Remote Sensing Lithology Information Extraction Of Ultrahigh Pressure Metamorphic Zone

Remote sensing technology provides a more macro windows for geological workers to observe earth,which has enriched the method of geological survey to a certain extent.The extraction of rock or mineral information based on spectroscopy has became a hotspot in the field of remote sensing and geological integration.The West Altyn locates at the gathering place of the tarim plate and the qaidam plate,because of steep terrain and disorder of the Non-Smith Strata-Altyn Rock Group,resulting in section survey and geological route survey so difficult to carry out.This paper is under the reinterpretation of the regional tectonic framework using multispectral,thermal infrared data,adopts 2 modified PCA methods and mineral index to extraction lithological information respectively and discuss the lithological method in this area.The results and cognitions of this study as follow:(1)This paper collects the previous work and research achievements of the research area and summarizes the regional geological characteristics.The overall work in the study area is not abundant,the existing each kind of lithologic units,structures insufficiently according with the remote sensing images,therefore,it is desiderated to launch research on the extraction of remote sensing geological information with higher precision.Based on the priority of structure,using Landsat8 and its 3D images,this research updates and supplyments the predecessors' work about tectonic division,and re-draws the tectonic framework,to process lithological information extraction of the new structures.(2)The main metamorphic rocks and intrusive rocks in the study area were obtained their spectral.Results indicate that mica schist,quartz-feldspathic schist and gneiss has similar absorption peak in the spectrum curve;the overall reflectivity of the amphibolite is lower,and the strong absorption of Mg-OH mineral at 2.35 um is shown;granite integral reflectivity,with different curve slope at 0.42-0.63 um,is higher,which shows absorption of black mica,plagioclase and potassium feldspar at SWIR,especially in TIR.(3)Two improved PCA technologies,mineral index and edge detection algorithm were used to identify lithology.The principle of classification extraction and recognition for the main lithology of the five categories of the predecessors divided: schist(mica schist,quartz-feldspathic schist),gneiss,metamorphic volcanic rocks,marble and granite.By adding thermal infrared PCA technology,the granite rocks are enhanced and distinguishes metamorphic rocks and intrusive rocks;based on the PCA technique of adding constraint conditions,the marbles of the whole area are deduced with known marble as input condition;calculating the ASTER mineral index,and discussing distribution of major minerals,the distribution of lithology is preliminarily inferred according to the mineral assemblage and the regional tectonic framework;using 3 kinds of ASTER band ratios and worldview-2 image,the granites containing various lithological features were identified that including moyite granite,monzonite granite and gneiss granite;Experiments show that the heterogeneity of various minerals is strictly controlled by the structure,and prove that it is difficult to distinguish schist and gneiss from the mineral Angle,and it is still necessary to analyze and identify the schist and the area,too.(4)This paper put forward that the distribution of major lithologic units in the study area should be discussed from three aspects: color(mineral)---texture(rock structure)---tectonic.Through field investigation,verifying the distribution of lithology,the investigation indicates the tectonic controlling takes action on main lithology.In conclusion,under this condition that the remote sensing lithology extraction technology for the ultrahigh pressure metamorphic belt has not yet been recognized uniformly,based on the reflection spectrum and regional geological characteristics of rock ore,this paper makes clear the distribution of large structures in the region,and then applies remote sensing image processing method to excavate scattered rock ore information.The image characteristics and spatial relationship of the target lithology are discussed under the regional tectonic framework.,in this way,we can obtain more accurate geological map of remote sensing interpretation and provide reference for regional geological survey.