基于MAPGIS数字高程模型背景校正法的应用——以湖南省铜山岭—祥霖铺地区为例

Application of Background Corretion Based on the MAPGIS Digital Elevation Model to the Tongshanling-Xianglinpu Area in Hunan Province

本文运用Mapgis数字高程模型背景校正法对湖南省铜山岭-祥霖铺地区1∶20万水系沉积物数据进行了地球化学异常信息的提取。借助Mapgis高程库管理系统中的像元邻域统计功能,模拟出研究区内W和Sn元素的背景变化趋势,在此基础上对元素含量做背景校正,并利用残差(矿化叠加值)圈定异常。在背景模拟过程中,通过窗口大小对比试验发现,窗口越大,高背景区异常面积越大,而低背景区异常面积越小。因此,应用该法时,需要通过试验以便选出合理大小的窗口。经过背景校正后,区内W、Sn高背景场引起的非矿化异常得以抑制,传统方法圈定的大面积异常被分解成多个强异常,其空间分布规律性较好,并具有三级浓度分带特征。在低背景区发现了一系列新异常,如W’-7、8、9、13、14、15、21、22、30和Sn’-1、7、11、13、21。校正后的部分异常与已知矿点和成矿岩体或岩脉具有较好的对应关系。

This paper extracts the geochemical anomaly information in the Tongshanling-Xianglinpu area, Hunan province utilizing the 1：200, 000 stream sediment data with the method of background correction based on the Mapgis digital elevation model. The background variation trends of W and Sn elements are simulated by the statistical function of pixel neighbourhood in the Mapgis elevation base management system. And the element concentrations are corrected by the background model, and then the residual （the values of mineralized superposition） are used to determine the geochemical anomalies. By comparing the window size, we find that the bigger the window is, the greater area of anomalies in high background is, but the smaller area of anoma- lies in low background is. Therefore, when using this method, we need to test different window sizes to pick out the most suitable one. After background correction, the non-mineralized anomalies caused by the high background of W and Sn are restrained. The large anomalies delineated by the traditional methods are broken up into several strong anomalies. The spatial distribution regularities are much better, and they have three level concentration zones of three levels. Some new anomalies are found in the low background, such as W＇ - 7,8,9,13,14,15,21,22,30 and Sn＇ - 1,7, 11, 13,21. And some anomalies are related to the mineral occurrences and magmatic bodies after correction.