STRUCTURAL GIS ANALYSIS OF THE KHOY OPHIOLITE COMPLEX, NORTHWESTERN IRAN

The Khoy ophiolite complex, a stack of tectonically emplaced thrust sheets, occurs at the northeastern edge of the Sanandaj-Sirjan block, in northwestern Iran. Amphibolites occur at the highest structural levels above ultramafic rocks which lie above thrust sheets of basalt. Radiolarian chert, sedimentary mélange, limestone, and pelite occur at the lowest structural levels, in the southwestern part of the allochthon, near the border with Turkey. Amphibolite-facies mylonite defines the shear zones between the higher thrust sheets, with lineations representing reverse sense of motion along northeast-dipping C-foliation. Greenschist facies, foliated serpentinite cataclasite and fault breccia represent the low-temperature shear zones in the lower structural levels, and the sole thrust of the ophiolite complex. We have applied the GIS to decipher the internal architecture of the ophiolite complex from geologic and geomorphologic features which are apparent on the satellite images and published geologic maps of the area. Digital elevation model (DEM) data were used to construct the topographic contours of the area. Using Arc View GIS 3.2, Arc GIS, Erdas Imagine,, we first superimposed the topographic contours on the geological map, and on the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) image of the area. We then constructed the structural contours for the contacts between the thrust sheets, and calculated the attitude of the thrusts. The contact between the ultramafic rocks and the amphibolites dips moderately to the northeast, subparallel to the field-measured, dominant mylonitic foliation along this contact. The conformity between the results of the GIS analysis and field data of mylonitic and cataclastic fabric supports the idea that the ophiolite complex was assembled in a SW-NE directed subhorizontal contraction above a northeast-dipping subduction zone. Fractal and GIS analyses of the fault and drainage system would help us to better understand the distribution of these large structures and the internal architecture of the ophiolite complex.