In south of Kashan, early Paleozoic volcanic rocks are a part of Ghohrudmountains. In Iran structural- sedimentary division, these volcanic rocks located inUrumieh- Dokhtar zone. These volcanic rocks are basic to semibasic and mostly involved basalt. Geochemical investigations of these rocks show the alkaline nature and the intra-continental rift geotectonic setting in their formation time. The Isfahan fault is a north-trending fault across the Sanandaj-Sirjan zone. This fault is one of the old and basement fault that was active in the early Paleozoic. The unique present of Silurian volcanic rocks in this area can refer to the activation of the north part of this fault that was created by extension phases after Caledonian orogeny.