江西冷水坑斑岩银矿床的蚀变碳酸盐矿物与银矿化关系   总被引：10，自引：0，他引：10  

魏明秀 《矿产与地质》1997,11(1):39-45

冷水坑斑岩银矿由斑岩岩体中心向围岩，以铁绿泥石化和菱铁矿化为主的铁质交代作用广泛发育。蚀变碳酸盐亚种为以菱铁矿为主的ＦｅＣＯ３－ＭｎＣＯ３系列，菱铁矿中含Ｍｎ高对银矿化有利。含锰菱铁矿化在外带与浅部有增高的趋势，与银铅锌矿化关系密切  相似文献   

Lithodiversity and Its Spatial Association with Metallic Mineral Sites,Great Basin of Nevada     

Mihalasky  Mark J.  Bonham-Carter  Graeme F. 《Natural Resources Research》2001,10(3):209-226

Geographical information system (GIS) techniques were used to investigate the spatial association between metallic mineral sites and lithodiversity in Nevada. Mineral site data sets include various size and type subsets of about 5,500 metal-bearing occurrences and deposits. Lithodiversity was calculated by counting the number of unique geological map units within four sizes of square-shaped sample neighborhoods (2.5-by-2.5, 5-by-5, 10-by-10, and 20-by-20 km) on three different scales of geological maps (national, 1:2,500,000; state, 1:500,000; county, 1:250,000). The spatial association between mineral sites and lithodiversity was observed to increase with increasing lithodiversity. This relationship is consistent for (1) both basin-range and range-only regions, (2) four sizes of sample neighborhoods, (3) various mineral site subsets, (4) the three scales of geological maps, and (5) areas not covered by large-scale maps. A map scale of 1:500,000 and lithodiversity sampling neighborhood of 5-by-5 km was determined to best describe the association. Positive associations occurred for areas having >3 geological map units per neighborhood, with the strongest observed at approximately >7 units. Areas in Nevada with more than three geological map units per 5-by-5 km neighborhood contain more mineral sites than would be expected resulting from chance. High lithodiversity likely reflects the occurrence of complex structural, stratigraphic, and intrusive relationships that are thought to control, focus, localize, or expose mineralization. The application of lithodiversity measurements to areas that are not well explored may help delineate regional-scale exploration targets and provide GIS-supported mineral resource assessment and exploration activity another method that makes use of widely available geological map data.  相似文献   

广东省居民潜在国内出游力的地区差异分析   总被引：19，自引：1，他引：19  

郑海燕  保继刚 《地域研究与开发》2001,20(3):70-74

用因子分析方法对广东省居民的潜在国内出游力作了地区差异分析，得出对居民潜在出游力影响最大的3个因子，验证了吴必虎等提出的结论，同时还提出了户均人口和农业人口百分比对潜在出游力的影响。根据21个地级市的因子总得分进行聚类分析，得出广东省内居民潜在出游力强弱的5个不同级别的地区，指出了目前广东省居民潜在出游力最强的地区，这对于各旅游目的地如何利用有限的资金在广东地区进行促销宣传具有一定的指导意义。  相似文献   

黄土丘陵区典型小流域土地利用变化研究——以陕西延安地区大南沟流域为例   总被引：50，自引：12，他引：50  

陈利顶  傅伯杰  王军 《地理科学》2001,21(1):46-51

利用航片解译和景生态学方法研究了陕北黄土丘陵区大南沟流域在20世纪70年代和90年代的土地利用结构的特点和变化，结果表：从1975年到1999年，梯田，坡耕地，稀疏林地，灌丛面积减少，所占百分比呈下降趋势，而有林地，果园，荒地所占百分比呈上升趋势，梯田，有林地，灌丛和茺地平均斑块面积在增大，而坡耕地，稀疏林地，果园的平均斑块面积在减小，果园和坡耕地分维数在变大，斑块形状趋于复杂化，而有林地，稀疏林地，灌丛，梯田和荒地的斑块分维数在变小，斑块形状趋势规则小，有林地，灌丛，果园，荒地的分离度在下降，稀疏林地，梯田和坡耕地的分离度在上升，说明有林地，罐丛，果园和荒地的地位在上升，而稀疏林地，梯田和坡耕地的地位在下降，全区单位面积的斑块数目的磁大，在一定程度上表明农田中地块之间的边界增多，其结果是导致一些土地资源和浪费和不利于土地管理，景观多样性指数和土地利用相对合理指数在增大，但变化较小，1997年与1975年相比，整体上土利用结构稍有好转，但这种土地利用结构远未达理想状态。  相似文献   

电测深曲线的遗传算法反演   总被引：12，自引：3，他引：12       下载免费PDF全文

王兴泰  李晓芹  孙仁国 《地球物理学报》1996,(2)

