Scattering of SH waves by a scalene triangular hill with a shallow cavity in half-space

In this study, a theoretical approach is used to investigate the scattering problem of circular holes under a scalene triangle on the surface. The wave displacement function is obtained by solving the Helmholtz equation that meets the zero-stress boundary conditions by adopting the method of separation of variables. Based on the complex function,multi-polar coordinate method, and region-matching technique, algebraic equations are established at auxiliary boundaries and free boundaries conditions...     

浅谈线性地物在CAD中的定义

我们在CAD环境中处理、修改陆上地形测图时,一旦离开了绘图软件(清华三维等)环境,就会碰到不能很方便的修改线性地物的问题,如增加点、线,修改已经绘好的线性地物,但通过调用自己定义好的CAD acad lin文件中已有的各种线型,便能实现所需陡坎、斜坡等线性地物的绘制.文章讨论了如何进行这些形文件的定义和调用,从而达到方便修改线性地物的目的.     

海相辫状河三角洲沉积基准面旋回划分及砂体叠置样式分析：以西江W油田珠江组为例

西江W油田珠江组储层为一套海相辫状河三角洲前缘沉积砂体,内部结构复杂,微相类型多样。运用高分辨率层序地层学原理及测井频谱旋回分析技术,综合岩心、测井等资料,在西江W油田珠江组内部识别出5个长期和18个中期基准面旋回,搭建了精细层序地层格架。通过几何参数的统计和砂体发育规律的总结,在精细层序格架约束下,把辫状河三角洲砂体构型样式划分为孤立型、侧叠型、双向迁移型和堆叠型4种。研究表明基准面旋回变化控制了储层构型叠置样式和演化规律,不同的中期基准面旋回位置发育不同的构型样式,在中期基准面旋回上升早期或下降晚期,砂体以堆叠和侧叠为主,而中期基准面旋回上升晚期或下降早期则以双向迁移型和孤立型为主。构型分析成果有效指导了H11层剩余油的挖潜,并为海上油田三角洲储层构型研究提供了一定思路。     

Origin of C type adakite magmas in the NE Xing’an block,NE China and tectonic implication

In this paper, we report new whole-rock geochemical and zircon U–Pb data for monzogranites in the NE Xing’an block. These data constrained the petrogenesis of C type (high Sr/Y) adakitic rocks and showed the spatial extent of the influence of the Mongol-Okhostsk ocean tectonic regime and the collision between the Jiamusi Massif and Songliao Terrane. New zircon laser-ablation inductivity coupled plasma mass spectrometry (LA-ICP-MS) U–Pb data indicated that the monzogranites in the studied area were emplaced in the Early Jurassic (~180 Ma). These rocks were characterized by unusally high SiO₂ (≥67.49), and Sr (461–759 ppm), but strikingly low Y (4.63–8.06 ppm) and HREE (∑HREE = 3.83–6.49 ppm, Yb = 0.5–0.77 ppm) contents, with therefore high Sr/Y (67.2–119) and (La/Yb)_N (29.7–41.5) ratios, showing the geochemical characteristics of C type adakitic granite. The data displayed negligible Eu anomalies (Eu/Eu* = 0.77–1.08), LREE-enriched and pronounced negative Nb and Ta anomalies. The C-type adakites in the studied area were most likely derived from the partial melting of a thickened lower continental curst. The magma source is most likely dominated by amphibolites and garnet amphibolites. In combination with previously-reported data from igneous rocks from the Mesozoic in NE China, we conclude that the Xing’an block was influenced by the Mongol-Okhotsk subduction tectonic system, and experiences compressive settings from the amalgamation of the Jiamusi block in the east of the CAOB.     

The Characteristics and Distribution Pattern of Seafloor Sinuous Pockmark Train in the Niger Delta Basin, West Africa

正Objective The term"pockmark"was introduced by King and Mac Lean(1970)to describe small"circular"on echosounder records in Nova Scotia.Pockmarks are usually described as circular,near circular or elongated depressions,generally 10–400 m in diameter and 30–50 m     

