青藏高原新生代火车头山碱性及钙碱性两套火山岩的地球化学特征及其物源讨论   总被引：3，自引：3，他引：3  

赖绍聪秦江锋  李永飞隆平 《岩石学报》2007,23(4):709-718

藏北羌塘火车头山新生代火山岩可区分为钙碱性及碱性两个不同的系列。钙碱性火山岩主要岩石组合为玄武岩-安山岩-英安岩,其SiO_2介于49%～70%之间,Al_2O_3>10%,Na_2O/K_2O>1;其中玄武岩具平坦型稀土配分型式,LREE/HREE为1.3～1.8,(La/Yb)_N为2.87～4.45,无明显铕异常,δEu为0.96～1.09;该套岩石的Mg~#与SiO_2相关关系以及La/sm-La等亲岩浆元素与超亲岩浆元素协变关系表明,它们应为幔源岩浆经分离结晶演化的产物,其岩石组合类型以及低的Sm/Yb值(Sm/Yb=1.53～5.35)表明它们的原始岩浆应来源于岩石圈地幔尖晶石二辉橄榄岩的局部熔融。本区碱性火山岩为一套典型的钾质岩石系列,主要岩石组合类型为碱玄岩-碱玄质响岩-响岩,其SiO_2介于44%～59%之间,Al_2O_3>14%,Na_2O/K_2O介于0.47～1.51之间;岩石轻稀土强烈富集,LREE/HREE为13.20～15.76,(La/Yb)_N=50.44～91.99;其岩石组合类型以及Mg~#与SiO_2相关关系以及La/Sm-La协变关系同样表明它们为共源岩浆分离结晶演化的产物;然而,其较高的Sm/Yb值(Sm/ Yb=2.63～13.98)表明它们并非地幔橄榄岩直接局部熔融的产物,岩石弱的负Eu异常(δEu=0.77～0.85)以及Th、U的强烈富集和Nb、Ta的相对亏损,又反映了原始岩浆中有显著的地壳物质的贡献;该套钾质碱性系列岩石在La/Co-Th/Co同分母协变图上呈直线型分布,而在La/Co-Sc/Th异分母协变图上呈显著的双曲线分布,从而表明其源区为二源混合型,是青藏高原特殊的壳幔混合层局部熔融的产物,这些特征是新生代青藏高原壳幔层圈物质交换的重要岩石学证据。  相似文献   

遥感影像混合像元分解中的端元选择方法综述   总被引：7，自引：1，他引：7  

李素  李文正  周建军  庄大方 《地理与地理信息科学》2007,23(5):35-38,42

端元选择是进行遥感影像混合像元分解的首要步骤,也是最关键的步骤,其直接影响混合像元分解的精度。该文对遥感影像混合像元分解中端元产生的特定背景、当前存在的端元选择途径和端元选择方法进行综述,并通过对当前端元选择方法的分析,提出了选择或构造端元选择方法应遵循的几个原则。  相似文献   

断陷湖盆碳酸盐与陆源碎屑混合沉积——以东营凹陷金家地区古近系沙河街组第四段上亚段为例   总被引：3，自引：0，他引：3       下载免费PDF全文

张金亮  司学强 《地质论评》2007,53(4):448-453,I0001

混合沉积是一种特殊的沉积类型,研究程度较低。金家地区处于东营凹陷的斜坡带,该区古近系沙河街组第四段上亚段发育了碳酸盐与陆源碎屑的混合沉积,研究认为该混合沉积为古湖泊内的混合沉积,可划分为混积砂滩亚相、混积砂坝亚相及半深湖混积亚相,混合沉积物既包括同层混合沉积物（灰质砂岩、砂质灰岩、泥质灰岩等）,又包括互层混合沉积物（砂岩与颗粒灰岩互层沉积等）,研究区的混合沉积受当时构造运动、碎屑物质供给量、湖平面的变化等诸多因素控制。  相似文献   

陆源碎屑与碳酸盐混合沉积研究中的几点思考   总被引：11，自引：0，他引：11  

董桂玉  陈洪德  何幼斌  秦志勇  罗进雄  辛长静 《地球科学进展》2007,22(9):931-939

在前人研究的基础上，结合一些具体研究实例，对混合沉积的定义进行了修正和补充；对混积岩和混积层系重新进行分类和命名；根据混合沉积的定义、成因、成分、结构、沉积构造及接触关系等因素，按照“沉积事件+剖面结构”的原则，提出了渐变式、突变式和复合式3种成因类型，对前人的研究成果进行了概括和归纳；对混合沉积的控制因素进行了深入讨论；在以碳酸盐沉积为主和以陆源碎屑沉积为主的2类沉积背景下详细论述了层序格架中混合沉积的发育情况；结合混合沉积本身的特点讨论了混合沉积与油气的关系。最后针对混合沉积研究现状，指出了该领域研究中存在的问题，并对未来的研究方向进行了展望。  相似文献   

用生物标志物定量计算混合原油油源的数学模型   总被引：9，自引：0，他引：9  

陈建平  邓春萍  宋孚庆  张大江 《地球化学》2007,36(2):205-214

多烃源层叠合盆地混源油油源的定量计算是十分困难的问题.典型原油的人工混合配比实验显示,当两个生物标志物浓度不同的原油相混合时,各类生物标志物的比值参数随端元原油混入量呈非线性变化,以生物标志物比值参数和简单的二元线性关系方程定量计算混源油的混合比例将导致错误的结论.三个或者三个以上原油相混合时,各类生物标志物比值参数的变化更加复杂,各端元原油的贡献更加难以判识.但是,人工混合模拟实验表明混合油中生物标志物绝对含量与端元油的混入量呈线性关系,数学推导证明了这种线性关系,由此推导出相应的数学计算模型,其中:二元混合时比值参数与混入量呈双曲线关系,三元混合呈双曲面关系,四元及其以上的多元混合呈多维曲面,可以矩阵的方式定量计算各端元油的比例.依据这些数学模型,应用生物标志物的绝对含量和(或)生物标志物比值参数均可以定量计算出混源原油中各类原油的贡献比例.数学模型比通常的人工模拟实验方法更加经济、方便、精确和可靠.  相似文献   

