The Alteration Information Extraction Research By Remote Sensing On Xiangshan Uranium Ore Field, Jiangxi Province

Jiangxi Xiangshan uranium ore field is the largest volcanic-type uranium ore field inChina. It locates in the intersection area of Gan-Hang volcanic metallogenic belt and kingmountain-Yu mountain granite-type uranium ore field. The hematitization, chloritization,albitization and fluorite alteration are well-developed in there. Remote sensing alterationextraction uses remote sensing technology to extract alteration information which is relatedto mineralization. The theory basises are geological and spectral abnormal. In geological,hydrothermal type deposits can form a range of mineralized alteration, and the size is muchlarger than the range of deposit, therefore, it can indicate the existence of deposits in someextent, and it is one of the most important prospecting marks; In spectrum, somemineralized alterations have diagnostic spectral characteristics because it contains specialions and groups. The remote sensing satellite records these features on images, then usesdigital image processing techniques, we can extract these abnormal information from theimages. The author choosed Jiangxi Xiangshan uranium ore field as study area and usedthe ASTER datas to extract various mineralized informations which related to uraniummineralization and alteration.During the research work, on one hand, we should do some image preprocessingssuch as radiation correction, image registration, geometric precision correction and imagemosaic. In the process of image mosaic, we adjusted the color through histogram matchingmethod because the left and right image’s acquisition time was different and had a largecolor difference. In the process of geometric precision correction, we used standard digitaltopographic map to correct remote sensing image. On the other hand, during the alterationextraction, firstly I collected various mineralization alteration information which wasrelated to uranium mineralization in Xiangshan region and analysised the spectralcharacteristics. Then I used ASTER data to re-sampling USUG spectrum library datas inENVI software and analysised the spectral characteristics of all kinds of alteration in studyarea. Lastly, I determined the types and methods of the extracting of mineralizationalteration. Based on the above scheme, I used band ratio to extract iron and chloritealteration, principal component analysis to extract chlorite, ferric-bearing and carbonate alteration, used band method and principal component analysis to extract pyritemineralization alteration information.Finally, I evaluated the results of alteration extraction with the map of JiangxiXiangshan uranium ore fields and the results of field geological route validation. On thewhole, every kind of alteration information can partly indicate the existence of the uraniumore fields and ore mineralizations at some extent. But there were also some alteration can’tindicate the uranium ore fields, the reason may be that there were too much interferenceinformation around and the weak alteration information was removed during the maskprocessing; There were also may be part of the ore fields were deep deposit, the surfacewithout alteration.