Document Type : Original Article
Department of Geology, Faculty of Science, Bu-Ali Sina University, Hamedan
The studied area is located in theNE-Sonqor city (Sinavand Mountain) in the Sanandaj-Sirjan zone. The aim of this paper is investigation of field relationships, petrographic properties and mineral chemistry of host rock (granite and granodiorite) and mafic microgranular enclaves (MMEs) which sometimes led to evidence of magmatic mixing process. The enclaves are dioritic in composition and mainly have plagioclase, amphibole, small amount of K-feldspar and quartz with predominant microgranular texture. MMEs are elliptical to angular in shape and have a chilled margin at contact with their host rock. According to the results of electron microprop of minerals, the granodioritic host rock and dioritic enclaves have calcic amphiboles type and belong to the subset of magnesium hornblende but host granitic rock are hastingsite in composition. In granodioritic host rocks and enclaves have plagioclase of normal and oscillated zoning texture and they range from oligoclase to andesine. Macroscopic and microscopic features of MMEs such as contact surfaces, different shapes (morphology) of the enclaves, the presence of elongated and euhedral-shape plagioclase crystals, needle apatites, and finally microgranular and poikilitic textures, indicate that MMEs may be the result of rapid cooling and a magma mixing/ mingling of felsic and mafic magmas in the studied area. Based on the amount of Al in amphibole, the pressures in the dioritic enclaves are 2.46 kbar and for their hosts 2.77 kbar. Also, using a thermometer, the average temperature of 711 °C and 750 °C are determined for amphibole-plagioclase to replacing of granitoid and diorite magmas.