八面河地区原油、烃源岩中甾类化合物的分布特征及其应用

对渤海湾盆地八面河地区31个分别形成于还原性咸化水体和淡水环境的页岩和泥岩样、20个油样中甾类化合物进行了剖析。结果表明该区烃源岩、原油中的甾类化合物异常丰富，主要包括C27－29规则甾烷、C28－304－甲基甾烷、甲藻甾烷以及芳香甾类；不同层段烃源岩中甾类化合物的分布各具特色，发育于牛庄洼陷南斜坡咸化水体的富藻类沙四段页岩富含4－甲基甾烷及甲藻甾烷，形成于淡水环境的沙三段泥岩中甲藻甾烷不太发育。烃源岩、原油中规则甾烷的分布型式明显有别于甲基甾烷，指示两类化合物可能来源于不同的藻类属种。甾类化合物的分布特征受控于古环境、生物先质种类及热成熟度等多种因素。不同层段甾类化合物的特征性分布使其成为该区油源岩确认的关键指标。结果还表明，甲基甾烷在油源岩识别中比规则甾烷具有更好的应用效果。依据甾类化合物，可判断埋深超过2700m的Es4烃源岩与原油具有较好的相关性，发育于牛洼洼陷南斜坡的未熟－低熟特殊烃源岩－富藻类页岩与原油没有可比性，该结论是对近期油源调查结果的进一步确认。     

Analysis of Sediments and Soils by X-Ray Fluorescence Spectrometry Using Matrix Corrections Based on Fundamental Parameters

Wavelength dispersive X-ray fluorescence spectrometry (WD-XRF) is widely used for the analysis of soils and sediments using well characterised procedures. However, difficulties can occur with samples such as unknowns containing small amounts of ore materials and samples collected from contaminated sites where trace elemental concentrations can exceed the concentration range for routine analysis. We studied the performance of a commercially available method, based on fundamental parameters (FP) to correct matrix effects. The spectrometer was originally calibrated with elemental or simple compound calibrants. Samples were analysed as pressed powder pellets. Eighteen sediment and soil reference materials, three of them with certified values for some of their constituents, were used to evaluate accuracy, by comparing results with recommended values and their standard deviations (RV ± 2s) or certified values and their confidence intervals (CV ± Cl). When results fell systematically outside these intervals, calibrations were refined with geochemical reference materials. The best agreement of results with recommended and certified values was obtained when the contents of H₂O and C in each sample were included as matrix constituents during calculations. The detection limits of trace elements tended to be relatively high, because the measuring conditions employed were not maximised for sensitivity. The main advantage of the method tested was that it enabled the analysis of samples with high concentrations of trace elements and the determination of elements such as F, Bi, Sb and W, which are not commonly included in quantitative XRF analysis of geological samples.     

盆地的形成和充填过程模拟──以拉伸盆地为例

沉积盆地定量动力学模拟和分析是目前地学领域的一个研究热点。文中建立的拉伸盆地模拟系统可模拟拉伸盆地的沉降过程、估算盆地的拉伸量、分析盆地深部结构和热流背景;动态模拟盆地的充填过程及预测层序格架和沉积体系域的分布样式。沉降和热史模拟结合了二维的回剥法和简单或纯剪切的盆地形成模型。盆地充填模型综合考虑了盆地的构造沉降、均衡作用。沉积物供给。海（湖）平面变化等对盆地充填过程的控制作用。对莺、琼盆地模拟分析揭示了盆地的幕式拉伸过程和深部热演化;层序模拟提示了盆地沉降。海平面变化等对盆地充填演化的控制作用。     

土壤及河流沉积物中Hg、As、Sb的同时测定

Hg、As、Sb是土壤和河流沉积物的常规测定项目。本文采用新型三通道原子荧光分析仪,建立了同时测定土壤和河流沉积物中这三种元素的新方法。通过优化仪器工作条件,选择合适的样品处置方法,得到Hg、As、Sb的检出限分别为0.03mg/kg、0.009mg/kg和0.03mg/kg,精密度分别为3.5%、7.8%和5.5%,准确度分别为95%～103%、91%～107%(加标回收率)和±6.4%。与现有测定方法相比,本方法的样品消化完全,实验简便,分析速度和准确度高,能充分满足分析要求。     

Downstream patterns of bed sediment-borne metals,minerals and organic matter in a stream system receiving acidic mine effluent: A preliminary study

Different downstream variation patterns were observed for a range of bed sediment-borne metals (aqua regia-extractable fraction) in a subtropical stream system receiving acid mine drainage. Mine-originated Fe tended to be deposited in the acidic (mean pH < 4.9) upstream reach in forms of goethite and/or hematite. In contrast, other metals tended to be transported farther downstream and settled in a low-gradient reach with high pH (mean pH > 5.6). The peak of sediment-borne Al, Be, Ca, Cd, Co, Cu, La, Mn, Ni and Zn corresponded very well with the peak of the sediment-borne organic matter, suggesting a close association between the water-borne organic colloids and the inorganic metal oxides/hydroxides during their transport. The marked increase in the sediment-borne Al and Pb started more upstream than the other metals, suggesting that the water-borne Al and Pb were more susceptible to pH rise-induced precipitation, as compared to the other metals. It appeared that the organic colloids played no important role in Pb transport and settlement. The iron precipitates had a limited role to play in affecting the transport and fates of other metals since they were predominantly formed and deposited in the acidic reach, which made them incapable of scavenging cationic metals by co-precipitation or adsorption.     

