汉诺坝玄武岩中麻粒岩和辉石岩捕虏体Sr-Nd-Pb同位素五维空间特征及其地质意义

研究了汉诺坝玄武岩中麻粒岩和辉石岩捕虏体在Sr-Nd-Pb同位素五维空间中的特征 .结合捕虏体的空间分布相对位置, 认为层离作用可较好地解释不同类型捕虏体同位素之间的相互关系。published_or_final_versio

Petrochemistry and mineral chemistry studies on metamorphic ultramafic rocks in Yanghou area, Zhenghe Country, Fujian Province, China

Petrochemistry studies indicate that the Yanghou metamorphic ultramafic rocksare composed of metamorphosed harzburgite and burgite and ultramafic cumulate . Trace element geochemistry and mineral chemistry studies on the metamorphosed harzburgite indicate that it is the relict of the depleted mantle. From systematic studies on petrochemistry , mineral chemistry and geochronology, it s concluded that the Yanghou metamorphic ultramafic rocks are components of Later Sinian-Early Paleozoic ophiolite in South China.岩石化学研究表明, 洋后变质超镁铁岩是由变质方辉橄榄岩和变质超镁铁堆积岩组成。变质方辉橄榄岩的微量元素地球化学及矿物化学特征表明, 应为亏损的残余地慢产物。通过系统的岩石地球化学、矿物化学及年代学研究, 认为洋后变质超镁铁岩可能为华南晚震旦一早古生代的蛇绿岩组成部分。published_or_final_versio

Highly heterogeneous Late Mesozoic lithospheric mantle beneath the North China Craton: evidence from Sr–Nd–Pb isotopic systematics of mafic igneous rocks

The lithospheric mantle beneath the North China Craton changed dramatically in its geophysical and geochemical characteristics from Palaeozoic to Cenozoic times. This study uses samples of Mesozoic basalts and mafic intrusions from the North China Craton to investigate the nature of this mantle in Mesozoic times. Sr-Nd-Pb isotopic data demonstrate that the Late Mesozoic lithospheric mantle was extremely heterogeneous. In the central craton or the Luzhong region, it is slightly Sr-Nd isotopically enriched, beneath the Taihangshan region it has an EMI character (87Sr/86Sri = 0.7050-0.7066; εNd = -17--10), and beneath the Luxi-Jiaodong region, it possesses EM2-like characteristics (87Sr/86Sri up to 0.7114). Compositional variation with time is also apparent in the Mesozoic lithospheric mantle. Our data suggest that the old lithospheric mantle was modified during Mesozoic times by a silicic melt, where beneath the Luxi-Jiaodong region it was severely modified, but in the Luzhong and Taihangshan regions the effects were much less marked. The silicic melt may have been the product of partial melting of crustal materials brought into the mantle by the subducted slab during the formation of circum-cratonic orogenic belts. This Mesozoic mantle did not survive for a long time, and was replaced by a Cenozoic mantle with depleted geochemical characteristics. © 2004 Cambridge University Press.published_or_final_versio

下地壳及壳慢过渡带化学不均一性 -- 河北汉诺坝地区深源捕虏体元素地球化学证据

河北汉诺坝玄武岩中长英质麻粒岩、镁铁质麻粒岩和辉石岩捕虏体的主量元素和微量元素特征, 反映了下地壳及壳鳗过渡带组成具有高度化学不均一性。不相容元素原始地慢标准化曲线特征的差异表明捕虏体成因复杂。MgO 与不相容元素无或仅有很弱的相关性, 与相容元素的相关性则相对较明显。这些特征反映了下地壳及壳慢过渡带存在较强和多元的混合作用。捕虏体的加权平均值比基于麻粒岩地体资料估算的下地壳平均组成偏基性, 揭示了二者可能的成因差异。The major and trace element data of granulite and pyroxenite xenoliths, which are entrained in Hannuoba basalt Hebei Province, North China, suggest the highly chemical heterogeneity in the lower crust and crust-mantle transitional zone. There is no or only POor linear correlation between MgO and incompatible elements. Whereas a bit remarked correlations are observed between MgO and most compatible elements.The geochemical characteristics suggest that the strong and multiple mixing processes may have Occurred universally both in the lower crust and crust-mantle transitional zone. The weighed average composition of xenoliths shows a more mafic composition of the lower crust than that estimated from granulite data, which may imply the difference in the genesis.published_or_final_versio

Sr, Nd Pb isotopic characteristics of granulite and pyroxenite xenoliths in Hannuoba basalts, Hebei Province, and their implications for geologic processes

Rb-Sr, Sm-Nd and Pb isotopic systematics are reported for granulite and pyroxenite xenoliths in Hannuoba basalts, Hebei Province. The isotopic characteristics of xenoliths suggest t hat they might have formed recently , although there is no strict constraint on the precise age. The decoupling of low Rb/Sr and high [87]Sr/[86]Sr ratios implies the multi-stage evolution history and strong mixing processes. There are close ties between granulite and pyroxenites with different mineral assemblages on the Sr-Nd, Pb-Sr and Pb-Nd correlation figures. The granulite is the common end-member o f the three kinds o f pyroxenite. Combined with the distribution of the xenoliths in space and their isotopic relationships, It is proposed that delamination can be well used to explain the ties.系统研究了河北汉诺坝玄武岩中二辉麻粒岩和辉石岩捕虏体的Sr、Nd、Pb 同位素特征。虽然未确定捕虏体的形成时代, 但同位素特征显示它们可能为较近期( 中生代以来) 形成。低的Rb/Sr 与高 的[87]Sr/[86]Sr 比值的解耦表明捕虏体的形成经历了较强的混合作用。在二元同位素相关图上, 三类具不同矿物组成的辉石岩与二辉麻粒岩有密切关系, 即二辉麻粒岩投点位置是三类辉石岩的共同端点。综合考虑捕虏体的空间分布及其在Sr 、Nd、Pb 同位素协变图上的关系, 可以认为层离作用可较好地解释这些现象。published_or_final_versio

