Study On Extraction Methods Of Alteration Anomalies In Zhaotong Lead-zinc Deposit, Yunnan Province, China

Zhaotong Zn mining area is an important part of the lead-zinc mineralization belt of northeastern of Yunnan Province in China, research alteration information in this area, extracted by means of remote sensing to promote finding resources increasing reserves. In this paper, use of the Zhaotong lead-zinc study area Landsat7ETM+images and ALOS images, through analyzing, summarizing and studying the previous information, the stratum, tectonics, magmatic-rock and country rock alteration in-depth study, collected a number of spectral data acquisition of mining and trenches of the abnormal iron ions, carbonate rocks, metal sulfides information spectral matching work indoors spectroscopy to identify and establish the study area object spectrum library, used band ratios, MPH technology, the Principal Component Analysis of the threshold(PCA), Spectral Angle Mapper (SAM), these four methods of alteration minerals in the study area were extracted, analyzing the effects of the extraction method of evaluation alteration, and field verification to find the best adapted to the region this vegetation the high degree of coverage, terrain cut into dramatic lead-zinc district’s best remote sensing alteration the exception information extraction method.The content and method of this study may be expressed as follows:(1) Through the analyzing, summing up the information, geological altered information are mainly including dolomitization, pyritized, barite, calcite and silicified. Ore bodies mainly occur in Devonian zaige Fm (D3zg) and in Carboniferous Weining Fm (C2w), by means of remote sensing of iron ion, carbonate rock, metal sulfide abnormal information extraction is of great significance.(2) Applying the United States ASD FieldSpec(?)3portable feature spectrometer to collect data of main rock types on the of Zhaotong Zn mining area surface and trenches spectral. The total of839spectral curve in indoor collected Popecurve format conversion to spike smoothing preprocessing using ENVI software set up the surface of the study area and the trenches typical mineral spectral library and match the USGS standard mineral spectral library, finding out a suitable spectral identification matching pattern to achieve mineral spectroscopy to identify, spectral identification of minerals for the study area remote sensing information to identify mineral alteration spectral basis for extracting the information of remote sensing alteration anomaly.(3) Applying band ratio computing to study the area of water, vegetation and shadow extraction, the establishment of the mask and masked images with high-resolution ALOS image than most of the water, vegetation, shadow masked, to achieve the effect of removing the interference information.(4) Applying a "MASK+Principal Component Analysis(PCA)+color space conversion (HIS)" of MPH technology to study this area Alteration Information Extraction: the mine in northeast Permian Emeishan Basalt and Permian Qixia Maokou Fm stratum dividing line, the mine east of the Carboniferous and Devonian stratum dividing line, the mine in the middle of NE to maomao mountain overturned anticline and in image of multiple ring structure visible, which is the follow-up prospecting projections provide an important basis.(5)Applying Principal Component Analysis extraction threshold of hydroxy iron stained alteration exception information:abnormal circled area with known high degree of agreement of the known deposits, the Maoping mine area with Red jian mountain mine sites are within the scope of the multistage anomaly extraction; in the Lin jiaping Village, the mine southeast Luo ze river Shatt South of Lin jiaping village lkm range、the mining area in south-central Zhujia Village South lkm the maomao mountain anticline northwest wing, there is abnormal alteration of hydroxyl and iron stained the two vision forecast area.(6)Applying the mapping of Spectral Angle Method (SAM) of mine Alteration Information Extraction:effectively extracted from the mine the abnormal iron ions, carbonates, metal sulfides abnormal, and in MaoPing mine area with Red jian mountain mine sites exist abnormal iron ion and metal sulfide mines area coverage,and high degree of agreement with known deposits, the other in the presence of iron mining area southeast of the Lin jiaping Village southwest of the mining area、in south-central Zhujia Village South1km the Maomao mountain anticline northwest wing abnormal iron ion and metal sulfides coverage, in accordance with alteration anomaly range PCA method.Alteration minerals were extracted by the above four methods of the study, analyzing and comparing the results, that the ideal effect of alteration information the MPH technology and SAM extraction of study area. There are two known deposits to be proved, identified two mineralization favorable area field validation.