A model of oscillatory zoning in solid solutions grown from aqueous solutions: Applications to the (Ba,Sr)SO₄ system     

Ivan L’Heureux  Bjørn Jamtveit 《Geochimica et cosmochimica acta》2002,66(3):417-429

Barite-celestite crystals can be synthesized from aqueous solutions during counter-diffusion in a gel column connecting two reservoirs. It is known that such crystals may exhibit oscillatory zoning, whereby the barium composition in the crystal fluctuates more or less regularly from the core of the crystal to its rim. We present here a simple model of oscillatory zoning in such binary solid solutions A₁A₂ grown from aqueous solutions. The model combines diffusive transport of the relevant ions with an autocatalytic growth process. The latter is formulated as a continuous growth in which the probability of finding a kink site on the growing surface depends on the chemical composition of that surface. Thus, an A₁-rich surface favors the growth of A₁ over A₂, as long as A₁ is present in the vicinity of the surface. Precipitation results in a local depletion of A₁ in the aqueous solution, and the system may switch to a A₂ growth mode, until diffusion replenishes the amount of A₁, and so on. We use a dynamical equation for the molar fraction of component A₁ in the crystal, which results from mass conservation across the rough crystal-solution interface. Linear stability analysis and direct numerical solutions show that the system exhibits oscillatory behavior. Using the barite-celestite system as a framework, the scaling is consistent with the experimental observations. We discuss the variety of zoning patterns and textures numerically obtained as the concentrations of reactants in the reservoirs vary. This model might help in understanding the formation of oscillatory zoning in hydrothermal environments.  相似文献   

Wave velocities and attenuation of shaley sandstones as a function of pore pressure and partial saturation   总被引：3，自引：0，他引：3  

Nam H. Pham  †  José M. Carcione  Hans B. Helle  Bjørn Ursin 《Geophysical Prospecting》2002,50(6):615-627

We obtain the wave velocities and quality factors of clay‐bearing sandstones as a function of pore pressure, frequency and partial saturation. The model is based on a Biot‐type three‐phase theory that considers the coexistence of two solids (sand grains and clay particles) and a fluid mixture. Additional attenuation is described with the constant‐Q model and viscodynamic functions to model the high‐frequency behaviour. We apply a uniform gas/fluid mixing law that satisfies the Wood and Voigt averages at low and high frequencies, respectively. Pressure effects are accounted for by using an effective stress law. By fitting a permeability model of the Kozeny– Carman type to core data, the model is able to predict wave velocity and attenuation from seismic to ultrasonic frequencies, including the effects of partial saturation. Testing of the model with laboratory data shows good agreement between predictions and measurements.  相似文献   

Comparison of Seismic Dispersion and Attenuation Models   总被引：2，自引：0，他引：2  

Ursin  Björn  Toverud  Tommy 《Studia Geophysica et Geodaetica》2002,46(2):293-320

The frequency-dependent attenuation of seismic waves causes decreased resolution of seismic images with depth, and the difference in transmission losses induces amplitude variations with offset. Transmission losses may occur due to friction or fluid movement, or may result from scattering in thin-layer. Whatever the physical mechanism, they can often be conveniently described using an empirical formulation wherein the elastic moduli and propagation velocity are complex functions of frequency.We have compiled and compared algebraically and numerically eight different models involving complex velocity: the Kolsky-Futterman model, the power-law model, Kjartansson's model, Müller's model, Azimi's second and third model, the Cole-Cole model, and the standard linear-solid model.For two different parameter sets, the attenuation and phase velocity are computed in the seismic frequency band, and the plane-wave propagation of a Ricker wavelet for the other models is compared with that for the Kolsky-Futterman model. The first parameter set consists of parameters for each of the models calculated from expressions given in the appendix. These expressions make the different models behave similarly to the KF model. The second parameter set consists of model parameters that are numerically adapted to the KF model.By selecting proper parameters, all models, except the standard linear-solid model, show behavior similar to that of the Kolsky-Futterman model. The SLS model behaves differently from the other models as the frequency goes to zero or infinity. Broadband measurement data is needed to select a specific model for a given seismic experiment.  相似文献   

Erratum: Comparison of Seismic Dispersion and Attenuation Models: Stud. Geophys. Geod., 46(2002), 293-320     

Ursin  Björn  Toverud  Tommy 《Studia Geophysica et Geodaetica》2002,46(4):809-809

Studia Geophysica et Geodaetica -  相似文献   

新时期我国区域经济地理学发展问题初探   总被引：4，自引：0，他引：4  

刘曙光 《地域研究与开发》2002,21(2):1-4

我国新时期的区域经济地理学在取得全面发展的同时，在理论体系，研究方法和实践领域等方面还需要进一步的发展，文章根据学习和实践区域经济地理学的体会，初步提出基础理论和应用理论，思维方法和技术方法等方面发展见解，并指出区域创新系统和国际经济技术合作等学科应注意拓展的重要实践领域，最后提出我国区域经济地理学科发展的建议。  相似文献   

华南地区凉果加工业与凉果资源的匹配关系分析——以广东省新兴县为例     

刘一明  胡新艳  牛宝俊 《地域研究与开发》2002,21(2):60-63

文章以广东省新兴县为例，从凉果资源分布与加工能力的匹配关系角度对华南地区凉果资源的分布，凉果加工业的分布与布局，凉果市场分布与竞争力，凉果加工业与资源的匹配关系等进行了分析，并针对华南地区凉果加工业面临的主要问题提供了一些建议。  相似文献   

成都市民消费结构与休闲活动关系研究   总被引：6，自引：0，他引：6  

杨国良 《地域研究与开发》2002,21(2):77-80

城市居民消费水平，消费结构会影响其休闲消费能力，消费意愿，消费方式，消费态度和休闲时空结构，文章以成都市7个城区歌舞，茶棋牌，电影及城市公园休闲活动调查为基础，探讨了城市居民消费结构及其变化与休闲活动特征的关系。研究结果表明，城市居民消费结构的改变对歌舞，茶棋牌娱乐活动影响最大。  相似文献   

南水北调中线工程建设与河南水资源可持续利用   总被引：2，自引：0，他引：2  

赵永江  刘荷芬  贾虎 《地域研究与开发》2002,21(2):85-88

文章通过对河南省水资源开发利用现状，存在的主要问题，水资源供需平衡以及南水北调工程对河南省水资源利用的影响论述，提出了在拟定南水北调工程供水方案中，应通过强化节水，加强水资源保护，严格控制地下水开采，将水资源作为商品等措施，促进河南省水资源的可持续开发利用。  相似文献   

区域视觉形象识别系统设计的理论与实践   总被引：6，自引：0，他引：6  

禹贡 《地域研究与开发》2002,21(4):7-9

目前，全国各地正在兴起区域形象设计与建设的浪潮，但如何把区域形象信息系统地传递出去，这方面的理论研究大大落后于实践。文章就区域形象信息传递的有效工具－区域视觉识别系统设计的主要内容，设计的原则，设计的基本流程等在理论与实践上作了较为详细的探讨，并就区域视觉识别系统设计方案的经济学论证作了一些有益探讨。  相似文献   

河南经济技术开发区发展前景与对策     

杨延哲  张教平  刘燕茹  杨文新 《地域研究与开发》2002,21(4):24-27

文章阐述了经济技术开发区在区域经济发展过程中的作用。根据河南省经济技术开发区的发展现状和存在的问题，分析了加入WTO后开发区所面临的机遇和挑战，并在此基础上从开发区环境营造，运行机制，筹资方式，产业发展，城市建设等方面提出了加快河南省经济技术开发区发展的对策。  相似文献