基于TM/ETM影像的复合法遥感蚀变异常提取应用研究

通过甘肃龙首山干旱基岩裸露区碱交代岩提取、青海玉树地区大面积蚀变异常提取、江西相山铀矿田植被覆盖区蚀变异常提取三个实例应用来验证"无损线性拉伸+去除和抑制干扰因素+波段比值法/主成分分析/(波段比值法+主成分分析)+密度分割"复合法在蚀变异常提取的应用效果。在甘肃龙首山提取的碱交代岩与在其两个子区实测的碱交代岩相比较,面积大于1个、1/2个、1/4个像元的碱交代岩提取率分别为100%、94.74%、80%。面积小于1/4个像元的碱交代岩成群出现,岩体之间相距较小,这些岩体也可以被提取出来,并且提取的面积有所扩大,结果显示面积大于1/4个像元的蚀变信息能够有效提取。在青海玉树地区提取的蚀变异常信息与与其区内的84个矿床(点)相比较,提取的蚀变与74个矿床(点)能够吻合,吻合率达88.1%。矿床(点)与提取的蚀变信息吻合关系为铁矿床>铜矿床>锌矿床>铅矿床,且多金属矿床多处于两种或多种蚀变异常叠合部位。在江西相山铀矿田植被覆盖区蚀变异常提取效果相对差,但是提取的蚀变信息在野外得到较好验证。西部矿区矿床(点)与铁化蚀变吻合较好,北部矿区矿床(点)吻合较好,同时分析了部分矿床(点)未能与遥感蚀变异常吻合的原因。

Application of Remote Sensing Alteration Anomaly Extraction with the Method of Composite Algorithm Based on TM/ETM Images

Abstract: This study is based on extraction of the distribution of alkali metasomatic rocks in the uncovered bedrock area in Longshoushan ,Gansu Province, abnormal alteration in a large area of Yushu county, Qinghai Province and abnormal alteration in the vegetation-covering area in the Xiangshan uranium field , Jiangxi Province. The purpose is to validate the effectiveness of the composite algorithm which includes perfect linear extension, removing and restraining interference, band radio, principal component analysis (PCA) and image masking and density segment. Comparing with the alkali metasomatic rocks in its subareas, the alkali metasomatic rock from the Longshoushan of Gansu Province larger than one pixel, 1/2 pixel, and 1/4 pixel have the extracting rates 100% , 94.74% , and 80% respectively. And alkali metasomatic rocks less than 1/4 pixel appear in groups with relatively small spacing. These rocks can be abstracted by the remote sensing, and the testing area is bigger than scheduled. It is found that the abnormal alteration can be effectively abstracted if the alkali metasomatic rock is larger than 1/4 pixel. In Yushu county, Qinghai Province, among the 84 mineral deposits or mineral occurrences, 74 objects are in accordance with alternation anomalies, meaning a successful rate of 88.1%. And these objects, from large to small, are iron mine, copper mine, zinc mine, and lead mine. In the polymetallic mines, the mines are overlapped by two or more alteration anomalies. In the Xiangshan uranium field covered by vegetation in Jiangxi Province, the abstracting result of alteration anomalies is worse than the uncovered, but the alteration is confirmed in the field. The mineral deposits and mineral occurrences in the west are in good agreement with the iron alteration. And it is the same in the north. Also, we analyze the reasons why some mineral deposits and mineral occurrences and the abnormal alteration cannot match well.