【摘要】 地球化学元素的异常下限值确定是地球化学中重要的问题之一,目前还没有一个令人满意的具有科学依据的计算方法。传统的化探异常下限值计算是基于元素的地球化学分布呈正态分布或元素含量在空间上呈连续的变化这一假设为基础的,而事实上地球化学元素含量的空间分布是极其复杂的,研究表明,地球化学景观可能是一个具有低维吸引子的混沌系统,元素的地球化学背景值和异常具有各自独立的幂指数关系,由此导致了一种多重分形分布,因而可以利用元素的分形分布求出其异常下限。利用元素的分形分布求异常下限的几种常用方法均是以求取不同尺度r下,对应的N(r)数。如果用手工统计方法计算,计算过程简单但繁琐,地理信息系统(GIS)可以实现图形单元的动态查询和属性统计,这种特性很适合于统计不同尺度r下对应的N(r) ,因此,可以将分形方法与地理信息系统加以结合,在GIS平台上对地学图形和属性信息进行分析及统计处理,将原来比较繁杂的分形计算操作变得方便简捷,易于实现。本文以武汉中地信息公司开发的MAPGIS地理信息系统为例,对河北某地1∶5万Cu元素化探数据进行了处理,具体说明了以MAPGIS为工具,利用分形方法求取元素化探异常下限的过程,并将计算结果与传统异常下限计算方法所得的结果进行了对比,所得的异常下限值相近?更多还原

【Abstract】 The determination of thresholds of chemical elements is an important problems in geochemical exploration. At present, there is not a satisfactory scientific way to confirm the thresholds. The traditional way of determining thresholds of chemical elements is based on the assumption that chemical elements are in normal distribution or element contents are continuously changed in space. Nevertheless, the spatial distribution of chemical elements is extremely complicated, and researches show that geochemical landscape may be a chaotic system of low dimension. The background and anomaly values of elements usually show independent power index relationship, resulting in the multifractal distribution of chemical elements. We can therefore use the fractal method of chemical elements to determine thresholds. Several fractal methods for determining thresholds of chemical elements often compute r of different scales and the corresponding number of N(r) . Geographical Information System (GIS) can realize dynamic inquiry and attribute analysis of figure units, and hence GIS is very suitable for statistic analysis of r of different scales and corresponding N(r) . So we can combine the fractal method with the geographical information system. With MAPGIS geographical information system designed by Wuhan Zondy Info-Engineering Co. Ltd. as an example, This paper deals with the determination of thresholds of chemical elements by using fractal methods based on GIS platform. The results obtained are compared with those obtained by traditional methods. The traditional methods for determining thresholds require pretreatment of original data and consideration of practical geological setting. However, the operation of the fractal methods based on MAPGIS platform is very simple and not affected by abnormally high values. Therefore, the fractal methods are less affected by artificial interference. A comparison with the traditional methods has led to the conclusion that the fractal method is an effective method for determining thresholds of chemical elements.更多还原