北京西山沿河城东岭台组火山岩成因及其地质意义

北京西山沿河城东岭台组火山岩由底部(第1岩性段)玄武粗安岩、下部(第2岩性段)酸性火山碎屑岩和上部(第3、4岩性段)粗面岩、流纹岩组成。根据地球化学特征,东岭台组下部第1岩性段玄武粗安岩属于碱性系列,具有Coombs成分变异趋势,上部的中、酸性岩属于高钾钙碱性;东岭台组火山岩整体具有从碱质富集的基性岩向硅饱和的中酸性岩变化的跨越式成分变异趋势。东岭台组中—基性岩是富集Ba、Sr、LREE和K的幔源原始玄武质岩浆在中等压力条件下分离结晶的产物,岩石在成岩过程中受到了下地壳物质的混染。东岭台组上部第3、4岩性段的粗面岩或英安岩依据地球化学特征分为3大类——富铝钾质粗面岩、富铝钠质粗面岩或英安岩与贫铝粗面岩或英安岩。富铝钾质粗面岩是玄武质岩浆与中地壳岩石发生熔融反应的产物;富铝钠质粗面岩或英安岩是内侵的基性岩含水熔融的产物;贫铝粗面岩或英安岩有可能由中—基性岩分异而来,成岩过程中受到围岩混染。东岭台组下部第2岩性段的酸性火山岩形成于下地壳低钾岩石在高氧逸度条件下的低程度部分熔融。东岭台组上部第3、4岩性段的酸性火山岩中的低硅端元是基性岩浆与中地壳岩石发生熔融反应的产物;高硅端元由低硅酸性火山岩分离结晶演化而来。燕山早白垩世早、中期大规模高钾钙碱性岩浆活动很可能是幔源岩浆与陆壳发生熔融反应的产物。东岭台组火山岩是早白垩世中期地壳被内侵玄武质岩浆加热,进而导致地温梯度增高的直观表征;地壳深部温度升高和部分熔融直接促使地壳发生侧向韧性流动,致使早白垩世时期的燕山地区由山地演变为高原。     

水道加朵体型深水扇形成机制与模式:以白云凹陷荔湾3-1地区珠江组为例

深水扇储层的沉积特征是油气勘探开发中的一个热点问题。通过分析珠江口盆地白云凹陷荔湾3-1地区珠江组深水扇的沉积特征,明确了研究区具备深水扇形成的有利条件,受白云凹陷总体构造沉积背景影响,形成了富砂型的深水扇。本区深水扇是多种流体动力学机制共同作用的结果,碎屑流、浊流及底流相互作用与复合,形成了平面上具水道复合朵体的分布特征。在建立深水扇沉积模式的基础上,提出了水道加朵体型深水扇沉积微相划分方案,研究区储层以重力流水道、天然堤及滑塌朵体为主;而水道逐渐由相对近源的宽浅下切型变为远离物源的窄深型,其深度与天然堤宽度呈正比。     

海上油田开发中后期砂岩储层构型剖析与表征

在油田开发中后期,砂层组或小层级别的砂岩储层内部构型剖析与表征逐渐成为储层研究的重点。在少井条件下充分挖掘地震资料信息,建立储层内部结构特征的地震响应关系,发展“以地震信息为导向,井震联合”的方法,成为海上油田储层构型研究的有效途径。通过井点处曲线形态、砂体厚度、垂向高程差异等信息对砂体期次的刻画,以及结构类敏感地震属性对砂体边界的预测,开展复合砂体的垂向分期与侧向划界,能够实现储层构型的剖析。结合海上油田的资料基础和开发特点,形成一套储层构型的结构和成因表征方法：分析沉积类型及其对砂体展布的控制机理,构建沉积模式;优选敏感地震属性,预测储层内部结构;标定井震资料的地质含义并转化为合理参数;综合多信息编制地质图件。     

精密单点定位在GNSS区域网监测中的应用

基于精密单点定位软件PANDA,对陆态网络海南区域网2009、2011、2013年连续3期GNSS观测数据进行处理,得到各点在ITRF2008下的坐标;对各期结果进行分析,得出海南区域网的平均变化速度E方向为32.16 mm/a,N方向为-10.08 mm/a。结果表明,基于精密单点定位方法,可获得与基线解基本一致的速度信息。     

Impact of redox-stratification on the diversity and distribution of bacterial communities in sandy reef sediments in a microcosm

Relationships between microbial communities and geochemical environments are important in marine microbial ecology and biogeochemistry. Although biogeochemical redox stratification has been well documented in marine sediments, its impact on microbial communities remains largely unknown. In this study, we applied denaturing gradient gel electrophoresis (DGGE) and clone library construction to investigate the diversity and stratification of bacterial communities in redox-stratified sandy reef sediments in a microcosm. A total of 88 Operational Taxonomic Units (OTU) were identified from 16S rRNA clone libraries constructed from sandy reef sediments in a laboratory microcosm. They were members of nine phyla and three candidate divisions, including Proteobacteria (Alpha-, Beta-, Gamma-, Delta-, and Epsilonproteobacteria), Actinobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Firmicutes, Verrucomicrobia, Spirochaetes, and the candidate divisions WS3, SO31 and AO19. The vast majority of these phylotypes are related to clone sequences from other marine sediments, but OTUs of Epsilonproteobacteria and WS3 are reported for the first time from permeable marine sediments. Several other OTUs are potential new bacterial phylotypes because of their low similarity with reference sequences. Results from the 16S rRNA, gene clone sequence analyses suggested that bacterial communities exhibit clear stratification across large redox gradients in these sediments, with the highest diversity found in the anoxic layer (15–25 mm) and the least diversity in the suboxic layer (3–5 mm). Analysis of the nosZ, and amoA gene libraries also indicated the stratification of denitrifiers and nitrifiers, with their highest diversity being in the anoxic and oxic sediment layers, respectively. These results indicated that redox-stratification can affect the distribution of bacterial communities in sandy reef sediments.