I-Type magmatism in granitoids from e-ne Tafresh

The polyphase Nevis granitoid pluton extends 70 km2, is located in Urmieh-Dokhtar zone, shows variation which in terms of emplacement depth is related to epizonal to mesozonal environments [16], and in range of acidic to basic including tonalite, granodiorite, granite, monzonite, diorite and gabbro. The mentioned pluton is intruded to different units of volcano-sediments (according to the 1:250000 Geological Survey map) of Eocene sequences (E1, E2, E3, E4,E5, E6) and has imposed a contact metamorphism in Eocene 3]. Existance of mafic enclaves in the main body could confirm the initial basic-intermediate magma replacement. According to the coarse granular texture of these basic-intermediate rocks can be said that they have been replaced in crust middle depths (mesozonal) and in later stages, a large size of tonalitic magma intruded to the region shows variation in texture. Part of this tonalitic magma get to higher levels and show porphyry textures. Then they involved in mylonitic textures under tectonic stresses. Stress effects produced subgrain minerals and undulose extinction. The final phase of plutonism was made up leucocratic micro-granite and granophyres, comparing to tonalite they have limited volume and they are the most shallow plutonism in the area. Another pervasive process had been the effects of heat and fluid (hydrothermal process) caused by successive injections which had different influences on the rocks, and created secondary mineral paragenesis of greenschist facies including epidote, chlorite, calcite, albite, sphene and opaque minerals, represent the geothermal system activities in different phases and the formation history of polyphase Nevis pluton. Based on field surveys, lithology and geochemical, granitoids are I-type. These rocks are calc alkaline and metaluminous.