تحليل ساختاري پهنه گسلي زفره در شمال غرب باغ گل، شمال شرق شهر اصفهان

The northwestern area of the Bagh-e-Gol region, located north of Zefreh village, encompasses the central segment of the Urumieh-Dokhtar magmatic arc. In this area, metamorphosed conglomerate units (Ec1), dated to the early Eocene according to the Ardestan 1:100,000 geological map, crop out an‎d exhibit abundant evidence of deformation. Structurally, they are of particular significance due to plastic deformation an‎d the development of foliation. This study, aimed at gaining a better understan‎ding of tectonic trends an‎d deformation conditions of this lithological unit at various scales, involved a combination of field studies, macroscopic an‎d microscopic examinations, an‎d high-resolution Google Earth image analyses. The presence of the Zefreh fault zone in the area has led to the formation of numerous fault structures, mostly trending northwest-southeast, which play a critical role in organizing the overall structural framework of the region. Fault analysis reveals that strike-slip mechanisms, especially right-lateral strike-slip faults, are predominant. Satellite imagery from Google Earth also confirms a concentration of faults along this same orientation. In this region, statistical analysis of foliation patterns within the deformed conglomerate unit was conducted across five zones, indicating intense schistosity an‎d deformation particularly in the central sections, most notably in zones one an‎d two. The prevailing compressive stresses are mainly concentrated along the directions of 225°-045° an‎d 230°-050°. In line with these results, data from fold analysis an‎d fold axis measurements reveal small-scale structures with chevron an‎d ptygmatic folding patterns in this area. Strain analysis of the samples, derived from field photographs an‎d thin sections, was performed using the Ramsay method. Results indicate that the maximum amount of strain (shortening) in the central part of the region reaches up to 70%, categorizing the deformation intensity as moderate to high. Grain elongation analysis-based on the ratio of the long to short axes an‎d comparisons of initial to final lengths at both macroscopic an‎d microscopic scales-also points to a significant increase in strain near fault structures, especially in proximity to the Zefreh fault. In terms of shear sense, both dextral (right-lateral) an‎d sinistral (left-lateral) movements were observed in field an‎d microscopic investigations. Given the recent documented movements along the Zefreh fault an‎d its subsidiary branches in the region, it can be concluded that the deformed rock units reflect evidence of stress field changes during their uplift an‎d exhumation. As a key structural element of the region, the Zefreh fault has played a prominent role in influencing foliation orientation, strain distribution, an‎d the formation of lens-shaped structures within the conglomerates, thereby contributing significantly to the tectonic evolution of the area. The spatial relationship among major faults, foliation orientations, an‎d high-strain zones reveals a complex an‎d dynamic system. This system has undergone progressive deformation under the combined effects of strike-slip motion, tectonic compression, high temperature, an‎d deep-seated pressure-conditions that have culminated in the present structural configuration, as reflected in the evolutionary model proposed for the region.

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