任意色阶区间精细选区创建方法初探     

江王记 《现代测绘》2007,30(6):37-38

在通道中利用“阂值”命令创建选择X-255。在通道混合中创建任意色阶区间选择X1～X2。利用通道混合“减去”模式中“缩放”“补偿值”实现深度自由选择。  相似文献   

A computational method for approximating a Darcy–Stokes system governing a vuggy porous medium     

Todd Arbogast  Dana S. Brunson 《Computational Geosciences》2007,11(3):207-218

We develop and analyze a mixed finite element method for the solution of an elliptic system modeling a porous medium with large cavities, called vugs. It consists of a second-order elliptic (i.e., Darcy) equation on part of the domain coupled to a Stokes equation on the rest of the domain, and a slip boundary condition (due to Beavers–Joseph–Saffman) on the interface between them. The tangential velocity is not continuous on the interface. We consider a 2-D vuggy porous medium with many small cavities throughout its extent, so the interface is not isolated. We use a certain conforming Stokes element on rectangles, slightly modified near the interface to account for the tangential discontinuity. This gives a mixed finite element method for the entire Darcy–Stokes system with a regular sparsity pattern that is easy to implement, independent of the vug geometry, as long as it aligns with the grid. We prove optimal global first-order L ² convergence of the velocity and pressure, as well as the velocity gradient in the Stokes domain. Numerical results verify these rates of convergence and even suggest somewhat better convergence in certain situations. Finally, we present a lower dimensional space that uses Raviart–Thomas elements in the Darcy domain and uses our new modified elements near the interface in transition to the Stokes elements.  相似文献   

Subtropical to temperate facies from a transition zone, mixed carbonate–siliciclastic system, Palaeogene, North Carolina, USA     

BRIAN P COFFEY  J. FRED READ† 《Sedimentology》2007,54(2):339-365

Palaeogene passive margin sediments on the US mid‐Atlantic coastal plain provide valuable insight into facies interaction and distribution on mixed carbonate–siliciclastic shelves. This study utilizes well cuttings, outcrop, core, and seismic data to document temporal and spatial variations in admixed bryozoan‐rich skeletal carbonates and sandy siliciclastic units that were deposited on a humid passive margin located in the vicinity of a major marine transition zone. This zone was situated between north‐flowing, warm waters of the ancestral Gulf Stream (carbonate dominated settings) and south‐flowing, cold waters of the ancestral Labrador Current (siliciclastic dominated settings). Some degree of mixing of carbonates and siliciclastics occurs in all facies; however, siliciclastic‐prone sediments predominate in nearshore settings, while carbonate‐prone sediments are more common in more open marine settings of the inner shelf break and deep shelf. A distinctive dual‐break shelf depositional profile originated following a major Late Cretaceous to Palaeocene transgression that drowned the earlier shallow platform. This profile was characterized by prominent mid‐shelf break dividing the shallow shelf from the deep shelf and a major continental shelf/slope break. Incomplete filling of available accommodation space during successive buildup of the shallow shelf preserved the topographic break on this passive margin. Storm wave base also contributed to the preservation of the dual‐break shelf geometry by beveling shallow shelf sediments and transporting them onto and seaward of the mid‐shelf break. Sediment fines in deep shelf facies were produced in place, transported downdip from the shallow shelf by storm ebb currents and boundary currents, and reworked from adjacent areas of the deep shelf by strike‐parallel boundary currents. Regional climate and boundary currents controlled whether carbonate or siliciclastic material was deposited on the shelf, with warmer waters and more humid climates favouring carbonate deposition and cooler, more arid conditions favouring glaucony and siliciclastic dominated deposition. Continuous wave and current sweeping of the shallow shelf favoured deposition of mud‐lean facies across much of the shallow shelf. Skeletal components in much of the carbonate‐rich strata formed in warm, nutrient‐rich subtropical waters, as indicated by widespread occurrences of larger benthic foraminifera and molluscan assemblages. These indicators of warm water deposition within the bryozoan‐mollusk‐rich carbonate assemblage on this shelf provide an example of a warm water bryomol assemblage; such facies generally are associated with cooler water depositional settings.  相似文献   

Modelling peak accelerations from earthquakes   总被引：1，自引：0，他引：1  

Debbie J. Dupuis  Joanna Mills Flemming 《地震工程与结构动力学》2006,35(8):969-987

This paper deals with the prediction of peak horizontal accelerations with emphasis on seismic risk and insurance concerns. Non‐linear mixed effects models are used to analyse well‐known earthquake data and the consequences of mis‐specifying assumptions on the error term are quantified. A robust fit of the usual model, using recently developed robust weighted maximum likelihood estimators, is presented. Outlying data are automatically identified and subsequently investigated. A more appropriate model accounting for the extreme value nature of the responses, is also developed and implemented. The implication on acceleration predictions is demonstrated. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

基于正则MAP模型的遥感影像亚像元定位     

吴柯  李平湘  张良培  沈焕锋 《武汉大学学报(信息科学版)》2007,32(7):593-596

为了更好地解决亚像元的定位问题，基于超分辨率影像重建的技术，结合亚像元定位理论，提出了一种应用于亚像元定位的正则MAP估计模型，并且通过真实数据进行了检验。实验表明，该模型是一种简单、有效地解决亚像元定位问题的方法。  相似文献