Information Extraction of Typical Alteration Mineral Assemblage in Porphyry Copper Using ASTER Satellite Data, Arequipa Province of South Peru

Abstract

In this paper we studied the information extraction technology of alteration mineral assemblages.Using the standard laboratory spectral database of U.S.Geological Survey,we rebuilt the reflectivity curve of key alteration minerals in porphyry copper alteration zones with ASTER data.After comparative analysis of these key alteration minerals spectral curves,we found the characteristic of absorption valley at the spectral 2.2 μm(which is corresponding to the B6 of ASTER data) of the argillic-and phyllic-altered mineral assemblage(which include muscovite,kaolinite,montmorillonite,alunite,illite,etc.),and with the characteristic of high reflection peaks at B4 and B7.The characteristic of absorption valley at the spectral 2.3 μm(which is corresponding to the B8 of ASTER data) of the propylitization altered mineral assemblage(which include chlorite,epidote,calcite,etc.,),and with the characteristic of a high reflection peaks at B4,while the B9 has a higher reflectivity than the B8.Accordingly,the principal component analysis model was developed.This model can make component analysis based on ASTER B1,B4,B6 and B7 to extract the argillic-and phyllic-altered mineral assemblage;component analysis based on ASTER B1,B3,B4 and B8 to extract propylitization altered mineral assemblage.At the same time,the process was established for the alteration mineral assemblage information extraction.Taking porphyry copper region in Arequipa Province of south Peru as an example,based on comprehensive analysis of the geological background of the study area,especially its typical alteration zoning and alteration mineral assemblages in the area,we found a typical porphyry alteration zonation in Arequipa Province.So we can take advantage of the technical processes and methods,and after ASTER data preprocessing,interfering surface features removal,principal component analysis and threshold setting,to extract argillic-and phyllic-altered mineral assemblage and propylitization altered mineral assemblage.Meanwhile,together with remote sensing interpretation and regional geochemical data,we forecasted the prospecting target of porphyry copper,and delineated 4 remote sensing exploration targets.Comparing with the verified of high-resolution satellite images and the known porphyry copper deposit,the result this study is reliable.