Origin and tectonic setting of granitic rocks and dolerite dikes in the Nasrand pluton, southeast of Ardestan

The Nasrand pluton of Oligo-Miocene age، which is located approximately 40 km south-east of Ardestan، intruded into the Eocene volcanic rocks of the Urumieh-Dokhtar magmatic belt. This pluton consists mainly of granite and granodiorite. The Nasrand plutonic rocks are metaluminous، weakly peraluminous، with mineralogical and geochemical characteristics of I-type، calc-alkaline to K bearing calc-alkaline granite. The granitic rocks as well as their host volcanic rocks have been crosscut by a series of NE-SW trending diabasic dikes. The plutonic rocks are characterized by enrichment of LREE and LILE، depletion of HREE and HFSE، the negative anomalies of Ti، Nb interpreted to reflect the emplacement of the granitic rocks as well as the diabasic dikes in an active continental margin. The positive anomalies of Rb، K، Th، U and the negative anomalies of Nb،Ti، Eu، Ba، Sr associated with high Ba/Nb (46-139) and Ba/La (17-77) ratios suggest that fusion of continental crust has played an important role in the genesis of the Nasrand granitic rocks and diabasic dikes.