پترولوژي شوشنيت هاي آتشفشاني جنوب عشين و تعيين سن كربناتهاي آذرين منطقه با استفاده از روش شكافت (Fission Track) (غرب انارك، شمال شرق استان اصفهان)

Petrology of Volcanic Shoshonites in South of Ashin, and Age Determination of Igneous Carbonates by Using the Fission Track Method (West of Anarak, North-east of Isfahan Province)

Ashin area is situated in west of Anarak city (NE of Isfahan province). In this area, ail rock types of shoshonitic series including Absarokite, Shoshonite, Banakite and Toscanite can be observed. The most important charactristic of these shoshonitic association is high abundance of feldspars, and igneous carbonate droplets. Geochemical investigations show that the parent magma of these rocks originated from an enriched mantle and their source rock is a metasomatized peridotite. The parent magma that, an Alkali-Basalt was produced by low grade pratial melting of the source rock. Ascent of shoshonitic melt through the thick continental crust causes a series of ion exchanges. The evidence of this ion exchange can be observed in petrographic studies. In fact, the toscanites are banakites that have intercalations of granitic bands. Fission Track Dating of igenous carbonates of shoshonites shows 42±3 million years of age (Middle Eocene) that is higher than age of shoshonites of middle part of Uromiyeh-Dokhtar magmatic belt (Upper Eocene).