T Nabaei; A Khakzad; M Hoseini; S.R Mehrnia
Abstract
The study area is a portion of Urmia-Bazman Magmatic Belt in the Central Iran Structural Zone that located in the south of Boein-Zahra city (Qazvin province). In this area, volcanic and pyroclastic rocks incised by a plutonic body and around and within this pluton, a large extensive alteration occurred. ...
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The study area is a portion of Urmia-Bazman Magmatic Belt in the Central Iran Structural Zone that located in the south of Boein-Zahra city (Qazvin province). In this area, volcanic and pyroclastic rocks incised by a plutonic body and around and within this pluton, a large extensive alteration occurred. In this study, Landsat 7 data (ETM+) employed and general alteration trend in the area was mapped by conventional methods of Color Composite (RGB), Band Rationing and specially Principal Components Analysis (PCA). All of the three methods are found to be effective for obtaining generalized information about the alteration of the image area. Principal Components Analysis (PCA) and especially Selective Principal Components Analysis (Crosta technique) found to be the best effective method in delineating the borders of clay and iron oxide altered areas. In the high altered wall rocks, mineralogical analysis results (XRD method) indicated two forms of vertical and horizontal zoning. In this case, in vertical zoning in order from down to up, advanced argillic, alunitic and silicified zones and in horizontal zoning from fault surface toward wallrocks, advanced argillic and propylitic zones were distinguished. The mineralogical composition of zones and form of zoning indicates that this type of alteration is "acid sulfate". The study of fluid inclusion of quartz crystals in silicic veins, indicated that liquid and vapor phases (LV) are present and study of them resulted in calculation of salinity percentages between 16.8 to 19.2 (NaCl wt%) and homogenization temperatures between 204oC to 280oC.
F. Masoumi; H. Ranjbar
Abstract
The study area covers the northern half of the Baft 1/100000 geological map in Dehaj-Sarduiyeh volcanic-sedimentary and ophiolitic belts. The aim of this research was application of multispectral ASTER and ETM+ data for determining the altered areas by using different image processing techniques. In ...
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The study area covers the northern half of the Baft 1/100000 geological map in Dehaj-Sarduiyeh volcanic-sedimentary and ophiolitic belts. The aim of this research was application of multispectral ASTER and ETM+ data for determining the altered areas by using different image processing techniques. In order to separate altered zones, false color composite of the ratios was applied on ASTER data that separated propylitic and phyllic/argillic altered zones. Separation of carbonate areas from the altered areas was achieved by making false color composite ratios. Another method for separation of carbonate areas from the altered zone was by applying principal component analysis (PCA) on short wave bands of ASTER data. A color composite of PC2, PC3, -PC4 in red, green and blue respectively was useful for separating carbonate from altered areas. Spectral Angle mapper method was also used for recognizing and mapping the minerals such as muscovite, chlorite, kaolinite, calcite and epidote in altered zones. Sampling from the altered areas and their analysis showed that this method could be used for recognizing the minerals in the altered areas, if they have enough spatial extent.
