Amelioration of soil fertility by woody perennials in cropping fields: evaluation of three tree species in the semi-arid zone of Nigeria     

I. A. Jaiyeoba 《Journal of Arid Environments》1996,33(4):473-482

Soil was sampled from cropping fields in radial patterns from beneathAcacia albida, Parkia bigloboza(Jacq.) Benth. andEucalyptus camaldulensisDehnh. near Zaria, Nigeria. Results of analysis show a significant coarsening of soil texture and a decrease in organic matter and cation exchange capacity with increasing distance from all three tree species at a depth of 0–15 cm. Concentrations of nitrogen and some exchangeable cations decreased significantly with increasing distance from beneath acacia and parkia, and soil pH decreased with increasing distance from eucalyptus. The implication of the results for land management are discussed in relation to increasing productivity and soil use sustainability.  相似文献   

有机质热演化与极低级变质作用   总被引：8，自引：0，他引：8  

李荣西 《地质科技情报》1996,15(3):64-66

岩石中有机质热演化特征可以灵敏于反映岩石的成岩作用到变质作用之间（即极低级变质作用）的温度、压力变化情况。笔者对有机质热变指标在极低级变质作用界线、变质带划分和变质作用温度、压力和时间演化等方面的应用进行了综述和探讨。  相似文献   

动态指标层析法介绍     

钱晓军  费琪 《地质科技情报》1996,15(3):71-75

参数值是影响模拟结果正确可信的重要因素。介绍了一、二维模拟中参数值确定的动态指标层析法，以及作为其发展基础的由多种热指标确定古充的反演方法，简述了动态指标和热指标相结合的确定参数值层析方法。  相似文献   

东秦岭北缘煤的变质作用与板块构造的关系   总被引：2，自引：1，他引：2  

何建坤 《地质论评》1996,42(1):7-13

以河南省东秦岭造山带北缘山西组二１煤层的煤岩、煤质、煤有机地球化学和“晶核”结构的综合研究为前提，结合板块构造和地球物理场的研究分析，认为该区二１煤的变质热源主要与长期复杂的板块俯冲、Ａ型碰撞所引起的地壳结构调整而使前陆盆地区岩石圈结构变化，大地热流急增的结果有关。二１煤的变质主要经历了早期（印支期前）的区域深成变质（达肥－气煤）和后期（印支－燕山期）的典型异常热变质作用（达无烟煤－高阶无烟煤）。  相似文献   

华北地台南缘中元古代官道口群热水沉积硅质岩的地球化学特征   总被引：5，自引：0，他引：5       下载免费PDF全文

魏俊浩  王思源  吕国芳  潘振祥  马旭东 《地球科学》1996,(1)

在简要介绍了硅质岩基本地质特征的基础上，详细讨论了该套硅质岩的常量元素、微量元素以及氧同位素化学成分及组成．研究表明，该套硅质岩富集了与热水成因有关的Ａｇ、Ａｓ、Ｃｒ、Ｐｂ、Ｚｎ、Ｃｕ、Ｂ、Ｓｂ等微量元素和ＣａＯ、ＦｅＯ、Ｆｅ２Ｏ３等氧化物中常量元素，贫化了ＴｉＯ２、Ａｌ２Ｏ３、ＭｎＯ等氧化物中的常量元素．氧同位素组成及利用氧同位素估算的硅质岩的形成温度，均反映了热水沉积成因的特点  相似文献   

华南-古岩溶型铀矿床中有机质的热成熟异常及其矿床成因意义     

闽茂中  张祖还  刘兰忠 《矿床地质》1996,15(1):64-70

华南某层控铀矿床中有机质可分为原生沉积型、热液变质型和运移型三种类型，其母质类型为腐泥－腐殖型，主要来源于海相微体生物、藻类及少量源于陆相高等植物。根据镜质体反射率、饱和烃气相色谱和某些地球化学指标，表明矿石中有机质呈现异常热成熟特征，这对揭示该矿床热水叠造成矿机制具有指纹意义。本文还首次合理解释矿石中铀与有机碳含量间复杂关系的原因。  相似文献   

恐龙蛋化石物质组分研究     

陈克樵  王毅民 《岩矿测试》1996,15(3):192-197

研究了ＸＬ０１恐龙蛋化石蛋腔内壁和腔内絮状物质的无机组分。采用常规的双目实体显微镜、偏光显微镜及扫描电子显微镜、电子探针和Ｘ光衍射仪，对蛋腔内主要三种矿物物相的物理性质、化学组成及矿物晶体结构进行了研究。并对腔内的矿物形态、结构特点及有利于有机大分子ＤＮＡ保存的条件做了讨论  相似文献   

High Pressure-Differential Thermal Analysis and Ultrasonic Wave Amplitude Analysis of Ice-Water Equilibrium at 1.5-5.0GPa     

Xu Yousheng  Zheng Haifei  Xie Hongsen  Zhang Yueming  Xu Huigang  Guo Jie 《中国地球化学学报》1996,15(2):153-158

Water is the most active component in all geological systems.It has an important effect on the physical properties of minerals and melts.It also plays a key role in the evolution of the Earth.Accurate thermodynamics data on water are currently confined to pressures below 1.0GPa and temperatures below 900℃.Presented in this paper are new data available on the P-T properties of water at pressures up to 5.0GPa,develoged from differential thermal analysis and ultrasonic wave amplitude analysis.It has been found that there may exist another ternary point at 3.0GPa and that ultrasonic wave amplitude change of ice-water transition shows two inflection points above 2.0GPa, consistent with the two peaks of differential thermal curves above 2.0GPa .It may be a new phenomenon which needs further study.  相似文献   

内蒙古科尔康油田沙海组储集层的岩石学特征   总被引：1，自引：0，他引：1  

刘林玉  叶俭 《西北地质科学》1997,18(1):46-49

根据碎屑岩铸体薄片和扫描电镜观察分析资料，研究了科尔康油田沙海组储集层的岩石学特征。科尔康油田沙海组储集层的岩石类型主要为岩屑砂岩和岩屑砂砾岩。碎屑岩的岩性特征对沙海组储集层的成岩作用具有显著的影响作用。  相似文献   

Flexible spectral methods for the generation of random fields with power-law semivariograms     

Johannes Bruining  Diederik van Batenburg  Larry W. Lake  An Ping Yang 《Mathematical Geology》1997,29(6):823-848

Random field generators serve as a tool to model heterogeneous media for applications in hydrocarbon recovery and groundwater flow. Random fields with a power-law variogram structure, also termed fractional Brownian motion (fBm) fields, are of interest to study scale dependent heterogeneity effects on one-phase and two-phase flow. We show that such fields generated by the spectral method and the Inverse Fast Fourier Transform (IFFT) have an incorrect variogram structure and variance. To illustrate this we derive the prefactor of the fBm spectral density function, which is required to generate the fBm fields. We propose a new method to generate fBm fields that introduces weighting functions into the spectral method. It leads to a flexible and efficient algorithm. The flexibility permits an optimal choice of summation points (that is points in frequency space at which the weighting function is calculated) specific for the autocovariance structure of the field. As an illustration of the method, comparisons between estimated and expected statistics of fields with an exponential variogram and of fBm fields are presented. For power-law semivariograms, the proposed spectral method with a cylindrical distribution of the summation points gives optimal results.  相似文献