台湾西南部泥岩土地利用型态与环境劣化趋势之分析   总被引：5，自引：2，他引：5  

林信辉  张俊斌  周跃 《云南地理环境研究》2003,15(3):40-47

台湾泥岩恶地因其特殊之土壤理化性质及区域微气候的相互恶性循环，衍生生态环境等问题。在以往之35年，裸化面积从1967年的2532hm^2，至2001年11月已扩大为15539hm^2。其表土大量流失、崩塌、河川含砂量激增、植被退化与微气候变异等破坏，更显示泥岩之环境劣化问题。以SPOT卫星影像判识泥岩裸露面积，探讨不同时期之地景变异，并应用地景生态理论量化泥岩地表不同土地利用之空间结构变化，分析地景结构变迁之生态内涵与生态指标意义。因子分析结果其主要变异为多样性因子与形状破碎型因子所影响，而应用马可夫链模式计算出不同时期之土地利用变迁内涵，此结果搭配指标分析可解释泥岩裸露面积与竹林面积皆持续扩大，乃由人为土地利用之活动及植被变迁所引起。  相似文献   

Sensitivity Analysis of a Feedforward Neural Network for Considering Genetic Mechanisms of Kuroko Deposits     

Matsuda  Setsuro  Koike  Katsuaki 《Natural Resources Research》2003,12(4):291-301

Exploration for volcanogenic massive sulfide deposits of the kuroko-type is underway in many places. Clarifying the spatial patterns of the metals in kuroko deposits will be useful for understanding their genetic mechanisms and for future exploration of such types of deposits. This study represents a spatial distribution analysis on the contents of principal metals of kuroko deposits: Cu, Pb, and Zn, in the Hokuroku district, northern Japan, by a feedforward neural network and 1917 sample data at 143 drillhole sites. The network, which consists of three layers, was trained by the principle of SLANS in which the numbers of neurons in the middle layer and training data are changed to improve estimation accuracy. Using the weight coefficients connecting adjacent neurons, sensitivity analysis of the neural network was carried out to identify factors influencing spatial distributions of the three metals. The coordinates depth (z) direction, Bouguer gravity, and specific lithology such as dacite were determined to be influencing factors. The high frequency of the z coordinate signifies that the metal contents differ to a large extent by depth. The sensitivity vector was defined using sensitivity coefficients for x, y, and z coordinates of an estimation point. We determined that the directions of large vectors were different inside and outside of the Hanawa-Ohdate area. This characteristic is considered to originate from the differences in the permeability of fractures that became the paths for rising ore solutions, and the depths that the solutions mixed with sea water.  相似文献   

大兴安岭北部砂宝斯金矿床控矿因素及成因   总被引：7，自引：0，他引：7  

王献忠  舒本耀  梁海军  陈满 《黄金地质》2003,9(3):45-48

砂宝斯金矿床产于中侏罗统陆相碎屑岩中，共有6条矿脉，走向近SN。矿床的形成经历了4个成矿期和6个成矿阶段。矿石类型主要为蚀变砂岩和构造破碎蚀变岩型。金矿体严格受SN和NNW向断裂控制，围岩和侵入岩参与了成矿作用。矿石Pb、S、H和O同位素分析和成矿温度研究表明，金矿成矿物质来源于深部岩浆和地层，成矿溶液是岩浆热液和大气降水的混合流体，成矿温度为200～230℃，属中低温蚀变砂岩型。  相似文献   

大兴安岭浅覆盖区生态地质评价方法初探——以1∶25万区调呼中镇幅为例   总被引：1，自引：0，他引：1       下载免费PDF全文

马江水李仰春  任凤和尤福珍 李清伟 《中国地质》2003,30(3):330-336

通过野外调查，在收集统计大量基础地质、经济地质、环境地质、旅游地质、农(林)业地质等数据信息的基础上，在GIS技术指导下，采用定量定性相结合的半定量分析评价方法，对森林浅覆盖区生态地质现状及各类资源的开发利用潜力进行了综合评价。在研究和探讨森林浅覆盖区生态地质综合评价方法的基础上，提出了森林浅覆盖区生态地质评价模型，确定了综合参数，划分了生态地质类型。  相似文献   