电测深曲线作为地下介质电阻率和深度的非线性函数，其解具有高度的非唯一性．常规的基于局部线性化的最优化反演方法易使解估计陷入局部极大值中，而且严重地依赖初始模型的选择．遗传算法作为一种全局最优化方法，对初始模型的依赖性大为减弱，且不易陷人局部极大值之中，从而能有效地解决这类非线性最优化问题．本文首次将遗传算法用于电测深解释并对实测曲线进行反演，效果很好，显示了遗传算法独特的优越性．  相似文献   

论工程地质学基本理论   总被引：1，自引：0，他引：1  

罗国煜 《江苏地质》2001,25(4):196-199

概括和总结了我国工程地质50年来的发展历史和所取得的科学成就。分析认为，岩土特性成因控制论、岩土体稳定性的结构控制论和人地协调论是工程地质学的基本理论。强调了在基本理论和学科交叉的基础上创新发展，是工程地质向新水平迈进的重要途径，并以优势面理论为例作了介绍说明。同时对我国工程地质学的发展方向和前景作了讨论。  相似文献   

应用遗传算法研究新疆北天山地震带地震预报规则   总被引：1，自引：1，他引：1  

李莹甄  龙海英 《内陆地震》2001,15(4):338-346

依据遗传算法基本原理，选用5种地震学参数，对北天山地震西段（乌苏－精河地区）1970－1995年地震资料进行拟合迭代演化，提取该区具有不同适应度和层次结构的地震学参数预报规则集，以此对该区1996－2000年发生的地震作回顾性检验。结果表明，基于遗传算法建立的北天山地震预报规则，能对研究区未来一定时间的地震事件给与客观的判别和预测。  相似文献   

东营凹陷早第三纪介形类复合分异度研究          下载免费PDF全文

郑德顺  李守军 《古地理学报》2002,4(2):64-70

复合分异度不仅能表明化石群内属种的多寡，而且能反映各种个数分配是否均匀。它对划分生物群落和恢复沉积环境具有重要意义。文中讨论了复合分异度的概念，并选用了信息函数熵H(s)作为分异度的计算方法，分析统计了山东济阳坳陷东营凹陷沙三段至沙一段沉积时期的介形类分析化验资料，并计算了东营凹陷现有资料井各时期的分异度值，做出了分异度等值线图。根据分异度的值及区域内的优势种，共划分出了各时期的11个生物群落，即Limnocythere armata（具刺湖花介）、Phacocypris huiminensis（惠民小豆介），Pseudocandona boxingsis（博兴假玻璃介），Camarocypris elliptica（椭圆拱形介），Huabeinia unispinata（单刺华北介），Camarocypris ovata（卵形拱星介），Huabeinia chinensis（中国华北介），Camarocypris ovata（卵形拱星介），Huabeinia chinensis（中国华北介），Cyprois mina（小型拟星介），Huabeinia obscura（隐瘤华北介）。个体古生态资料和复合分异度值对生物相划分和环境划分起着重要的作用，结合生物群落划分出了东营凹陷各时期的沉积环境。  相似文献   

Management of the old field vegetation in the Namaqua National Park, South Africa: conflicting demands of conservation and tourism   总被引：1，自引：0，他引：1  

M W. Van Rooyen 《The Geographical journal》2002,168(3):211-223

Springtime mass displays of wild flowers are especially prominent on old fields and other disturbed sites in Namaqualand, an arid region in the north–western part of South Africa. This springtime floral spectacle draws thousands of tourists annually. However, there is a potential conflict between biodiversity conservation and the mass flowering that is a valuable source of income to the region. To develop a management plan for the old field vegetation in the Namaqua National Park, the questions of whether to disturb or not, how often to disturb and what type of disturbance should be applied are of vital importance. The aim of this paper is to report on experimental work to determine the impact of disturbance on mass flowering displays and biodiversity. Results show that although species diversity increased with time since last cultivation, the mass effect of the flowering display diminished. The loss of the mass effect appears to be primarily caused by the increased abundance of a short–lived perennial species ( Leysera gnaphalodes ) that suppressed the flowering display of the prominent annual species. To maintain mass displays as a tourist attraction, regular disturbance by tilling therefore seems essential. Initially, a four–year rotational tilling programme is proposed to produce a mosaic of fields of different ages to ensure that there will always be some old fields producing a spectacular and uncluttered display. Frequency of disturbance should thereafter be determined by an adaptive management policy. If the management of the old field vegetation is seen in the context of conserving total landscape ecodiversity, this includes conserving cultural bio–landscapes and their intrinsic values. Viewed in this context, human–induced disturbance in the small area set aside for mass displays in the Namaqua National Park (less than 0.05% of the park) becomes justified.  相似文献   

The geography of choice and diversity in the 'new' secondary education market of England   总被引：1，自引：0，他引：1  

Chris Taylor 《Area》2002,33(4):368-381

The geography of education remains an under-researched area, particularly in light of major transformations in education provision over the last two decades. This paper reaffirms the position of a geographical approach to studying the education system by focussing upon the differential impact of two major features of national policy reforms on secondary school admissions in England: the desire to enhance choice and diversity in the provision of schooling.  相似文献