Investigation of the role of fractional crystallization, crustal assimilation and magma mixing in turquoise hosted sub-volcanic intrusion rocks in south of Damghan mine, Iran.

Granodiorite and dioritic intrusive rocks (Middle Eocene age) intruded the Lower-Middle Eocene volcanic rocks at the northern parts of the Torud-Chah Shirin volcano-plutonic belt in north east of Iran. This granodiorite is intruded by small rhyolitic dome in the Damghan turquoise-gold mine. According to all data, these intrusive rocks are related to a common source. The primary magma evolved by the assimilation, fractional crystallization, contamination (AFC) and magma mixing during the ascent. These processes formed granodiorite, diorite and rhyolitic magmatic rocks. Fractional crystallization of olivine, zircon, clinopyroxene, plagioclase and hornblende has been effective in the formation of granodioritic magma. Crustal contamination and fractional crystallization of apatite and Ca- plagioclase have played a major role in the formation of rhyolitic magma. Potassic feldspar has been present until the last stages of magma evaluation. In addition to the field evidences, present of apatite needles solid inclusions in plagioclase, corrosion, and oscillatory- reverse zoning in zoned plagioclases, enclave type and geochemical characteristics of whole rock (Nb/Y, Nb/Zr to Nb, Rb/Sr and Sr/Zr ratios) (Zr/Rb to Rb / Sr) confirm mixing between mafic and granodioritic magmas.