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A Predictive GIS Model for Potential Mapping of Gold and Base Metal Mineralization in Takab Area, Iran

ASADI HARONI, Hooshang (Harouni@itc.nl), Ministry of Culture and Higher Education, Dr. Beheshti Avenue, Shahid Sabounchi Cross, Tehran, Iran; and HALE, Martin, International Institute for Aerospace Survey and Earth Sciences (ITC), Kanaalweg 3, 2628 EB, Delft, The Netherlands

Key Words: sediment-hosted gold deposits, epithermal mineralization, hydrothermal alteration mapping, structural mapping, magnetic signatures, weights of evidence analysis, predictive GIS model

Interpretation of aeromagnetic, Landsat Thematic Mapper (TM), geological and mineral occurrence data are used to recognize the combination of mapped geological features, hydrothermal alteration, and magnetic signatures that could be associated with the known epithermal gold, arsenic, antimony, and base metal deposits in a 1,600 km² area near Takab, northwest Iran. This area, part of the suture zone located between the Afro-Arabian and Iranian plates, which extends more than 2,000 km to northeast of, and parallel to, the Zagros thrust fault, comprises Precambrian metamorphics, Tertiary volcano-sedimentary rocks, and Quaternary sediments.

A principal component (PC) transformation applied to selected reflective Landsat-TM bands identifies iron oxides and hydroxyl-bearing minerals, some of which are hydrothermal alterations associated with the known mineralization in the area. Gradient images of aeromagnetic data depict major structures in the area, which appear to control the hydrothermal fluid flow and mineral deposition. Reduction to the pole of total magnetic intensity aids recognition of weak magnetic responses that could be associated with zones of iron oxide hydrothermal alteration; two such zones characterize major mineral deposits in the area. Analytical signal analysis of aeromagnetic data reveals that high amplitude anomalies characterize many of the known mineral deposits and their associated high magnetic-susceptibility igneous rocks both at surface and at depth.

Geological data such as permeable and reactive host rocks, surface igneous rocks, and structures are integrated with the hydrothermal alteration and the subsurface igneous heat sources, and four important parameters that could act as indicators of the occurrence of further mineralization are determined. Four binary maps representing diagnostic deposit recognition criteria have been combined using a weight of evidence model. The model uses the spatial distribution of 19 known mineral occurrences to calculate a final map of gold and base metal potential, based on the binary predictor patterns, for undiscovered mineral deposits in the Takab area.