Sub-pixel Mapping of Copper- and Iron-Bearing Metamorphic Rocks Using ASTER Data: A Case Study of Toutak and Surian Complexes, NE Shiraz, Iran

Metamorphic rock units of Toutak and Surian complexes located in the Sanandaj-Sirjan metamorphic zone, NE Shiraz, Iran, were mapped using the matched filtering (MF) method on the visible near-infrared (VNIR) and shortwave infrared (SWIR) bands of advanced spaceborne thermal emission and reflection radiometer (ASTER) sensor. These complexes host magnetite and Cu-Zn-Ag volcanogenic massive sulfide (VMS) deposits. Mixed pixels of lithologic-mineralogic indicators of these deposits were detected to identify the prospecting areas. The spectra of end-members were extracted from imagery using sequential maximum angle convex cone (SMACC) model and were compared to the field and laboratory spectra to examine their characteristics. The key minerals including chlorite + epidote (greenschist), muscovite + biotite (mica schist), calcite + dolomite (marble), and muscovite + oligoclase (gneiss) were identified and were input to the algorithm for estimating the sub-pixel fractions of desired minerals. A generalized map of lithologies was then produced by combining the fraction maps of greenschist, mica schist, marble, and gneiss using a GIS. Finally, this lithologic association was applied to define the prospecting areas. The accuracy of results was assessed using R-2 coefficient, field observations, and XRD analysis. The R-2 coefficient was 0.74 for greenschist, 0.63 for mica schist, 0.65 for marble, and 0.53 for gneiss. The results also showed good agreement with field evidence, and thus, they can be used for finding potential targets for copper and iron deposits.