveal the geochemical characteristics of the paleoseawater depending on the type of material(authigenic carbonate and terrigenous detritus).The results show the following:(1)during the late Miocene,the Red River transported a large amount of detrital sediments from the ancient continental block(South China)to the Qiongdongnan Basin.(2)The authigenic carbonates accurately record changes in the 87Sr/86Sr ratios in the South China Sea since the Oligocene.These ratios reflect the semi-closed marginal sea environment of the South China Sea(relative to the ocean)and the sedimentary paleoenvironment evolution process of the deep-water area of the Qiongdongnan Basin from continental to transitional and then to bathyal.(3)Since the Neogene,the variations in the 87Sr/86Sr ratio in the authigenic carbonates have been consistent with the variations in the uplift rate of the Tibetan Plateau and the sediment accumulation rate in the Qiongdongnan Basin.These consistent changes indicate the complex geological process of the change in the rock weathering intensity and terrigenous Sr flux caused by changes in the uplift rate of the Tibetan Plateau,which influence the Sr isotope composition of seawater.

Geochronological and geochemical constraints on the petrogenesis of late Mesoproterozoic mafic and granitic rocks in the southwestern Yangtze Block

Late Mesoproterozoic igneous rocks in the SW Yangtze Block are important for understanding the role of it in reconstruction of the Rodinia supercontinent.In the present study,we report new geochronological,geochemical,and Nd-Hf isotopic data for the Cuoke plagioclase amphibolites and granites in the SW Yangtze Block.Geochronological results show that the plagioclase amphibolites and granites have similar late Mesoproterozoic zircon U-Pb ages of 1168-1162 Ma,constituting a bimodal igneous assemblage.The plagioclase amphibolites have high and variable TiO2 contents(1.15-4.30 wt.%)and Mg#(34-66)values,similar to the tholeiitic series.They are characterized by enrichment in LREEs and LILEs,and have OIB-like affinities with positive Nb and Ta anomalies.The plagioclase amphibolites have positive whole-rockεNd(t)(+3.2 to+4.3)and zirconεHf(t)(+4.3 to+10.7)values,indicating that they were derived from an OIB-like asthenospheric mantle source.The granites belong to the reduced peralkaline A-type series and have negativeεNd(t)value of-6.0 andεHf(t)values of-5.8 to-13.8,indicating a derivation from the partial melting of ancient mafic lower crust.In combination with the~1.05-1.02 Ga bimodal igneous assemblage in the SW Yangtze Block,we propose that the Cuoke 1168-1162 Ma igneous rocks were likely formed in a continental rift basin and argue against the existance of Grenvillian Orogen in the SW Yangtze Block during the late Mesoproterozoic.

Stable Isotope and Element Geochemistry of Saline Springs in Evaporite-bearing Mengla Basin,South Yunnan,China

1 Introduction Mengla Basin is a sub-basin in southern evaporitebearing Lanping-Simao Basin.There are many salt springs in the basin.In 2012,11 spring samples were collected for analyses of chemistry and boron,hydrogen and oxygen

Chemical characteristics and Pb isotopic compositions of PM2.5 in Nanchang, China

In mid-September 2013, PM2.5 samples were collected at six sites in Nanchang, Jiangxi Province, China, to quantify nine water-soluble ions （Ca2＋, Mg2＋, K＋, Na＋, NH4＋, SO42-, Cl-, F , NO3 ）, 29 trace elements （Ba, Zn, Pb, Ni, Mo, Cr, Cu, Sr, Sb, Rb, Cd, Bi, Zr, V, Ga, Li, Y, Nb, W, Cs, Tl, Sc, Co, U, Hf, In, Re, Be, and Ta）, and to characterize Pb isotopic ratios （^207pb/^206pb, ^208pb/^206pb, and ^207pb/^204pb） for identifying the main source（s） of Pb. The results showed that the average daily PM2.5 concentration （53.16 ± 24.17） Dg/m3 was within the secondary level of the Chinese ambient air quality standard. The combined concentrations of SO42-, NH4＋, and NO3- to total measured water-soluble ion concentrations in PM2.5 ranged from 79.40% to 95.18%, indicating that anthropogenic sources were significant. Coal combustion and vehicle emissions were both contributors to PM2.5 based on the NO3-/SO4^2- ratios. Wushu School experienced the lowest concentrations of PM2.s and most trace elements among the six sampling sites. Enrichment factor results showed that TI, Cr, In, Cu, Zn, Pb, Bi, Ni, Sb, and Cd in PM2.5 were affected by anthropogenic activities. Cluster analysis suggested that Cd, Sb, Pb, Re, Zn, Bi, Cs, Tl, Ga, and In were possibly related to coal combustion and vehicle exhaust, while Ni, Nb, Cr, and Mo may have originated from metal smelting. Pb isotopic tracing showed that coal dust, cement dust, road dust and construction dust were the major Pb sources in PM2.5 in Nanchang. Combined, these sources contributed an average of 72.51% of the Pb measured, while vehicle exhaust accounted for 27.49% of Pb based on results from a binary Pb isotope mixed model,

Quantification,morphology and source of humic acid,kerogen and black carbon in offshore marine sediments from Xiamen Gulf,China

Three types of macromolecular organic matters （MOMs）, i.e. humic acid （HA）, kerogen＋black carbon （KB）, and black carbon （BC） were extracted from marine sediments of Xiamen Gulf, southeast of China. The chemical composition, morphological property and source of the three extractions were characterized by elemental analyzer/isotope ratio mass spectrometry （EA/IRMS） and scanning electron microscope （SEM）. The results showed that KB was the predominant fraction in MOMs, which accounted for 61.79%-89.15% of the total organic content （TOC）, while HA consisted less than 5%. The relative high contents of kerogen and BC, and low contents of HA in the samples indicated that anthropogenic input might be the major source of organic matter in marine sediments near the industrial regions. The characterization of SEM, not only revealed morphological properties of the three fractions, but also allowed a better understanding of the source of MOMs. The δ 13 C values of the three fractions suggested that materials from terrestrial C 3 plants were predominant. Furthermore, the anthropogenic activities, such as the discharge of sewage, coal and biomass combustion from industry nearby and agricultural practices within drainage basin of the Jiulong River, were remarkably contributed to the variations in δ 13 C values of MOMs in the offshore marine sediments.