Application Of Multi-spectral Remote Sensing To Chromite Prospecting In Yarlung Zangbo Suture Zone,Tibet

Chromite,as an important raw ore,is mainly found in ophiolite in Yarlung Zangbo suture zone and takes lentoid forms in China.There are two types of chromite in the Ophiolite belt of the Yarlung Zangbo River.One is from the mantle peridotite below the Moho interface;The other occurs in the heap peridotite above the Moho interface.Remote sensing technology,with its macroscopic application in geology,can improve the efficiency of mineral exploration and make up for the deficiency caused by topography in exploration.As an advanced science and technology,remote sensing has been well integrated with geology and can provide powerful technical means for mineral exploration and geological research.In this paper,the yarlung Zangbo River suture zone is taken as the research area.Combined with the known geological background and multi-source remote sensing data,we have used digital image processing,spectral extraction and analysis,and remote sensing geological interpretation to predict the chromite prospecting potential in the ophiolite belt.The main research contents and achievements are as follows:(1)Combined with the geological characteristics of Yajiang suture zone,such as stratigraphy,lithology,structure and lithofacies,the study has analyzed the main occurrence,metallogenic environment and the controlling ore-forming factors of chromite.The chromite produced in Yajiang suture zone is podiform chromite,which mainly occurs in the mantle peridotite of ophiolite zone.It is an important task of this study to extract peridotite using remote sensing images.(2)This study analyzes the spectral range of remote sensing images and select appropriate methods for image preprocessing and information enhancement,to carry out lithology interpretation and structural interpretation.(3)Lithology interpretation is based on the existing spectral database,matching with the remote sensing image pixel spectrum,fitting and matching the lithology in the study area,and obtaining the compatible lithologic area range on the spectrum.The interpretation process is based on the known spectral information of related peridotite,using remote sensing technology processing methods,such as pure pixel index(PPI),spectral angle classification(SAM),spectral feature fitting(SFF)to perform spectral fitting of peridotite and extract the corresponding space.(4)Structural interpretation is to enhance the marginal information through remote sensing images,highlight the structural related information,and visually interpret the structures that are most likely to form a mineralized environment.The main filtering enhancement methods are high-pass filtering and sober space filtering to interpret the structure.(5)Combined with the spectral features of the remote sensing alteration anomaly information,the alteration anomaly was extracted for the metamorphism of the Yarlung Zangbo ophiolite belt.According to the type of mineralization alteration and the spectral characteristics of the altered rock,the alteration anomalies containing Fe³⁺and OH^-were extracted,respectively,and the areas of iron staining anomaly and hydroxyl anomaly were determined.The principal component analysis method can be selected,the principal component is selected for classification,irrelevant information is eliminated,the anomaly range in the study area is obtained,and the ore-showing effect of alteration anomaly information can be analyzed.(6)The metallogenic geological characteristics of the Yarlung Zangbo suture zone were sorted out by conditions,and the results of lithology extraction and alteration information extraction were superimposed by using the spatial analysis function of geographic information technology.In this paper,the average spectral characteristic curve of peridotite is extracted,which is matched with the hyperspectral image,and the spectral Angle is classified,and the peridotite is identified successfully.Certain fault structures can be extracted by structural interpretation,which can assist lithologic interpretation to distinguish.Hydroxyl anomaly is a good indicator of serpentine mineralization and iron anomaly is a good indicator of chromite deposits.Through the superposition of multiple information,the comprehensive mineralization analysis is carried out,and the prospecting potential areas are delineated in the research area.