堆浸生产黄金浸出周期浅析     

曾祥平 《云南地质》2003,22(2):217-222

云南富源胜境关金矿开发生产初期，运用堆浸理论，根据矿山工业场地实际和矿石的物理化学性质，及矿石中的有害杂质(组织)的含量，多次试验、调整技术参数(堆浸场地物理性质、矿石粒度、矿堆高度、矿堆渗透性、氰化物浓度、浸出液碱性、浸出温度、喷淋强度、吸附流速或流量等)，完善浸出工艺，缩短浸出周期，提高浸出率，取得了良好的经济效益。  相似文献   

Z油田低阻油层影响因素分析     

李玉宏  魏仙样  张化安  武富礼 《西北地质》2003,36(4):65-67

通过对Y油田和Z油田电阻率影响因素对电阻率的影响对比，分析了Z油田低阻的原因及各影响因素影响程度。  相似文献   

金属因素在激电异常评价中的应用   总被引：2，自引：0，他引：2  

杨天春  吕绍林  姚成华  王齐仁 《物探与化探》2003,27(4):305-306

当激电异常较为复杂时,利用η_s(或F_s)这些激电法的基本参数难以对异常源的性质进行合理的解释.通过具体实例,说明应用激电法的二次信息--金属因素解释复杂激电异常的有效性.金属因素能将矿致异常与非矿致异常分离,对异常的定性及定量解释有很好的作用.  相似文献   

PLS法与隧道围岩稳定性分类   总被引：5，自引：0，他引：5  

解华明  丁华 《物探与化探》2003,27(4):320-322

围岩稳定性是隧道工程支护设计的基本参数,采用偏最小二乘回归法,综合考虑多因变量影响因素,对隧道围岩稳定性分类进行回归建模,并取得较好效果.  相似文献   

太平庄井地下流体动态主要干扰因素研究   总被引：1，自引：0，他引：1  

刘成龙  陶京玲  王志敏 《华北地震科学》2003,21(3):59-64

通过分析多年的观测资料，认为太平庄井地下流体动态的主要干扰因素为区域地下热水开采，其次为降雨。气压的明显变化对水位、水温也有一定干扰。区域开采造成太平庄井水位、水温同步下降，氢气测值升高；降雨导致太平庄井水位上升、水温下降。  相似文献   

Seismic scattering at the top of the mantle Transition Zone     

H. Thybo  L. Nielsen 《Earth and Planetary Science Letters》2003,216(3):259-269

We document strong seismic scattering from around the top of the mantle Transition Zone in all available high resolution explosion seismic profiles from Siberia and North America. This seismic reflectivity from around the 410 km discontinuity indicates the presence of pronounced heterogeneity in the depth interval between 320 and 450 km in the Earth’s mantle. We model the seismic observations by heterogeneity in the form of random seismic scatterers with typical scale lengths of kilometre size (10-40 km by 2-10 km) in a 100-140 km thick depth interval. The observed heterogeneity may be explained by changes in the depths to the α-β-γ spinel transformations caused by an unexpectedly high iron content at the top of the mantle Transition Zone. The phase transformation of pyroxenes into the garnet mineral majorite probably also contributes to the reflectivity, mainly below a depth of 400 km, whereas we find it unlikely that the presence of water or partial melt is the main cause of the observed strong seismic reflectivity. Subducted oceanic slabs that equilibrated at the top of the Transition Zone may also contribute to the observed reflectivity. If this is the main cause of the reflectivity, a substantial amount of young oceanic lithosphere has been subducted under Siberia and North America during their geologic evolution. Subducted slabs may have initiated metamorphic reactions in the original mantle rocks.  相似文献