Document Type : Original Article
Authors
University
Abstract
Rock outcrops are generally covered by vegetation and the Quaternary deposits, so their enhancement on the satellite imagery can be impeded, and the identification of pixels of rock outcrops be a challenging task for field sampling in lithogeochemical surveys. Therefore, in order to map outcrops of different rock types, it is required, first, to estimate the distribution of vegetation and the Quaternary deposits as the major step for field sampling in lithogeochemical surveys. This paper is an attempt to map outcrops of different rock types as a prerequisite for lithogeochemical sampling surveys in Kowli-kosh metamorphic complex in Sanandaj-Sirjan zone (SSZ). To evaluate the efficacy of this approach, geochemical anomalies of Cu, Au, and Fe in samples collected from enhanced rock outcrops of a metamorphosed area were analyzed. In order to obtain the objectives of study, we firstly utilized the maximum likelihood (ML), soil-adjusted vegetation index (SAVI), and mixture-tuned matched filtering (MTMF) methods on reflective bands of advanced space-borne thermal emission and reflection radiometer (ASTER) to map the Quaternary deposits, vegetation, and lithological units in Kowli-Kosh metamorphic complex, SW Iran. Pixels matched to lithological units were identified wherever the matched filter (MF) scores were > 0.65. These areas were then cross-tabulated with vegetation and Quaternary maps to differentiate the representative areas of rock outcrops. A grid network was subsequently generated and overlaid on the map of rock outcrops, and the rock chip samples for lithogeochemical analysis were collected from cells containing more than 15 pixels of rock outcrops. The spatial distribution analysis of rock types and the geochemical statistics showed that there is a strong relationship between outcrops and the anomalies of the desired elements. It was concluded that the approach introduced by this study improved the potentials usage of ASTER data in mapping of the areas covered by vegetation and Quaternary deposits. This approach help inobtaining a perspective on conducting lithogeochemical sampling surveys in order to manage cost-effective exploration operations in such areas.
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