珠江口盆地白云凹陷地温场特征及烃源岩热演化

通过对珠江口盆地白云凹陷108口钻井的地温数据(BHT、MDT、DST)进行校正、分析,以点到面重构白云凹陷的现今地温场,再结合地质与地球化学资料,正演恢复白云凹陷烃源岩的热演化史及生烃史.研究结果显示:(1)白云凹陷具有变地温场,地温梯度分布在35～60℃/km之间,呈现出南高北低的分布特征.(2)受控于白云凹陷变地...     

碎屑沉积岩/沉积物Sm-Nd、U-Pb与Hf同位素的化学地球动力学意义

碎屑沉积岩能有效记录它们的源区。碎屑沉积岩的Nd同位素组成及其中锆石U-Pb年龄与Hf同位素组成是解析碎屑物质源区、源区壳-幔相互作用及不同块体间相互作用的关键方法。全岩/全样的Nd模式年龄可以指示其源区地壳从亏损地幔分离的平均时间,而锆石Hf同位素模式年龄能够揭示出所测锆石颗粒其形成时的源区特征。细粒碎屑沉积岩/沉积物化学组成代表了其源区上地壳在风化、搬运、沉积过程中不溶于水的Nb、Ta、Zr、Hf、Sc、Ti、Th、REE等的平均组成。实践表明,华北板块、扬子板块、以大兴安岭为代表的中亚造山带东部具有明显不同的形成与演化历史。大兴安岭的地壳增生主要发生于新元古代—古生代期间。由碎屑沉积岩进行化学动力学分析时,应充分系统考虑地质过程的复杂性,将宏观与微观相结合、局部与整体相结合。     

Reliable single-epoch ambiguity resolution for short baselines using combined GPS/BeiDou system

GNSS single-epoch real-time kinematic (RTK) positioning depends on correct ambiguity resolution. If the number of observed satellites in a single epoch is insufficient, which often happens with a standalone GNSS system, the ambiguity resolution is difficult to achieve. China’s BeiDou Navigation Satellite System has been providing continuous passive positioning, navigation and timing services since December 27, 2012, covering China and the surrounding area. This new system will increase the number of satellites in view and will have a significant effect on successful ambiguity resolution. Since the BeiDou system is similar to GPS, the procedure of data processing is easier than that for the Russian GLONASS system. We briefly introduce the time and the coordinate system of BeiDou and also the BeiDou satellite visibility in China, followed by the discussion on the combined GPS/BeiDou single-epoch algorithm. Experiments were conducted and are presented here, in which the GPS/BeiDou dual-frequency static data were collected in Wuhan with the baseline distance varying from 5 to 13 km, and processed in separate and combined modes. The results indicate that, compared to a standalone GPS or BeiDou system, the combined GNSS system can increase the successful ambiguity fixing rate for single epochs and can also improve the precision of short baselines determination.     

Triple-frequency carrier ambiguity resolution for Beidou navigation satellite system

The Chinese Beidou system, also known as Compass, has entered its trial operational stage and can already provide services for triple-frequency users. Using triple-frequency signals is expected to be of great benefit for ambiguity resolution. Based on error characteristic analysis of the Beidou frequencies, we introduce the procedure of selecting the best combinations of triple-frequency signals. The geometry-based model and geometry-free model of triple-frequency signals are presented. Three triple-frequency carrier ambiguity resolution (TCAR) methods are described, which include the cascading rounding method, the stepwise AR method and the modified stepwise AR method. In order to evaluate the performance of these methods, observations from baselines of various lengths were collected using Beidou triple-frequency receivers and were processed epoch-by-epoch using the three methods. The same observation data were also processed in a dual-frequency mode for comparison. The results show that, compared to the dual-frequency based solution, the single epoch ambiguity resolution success rate with triple frequency improved nearly 30 % for the short baselines (<20 km) and 100 % for the mid-length baselines (20–50 km) using the proposed modified stepwise AR method.     

