Sub-pixel Mapping of Copper- and Iron-Bearing Metamorphic Rocks Using ASTER Data: A Case Study of Toutak and Surian Comp
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Original Paper
Sub-pixel Mapping of Copper- and Iron-Bearing Metamorphic Rocks Using ASTER Data: A Case Study of Toutak and Surian Complexes, NE Shiraz, Iran Soheyla Esmaeili,1 Majid H. Tangestani ,1,3 and Mohammad H. Tayebi2 Received 30 October 2019; accepted 12 February 2020
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 R2 coefficient, field observations, and XRD analysis. The R2 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. KEY WORDS: Lithologic mapping, ASTER, Copper deposit, Iron deposit, Toutak, Surian, Matched filtering.
INTRODUCTION Mapping of metamorphic complexes using remote sensing technology is essential for searching metallic and nonmetallic ore deposits (Kotnise and Chennabasappa 2015). Many of the largest deposits 1
Department of Earth Sciences, Faculty of Sciences, Shiraz University, Shiraz, Iran. 2 Department of Urban Planning, Apadana Institute of Higher Education, Shiraz, Iran. 3 To whom correspondence should be addressed; e-mail: [email protected]
of base and precious metals are located in metamorphic terrains (Spry et al. 2000) which are important geological features in orogenic systems (Eskola 1948; Teyssier and Whitney 2002). Mapping metamorphic rocks is important for studying the evolutionary processes of orogenic belts (Sarkarinejad and Alizadeh 2009) and understanding the pressure, temperature, fluid migrations, and stress regimes of the system as well (Rajendran and Nasir 2015). Moreover, extracting information on the extent of metamorphic rocks using earth observation technology and satellite image processing
2020 International Association for Mathematical Geosciences
Esmaeili,
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