Alteration Abnormity Information Extraction from ETM data with Application in North-western Yunnan, China
Regional alteration normality extraction based on ETM data with application was developed in northwest Yunnan, where belongs to Sanjiang area, a famous mineralization belt in China. Through the study on the spectral feature of OH- and Fe2+ and Fe3+ related to alteration, specific image processing methods were improved and the related operation flow was developed. As interferential factors to alteration, vegetation influence was lessened by the criterion in which the ratios 5/4 more than 1 mean wholly vegetated then were masked in the process, whereas the ratios 5/4 less than or equal to 1 mean semi-vegetated and useful information-bearing then were taken into data process; snow and shadow were lessened by the criterion in which the ratios 7/1 less than 0.8 mean snow and shadow fully covered then were masked also. With interferential factors masked, Principal Component Analysis (PCA) with ETM bands 1, 4, 5 and 7 for alteration related to OH- was conducted, which is on the basis of the principle that OH- has high reflectance in band 5 but high absorption in band 3. Similarly, PCA with bands 1,3,4 and 5 for alteration related to Fe2+, Fe3+ was conducted, which is on the basis of the fact that Fe2+ Fe3+ has high reflectance in band 3 but high absorption in bands 1,4 and 5 as well. As the result of PCA, alteration abnormality component was ascertained by the contribution of characteristic bands. Meanwhile, alteration grades were delineated by the standard deviation δ of pixel value of abnormality component. Furthermore, through rational abnormity explanations and alteration type analyses from the view of regional geographic and geological characters, information was obtained that OH- -related alteration mainly designates K-feldspar alteration, phyllic alteration and prophilized alteration which is closely related to porphyry type copper deposit. Meanwhile, Fe2+,Fe3+ -related alteration designates pyritization which is commonly distributed and mainly related to hydrothermal type or skarn type multi-mineral deposit. Accordingly, the remote sensing alteration models for porphyry type copper deposit and skam type multi-mineral deposit were set up, by which more potential mineral areas were delineated. By drill verifications conducted in target areas, new mine areas were found. By this way, the study not only reveals that original alteration-related information could be directly extracted from ETM, but also shows that the alteration extraction flow and remote sensing alteration application developed in this study is practical in mineral application, especially with ETM data which are so commonly used and readily available.
Zhifang Zhao Yujun Zhang Jianping Chen Qiuming Cheng Yingxiang Lu Debing Cao
China University of Geosdences, 29 Xueyuan Road, Beijing, 100083 China;Beijing Key Laboratory of Res China Aero Geophysical Survey and Remote Sensing Ceraer for Land and Resources, 31 Xueyuan Road, Bei China University of Geosdences, 29 Xueyuan Road, Beijing, 100083 China;Beijing Key Laboratory of Res York University, 4700 Keele St., Toronto, Canada M3J1P3 Yunnan Institute of Geology Survey, 87 Dongfeng Lane, Kunming 650051, Yunnan, China
国际会议
The 12th Conference of the International Association for Mathematical Geology(第12届国际数学地质大会)
北京
英文
494-497
2007-08-26（万方平台首次上网日期，不代表论文的发表时间）