Introduction
Magma mixing or mingling is one of the significant processes in the evolution of magmas. The term mixing (Sparks and Marshal, 1986) is applied when the magmas have a homogeneous composition, whereas the term mingling is used if the magmas are mixed physically but heterogeneously, with banding or enclaves/inclusions present.
In the mixed magmas, the compositions and temperatures of the end-member magmas can be determined from the compositional and textural features of phenocrysts (Wallace and Carmichael, 1994). However, in the petrological literatures, magma mixing or mingling is the most common process for the origin of intermediate volcanic rocks.
Petrology and mineral chemistry of the Plio-Quaternary volcanic rocks within this part of Iran have been little studied. Although, there are a number of studies on the Jurassic Shir-Kuh batholith (i,e Khalili, 1997) and the Oligo-Miocene granitoids associated with porphyry copper deposits in the study area (Zarrasvandi, 2005), the study of Plio-Quaternary subvolcanic rocks is generally overlooked.
The research area lies in Central Iran and located in west and southwest of Yazd province. Based on subdivision of Iran, this area belongs to Central Iranian Magmatic Belt (Stocklin, J., 1968) known as Urumieh-Dokhtar Volcanic Belt (UDVB). This zone trending northwest- southeast, is parallel to the Zagros fold-and-thrust belt (Fig.1). Magmatic activity in the UDVB from Eocene to Quaternary age represents an Andean type magmatic arc (Takin, 1972; Sengör, 1990; Alavi, 1994) that peaked during the Eocene. Plio-Quaternary volcanic rocks that studied in this paper, consist of several domes and lava flows. Surk and Ernan mountains are the northern and southern part of this area, respectively. Other bodies are located between them in Shamsabad, Aliabad, Abdollah, Ostaj and Bouragh regions.
The purpose of this paper is to describe the petrography, mineral-chemistry and geochemistry of the Plio-Quaternary rocks of this part of UDMA as well as discussing the petrogenesis of these rocks.
