Study On Extraction Of Uranium Mineralization Alteration Information In Xiangshan Volcanic Basin From ASTER Data And Rock Reflection Spectrum Testing

Xiangshan volcanic basin is located in the intersection of the Le'an-Guangfeng uranium polymetallic metallogenic belt and Dawangshan-Yushan uranium polymetallic metallogenic belt.It possesses the largest and richest volcanic-type uranium ore field in China.Albitization,hydromica,hematite and carbonation are closely related to uranium mineralization in the basin.It is of great significance to identify alteration types and distribution characteristics by remote sensing technology for guiding uranium polymetallic prospecting.Based on a large number of previous research results and the rock spectral characteristics of Xiangshan altered rocks,the alteration information extraction technology is optimized,and effective methods are chosen to extract the mineralization alteration information in the study area.By comparing the application effects of different alteration information extraction methods in the study area,the following results are demonstrated.(1)Porphyry lava,rhyolite and monzogranite porphyry all have a reflectance variation within 15%.The spectrum of porphyry lava shows a free water-related absorption peak at 1950.0 nm and a characteristic absorption peak at 2209.0 nm.The spectrum of rhyolite has obvious characteristic absorption peaks at 1950.0 and 2209.0 nm.The spectrum of monzogranite porphyry has characteristic absorption peaks at 222.0 and 2350.0 nm.(2)The ASTER image is preprocessed by ENVI 5.3 software,including band resampling,band synthesis,atmospheric correction,topographic correction,geometric correction,image mosaic clipping and so on.In the pretreatment process,according to the characteristics of terrain fluctuation in the study area,the terrain correction is introduced to reduce the terrain interference factors.Employing NDVI method,the disturbance of vegetation on alteration information extraction is reduced effectively,and the accuracy of alteration information extraction is improved.(3)Combined with the reflection spectrum characteristics of altered wall rock,the suitable bands for the study area are selected for extraction.The band ratio method is used to extract the iron alteration anomaly and hydroxyl alteration;PCA is used to extract alteration information of iron,hydroxyl and carbonate;and the complex method of ratio + principal component analysis is used to extract illite alteration information.Comparing the extraction effect of the three methods,the compound method has the best extraction effect.(4)The distribution of alteration in Xiangshan volcanic basin is mastered,and the extracted alteration information is basically consistent with the known ore deposits.The alteration information is not extracted near the deposit in the middle of Xiangshan because of the vegetation mask.In the southern and north-western parts of Xiangshan,there are some obvious abnormal alteration areas without mineralization points distribution,thus further exploration is required.