The Parishan Pluton in Qorveh Area, an Example for Magma Mingling Process, Southeastern Sanandaj, Iran

Abstract

The area under investigation is located between 47°42′ and 48° E-Longitude and 34°50′ and 50°10′ N-Latitude and south of Qorveh town about 70 km SE Sanandaj city. The Parishan pluton is an elliptical pluton which covers an area of approximately 40 km² and it is a part of the Qorveh Granitoid Complex (QGC). The combination of field, petrographic and geochemical data show that the Parishan pluton composed of the dioritic and granodioritic-granitic units and dykes of dioritic to melanodioritic in composition. The granodiorite commonly contains microgranular enclaves (MME). The MMEs are dioritic-meladioritic rocks in composition, typically about 10–40 cm in diameter and subangular to near-oval in shape with chilled to fine grained contacts. This investigation attempts to describe mingling of felsic and mafic magmas (mafic dykes) in Parishan pluton. Field (e.g. contacts sharp boundaries enclaves, lack compositional or textural zones related to their margins and heterogeneous distribution of enclaves), textural (e.g. the chemical zonation of plagioclase crystals) and geochemical (e.g. compositional gap between 55 and 65 wt% SiO₂ contents, curvilinear trends in Harker variations diagrams) evidences suggest that this could not have occurred by significant interaction with the enclosing host rocks. Therefore, enclaves could have been formed by magma mingling process by rapid cooling within the host granitoid magma.