Vegetation recovery and landscape change assessment at Chiufenershan landslide area caused by Chichi earthquake in central Taiwan

This study discusses vegetation recovery and land cover change with reference to the Chiufenershan landslide, a major disaster caused by the Chichi earthquake, 21 September 1999. Image classification technology, landscape indicators from multi-temporal remotely sensed data and a field survey provide the data. Image differencing methods and threshold values coupled with pre- and post-quake satellite images were used. Multi-temporal images in combination with various vegetation indices were drawn on to classify land cover patterns and discuss differences and suitability of indices. Landscape indicators and field investigations fed into an investigation of vegetation recovery and landscape change. The study results show that the best image classification system is original wavebands coupled with a cropping management factor index (CMFI). The land cover analysis shows that areas of forest and grass are increasing and areas of landslide are decreasing. From the field investigation, because the left and right sides of the landslide area were not disturbed by the earthquake, their calculated similarity index is the highest (30.08%). Miscanthus floridulus is the most dominant pioneer plant at the landslide collapse area with an importance value index (IVI) of 63.6%.     

Pore and Pore-Throat Size Distributions of Low Permeability Sandstone Reservoir and Their Differential Origin

应用筛析粒度、铸体薄片、图像孔隙、扫描电镜与高压压汞等方法,对苏北盆地沙埝地区E1f3和三塘湖盆地牛圈湖地区J2x两类不同低渗储层的孔喉类型和分布特征进行了分析对比,对其差异性成因进行了探讨.研究表明,E1f3储层孔隙类型主要为碳酸盐胶结物和长石溶孔,J2x储层主要为凝灰质和长石溶孔,前者溶蚀成因的粗大孔隙较多,而后者细小的晶间孔较多.E1f3储层喉道分布为溶蚀成因的粗单峰分布、压实或压实胶结混合成因的细单峰分布、管束状喉道的无峰分布,以及溶蚀成因与压实或压实胶结混合成因组成的双峰分布四类;J2x储层喉道为溶蚀成因的粗单峰分布、管束状喉道的细单峰分布,及管束状喉道与压实或压实胶结成因组成的双峰分布三类,未见溶蚀成因喉道与其他成因喉道组成的双峰分布.两区孔隙半径、喉道半径均随粒级变细呈减小趋势,平均孔隙半径也总是小于碎屑颗粒半径;在粒度相近的情况下,J2x储层孔隙、喉道半径均小于E1f3储层.E1f3储层较高的成分成熟度与结构成熟度和早期碳酸盐胶结作用使其在压实过程中保存了较大的原始粒间孔隙空间,且为后期溶蚀作用所扩大,牛圈湖地区J2x储层较高的塑性岩屑含量和同沉积期形成的凝灰质,使储层原始孔隙空间在压实过程中大量减少,后期溶蚀作用较弱.杂基对原始孔隙空间的充填程度及其与塑性岩屑共同造成的压实与溶蚀强度的差异,是造成两区目前孔隙结构差异的主要原因.     

群智能优化算法在水文频率曲线适线中的应用

根据不同适线准则,研究群智能优化算法在水文频率曲线适线中的计算问题,为水利工程规划、水资源优化配置等提供依据。以陕北地区12个主要测站的年径流系列为例,选取五大分布类共12种分布线型,根据我国现行水利水电工程设计洪水计算规范,按照离(残)差平方和最小准则(OLS)、离(残)差绝对值和最小准则(ABS)、相对离差平方和最小准则(WLS),以MATLAB7.6为计算平台,研究模拟退火算法、遗传算法、粒子群算法和蚁群算法进行水文频率参数的估计。在不同适线准则下,陕北地区年径流最优频率分布模型为广义Logistic分布(Generalized Logistic Distribution,GLO),粒子群算法进行参数估算偏差最小。与传统优化方法相比,群智能优化算法对优化目标函数要求低,是一种推求年径流频率曲线统计参数的新途径。     