Ozone production in four major cities of China: sensitivity to ozone precursors and heterogeneous processes

Abstract. Despite a large volume of research over a number of years, our understandings of the key precursors that control tropospheric ozone production and the impacts of heterogeneous processes remain incomplete. In this study, we analyze measurements of ozone and its precursors made at rural/suburban sites downwind of four large Chinese cities – Beijing, Shanghai, Guangzhou and Lanzhou. At each site the same measurement techniques were utilized and a photochemical box model based on the Master Chemical Mechanism (v3.2) was applied, to minimize uncertainties in comparison of the results due to differences in methodology. All four cities suffered from severe ozone pollution. At the rural site of Beijing, export of the well-processed urban plumes contributed to the extremely high ozone levels (up to an hourly value of 286 ppbv), while the pollution observed at the suburban sites of Shanghai, Guangzhou and Lanzhou was characterized by intense in-situ ozone production. The major anthropogenic hydrocarbons were alkenes and aromatics in Beijing and Shanghai, aromatics in Guangzhou, and alkenes in Lanzhou. The ozone production was found to be in a VOCs-limited regime in both Shanghai and Guangzhou, and a mixed regime in Lanzhou. In Shanghai, the ozone formation was most sensitive to aromatics and alkenes, while in Guangzhou aromatics were the predominant ozone precursors. In Lanzhou, either controlling NOx or reducing emissions of olefins from the petrochemical industry would mitigate the local ozone production. The potential impacts of several heterogeneous processes on the ozone formation were assessed. The hydrolysis of dinitrogen pentoxide (N2O5), uptake of the hydroperoxyl radical (HO2) on particles, and surface reactions of NO2 forming nitrous acid (HONO) present considerable sources of uncertainty in the current studies of ozone chemistry. Further efforts are urgently required to better understand these processes and refine atmospheric models

激光探针等离子体质谱用于错石Pb-Pb定年的分析和校正方法的进一步探讨

激光探针等离子体质谱可对错石进行快速准确的Pb一Pb 同位素定年。本文进一步探讨了该方法应用中的几个问题。对不同样品采用不同的聚焦方式可以对U/Pb 分异有一定的控制作用。在一定的条件下, 不连续和连续采样模式都可以得到较高精度和准确度的结果。连续采样模式还可以得到同位素计数的深度剖面。不同的侧量滞留时间会影响测量结果的精度。20Ins 为适合错石ZO7Pb/206Pb 分析的最佳侧量滞留时间。在对侧定结果进行校正时, 可以采用玻璃标样NIST61O 和错石标样两种不同的校正方法。Laser probe-inductively coupled plasma mass spectrometry (LP-ICPMS) provides a rapid,precise and accurate technique for Pb-Pb zircon chronology. Different conditions affect massfractionation during laser ablation. Fixed-focus-mode and active-focus-mode, focus-mode anddefocus-mode, time-average mode (single point method) and time-resolved mode (depth pro-filing method), are compared. Both time-average mode and time-resolved mode can give rel-atively high precise, accurate results, and depth profile can only be obtained by time-resolvedmode. Comparing the results of time-resolved mode using different dwell time, it is found that20 ms is the best dwell time with highest precision and accuracy. It is shown that both NIST610and Zircon Standard give satisfactory calibration results for zircon 207Pb/206Pb isotopic age.Therefore, time resolved mode with dwell time of 20 ms is preferred for zircon analysis.published_or_final_versio

Do unsaturated fatty acids have beneficial effect on reduction of stroke risk in hypertensive population?

Abstracts for Chaired Posters: no. CP10BACKGROUND: It has been suggested that monospecific unsaturated fatty acids have potential effect on protection against stroke. Studies on the effect of different categories of fatty acids are lacking. The stroke incidence is high in hypertensive patients. Therefore, we studied the relationship between serum level of 6 categories of fatty acids and stroke incidence in ...postprin

The US stock market leads the Federal funds rate and Treasury bond yields

Using a recently introduced method to quantify the time varying lead-lag dependencies between pairs of economic time series (the thermal optimal path method), we test two fundamental tenets of the theory of fixed income: (i) the stock market variations and the yield changes should be anti-correlated; (ii) the change in central bank rates, as a proxy of the monetary policy of the central bank, should be a predictor of the future stock market direction. Using both monthly and weekly data, we found very similar lead-lag dependence between the S&P500 stock market index and the yields of bonds inside two groups: bond yields of short-term maturities (Federal funds rate (FFR), 3M, 6M, 1Y, 2Y, and 3Y) and bond yields of long-term maturities (5Y, 7Y, 10Y, and 20Y). In all cases, we observe the opposite of (i) and (ii). First, the stock market and yields move in the same direction. Second, the stock market leads the yields, including and especially the FFR. Moreover, we find that the short-term yields in the first group lead the long-term yields in the second group before the financial crisis that started mid-2007 and the inverse relationship holds afterwards. These results suggest that the Federal Reserve is increasingly mindful of the stock market behavior, seen at key to the recovery and health of the economy. Long-term investors seem also to have been more reactive and mindful of the signals provided by the financial stock markets than the Federal Reserve itself after the start of the financial crisis. The lead of the S&P500 stock market index over the bond yields of all maturities is confirmed by the traditional lagged cross-correlation analysis.Comment: 12 pages, 7 figures, 1 tabl