青海赛什腾地区遥感影像岩石信息提取研究

Study on rock information extraction from remote sensing images in Saishiteng area,Qinghai Province

赛什腾地区隶属柴北缘构造带,岩性复杂多变,前人对研究区岩性界线的划分较为笼统,笔者等选择Landsat-8 OLI、ASTER和Sentinel-2A为数据源,采用最佳波段指数确定各影像的波段组合,凸显不同岩石的边界;将ASTER短波红外波段与Landsat-8 OLI、Sentinel-2A可见光—近红外波段协同处理,构成Landsat-8+ASTER(LA)数据和Sentinel-2A+ASTER(SA)数据,分析重采样岩石标准光谱信息,拟定不同岩石波段运算公式,基于多重分形理论选定不同岩石类型的阈值范围,获取主要岩性的分布;根据重采样的黑云母标准光谱曲线,选取SA数据2262 nm波段和2336 nm波段进行定向主成分分析,采用Crosta法阈值分割第二主成分,划分黑云母异常等级,将其与岩性分布相关联,识别出研究区主要岩性分布。通过岩石实测光谱分析、薄片镜下鉴定与野外地质调查相结合的方法完善解译结果。岩性提取结果显示,小赛什腾山东侧新发现“U”型条带,为辉长岩—英云闪长岩—二长花岗岩,重新圈定达肯大坂群第三岩组和第四岩组,滩间山群一组,花岗岩,二长花岗岩,黑云母花岗岩,流纹岩,似斑状石英闪长岩,石英闪长岩,英云闪长岩,辉长闪长岩和辉长岩等岩石的边界。此次基于多源遥感数据岩性识别方法研究对青海赛什腾地区野外地质调查工作具有指导意义,可为高山峡谷区地质填图提供技术参考。

Objectives:Saishiteng belongs to the tectonic belt in the northern margin of Qaidam Basin,and its lithology is complex and changeable.The lithologic boundary of the study area is generally divided by predecessors.Land sat-8 OLI,ASTER and Sentinel-2 A image data are selected to identify the main lithology by information enhancement method.Methods:The optimal band index was adopted to determine the band combination of each image,which highlighted the boundary of different rocks.Landsat-8+ASTER(LA)data and Sentinel-2 A+ASTER(SA)data were formed by combining ASTER short-wave infrared band with Landsat-8 OLI and Sentinel-2 A visible-near infrared band.The standard spectral information of resampled rocks was analyzed,and the calculation formulas of different rock bands were drawn up.Based on multifractal theory,the threshold range of different rock types was selected to obtain the distribution of main lithology.According to the resampled standard spectral curve of biotite,2262 nm band and 2336 nm band of SA data were selected for directional principal component analysis,and the second principal component was segmented by Crosta threshold method,and the anomaly grade of biotite was divided,which was associated with lithology distribution and identified the main lithology distribution.Results:The remote sensing interpretation results were improved by combining the measured spectral analysis of rocks,the identification under thin section microscope and the field geological investigation.The results of lithologic extraction showed that the newly discovered U-shaped belt on the east side of Xiaosaishiteng was gabbrotonalite—monzogranite.The boundaries of the third and fourth rock groups of Dakendaban Group,the first group of Tanjianshan Group,granite,monzogranite,biotite granite,rhyolite,porphyritic quartz diorite,quartz diorite,tonalite,gabbro diorite and gabbro were re-delineated.Conclusions:Based on the spectral resolution advantage of Sentinel-2 A and Landsat-8 data in visible-near infrared band,the optimal band combination is used to enhance the image color.The results show that the pseudocolor composite image obtained by this method is rich in color and clear in boundary,and has more advantages in boundary division than ASTER data with the same resolution.The short-wave infrared band of ASTER data is processed with the visible-near infrared band of Landsat-8 data and Sentinel-2 A data,and the SA data and LA data obtained can retain the spectral diagnostic characteristics of rocks and minerals to the greatest extent.Based on the different characteristics of spectral diagnosis of rocks and minerals,the band operation method is used to highlight the different lithologic information in collaborative data,which can provide guidance for the next field geological work.According to the spectral characteristics of biotite minerals in short-wave infrared band,Based on directional principal component analysis and field investigation,it can be seen that the anomaly grade of biotite is related to the rock type in the area.When the anomaly grade of biotite is concentrated in a specific range,it can indicate the range of Dakendaban Group(Pt1D)and provide reference for lithologic mapping in adjacent areas.