藏东吉塘地区冈瓦纳相冰海杂砾岩的特征及其意义

察雅县吉塘镇澜沧江以西的酉西和泄巴发现冰海杂砾岩,是藏东地区班公湖－怒江缝合带以东首次发现的冈瓦纳相沉积岩,基本特征与青藏高原南部的冈瓦纳相冰海杂砾岩相同,而吉塘镇澜沧江以东的石炭纪—二叠纪地层与古生物则是典型扬子型的。冰海杂砾岩的分布范围大致代表冈瓦纳大陆塔尔切尔冰期影响的空间,并具有时代对比价值。这些资料可能说明一个事实,藏东地区石炭纪—二叠纪冈瓦纳大陆的东部边界为北澜沧江断裂带。     

Flow dynamics at the origin of thin clayey sand lacustrine turbidites: Examples from Lake Hazar,Turkey

Turbidity currents and their deposits can be investigated using several methods, i.e. direct monitoring, physical and numerical modelling, sediment cores and outcrops. The present study focused on thin clayey sand turbidites found in Lake Hazar (Turkey) occurring in eleven clusters of closely spaced thin beds. Depositional processes and sources for three of those eleven clusters are studied at three coring sites. Bathymetrical data and seismic reflection profiles are used to understand the specific geomorphology of each site. X‐ray, thin sections and CT scan imagery combined with grain‐size, geochemical and mineralogical measurements on the cores allow characterization of the turbidites. Turbidites included in each cluster were produced by remobilization of surficial slope sediment, a process identified in very few studies worldwide. Three types of turbidites are distinguished and compared with deposits obtained in flume studies published in the literature. Type 1 is made of an ungraded clayey silt layer issued from a cohesive flow. Type 2 is composed of a partially graded clayey sand layer overlain by a mud cap, attributed to a transitional flow. Type 3 corresponds to a graded clayey sand layer overlain by a mud cap issued from a turbulence‐dominated flow. While the published experimental studies show that turbulence is damped by cohesion for low clay content, type 3 deposits of this study show evidence for a turbulence‐dominated mechanism despite their high clay content. This divergence may in part relate to input variables, such as water chemistry and clay mineralogy, that are not routinely considered in experimental studies. Furthermore, the large sedimentological variety observed in the turbidites from one coring site to another is related to the evolution of a sediment flow within a field‐scale basin made of a complex physiography that cannot be tackled by flume experiments.     

用X射线荧光光谱法测定Cl、S等31个元素

采用硼酸镶边垫底的粉末样品压片制样,用ARL ADVANT′XP＋型X射线荧光光谱仪对土壤和水系沉积物样品中Na、Mg、Al、Si、P、S、Cl等31个组分进行测定。重点研究了Cl和S等元素的测定条件、痕量元素的背景选择和谱线重叠校正问题。使用经验系数法和康普敦散射作内标校正基体效应。经标准物质校验,结果与标准值吻合。方法的检出限、精密度和准确度能满足多目标地球化学调查样品的分析要求。     

Vertical variation of phosphorus forms in surface sediments from Wuli Bay, Taihu Lake, China

1IntroductionPhosphorus,an essential nutrient for the primaryproductivity in freshwater systems,is an important fac-tor controlling lacustrine eutrophication.Although ex-ternal input of phosphorus has been assumed as the vi-tal responsibility for the eutrophication of lakes(ZhuJun et al.,2005),the remobilization of phosphorus insediments has a distinct influence on it as well(Bostr m et al.,1982).The concentrations of totalphosphorus(Ptotal)in the sediments are often related tothe trophic st…     

Estimating the settling velocity of bioclastic sediment using common grain‐size analysis techniques

Most techniques for estimating settling velocities of natural particles have been developed for siliciclastic sediments. Therefore, to understand how these techniques apply to bioclastic environments, measured settling velocities of bioclastic sedimentary deposits sampled from a nearshore fringing reef in Western Australia were compared with settling velocities calculated using results from several common grain‐size analysis techniques (sieve, laser diffraction and image analysis) and established models. The effects of sediment density and shape were also examined using a range of density values and three different models of settling velocity. Sediment density was found to have a significant effect on calculated settling velocity, causing a range in normalized root‐mean‐square error of up to 28%, depending upon settling velocity model and grain‐size method. Accounting for particle shape reduced errors in predicted settling velocity by 3% to 6% and removed any velocity‐dependent bias, which is particularly important for the fastest settling fractions. When shape was accounted for and measured density was used, normalized root‐mean‐square errors were 4%, 10% and 18% for laser diffraction, sieve and image analysis, respectively. The results of this study show that established models of settling velocity that account for particle shape can be used to estimate settling velocity of irregularly shaped, sand‐sized bioclastic sediments from sieve, laser diffraction, or image analysis‐derived measures of grain size with a limited amount of error. Collectively, these findings will allow for grain‐size data measured with different methods to be accurately converted to settling velocity for comparison. This will facilitate greater understanding of the hydraulic properties of bioclastic sediment which can help to increase our general knowledge of sediment dynamics in these environments.