中尺度对地观测系统支持下中国综合自然 地理区划新方法论研究

在中国地理学发展史上,最值得纪念的成就之一是我国地理学家对中国综合自然地理环境采用区划的方法进行的研究。我国首次发布完整的综合自然地理区划方案至今已有50年历史。在这期间,产生了7个中国综合自然地理区划主要方案,建立了经典的区划方法论。近年来,中国生态区划研究、全球变化区域响应与适应研究对发展我国综合自然地理区划方法论做出了特殊的贡献。在全球和中国对地观测系统数据加速发展的支持下,本文对比了新形势下区划目的、内容、途径、范围、原则、依据、指标、等级系统、界线、研究单元、数据信息、分析计算、基础设施与研究环境条件发生的新变化,认为在中国未来20年发展的过程中,中国综合自然地理区划的目的将由主要为农业生产服务转向资源、环境、生态综合考虑,为可持续发展服务。全球对地观测系统,特别是中尺度对地观测系统数据资源和相关技术的发展和广泛应用,必将对以信息化、数字化为时代特点的中国综合自然地理区划新方法论的产生和体系的建立起到划时代意义的促进作用。     

南秦岭西坝花岗质岩体矿物学特征及成岩意义

西坝花岗质岩体位于南秦岭构造-岩浆带中部,为南秦岭印支期花岗岩带五龙岩体群的重要组成部分,与双王金矿有密切的空间关系。该岩体主要由石英二长闪长岩和花岗闪长岩组成,岩体中发育较多的镁铁质包体。通过对岩体及镁铁质包体的系统的矿物学特征研究发现,本区花岗质岩体属于I型花岗岩类,成岩物质主要来源于地壳,并且有地幔物质的加入。岩体及镁铁质包体显示有多种壳-幔岩浆混合的岩相学证据:如包体的冷凝边、斜长石环带成分显示核部和边缘偏基性,而幔部偏酸性,包体中见大量的长针状磷灰石及角闪石,包体中有两种产状的角闪石等。根据矿物温度压力计计算,西坝岩体的结晶温度为646.72~703.84℃,压力为1.67×108~3.66×108Pa,平均为3.12×108Pa。岩体形成于相对高氧逸度(lgfO2为-16.16×105~-17.06×105Pa)、中等水逸度(fH2O为46.82×105~136.85×105Pa)和氢逸度(fH2为0.32×105~0.91×105Pa)环境。岩体的这种高氧逸度条件有利于金进入熔体相或流体相,是金矿形成的有利条件。     

松辽盆地徐家围子营城组流纹岩地球化学特征及构造指示意义

松辽盆地徐家围子营城组发育一套以流纹岩为主的中酸性火山岩。岩石薄片观察和主量、微量元素研究发现,后期热液蚀变、区域埋深及低温水合作用对流纹岩的Si、K、Rb等元素含量产生一定影响; 流纹岩明显富集Rb、Th、U、Pb等强不相容元素,Ba、Sr、Ti、Eu、P 负异常,暗示其经历了斜长石、磷灰石和钛铁矿分离结晶作用。流纹岩的(⁸⁷Sr/⁸⁶Sr)_i(0.705265 ~ 0.711895)值变化范围较大,大多数ε_Nd(t)为正值(1.83 ~ 3.38),Pb同位素比值相对集中,(²⁰⁶Pb/²⁰⁴Pb)_i=18.09～18.32,(²⁰⁷Pb/²⁰⁴Pb)_i=15.50 ~ 15.54,(²⁰⁸Pb/²⁰⁴Pb)_i=37.80 ~ 38.10。研究表明,岩石的源区为大比例年轻成分与少量古老地壳的混合部分熔融,其演化过程中经历了不同程度的地壳混染。松辽盆地早白垩世火山岩为板内伸展环境喷发的产物,可能与太平洋板块俯冲导致的中国东部岩石圈减薄、软流圈上涌密切相关。