The Application Of Remotely Sensed Data To Geological Survey In The Luobusa Chromitite Deposit,Tibet

The economically viable chromite deposits are widespread in Yarlung Zangbo ophiolite massifs,particularly in the dunite and harzburgite unit of the mantle section,the research of ophiolite massifs and chromite has been attract the interest of exploration geologists all over the world.As a kind of advanced method and technique for the modernization of geological work,the remote sensing has the characteristics of macroscopic,comprehensive,multi-scale and multi-level,which has become potent technical method for geological research.This paper study the Luobusa area based on the geological background investigation work and multi-spectral remote sensing technologies,through digital image processing,remote sensing geological interpretation and field verification to carry out the remote sensing geological survey.The first step is to collect the basic geological data of the study area and determine the Landsat8 OLI multispectral,WorldView-2 high spatial resolution remotely sensed data,DEM and Google Earth ^TM as the data source.The image preprocessing is carried out according to orthorectification,atmospheric correction,mosaic,spatial subset and fusion process.Secondly,using a number of spectral enhancement techniques on Landsat 8 OLI data to distinguish mantle peridotite,which including optimal band selection,decorrelation stretch,band ratio,principal component analysis,minimum noise faction,false color composite and supportive vector machine classification.Results show that the processed VNIR and SWIR spectral wavelength regions are promising in detecting mantle section within the ophiolite region;Then by geomorphological stereo images and remote sensing interpretation marks to obtain remote sensing information of structure;Meanwhile,choosing principal component analysis method to extract alteration information and result shows that iron stained alteration for chromite deposit has a good effect on indicating significance.Thirdly we take advantage of WorldView-2 high spatial resolution remotely sensed data to establish the remote sensing interpretation signs of main lithology units and structure by analyzing optimum index factor to select optimal bands combination so as to highlight the tone difference of different lithological units.It is recognized that high spatial resolution data can clearly identify the properties,scale of lithology units and geological structure in the area through the correspondence between field verification and remote sensing images.We can conclude that high spatial resolution remotely sensed data has the technical advantage and application prospect in geological resource exploration in those regions with high altitude and poor working conditions.Finally,we summarize remote sensing geological prospecting model of alpine type chromite deposit based on the analysis of the ore-forming geological characteristics in the study area,the results of remote sensing geological interpretation,geophysical and geochemical information.According to this model,it will provide the basis for the future in the Yarlung Zangbo river ophiolite belt to find similar chromite deposit.